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chemical

chemical

chemical Sentence Examples

  • The chemical smell suggested they were going in the right direction.

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  • The advances were not merely mechanical but chemical as well.

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  • In both these doctrines of a priori science Descartes has not been subverted, but, if anything, corroborated by the results of experimental physics; for the so-called atoms of chemical theory already presuppose, from the Cartesian point of view, certain aggregations of the primitive particles of matter.

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  • In both these doctrines of a priori science Descartes has not been subverted, but, if anything, corroborated by the results of experimental physics; for the so-called atoms of chemical theory already presuppose, from the Cartesian point of view, certain aggregations of the primitive particles of matter.

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  • But on account of experimental errors in weighing and measuring, and through loss of material in the transfer of substances from one vessel to another, such analyses are rarely trustworthy to more than one part in about Soo; so that small changes in weight consequent on the chemical change could not with certainty be proved or disproved.

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  • This was the principle of the chemical telegraph proposed by Edward Davy in 1838 and of that proposed by Bain in 1846.

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  • This system is of much service in following out mathematical, physical and chemical problems in which it is necessary to represent four variables.

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  • There are well-known chemical works at Dombasle (close to Nancy) and Chauny (Aisne) and in Rhhne.

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  • Photosynthesis is what converts light energy from the sun into chemical energy for plants.

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  • The chemical characters of the well-waters, the irregular distribution of the water-pressure, the distribution of the underground thermal gradients, and the occurrence in some of the wells of a tidal rise and fall of a varying period, are facts which are not explained on the simple hydrostatic theory.

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  • Properties.--All attempts to make helium enter into stable chemical union have hitherto proved unsuccessful.

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  • If chemical compounds can be proved by experiment to obey these laws, then the atomic theory acquires a high degree of probability; if they are contradicted by experiment then the atomic theory must be abandoned, or very much modified.

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  • If chemical compounds can be proved by experiment to obey these laws, then the atomic theory acquires a high degree of probability; if they are contradicted by experiment then the atomic theory must be abandoned, or very much modified.

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  • In 1781 he followed this up with an introductory manual of Chemical Essays.

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  • We cannot determine the chemical composition of soil simply by touching it.

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  • Landolt and others, made it at first appear that the change in weight, if there is any, consequent on a chemical change can rarely exceed one-millionth of the weight of the reacting substances, and that it must often be much less.

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  • Landolt and others, made it at first appear that the change in weight, if there is any, consequent on a chemical change can rarely exceed one-millionth of the weight of the reacting substances, and that it must often be much less.

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  • And as the undefinable essence of the force moving the heavenly bodies, the undefinable essence of the forces of heat and electricity, or of chemical affinity, or of the vital force, forms the content of astronomy, physics, chemistry, botany, zoology, and so on, just in the same way does the force of free will form the content of history.

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  • Chemical industries: total - - - 110,000 49,000

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  • Or consider a well-marked case of what we are in the habit of calling chemical combination.

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  • Or consider a well-marked case of what we are in the habit of calling chemical combination.

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  • The above gives some idea of the evidence that has been accumulated in favour of the laws of chemical combination, laws which can be deduced from the atomic theory.

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  • The fundamental conception that underlay all Berthelot's chemical work was that all chemical phenomena depend on the action of physical forces which can be determined and measured.

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  • Cotton spinning and printing works, cotton-mill machinery works, dye-works and chemical manufactures, and neighbouring collieries maintain the industrial population.

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  • In the future, we'll not only know if that is so, but why: Perhaps mental agility is a result of their extensive exposure to a chemical in pencil lead and newsprint that they got by doing all those puzzles.

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  • 1842 -),whom he had met when he was at Widnes, and thus founded the great chemical manufacturing firm of Brunner, Mond & Co.

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  • materia, matter), in philosophy, the theory which regards all the facts of the universe as explainable in terms of matter and motion, and in particular explains all psychical processes by physical and chemical changes in the nervous system.

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  • "I buried myself," he says, "in my laboratory, and in fourteen months read a course of chemical lectures to a very full audience."

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  • The law of reciprocal proportion, of which some examples have been already given, is part of a larger law of equivalence that underlies most of our chemical methods and calculations.

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  • The investigations of Lord Rayleigh and Sir William Ramsay had shown that indifference to chemical reagents did not sufficiently characterize an unknown gas as nitrogen, and it became necessary to reinvestigate other cases of the occurrence of "nitrogen" in nature.

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  • Its most important industrial establishments are the mirror manufactory of St Gobain and the chemical works at Chauny, and the workshops and foundries of Guise, the property of an association of workpeople organized on socialistic lines and producing iron goods of various kinds.

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  • The resulting compound, nickel carbonyl, which was described to the Chemical Society in 1890, is both formed and decomposed within a very moderate range of temperature, and on this fact he based a successful process for the extraction of nickel from its ores.

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  • The principal classes of products affected are foods, wearing apparel, building materials, furniture, &c., chemical products, printing and allied trades, and sundry others, such as cigars, matches, tanning, paints, &c. In some manufactures the raw material is imported partly manufactured, such as thread for weaving.

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  • He carried out a number of magnetic investigations which resulted in the discovery of many interesting phenomena, some of which have been rediscovered by others; they related among other things to the effect of mechanical strain on the magnetic properties of the magnetic metals, to the relation between the chemical composition of compound bodies and their magnetic properties, and to a curious parallelism between the laws of torsion and of magnetism.

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  • It should know what the food on my fork weighs, run a chemical analysis of every bite I take, and log it in my Digital Echo file for my future reference.

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  • Over the surface of the plate and between it and the indicator there was passed, at a regularly uniform speed, in a direction perpendicular to the line of motion of the indicator, a material capable of being acted on physically by the sparks, through either their chemical action, their heat, or their perforating force.

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  • Over the surface of the plate and between it and the indicator there was passed, at a regularly uniform speed, in a direction perpendicular to the line of motion of the indicator, a material capable of being acted on physically by the sparks, through either their chemical action, their heat, or their perforating force.

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  • ACID-AMIDES, chemical compounds which may be considered as derived from ammonia by replacement of its hydrogen with acidyl residues, the substances produced being known as, primary, secondary or tertiary amides, according to the number of hydrogen atoms replaced.

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  • He held that every fermentation consisted of molecular motion which is transmitted from a substance in a state of chemical motion - that is, of decomposition - to other substances, the elements of which are loosely held together.

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  • He drew simple diagrams, three of which, taken from Dalton's New System of Chemical Philosophy, part ii.

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  • But it seems pretty clear that if there is any change in weight consequent on chemical change, it is too minute to be of im- portance to the chemist, though the methods of modern physics may settle the question.

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  • It is evident that if our experiments are solely directed to the verification of this law, they should, if possible; be carried out in a hermetically closed vessel, the vessel and its contents being weighed before and after the chemical change.

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  • Simultaneously Hermann, a German chemical manufacturer, discovered the new metal in a specimen of zinc oxide which had been thought to contain arsenic, since it gave a yellow precipitate, in acid solution, on the addition of sulphuretted hydrogen.

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  • The following branches have especially felt his influence: - chemical physics, capillarity and viscosity, theory of gases, flow of liquids, photography, optics, colour vision, wave theory, electric and magnetic problems, electrical measurements, elasticity, sound and hydrodynamics.

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  • Some unions annually purchase large quantities ~cono of merchandise for their members, especially chemical mica.

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  • Oil-works jo,ooo Other chemical 1 industries 58,000 - -

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  • It is the principal seat of the linen trade in the county, and has extensive cloth and thread factories, bleachfields and chemical works.

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  • the formation of nitrites and nitrates from ammonia and its compounds in the soil, was formerly held to be a purely chemical process, until Schloesing and Mintz suggested in 1877 that it was biological.

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  • ijXcos, the sun), a gaseous chemical element, the modern discovery of which followed closely on that of argon.

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  • YTTRIUM [[[symbol]], Y; atomic weight, 89 o (0= 16)], a metallic chemical element.

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  • Chemical industries show an output worth 2,640,000 in 1902 al against 1,040,000 in 1893.

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  • phosphates and chemical manures; calcitim carbide; explosivi powder; dynamite and other explosives.

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  • In the mining and woollen industries they have fallen, but have increased in mechanical, chemical, silk and cotton industries.

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  • Asparagus, figs, and wine of medium quality are grown in the district; and heavy iron goods, chemical products, clocks and plaster are among the manufactures.

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  • (After Kleinenberg, from Gegenbaur.) access of water to the contents; when the cnidocil is stimulated it sets in action a mechanism or perhaps a series of chemical changes by which the plug is dissolved or removed; as a result water penetrates into the capsule and causes its contents to swell, with the result that the thread is everted violently.

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  • The curious signs on the coloured carboys in chemists' windows, which were commonly to be seen until the middle of the 19th century, were signs used by the alchemists to indicate various chemical substances.

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  • The chemical laboratory in connexion with the school was, when first instituted, the only one in England for teaching purposes, and the museum is now reputed to be the best pharmaceutical one in the world, the library now containing about 13,000 volumes.

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  • The society has also established a chemical research laboratory, in which much useful work has been done in connexion with the national pharmacopoeia under the direction of the Pharmacopoeia Committee of the Medical Council.

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  • MOLYBDENUM [[[symbol]], Mo; atomic weight, 96 (0=16)] a metallic chemical element.

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  • The study of the differentiation of protoplasm was at that time seldom undertaken, and no particular attention was paid either to fixing it, to enable staining methods to be accurately applied to it, or to studying the action of chemical reagents upon it.

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  • These vary considerably in completeness with its age; in its younger parts the outer cells wall undergoes the change known as cuticularization, the material being changed both in chemical composition and in physical properties.

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  • In addition, certain inorganic salts, particularly certain compounds of potassium, are apparently necessary, but they seem to take no part in the chemical changes which take place.

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  • The first chemical change suggested is an interaction between carbon dioxide and water, under the influence of light acting through chlorophyll, which leads to the simultaneous formation of formaldehyde and hydrogen peroxide.

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  • But the subject requires elucidation from both chemical and biological points of view.

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  • There is no direct connection between the two, the oxygen is absorbed almost immediately by the protoplasm, and appears to enter into some kind of chemical union with it.

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  • It has been suggested by several botanists, with considerable plausibility, that the ultra-violet or chemical rays can be absorbed and utilized by the protoplasm without the intervention of any pigment such as chlorophyll.

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  • observer that such perceptions exist, and that they are followed by certain purposeful changes in the plant, sometimes mechanical, sometimes chemical, the object being evidently to secure some advantage for the plant, to ward off some danger, or to extricate it from some difficulty.

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  • The protoplasm is sensitive to particular influences, perhaps of vibraticn, or of contact or of chemical action.

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  • Chemical I.

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  • Many maladies of plants are traceable to the chemical composition of soilse.g.

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  • But it is worthy of special attention that the mere chemical composition of agricultural and garden soils is, as a rule, the least important feature about them, popular opinion to the contrary notwithstanding.

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  • Church, A Chemical Study of Vegetable Albinism, Journ.

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  • However, until more is known of the exact chemical composition of naturalas contrasted with agriculturalsoils, and until more is known of the physiological effects of lime, it is impossible to decide the vexed question of the relation of limeloving and lime-shunning plants to the presence or absence of calcium carbonate in the soil.

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  • The staining reactions of the various parts of the nucleus depend to some extent upon their chemical constitution.

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  • Just as every crystallizable chemical substance assumes a definite and constant crystalline form which cannot be accounted for otherwise than by regarding it as one of the properties of the substance, so every living organism assumes a characteristic form which is the outcome of the properties of its protoplasm.

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  • But whereas the crystalline form of a chemical substance is stable and fixed, the organized form of a living organism is unstable and subject to change.

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  • Beryllium to a certain extent stands alone in many of its chemical' properties, resembling to some extent the metal aluminium.

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  • When that is done, colchicine may be found to exhibit a definite chemical interaction with this hitherto undiscovered substance.

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  • SULPHUR [[[symbol]] S, atomic weight 32.07 (0 = 16)], a non-metallic chemical element, known from very remote times and regarded by the alchemists, on account of its inflammable nature, as the principle of combustion; it is also known as brimstone.

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  • The substance known as "milk of sulphur" (lac sulphuris) is very finely divided sulphur produced by the following, or some analogous, chemical process.

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  • It combines with many metals to form sulphides, and also decomposes many metallic salts with consequent production of sulphides, a property which renders it extremely useful in chemical analysis.

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  • News, 1902, 86, p. 5) obtained a substance of composition S312 (which in all probability is a chemical individual) as a reddish-coloured powder by the action of sulphuretted hydrogen on a solution of iodine trichloride.

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  • In 1845 he was appointed to the chair of chemistry, physics and technology at the Wiesbaden Agricultural Institution, and three years later he became the first director of the chemical laboratory which he induced the Nassau government to establish at that place.

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  • The cable is slow; and unless development along new lines of com p ressed air or some sort of chemical engine takes place, electricity will monopolize the field.

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  • Straw-plaiting and the manufacture of small wooden wares are the principal industries, and there are large chemical works.

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  • He was twice president of the London Chemical Society, in 1863-1865, and again in 1869-1871.

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  • It might, for example, be suggested that the heat of the sun was supplied by chemical combination analogous to combustion.

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  • We cannot, therefore, admit that the source of the heat in the sun is to be found in any chemical combination taking place in its mass.

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  • THERMOCHEMISTRY, a branch of Energetics, treating of the thermal phenomena which are associated with chemical change.

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  • That vigorous chemical action is accompanied by a brisk evolution of heat is evident from such familiar examples as the combustion of fuel or the explosion of gunpowder.

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  • This affords an example of a principle which had been stated by Hess in a very general form under the name of the Law of Constant Heat Sums - namely, that the thermal effect of a given chemical action is the same, independently of the character and number of the stages in which it takes place.

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  • Whilst this principle is undoubtedly applicable to the great majority of chemical actions under ordinary conditions, it is subject to numerous exceptions, and cannot therefore be taken (as its authors originally intended) as a secure basis for theoretical reasoning on the connexion between thermal effect and chemical affinity.

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  • If we consider now the transformation of one system of chemical substances into another system under specified conditions, we shall find that in general the intrinsic energy of the second system is different from the intrinsic energy of the first.

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  • It occasionally happens that a change in dilution affects the chemical action that occurs.

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  • Each grammemolecule of a gas which appears under constant pressure during a chemical action (e.g.

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  • (5) The influence of temperature on the thermal effect of a chemical action is sometimes considerable, but.

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  • As a very great number of important chemical actions take place on mixing solutions, the method for such cases has been thoroughly studied.

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  • In the newer type (which was first proposed by Andrews for the combustion of gases) the chemical action takes place in a completely closed combustion chamber of sufficient strength to resist the pressure generated by the sudden action, which is often of explosive violence.

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  • To withstand the chemical action of the gases, the " calorimetric bomb " is lined either with platinum, as in Berthelot's apparatus, or with porcelain, as in Mahler's.

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  • Except for technological purposes, thermochemical data are not referred to unit quantity of matter, but to chemical quantities - i.e.

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  • The chemical symbols stand for quantities measured in grammes, and heat-evolution is reckoned as positive, heat-absorption as negative.

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  • Like Berthelot, he writes the chemical equation of the reaction, but in addition he considers the chemical formula of each substance to express not only its material composition, but also the (unknown) value of its intrinsic energy.

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  • With knowledge then of the heats of formation of the substances involved in any chemical action, we can at once calculate the thermal effect of the action, by placing for each compound in the energy-equation its heat of formation with the sign reversed, i.e.

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  • - What is commonly understood by thermochemistry is based entirely on the first law of thermodynamics, but of recent years great progress has been made in the study of chemical equilibrium by the application of the second law.

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  • For an account of work in this direction see Chemical Action.

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  • - Besides its use as a starting-point in the production of "nitroglycerin" (q.v.) and other chemical products, glycerin is largely employed for a number of purposes in the arts, its application thereto being due to its peculiar physical properties.

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  • Balard having given him an opportunity for chemical work by appointing him to the post of laboratory assistant.

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  • It simply consisted iri the application, to the elucidation of these complex problems, of the exact methods of chemical and physical research.

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  • "The chemical act of fermentation," writes Pasteur, "is essentially a correlative phenomenon of a vital act beginning and ending with it."

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  • Pasteur was now the acknowledged head of the greatest chemical movement of the time, the recipient of honours both from his own country and abroad, and installed at the E.

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  • Connected with it are a library of 150,000 volumes and Boo MSS., a chemical laboratory, a zoological museum, a gynaecological institute, an ophthalmological school, a botanical garden and at Eldena (a seaside resort on the Baltic) an agricultural school.

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  • He spent his time in making chemical experiments and in speculating upon legal abuses, rather than in reading Coke upon Littleton and the Reports.

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  • Limestone is quarried at Buxton, Millersdale and Matlock for lime, fluxing and chemical purposes.

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  • In the county town and neighbourhood are several important chemical and colour works; and in various parts of the county, as at Belper, Cromford, Matlock, Tutbury, are cottonspinning mills, as well as hosiery and tape manufactories.

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  • In the case of plants the method of procedure was to grow some of the most important crops of rotation, each separately year after year, for many years in succession on the same land, (a) without manure, (b) with farmyard manure and (c) with a great variety of chemical manures; the same description of manure being, as a rule, applied year after year on the same plot.

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  • Of the twenty plots into which this land is divided, two were left without manure from the outset, two received ordinary farmyard manure for a series of years, whilst the remainder each received a different description of artificial or chemical manure, the same being, except in special cases, applied year after year on the same plot.

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  • So much, indeed, does the character of the herbage vary from plot to plot that the effect may fairly be described as kaleidoscopic. Repeated analyses have shown how greatly both the botanical constitution and the chemical composition of the mixed herbage vary according to the description of manure applied.

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  • He also published chemical and physical papers, and translated chemical works by J.

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  • His next and most important publication was his famous paper "On the Equilibrium of Heterogeneous Substances" (in two parts, 1876 and 1878), which, it has been said, founded a new department of chemical science that is becoming comparable in importance to that created by Lavoisier.

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  • Ostwald (who styled its author the "founder of chemical energetics") in 1891 and into French by H.

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  • In 1901 the Copley medal of the Royal Society of London was awarded him as being "the first to apply the second law of thermodynamics to the exhaustive discussion of the relation between chemical, electrical and thermal energy and capacity for external work."

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  • There are numerous chemical and other manufactures which have been removed from London itself; and the large population can also be traced in part to the foundation of the Victoria and Albert docks at Plaistow.

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  • The mineral is usually found in a state of considerable chemical purity, though small amounts of strontium and calcium sulphates may isomorphously replace the barium sulphate: ammonium sulphate is also sometimes present, whilst clay, silica, bituminous matter, &c., may be enclosed as impurities.

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  • Other important industries are wood-carving (of an artistic excellence long unknown), artistic iron-working, jewelling, bronze-casting, the production of steam-engines, machinery, matches (largely exported to Turkey, Egypt, Russia, Austria-Hungary and Greece), clock-making, wool-weaving and the manufacture of chemical manures.

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  • A more careful study of the physical as well as the chemical properties of a soil must precede intelligent experimentation in rotation.

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  • These facts indicate that we have here an agricultural product the market price of which is still far below its value as compared, on the basis of its chemical composition, either with other feeding stuffs or with other fertilizers.

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  • Iron and quinine citrate is used as a bitter stomachic and tonic. In the blood citrates are oxidized into carbonates; they therefore act as remote alkalis, increasing the alkalinity of the blood and thereby the general rate of chemical change within the body.

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  • Although our information respecting the chemical composition of petroleum has been almost entirely gained since the middle of the 18th century, a considerable amount of empirical knowledge of the substance was possessed by chemists at an earlier date, and there was much speculation as to its origin.

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  • Even prior to the discovery of petroleum in commercial quantities, a number of chemists had made determinations of the chemical composition of several different varieties, and these investigations, supplemented by those of a later date, show that petroleum consists of about 84% by weight of carbon with 12% of hydrogen, and varying proportions of sulphur, nitrogen and oxygen.

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  • Berthelot was the first to suggest, in 1866, after conducting a series of experiments, that mineral oil was produced by purely chemical action, similar to that employed in the manufacture of acetylene.

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  • The products obtained by the distillation of petroleum are not in a marketable condition, but require chemical treatment to remove acid and other bodies which impart a dark colour as well as an unpleasant odour to the liquid, and in the case of lamp-oils, reduce the power of rising in the wick by capillary attraction.

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  • A large number of physical and chemical tests are applied both to crude petroleum and to the products manufactured therefrom.

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  • Even at this early period he had conceived the idea of founding a physical and chemical scientific journal, and the realization of this plan was hastened by the sudden death of L.

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  • SOAP, a chemical compound or mixture of chemical compounds resulting from the interaction of fatty oils and fats with alkalis.

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  • The silicate in the form of a concentrated solution is crutched or stirred into the soap in a mechanical mixing machine after the completion of the saponification, and it appears to enter into a distinct chemical combination with the soap. While silicate soaps bear heavy watering, the soluble silicate itself is a powerful detergent, and it possesses certain advantages when used with hard waters.

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  • The idea of transmutation, in the country of its origin, had a philosophical basis, and was linked up with the Greek theories of matter there current; thus, by supplying a central philosophical principle, it to some extent unified and focussed chemical effort, which previously, so far as it existed at all, had been expended on acquiring empirical acquaintance with a mass of disconnected technical processes.

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  • But according to one, the second part of the word comes from the Greek Xv��ia, pouring, infusion, used in connexion with the study of the juices of plants, and thence extended to chemical manipulations in general; this derivation accounts for the old-fashioned spellings " chymist " and " chymistry."

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  • Some are in Greek and demotic, and one, of peculiar interest from the chemical point of view, gives a number of receipts, in Greek, for the manipulation of base metals to form alloys which simulate gold and are intended to be used in the manufacture of imitation jewellery.

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  • A considerable body of Greek chemical writings is contained in MSS.

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  • at Paris and Leiden, are quite dissimilar from the Latin works attributed to Geber, and show few if any traces of the positive chemical knowledge, as of nitric acid (aqua dissolutiva or fortis) or of the mixture of nitric and hydrochloric acids known as aqua regis or regia, that appears in the latter.

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  • 1 But the chemical knowledge attributed to the Arabs has been so attributed largely on the basis of the contents of the Latin Geber, regarded as a translation from the Arabic Jaber.

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  • The chemical knowledge of Egyptian metallurgists and jewellers, he holds, was early transmitted to the artisans of Rome, and was preserved throughout the dark ages in the workshops of Italy and France until about the 13th century, when it was mingled with the theories of the Greek alchemists which reached the West by way of the Arabs.

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  • Though an alchemist, Boyle, in his Sceptical Chemist (1661), cast doubts on the " experiments whereby vulgar Spagyrists are wont to endeavour to evince their salt, sulphur and mercury to be the true principles of things," and advanced towards the conception of chemical elements as those constituents of matter which cannot be further decomposed.

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  • CARBON BISULPHIDE, CS 2, a chemical product first discovered in 1796 by W.

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  • All these are strikingly alike in appearance and general characters, differing essentially only in chemical composition, and it would seem better to reserve the name cerargyrite for the whole group, using the names chlorargyrite (AgC1), embolite (Ag(Cl, Bl)), bromargyrite (AgBr) and iodembolite (Ag(C1, Br, I)) for the different isomorphous members of the group. They are cubic in crystallization, with the cube and the octahedron as prominent forms, but crystals are small and usually indistinct; there is no cleavage.

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  • The colour varies somewhat with the chemical composition, being grey or colourless in chlorargyrite, greenish-grey in embolite and bromargyrite, and greenish-yellow to orange-yellow in iodembolite.

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  • 45 g 4 flour mills, 8 soap manufactories, 13 shipbuilding and engineering works, chair manufactories, dye works, chemical works, tanneries and a dynamite factory have been established.

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  • It possesses a famous academy of mining and forestry, founded by Maria Theresa in 1760, to which are attached a remarkable collection of minerals, and a chemical laboratory.

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  • The fundamental chemical classification of matter, on the other hand, recognizes two groups of substances, namely, elements, which are substances not admitting of analysis into other substances, and compounds, which do admit of analysis into simpler substances and also of synthesis from simpler substances.

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  • Chemistry and physics, however, meet on common ground in a well-defined branch of science, named physical chemistry, which is primarily concerned with the correlation of physical properties and chemical composition, and, more generally, with the elucidation of natural phenomena on the molecular theory.

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  • This section is restricted to an account of the relations existing between physical properties and chemical composition.

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  • Other branches of this subject are treated in the articles Chemical Action; Energetics; Solution; Alloys; Thermochemistry.

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  • The existence of a fundamental principle, unalterable and indestructible, prevailing alike through physical and chemical changes, was generally accepted.

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  • Towards the end of the 16th century the failure of the alchemists to achieve their cherished purpose, and the general increase in medical knowledge, caused attention to be given to the utilization of chemical preparations as medicines.

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  • At the same time, however, there were many who, opposed to the Paracelsian edefinition of chemistry, still labored at the problem of the alchemists, while others gave much attention to the chemical industries.

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  • At the hands of Stahl and his school, the phlogistic theory, by exhibiting a fundamental similarity between all processes of combustion and by its remarkable flexibility, came to be a general theory of chemical action.

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  • First and foremost, he demanded that the balance must be used in all investigations into chemical changes.

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  • Chemical literature was full of the phlogistic modes of expression - oxygen was '" phlogisticated air," nitrogen " dephlogisticated air," &c. - and this tended to retard its promotion.

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  • By his insistence upon the use of the balance as a quantitative check upon the masses involved in all chemical reactions, Lavoisier was enabled to establish by his own investigations and the results achieved by others the principle now known as the " conservation of mass."

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  • Matter can neither be created nor destroyed; however a chemical system be changed, the weights before and after are equal.'

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  • Investigations proceeded in two directions: - (I) the nature of chemical affinity, (2) the laws of chemical combination.

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  • The laws of chemical combination were solved, in a measure, by John Dalton, and the solution expressed as Dalton's " atomic theory."

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  • Lavoisier appears to have assumed that the composition of every chemical compound was constant, and the same opinion was the basis of much experimental inquiry at the hands of Joseph Louis Proust during 1801 to 1809, who vigorously combated the doctrine of Claude Louis Berthollet (Essai de statique chimique, 1803), viz.

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  • This controversy was unfinished when Dalton published the first part of his New System of Chemical Philosophy in 1808, although the per saltum theory was the most popular.

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  • (1) particles derived by limiting mechanical subdivision, the modern molecule, and (2) particles derived from the first class by chemical subdivision, i.e.

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  • We may here notice the important chemical symbolism or notation introduced by Berzelius, which greatly contributed to the definite and convenient representation of chemical composition and the tracing of chemical reactions.

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  • Gerhardt attempted a solution by investigating chemical reactions.

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  • This link was the full extension of Avogadro's theory to all substances, Cannizzaro showing that chemical reactions in themselves would not suffice.

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  • He regarded the chemical properties of a substance as due to (1) the chemical atoms composing it, and (2) the structure, and he asserted that while different compounds might have the same components (isomerism), yet only one compound could have a particular structure.

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  • The theory of valency as a means of showing similarity of properties and relative composition became a dominant feature of chemical theory, the older hypotheses of types, radicals, &c.

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  • Frankland had recognized the analogies existing between the chemical properties of nitrogen, phosphorus, arsenic and antimony, noting that they act as trior penta-valent.

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  • But the real founder of systematic instruction in our science was Justus von Liebig, who, having accepted the professorship at Giessen in 1824, made his chemical laboratory and course of instruction the model of all others.

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  • von Hofmann, who designed the laboratories and accepted the professorship in 1845 at the instigation of Prince Albert, and under his successor (in 1864) Sir Edward Frankland, this institution became one of the most important centres of chemical instruction.

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  • The growth of chemical literature since the publication of Lavoisier's famous Traite de chimie in 1789, and of Berzelius' Lehrbuch der Chemie in 1808-1818, has been enormous.

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  • In England the most important is the Journal of the Chemical Society of London, first published in 1848.

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  • The Chemical News, founded by Sir W.

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  • In America the chief periodical is the American Chemical Journal, founded in 1879.

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  • The Berichte der deutschen chemischen Gesellschaft, published by the Berlin Chemical Society, the Chemisches Centralblatt, which is confined to abstracts of papers appearing in other journals, the Zeitschrift fur Chemie, and Liebig's Annalen der Chemie are the most important of the general magazines.

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  • eilos, like), strictly belongs to certain elements which do not possess the properties of the true metals, although they more closely resemble them than the non-metals in many respects; thus, selenium and tellurium, which are closely allied to sulphur in their chemical properties, although bad conductors of heat and electricity, exhibit metallic lustre and have relatively high specific gravities.

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  • Com pounds .-A chemical compound contains two or more elements; consequently it should be possible to analyse it, i.e.

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  • The molecule of every compound must obviously contain at least two atoms, and generally the molecules of the elements are also polyatomic, the elements with monatomic molecules (at moderate temperatures) being mercury and the gases of the argon group. The laws of chemical combination are as follows: I.

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  • There is a fourth law of chemical combination which only applies to gases.

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  • Chemical Formulae.

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  • The distribution of weight in chemical change is readily expressed in the form of equations by the aid of these symbols; the equation 2HC1+Zn =ZnCl2+H2, for example, is to be read as meaning that from 73 parts of hydrochloric acid and 65 parts of zinc, 136 parts of zinc chloride and 2 parts of hydrogen are produced.

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  • Thus, the symbols 14 2 and P4 indicate that the molecules of hydrogen and phosphorus respectively contain 2 and 4 atoms. Since, according to the molecular theory, in all cases of chemical change the action is between molecules, such symbols as these ought always to be employed.

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  • Chemical Action.

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  • - Chemical change or chemical action may be said to take place whenever changes occur which involve an alteration in the composition of molecules, and may be the result of the action of agents such as heat, electricity or light, or of two or more elements or compounds upon each other.

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  • Changes of the first and second kind, according to our views of the constitution of molecules, are probably of very rare occurrence; in fact, chemical action appears almost always to involve the occurrence of both these kinds of change, for, as already pointed out, we must assume that the molecules of hydrogen, oxygen and several other elements are diatomic, or that they consist of two atoms. Indeed, it appears probable that with few exceptions the elements are all compounds of similar atoms united together by one or more units of affinity, according to their valencies.

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  • In all cases of chemical change energy in the form of heat is either developed or absorbed, and the amount of heat developed or absorbed in a given reaction is as definite as are the weights of the substance engaged in the reaction.

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  • Chemical change which merely involves simple decomposition is thus seen to be influenced by the masses of the reacting substances and the presence of the products of decomposition; in other words the system of reacting substances and resultants form a mixture in which chemical action has apparently ceased, or the system is in equilibrium.

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  • The earliest discoveries in inorganic chemistry are to be found in the metallurgy, medicine and chemical arts of the ancients.

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  • The phlogistic theory, which pervaded the chemical doctrine of this period, gave rise to continued study of the products of calcination and combustion; it thus happened that the knowledge of oxides and oxidation products was considerably developed.

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  • The chemical analogy of this substance to chlorine was quickly perceived, especially after its investigation by Davy and Gay Lussac. Cyanogen, a compound which in combination behaved very similarly to chlorine and iodine, was isolated in 1815 by Gay Lussac. This discovery of the first of the then-styled " compound radicals " exerted great influence on the prevailing views of chemical composition.

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  • Stromeyer detected a new metallic element, cadmium, in certain zinc ores; it was rediscovered at subsequent dates by other observers and its chemical resemblance to zinc noticed.

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  • C. Marignac, to whom is due the credit of first showing the true chemical relations of these elements.

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  • Of great importance is the chemical identity of the diamond, graphite and charcoal, a fact demonstrated in part by Lavoisier in 1773, Smithson Tennant in 1796, and by Sir George Steuart-Mackenzie (1780-1848), who showed that equal weights.

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  • BdXXo, a green bud, on account of a brilliant green line in its spectrum) in the selenious mud of the sulphuric acid manufacture; the chemical affinities of this element, on the one hand approximating to the metals of the alkalis, and on the other hand to lead, were mainly established by C. A.

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  • de Marignac, a noted worker in this field, delivered by Cleve, a high authority on this subject, before the London Chemical Society (J.

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  • It is true that by the distillation of many herbs, resins and similar substances, several organic compounds had been prepared, and in a few cases employed as medicines; but the prevailing classification of substances by physical and; superficial properties led to the correlation of organic and inorganic compounds, without any attention being paid to their chemical composition.

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  • The phlogistonists endeavoured to introduce chemical notions to support it: Becher, in his Physica subterranea (1669), stated that mineral, vegetable and animal matter contained the same elements, but that more simple combinations prevailed in the mineral kingdom; while Stahl, in his Specimen Becherianum (1702), held the " earthy " principle to predominate in the mineral class, and the " aqueous " and " combustible " in the vegetable and animal classes.

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  • But the belief died hard; the synthesis of urea remained isolated for many years; and many explanations were attempted by the vitalists (as, for instance, that urea was halfway between the inorganic and organic kingdoms, or that the carbon, from which it was obtained, retained the essentials of this hypothetical vital force), but only to succumb at a later date to the indubitable fact that the same laws of chemical combination prevail in both the animate and inanimate kingdoms, and that the artificial or laboratory synthesis of any substance, either inorganic or organic, is but a question of time, once its constitution is determined.'.

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  • In addition to the vitalistic doctrine of the origin of organic compounds, views based on purely chemical considerations were advanced.

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  • According to this theory a " chemical type " embraced compounds containing the same number of equivalents combined in a like manner and exhibiting similar properties; thus acetic and trichloracetic acids, aldehyde and chloral, marsh gas and chloroform are pairs of compounds referable to the same type.

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  • His unitary conceptions may be summarized: every chemical compound forms a complete whole, and cannot therefore consist of two parts; and its chemical character depends primarily upon the arrangement and number of the atoms, and, in a lesser degree, upon their chemical nature.

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  • The introduction of hydroxyl groups into the benzene nucleus gives rise to compounds generically named phenols, which, although resembling the aliphatic alcohols in their origin, differ from these substances in their increased chemical activity and acid nature.

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  • The development of the " structure theory " in about 1860 brought in its train an appreciation of the chemical structure of the derivatives of benzene.

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  • Analytical Chemistry This branch of chemistry has for its province the determination of the constituents of a chemical compound or of a mixture of compounds.

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  • The methods of chemical analysis may be classified according to the type of reaction: (I) dry or blowpipe analysis, which consists in an examination of the substance in the dry condition; this includes such tests as ignition in a tube, ignition on charcoal in the blowpipe flame, fusion with borax, microcosmic salt or fluxes, and flame colorations (in quantitative work the dry methods are sometimes termed " dry assaying "); (2) wet analysis, in which a solution of the substance is treated with reagents which produce specific reactions when certain elements or groups of elements are present.

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  • He realized that the composition by weight of chemical compounds was of the greatest moment if chemistry were to advance.

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  • Since then the subject has been extensively studied, more particularly by Alexander Classen, who has summarized the methods and results in his Quantitative Chemical Analysis by Electrolysis (1903).

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  • The ever-increasing importance of the electric current in metallurgy and chemical manufactures is making this method of great importance, and in some cases it has partially, if not wholly, superseded the older methods.

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  • Perkin, Qualitative Chemical Analysis, 1905).

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  • Comey, Dictionary of Chemical Solubilities).

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  • A physicist, however, does more than merely quantitatively determine specific properties of matter; he endeavours to establish mathematical laws which co-ordinate his observations, and in many cases the equations expressing such laws contain functions or terms which pertain solely to the chemical composition of matter.

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  • The limiting law expressing the behaviour of gases under varying temperature and pressure assumes the form pv= RT; so stated, this law is independent of chemical composition and may be regarded as a true physical law, just as much as the law of universal gravitation is a true law of physics.

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  • It may be surmised that the quantitative measures of most physical properties will be found to be connected with the chemical nature of substances.

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  • In the investigation of these relations, the physicist and chemist meet on common ground; this union has been attended by fruitful and far-reaching results, and the correlation of physical properties and chemical composition is one of the most important ramifications of physical chemistry.

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  • Another branch, related to energetics, is concerned with the transformation of chemical energy into other forms of energy - heat, light, electricity.

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  • Combustion is a familiar example of the transformation of chemical energy into heat and light; the quantitative measures of heat evolution or absorption (heat of combustion or combination), and the deductions therefrom, are treated in the article Thermochemistry.

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  • Photography is based on chemical action induced by luminous rays; apart from this practical application there are many other cases in which actinic rays occasion chemical actions; these are treated in the article Photochemistry.

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  • Transformations of electrical into chemical energy are witnessed in the processes of electrolysis (q.v.; see also Electrochemistry and Electrometallurgy).

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  • For the complete determination of the chemical structure of any compound, three sets of data are necessary: (I) the empirical chemical composition of the molecule; (2) the constitution, i.e.

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  • In any attempts to gain an insight into the relations between the physical properties and chemical composition of substances, the fact must never be ignored that a comparison can only be made when the particular property under consideration is determined under strictly comparable conditions, in other words, when the molecular states of the substances experimented upon are identical.

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  • He regarded these anomalies as solely due to the chemical nature of the elements, and ignored or regarded as insignificant such factors as the state of aggregation and change of specific heat with temperature.

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  • It is to be noted that although the correlation of melting-point with constitution has not been developed to such an extent as the chemical significance of other physical properties, the melting-point is the most valuable test of the purity of a substance, a circumstance due in considerable measure to the fact that impurities always tend to lower the melting-point.

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  • In the article Thermo Chemistry a general account of heats of formation of chemical compounds is given, and it is there shown that this constant measures the stability of the compound.

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  • it must remain constant for the same substance at any temperature and in any form) that quantitative relations between refractivity and chemical composition can be derived.

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  • He introduced the idea of comparing the refractivity of equimolecular quantities of different substances by multiplying the function (n-1)/d by the molecular weight (M) of the substance, and investigated the relations of chemical grouping to refractivity.

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  • Since molecular refractions are independent of temperature and of the state of aggregation, it follows that molecular dispersions must be also independent of these conditions; and hence quantitative measurements should give an indication as to the chemical composition of substances.

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  • A clear distinction must be drawn between colour and the property of dyeing; all coloured substances are not dyes, and it is shown in the article Dyeing that the property of entering into chemical or physical combination with fibres involves properties other than those essential to colour.

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  • Chemical Action and Energetics).

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  • The nitro group behaves very similarly to the hydroxyl group. The effect of varying the position of the nitro group in the molecule is well marked, and conclusions may be drawn as to the orientation of the groups from a knowledge of the crystal form; a change in the symmetry of the chemical molecule being often attended by a loss in the symmetry of the crystal.

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  • Isomorphism is most clearly discerned between elements of analogous chemical properties; and from the wide generality of such observations attempts have been made to form a classification of elements based on isomorphous replacements.

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  • For a detailed comparison of the isomorphous relations of the elements the reader is referred to P. von Groth, Chemical Crystallography.

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  • Reference may also be made to Ida Freund, The Study of Chemical Composition; and to the Annual Reports of the Chemical Society for 1908, p. 258.

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  • Pattison Muir, History of Chemical Theories and Laws (1907); Ida Freund, Study of Chemical Composition (1904); E.

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  • Julian, Textbook of Quantitative Chemical Analysis (1904); A.

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  • Crookes, Select Methods in Chemical Analysis (1894).

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  • In 1766 he was apprenticed to a storekeeper at Salem, in New England, and while in that employment occupied himself in chemical and mechanical experiments, as well as in engraving, in which he attained to some proficiency.

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  • BECQUEREL, the name of a French family, several members of which have been distinguished in chemical and physical research.

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  • The existence of sulphuretted hydrogen in great quantities below loo fathoms, the extensive chemical precipitation of calcium carbonate, the stagnant nature of its deep waters, and the absence of deep-sea life are conditions which make it impossible to discuss it along with the physical and biological conditions of the Mediterranean proper.

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  • A non-metallic chemical element, first isolated in 1772 by D.

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  • Ann., 1885, 24, Chemical Nitrogen.

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  • These methods have been purely chemical (either gravimetric or volumetric), physical (determinations of the density of nitrogen, nitric oxide, &c.) or physicochemical.

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  • Suidas says that the fleece was a book written on parchment, which taught how to make gold by chemical processes.

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  • In addition to these departments provided for in the organic act, the university included in 1909 colleges of dentistry (three-year course), pharmacy (two-year and three-year courses), a school of mines (1891; four-year course, leading to the degree of Engineer of Mines or Metallurgical Engineer), a school of analytical and applied chemistry (four-year courses, leading to the degree of Bachelor in Science in Chemistry, or in Chemical Engineering), a college of education (1906; three-year course, after two years of college work, leading to a Master's degree), a graduate school (with courses leading to the degrees of Master of Arts, of Science and of Laws, and of Doctor of Philosophy, of Science and of Civil Law), and a university summer school.

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  • albus, white), an organic substance typical of a group of bodies (albumins or albuminates) of very complicated chemical composition.

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  • A high molecular weight characterizes these substances, but so far no definite value has been determined by either physical or chemical means; A.

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  • The complexity of composition militates in a great measure against a rational classification of albumins by purely chemical considerations.

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  • Farther on are the chemical and the physical laboratories and the Hygienic Institute.

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  • Among other important articles of domestic industry are tobacco and cigars (manufactured mainly in bond, within the free harbour precincts), hydraulic machinery, electro-technical machinery, chemical products (including artificial manures), oils, soaps, india-rubber, ivory and celluloid articles and the manufacture of leather.

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  • Rhyolitic lavas frequently are more or less vitreous, and when the glassy matter greatly predominates and the; crystals are few and inconspicuous the rock becomes an obsidian; the chemical composition is essentially the same as that of granite; the difference in the physical condition of the two rocks is due to the fact that one consolidated at the surface, rapidly and under low pressures, while the other cooled slowly at great depths and under such pressures that the escape of the steam and other gases it contained was greatly impeded.

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  • Yet among the older rocks there are many which, though finely crystalline, have the chemical composition of modern obsidians and possess structures, such as the perlitic and spherulitic, which are very characteristic of vitreous rocks.

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  • Often this felsitic devitrified glass is so fine-grained that its constituents cannot be directly determined even with the aid of the microscope, but chemical analysis leaves little doubt as to the real nature cf the minerals which have been formed.

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  • Included in this group are some rocks which are more properly to be regarded as vitreous forms of trachyte than as glassy rhyolites (Iceland), but except by chemical analyses they cannot be separated.

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  • The typical obsidians exhibit the chemical peculiarities of the acid igneous rocks (viz.

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  • The chemical composition of typical obsidians is shown by the following analyses Obsidian, when broken, shows a conchoidal fracture, like that of glass, and yields sharp-edged fragments, which have been used in many localities as arrow-points, spear-heads, knives and razors.

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  • When the passage of an electric current through a substance is accompanied by definite chemical changes which are independent of the heating effects of the current, the process is known as electrolysis, and the substance is called an electrolyte.

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  • With other electrolytes similar phenomena appear, though the primary chemical changes may be masked by secondary actions.

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  • Immediately on its discovery intense interest was aroused in the new invention, and the chemical effects of electric currents were speedily detected.

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  • They also noticed that a similar kind of chemical action went on in the battery itself.

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  • The electromotive force of Volta's simple cell falls off rapidly when the cell is used, and this phenomenon was shown to be due to the accumulation at the metal plates of the products of chemical changes in the cell itself.

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  • Constant cells may be divided into two groups, according as their action is chemical (as in the bichromate cell, where the hydrogen is converted into water by an oxidizing agent placed in a porous pot round the carbon plate) or electrochemical (as in Daniell's cell, where a copper plate is surrounded by a solution of copper sulphate, and the hydrogen, instead of being liberated, replaces copper, which is deposited on the plate from the solution).

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  • Acting on this view, Faraday set himself to examine the relation between the flow of electricity round the circuit and the amount of chemical decomposition.

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  • He also found that, for the same current, the amount of chemical action was independent of the size of the electrodes and proportional to the time that the current flowed.

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  • of all these experiments may be summed up in the statement that the amount of chemical action is proportional to the quantity of electricity which passes through the cell.

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  • He found that the amounts of the substances liberated in each cell were proportional to the chemical equivalent weights of those substances.

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  • Now this ratio is the same as that which gives the relative chemical equivalents of hydrogen and copper, for r gramme of hydrogen and 31.8 grammes of copper unite chemically with the same weight of any acid radicle such as chlorine or the sulphuric group, SO 4.

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  • Similar relations were found to hold and the amounts of chemical change to be the same for the same electric transfer as in the case of solutions.

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  • We may sum up the chief results of Faraday's work in the statements known as Faraday's laws: The mass of substance liberated from an electrolyte by the passage of a current is proportional (I) to the total quantity of electricity which passes through the electrolyte, and (2) to the chemical equivalent weight of the substance liberated.

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  • The principal object of this more recent research has been the determination of the quantitative amount of chemical change associated with the passage for a given time of a current of strength known in electromagnetic units.

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  • Taking the chemical equivalent weight of silver, as determined by chemical experiments, to be 107.92, the result described gives as the electrochemical equivalent of an ion of unit chemical equivalent the value 1 036 X 5.

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  • The electrochemical equivalent of any other substance, whether element or compound, may be found by multiplying its chemical equivalent by I 036X Io-5.

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  • Here the ions are potassium and the group Ag(CN)2.1 Each potassium ion as it reaches the cathode precipitates silver by reacting with the solution in accordance with the chemical equation K--+KAg(CN) 2 =2KCN+Ag, while the anion Ag(CN) 2 dissolves an atom of silver from the anode, and re-forms the complex cyanide KAg(CN) 2 by combining with the 2KCN produced in the reaction described in the equation.

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  • The obvious phenomena to be explained by any theory of electrolysis are the liberation of the products of chemical decomposition at the two electrodes while the intervening liquid is unaltered.

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  • To explain these facts, Theodor Grotthus (1785-1822) in 1806 put forward an hypothesis which supposed that the opposite chemical constituents of an electrolyte interchanged partners all along the line between the electrodes when a current passed.

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  • Chemical phenomena throw further light on this question.

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  • If some of the anions, instead of being simple iodine ions represented chemically by the symbol I, are complex structures formed by the union of iodine with unaltered cadmium iodide - structures represented by some such chemical formula as I(CdI 2), the concentration of the solution round the anode would be increased by the passage of an electric current, and the phenomena observed would be explained.

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  • As we have seen, Grotthus imagined that it was the electric forces which sheared the ions past each other and loosened the chemical bonds holding the opposite parts of each dissolved molecule together.

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  • Clausius extended to electrolysis the chemical ideas which looked on the opposite parts of the molecule as always changing partners independently of any electric force, and regarded the function of the current as merely directive.

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  • An interesting relation appears when the electrolytic conductivity of solutions is compared with their chemical activity.

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  • Moreover, a study of the chemical relations of electrolytes indicates that it is always the electrolytic ions that are concerned in their reactions.

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  • The chemical activity of a substance is a quantity which may be measured by different methods.

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  • It must be remembered that, the so utions not being of quite the same strength, these numbers are not strictly comparable, and that the experimental difficulties involved in the chemical measurements are considerable.

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  • Nevertheless, the remarkable general agreement of the numbers in the four columns is quite enough to show the intimate connexion between chemical activity and electrical conductivity.

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  • We may take it, then, that only that portion of these bodies is chemically active which is electrolytically active - that ionization is necessary for such chemical activity as we are dealing with here, just as it is necessary for electrolytic conductivity.

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  • a V(I - a) This constant k gives a numerical value for the chemical affinity, and the equation should represent the effect of dilution on the molecular conductivity of binary electrolytes.

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  • This " replacement " of a " weak " acid by a " strong " one is a matter of common observation in the chemical laboratory.

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  • Similar investigations applied to the general case of chemical equilibrium lead to an expression of exactly the same form as that given by C. M.

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  • In order that the current should be maintained, and the electromotive force of the cell remain constant during action, it is necessary to ensure that the changes in the cell, chemical or other, which produce the current, should neither destroy the difference between the electrodes, nor coat either electrode with a non-conducting layer through which the current cannot pass.

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  • When the applied electromotive force is diminished by an infinitesimal amount, the cell produces a current in the usual direction, and the ordinary chemical changes occur.

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  • If the external electromotive force exceed that of the cell by ever so little, a current flows in the opposite direction, and all the former chemical changes are reversed, copper dissolving from the copper plate, while zinc is deposited on the zinc plate.

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  • If the chemical changes which occur in the cell were allowed to take place in a closed vessel without the performance of electrical or other work, the change in energy would be measured by the heat evolved.

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  • Thus, if L denote the heat corresponding with the chemical changes associated with unit electric transfer, Le will be the heat corresponding with an electric transfer e, and will also be equal to the change in internal energy of the cell.

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  • It is now evident that the electromotive force of an ordinary chemical cell such as that of Daniell depends on the concentration of the solutions as well as on the nature of the metals.

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  • Dolezalek, however, has attributed the difference to mechanical hindrances, which prevent the equalization of acid concentration in the neighbourhood of the electrodes, rather than to any essentially irreversible chemical action.

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  • If we connect together in series a single Daniell's cell, a galvanometer, and two platinum electrodes dipping into acidulated water, no visible chemical decomposition ensues.

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  • This current is accompanied by chemical decomposition.

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  • Only when the applied electromotive force exceeds this reverse force of polarization, will a permanent steady current pass through the liquid, and visible chemical decomposition proceed.

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  • It seems that this reverse electromotive force of polarization is due to the deposit on the electrodes of minute quantities of the products of chemical decomposition.

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  • In metals the electrons can slip from one atom to the next, since a current can pass without chemical action.

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  • When a current passes from an electrolyte to a metal, the electron must be detached from the atom it was accompanying and chemical action be manifested at the electrode.

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  • In these periodicals will be found new work on the subject and abstracts of papers which appear in other physical and chemical publications.

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  • The name is applied in commerce to a complex mixture of carbohydrates obtained by boiling starch with dilute mineral acids; in chemistry, it denotes, with the prefixes d, 1 and d+l (or i), the dextro-rotatory, laevo-rotatory and inactive forms of the definite chemical compound defined above.

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  • In its chemical properties glucose is a typical oxyaldehyde or aldose.

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  • The globules which furnish the cream gradually pass on standing into solid caoutchouc, a process which is facilitated by rapid stirring, or by the addition of an acid or other chemical agent.

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  • The effect of chemical agents in producing coagulation are in consonance with what is known of other instances of polymeric or condensation changes, whilst the fact that the collection of globules separated by creaming after thorough washing, and therefore removal of all proteid, is susceptible of solidification into caoutchouc by a merely mechanical act such as churning, strongly supports the view that the character of the change is distinct from that of any alteration which may occur in the proteid constituents of the latex.

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  • Under certain conditions, as when latex is allowed to stand or is centrifugalized, a cream is obtained consisting of the liquid globules, which may be washed free from proteid without change, but, either by mechanical agitation or by the addition of acid or other chemical agent, the liquid gradually solidifies to a mass of solid caoutchouc. The phenomenon therefore resembles the change known to the chemist as polymerization, by which through molecular aggregation a liquid may pass into a solid without change in its empirical composition.

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    0
  • The effect may, however, also be due to chemical change known as condensation, and be accompanied by the elimination of the elements of water.

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    0
  • So far the chemical nature of the liquid globules of the latex is unknown, and the exact character of the change into solid caoutchouc remains to be determined.

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    0
  • The chemical analysis of crude rubber is an important guide to its value.

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    0
  • The development of the rubber industry has now reached a stage at which more exact methods of determining the chemical composition and physical properties (strength and elasticity) of rubber are required.

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  • At present the caoutchouc present in crude rubber is usually estimated indirectly, and it is possible that what generally passes as caoutchouc may be in some instances a mixture of similar chemical substances, which if separated would be found to differ in those physical properties on which the technical value of rubber depends.

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  • When this volatile liquid hydrocarbon (isoprene) is allowed ro stand for some time in a closed bottle, it gradually passes into a substance having the principal properties of natural caoutchouc. The same change of isoprene into caoutchouc may also be effected by the action of certain chemical agents.

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    0
  • The exact chemical nature of caoutchouc is, however, not determined, and recent researches point to the view that its molecular structure may even be somewhat different from that of the terpenes.

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    0
  • There are many substances produced by plants which can be synthetically prepared by chemical means, but, as with quinine, the process involved is too costly to enable the synthetic product to compete with the natural product.

    0
    0
  • Similar products are also formed by heating gutta-percha which closely resembles caoutchouc in its chemical structure.

    0
    0
  • The study of the action of ozone on caoutchouc has thrown new light on the complex question of the chemical structure of this substance, and discloses relationships with the sugars and other carbohydrates from certain of which levulinic acid is obtained by oxidation.

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  • Ebonite takes a fine polish, and is valuable to the electrician on account of its insulating properties, and to the chemist and photographer because vessels made of it are unaffected by most chemical reagents.

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  • Three years later he was appointed an assistant in the meteorological department of the Radcliffe observatory, Oxford, and in 1855 he obtained a chemical post at Chester.

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  • In addition to many other researches besides those here mentioned, he wrote or edited various books on chemistry and chemical technology, including Select Methods of Chemical Analysis, which went through a number of editions; and he also gave a certain amount of time to the investigation of psychic phenomena, endeavouring to effect some measure of correlation between them and ordinary physical laws.

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  • He was knighted in 1897, and received the Royal (1875), Davy (1888), and Copley (1904) medals of the Royal Society, besides filling the offices of president of the Chemical Society and of the Institution of Electrical Engineers.

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  • In 1802, on the eve of Lord Lake's Mahratta war, his chemical knowledge enabled him to render a signal service to the administration by making available a large quantity of gunpowder which damp had spoiled.

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  • From 1827 to 1833 he was occupied mainly with chemical researches, which resulted in the discovery of the first of the platino-ammonium compounds ("Magnus's green salt" is Pt11 2j 2NH 3), of sulphovinic, ethionic and isethionic acids and their salts, and, in conjunction with C. F.

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  • It possesses worsted and cotton mills, iron works, dye works and chemical works.

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  • In making up a charge, the ores and fluxes, whose chemical compositions have been determined, are mixed so as to form out of the components, not to be reduced to the metallic or sulphide state, typical slags (silicates of ferrous and calcium oxides, incidentally of aluminium oxide, which have been found to do successful work).

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  • Miscellaneous Effects of Magnetization: Electric Conductivity - Hall Effect - Electro-Thermal Relations - Thermoelectric Quality - Elasticity - Chemical and Voltaic Effects.

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  • The results, together with the chemical analysis of each sample, are given in a table contained in this paper, some of them being also represented graphically.

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    0
  • The entosternites are cartilaginous in texture, but they have neither the chemical character nor the microscopic structure of the hyaline cartilage of Vertebrates.

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    0
  • Besides wool, leading imports are jute, cotton, flax, timber, petroleum, coal, pitch, wine, cereals, oil-seeds and oil-cake, nitrate of soda and other chemical products, and metals.

    0
    0
  • ALDEHYDES, a class of chemical compounds of the general formula R�CHO (R=an alkyl or an aryl group).

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    0
  • The aldehydes are characterized by their great chemical reactivity.

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    0
  • Most of Wollaston's original work' deals more or less directly with chemical subjects, but diverges on all sides into optics, acoustics, mineralogy, astronomy, physiology, botany and even art.

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  • Among his other papers may be mentioned those dealing with the formation of fairy rings (1807), a synoptic scale of chemical equivalents (1814), sounds inaudible to ordinary ears (1820), the physiology of vision (1824), the apparent direction of the eyes in a portrait (1824) and the comparison of the light of the sun with that of the moon and fixed stars (1829).

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  • megvizsgdlasa (Chemical Examination of the most famous Tobaccos of Hungary), by Dr Thomas Kosutany (1877).

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  • It was a favourite idea of his that chemical affinity and capillary attraction would eventually be included under the same law, and it was perhaps because of its recalcitrance to this cherished generalization that the undulatory theory of light was distasteful to him.

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  • Its manufactures include cardboard, glue, oils, colours, fertilizers, chemical products, perfumery, &c. During the middle ages and till modern times Aubervilliers was the resort of numerous pilgrims, who came to pay honour to Notre Dame des Vertus.

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  • Teleology had, indeed, an important part in the development of physiology - the knowledge of the mechanism, the physical and chemical properties, of the parts of the body of man and the higher animals allied to him.

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  • It abolished the conception of life s an entity above and beyond the common properties of matter, and led to the conviction that the marvellous and exceptional qualities of that which we call " living " matter are nothing more nor less than an exceptionally complicated development of those chemical and physical properties which we recognize in a gradually ascending scale of evolution in the carbon compounds, containing nitrogen as well as oxygen, sulphur and hydrogen as constituent atoms of their enormous molecules.

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  • We do not yet know whether such absolute blending is possible or not, or whether all apparent blending is only a more or less minutely subdivided " mosaic " of non-combinable characters of the parents, in fact whether the combinations due to heredity in reproduction are ever analogous to chemical compounds or are always comparable to particulate mixtures.

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  • The earliest is that of Quincke, who coated a glass grating with a chemical silver deposit, subsequently thickened with copper in an electrolytic bath.

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  • The town contains large iron foundries and chemical works, and has an active trade in fruit, cider, timber and live stock.

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    0
  • Besides the rock-salt, which is excavated by blasting, the saline deposits of Stassfurt yield a considerable quantity of deliquescent salts and other saline products, which have encouraged the foundation of numerous chemical factories in the town and in the neighbouring village of Leopoldshall, which lies in Anhalt territory.

    0
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  • The rock-salt works are mainly government property, while the chemical factories are in private hands.

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    0
  • URANIUM [[[symbol]] U, atomic weight 238.5 (0=16)], a metallic chemical element.

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    0
  • Cleve, printed in the Journal of the London Chemical Society for 1895, contains a list of Marignac's papers.

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  • Considered apart from the phenomena of consciousness, the phenomena of life are all dependent upon the working of the same physical and chemical forces as those which are active in the rest of the world.

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    0
  • stannum, whence the chemical symbol "Sn"; atomic weight =117.6, 0= 16), a metallic chemical element.

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  • The Bolivian tin ore is treated by first extracting the silver by amalgamation, &c., and afterwards concentrating the residues; there are, however, considerable difficulties in the way of treating the poorer of these very complex ores, and several chemical processes for extracting their metallic contents have been worked out.

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  • This colouring power is due to the presence of polychlorite, a substance whose chemical formula appears to be C4 8 1-160018, and which may be obtained by treating saffron with ether, and afterwards exhausting with water.

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    0
  • The chemical composition and constitution of guncotton has been studied by a considerable number of chemists and many divergent views have been put forward on the subject.

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    0
  • The publication of Ehrlich's chemical, or rather physical, theory of immunity has thrown much light upon this very intricate and obscure subject.

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  • 1 Thus they are pro vided with a nucleus which is the centre of cell activity; Pathological both of the reproductive and chemical (metabolic) pro- GelIs.

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  • Leber experimented with several chemical compounds to find what reaction they had on these cells; by using fine glass tubes sealed at the outer end and containing a chemical substance, and by introducing the open end into the blood vessels he found that the leucocytes were attracted - positive chemiotaxis - by the various compounds of mercury, copper, turpentin, and other substances.

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  • The irritant may be chemical, as is seen in the skin cancers that develop in workers in paraffin, petroleum, arsenic and aniline.

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  • However close the relationship is between chronic irritation and the starting of cancer, we are not in a position to say that irritation, physical or chemical, by itself can give rise to new growths.

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    0
  • There is neither any absolute difference nor a constancy in their chemical reactions, and there can be brought about a transition of the " colloid " material into the " mucoid," or conversely.

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    0
  • The chemical constitution is not certain.

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  • The substance is very resistant to the action of chemical reagents, to digestion, and possibly belongs to the glyco-proteids.

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    0
  • Stimuli comprise chemical, mechanical, thermal, photic and electrical changes in the environment of the organism.

    0
    0
  • The influence of the chemical substance is either that of attraction or repulsion, the one being known as positive, the other as negative chemiotaxis.

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    0
  • The female organs of certain cryptogams, for instance, exert a positive chemiotactic action upon the spermatozoids, and probably, as Pfeffer suggests, the chemical agent which exerts the influence is malic acid.

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  • Thus Ludwig was of opinion that the lymph-flow is dependent upon two factors, first, difference in pressure of the blood in the capillaries and the liquid in the plasma spaces outside; and, secondly, chemical interchanges setting up osmotic currents through the vessel-walls.

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  • There are boot and shoe factories, chemical works and a manufactory of fustians, with salt-works and iron-works in the adjacent township of Wheelock.

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    0
  • By their relations with the farther East, the Arabs became acquainted with valuable new remedies which have held their ground till modern times; and their skill in chemistry enabled them to prepare new chemical remedies, and form many combinations of those already in use.

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  • Others, of more learning and better repute, were distinguished from the regular physicians chiefly by their use of chemical remedies.

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  • In England "chemical medicine" is first heard of in the reign of Elizabeth, and was in like manner contemned and assailed by the College of Physicians and the Society of Apothecaries.

    0
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  • The practice and theory of medicine were mainly founded upon Hippocrates and Galen, with everincreasing additions from the chemical school.

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  • This, like the earlier German works of the same kind (on which it was partly founded), contains both the traditional (Galenical) and the modern or chemical remedies.

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  • It is enough to say that on this fantastic basis Helmont constructed a medical system which had some practical merits, that his therapeutical methods were mild and in many respects happy, and that he did service by applying newer chemical methods to the preparation of drugs.

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  • The principle which mainly distinguished it was not merely the use of chemical medicines in addition to the traditional, or, as they were called in distinction, "Galenical" remedies, but a theory of pathology or causation of disease entirely different from the prevailing "humoral" pathology.

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  • Chemical disturbances of these processes, called acridities, &c., were the cause of fevers and other diseases.

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  • The remedies he employed were partly galenical, partly chemical.

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  • In England they were not generally accepted till adopted with some modifications by Thomas Willis the great anatomist (1621-1675), who is the chief English representative of the chemical school.

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  • The chemical school met with violent opposition, partly from the adherents of the ancient medicine, partly from the iatro-mechanical school.

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  • Still less was his mind warped by either of the two great systems, the classical and the chemical, which then divided the medical world.

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  • This phase is most clearly developed in Archibald Pitcairne (1652-1713), who, though a determined opponent of metaphysical explanations, and of the chemical doctrines, gave to his own rude mechanical explanations of life and disease almost the dogmatic completeness of a theological system.

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  • By chemical warnings the defensive processes seem to be awakened, or summoned; and when we think of the infinite variety of such possible phases, and of the multitude of corresponding defensive agents, we may form some dim notion of the complexity of the animal blood and tissues, and within them of the organic molecules.

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  • Thus the reciprocity of the various organs, maintained throughout the divisions of physiological labour, is not merely a mechanical stability; it is also a mutual equilibration in functions incessantly at work on chemical levels, and on those levels of still higher complexity which seem to rise as far beyond chemistry as chemistry beyond physics.

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  • and museum of morbid anatomy, and was fusing these gains in the laboratory so as to claim for itself, as a special branch of science by virtue of peculiar concepts, its due place and provision - provision in the establishment of chairs and of special laboratories for its chemical and biological subdivisions - clinical medicine, by the formal provision of disciplinary classes, was illustrating the truth of the experience that teaching and research must go hand-in-hand, the one reinforcing the other: that no teacher can be efficient unless he be engaged in research also; nay, that for the most part even the investigator needs the encouragement of disciples.

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  • hope dealing elements of disease, with its first beginnings; and in the field of therapeutics, chemical and biological experiment, as in the case of digitalis, mercury and the iodides, was rapidly simplifying remedies and defining their virtues, so that these agents could be used at the bedside with more precision.

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  • Chemical, physiological and pathological research is exploring the secret of these more refined kinds of "anchorage" of molecules.

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  • In the mutual behaviour of such cells, toxins, and antitoxins, and again of microbes themselves, we may demonstrate even on the field of the microscope some of the modes of such actions, which seem to partake in great measure at any rate of a chemical quality (agglutinins, coagulins, chemotaxis).

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  • Thus the defects, whether of this secretion or of that, and again of motor activity, the state of the valvular junctions, the volume of the cavities, and their position in the abdomen, may be ascertained, and dealt with as far as may be; so that, although the fluctuations of chemical digestion are still very obscure, the application of remedies after a mere traditional routine is no longer excusable.

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  • Crafts, printed in the Journal of the London Chemical Society for 1900.

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  • Burlington House, in Piccadilly, built in 1872 on the site of a mansion of the earls of Burlington, houses the Royal Society, the Chemical, Geological, Linnaean and Royal Astronomical Societies, the Society of Antiquaries and the British Association for the Advancement of Science, of which the annual meetings take place at different British or colonial towns in succession.

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  • There are, however, several large breweries, among which that of Messrs Barclay & Perkins, on the riverside in Southwark, may be mentioned; engineering works are numerous in East London by the river, where there are also shipbuilding yards; the leather industry centres in Bermondsey, the extensive pottery works of Messrs Doulton are in Lambeth, there are chemical works on the Lea, and paper-mills on the Wandle.

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  • Kolbe had an important share in the great development of chemical theory that occurred about the middle of the 19th century, especially in regard to the constitution of organic compounds, which he viewed as derivatives of inorganic ones, formed from the latter - in some cases directly - by simple processes of substitution.

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  • There is a gold mine at Kyaukpazat in the Mawnaing circle of the Kathra district, where the quartz is crushed by machinery and treated by chemical processes.

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  • are many varieties of glass differing widely in chemical composition and in physical qualities.

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  • It is convenient to treat these glasses as " normal " glasses, but they are in reality mixtures of silicates, and cannot rightly be regarded as definite chemical compounds or represented by definite chemical formulae.

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    0
  • In the same way glass can be rendered more or less fusible, and its stability can be increased both in relation to extremes of temperature and to the chemical action of solvents.

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  • For this reason chemical agents are added to glass mixtures to remove or neutralize accidental colour.

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    0
  • Fraunhofer further initiated the specification of refraction and dispersion in terms of certain lines of the spectrum, and even attempted an investigation of the effect of chemical composition on the relative dispersion produced by glasses in different parts of the spectrum.

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  • Their object was to pursue the inquiry begun by Fraunhofer as to the effect of chemical composition on the distribution of dispersion.

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  • Aided by grants from the Prussian government, these workers systematically investigated the effect of introducing a large number of different chemical substances (oxides) into vitreous fluxes.

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  • A certain number of the most promising of these, from the purely optical point of view, had unfortunately to be abandoned for practical use owing to their chemical instability, and the problem of Fraunhofer, viz.

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    0
  • Further, these glasses, when made from properly proportioned materials, possess a very considerable degree of chemical stability, which is amply sufficient for most optical purposes.

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  • The newer glasses, on the other hand, contain a much wider variety of chemical constituents, the most important being the oxides of barium, magnesium, aluminium and zinc, used either with or without the addition of the bases already named in reference to the older glasses, and - among acid bodies - boric anhydride (B20 3) which replaces the silica of the older glasses to a varying extent.

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  • It must be admitted that, by the aid of certain of these new constituents, glasses can be produced which, as regards purity of colour, freedom from defects and chemical stability are equal or even superior to the best of the " ordinary " glasses, but it is a remarkable fact that when this is the case the optical properties of the new glass do not fall very widely outside the limits set by the older glasses.

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  • It is, in fact, admitted that some of the glasses, most useful optically, the dense barium crown glasses, which are so widely used in modern photographic lenses, cannot be produced entirely free either from noticeable colour or from numerous small bubbles, while the chemical nature of these glasses is so sensitive that considerable care is required to protect the surfaces of lenses made from them if serious tarnishing is to be avoided.

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  • The chemical stability, i.e.

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  • A high silica-content tends towards both hardness and chemical stability, and this can be further increased by the addition of small proportions of boric acid; in larger quantities, however, the latter constituent produces the opposite effect.

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  • The raw materials are selected with great care to assure chemical purity, but whereas in most glasses the only impurities to be dreaded are those that are either infusible or produce a colouring effect upon the glass, for optical purposes the admixture of other glass-forming bodies than those which are intended to be present must be avoided on account of their effect in modifying the optical constants of the glass.

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  • On the other hand, the chemical and physical nature of the fireclays used in the manufacture of such crucibles requires careful attention in order to secure the best results.

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    0
  • In the next stage of the process, the glass is raised to a high temperature in order to render it sufficiently fluid to allow of the complete elimination of these bubbles; the actual temperature required varies with the chemical composition of the glass, a bright red heat sufficing for the most fusible glasses, while with others the utmost capacity of the best furnaces is required to attain the necessary temperature.

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  • The surface of vessels may be spangled with gold or platinum by rolling the hot glass on metallic leaf, or iridescent, by the deposition of metallic tin, or by the corrosion caused by the chemical action of acid fumes.

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    0
  • In the " etching " process the surface of the glass is etched by the chemical action of hydrofluoric acid, the parts which are not to be attacked being covered with a resinous paint.

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    0
  • It has been proved that these variations depend to a great extent on the chemical nature of the glass of which the thermometer is made.

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    0
  • Among the many developments of the Jena Works, not the least important are the glasses made in the form of a tube, from which gas-chimneys, gauge-glasses and chemical apparatus are fashioned, specially adapted to resist sudden changes of temperature.

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    0
  • The essential qualities of a bottle are strength and power to resist chemical corrosion.

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  • SILICON [[[symbol]] Si, atomic weight 28.3 (0=16)], a nonmetallic chemical element.

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    0
  • This definition, however, is highly artificial and objectionable on principle, because when we speak of metals we think, not of their chemical relations, but of a certain sum of mechanical and physical properties which unites them all into one natural family.

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    0
  • The compounds formed in the first case, which may be either definite chemical compounds or solid solutions, are discussed under Alloys; in this place only combinations with non-metals are discussed, it being premised that the free metal takes part in the reaction.

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  • Action of the More Ordinary Chemical Agents on Simple Metals.

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    0
  • In chemical laboratories fusions with caustic alkalis are always effected in vessels made of gold or silver, these metals holding out fairly well even in the presence of air.

    0
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  • Yet tons of caustic soda are fused daily in chemical works in iron pots without thereby suffering contamination, which seems to show that (clean) iron, like gold and silver, is attacked only by the joint action of fused alkali and air, the influence of the latter being of course minimized in large-scale operations.

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  • For the characters of metals as chemical elements see the special articles on the different metals.

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    0
  • Large glass-bottle and earthenware-jar works, chemical works, and neighbouring collieries employ the inhabitants.

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  • A summary of its chemical transformations may be given here, and reference should be made to the articles on the separate compounds for further details.

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  • He next went to Paris, where he studied chemistry under Gerhardt, and on his return to London he was appointed director of the chemical laboratory at Guy's Hospital.

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  • He was successively fellow, secretary and president of the Chemical Society and was elected F.R.S.

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  • There are also iron, zinc and chemical manufactures, and the cultivation of agricultural seeds is carried on.

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    0
  • He held the doctrine that the chemical elements are compounds of equal and similar atoms, and might therefore possibly be all derived from one generic atom.

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  • Besides its copper works the town at present possesses extensive tinplate, steel and galvanized sheet works as well as iron and brass foundries, steam-engine factories, brick and tile works, engineering works, flannel factories and chemical works.

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  • sugar of lead, but it is now restricted to certain oxyaldehydes and oxy-ketones, which occur in the vegetable and animal kingdoms either free or in combination as glucosides (q.v.) and to artificial preparations of similar chemical structure.

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    0
  • Our knowledge of the chemical structure of the monosaccharoses may be regarded as dating from 1880, when Zincke suspected some to be ketone alcohols, for it was known that glucose and fructose, for example, yielded penta-acetates, and on reduction gave hexahydric alcohols, which, when reduced by hydriodic acid, gave normal and secondary hexyliodide.

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  • The moment the juice is expelled from the cells of the canes chemical inversion commences, and the sooner it is stopped the better.

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  • This, apart from the effect of the abolition of the sugar bounties, has been mainly the result of the increased employment of improved processes, carried on in improved apparatus, under skilled supervision, and with due regard to the importance of the chemical aspects of the work.

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    0
  • The oxygen of the air may also bring about chemical changes which result in the production of soluble substances removable by rain, the insoluble parts being left in a loosened state.

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    0
  • The peculiar character which clay possesses is probably due not to its chemical composition but to its physical state.

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    0
  • It has been found by experiment that plants need for their nutritive process and their growth, certain chemical elements, namely, carbon, hydrogen, oxygen, nitrogen, sulphur, phosphorus, potassium, magnesium, calcium and iron.

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    0
  • In the ordinary chemical analyses of the soil determinations are made of the nitrogen and various carbonates present as well as of the amount of phosphoric acid, potash, soda, magnesia and other components soluble in strong hydrochloric acid.

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    0
  • Too much stress, however, cannot be laid upon these figures, since the fertility of a soil is very greatly influenced by texture and physical constitution, perhaps more so by these factors than by chemical composition.

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  • Whereas the soil used to be looked upon solely as a dead, inert material containing certain chemical substances which serve as food constituents.

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  • They are responsible for many important chemical processes which make the soil constituents more available and better adapted to the nutrition of crops.

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    0
  • After this treatment the upper 2 or 3 in, of soil are well pulverized, and fertilizers added, usually, to prevent reintroduction of seeds of weeds, in the form of guano or chemical manures.

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  • Fermentation is essentially a chemical process due apparently to the presence of enzymes, developed in the leaf during the earlier curing stages.

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    0
  • To the chemical changes, mainly oxidation, which go on in this juice while it is exposed to the air, the characteristic aroma and flavour of Perique tobacco are mainly due.

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  • ZINC, a metallic chemical element; its symbol is Zn, and atomic weight 65.37 (0= 16).

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  • Chemical control of the metal purchased is not nearly as common as it should be, and the refining of zinc is at best an imperfect operation.

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  • Borchers, trace it to the presence of oxide, produced, for example, either by the use of a solution containing a trace of basic salt of zinc (to prevent which the bath should be kept just - almost imperceptibly - acid), or by the presence of a more electro-negative metal, which, being co-deposited, sets up local action at the expense of the zinc. Many processes have been patented, the ore being acted upon by acid, and the resulting solution treated, by either chemical or electrolytic means, for the successive removal of the other heavy metals.

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  • Having determined to make chemistry his profession, at the age of fifteen he entered the shop of an apothecary at Appenheim, near Darmstadt; -but he soon found how great is the difference between practical pharmacy and scientific chemistry, and the explosions and other incidents that accompanied his private efforts to increase his chemical knowledge disposed his master to view without regret his departure at the end of ten months.

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  • No laboratories were accessible to ordinary students, who had to content themselves with what the universities could give in the lectureroom and the library, and though both at Bonn and Erlangen Liebig endeavoured to make up for the deficiencies of the official instruction by founding a students' physical and chemical society for the discussion of new discoveries and speculations, he felt that he could never become a chemist in his own country.

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  • This laboratory, unique of its kind at the time, in conjunction with Liebig's unrivalled gifts as a teacher, soon rendered Giessen the most famous chemical school in the world; men flocked from every country to enjoy its advantages, and many of the most accomplished chemists of the 19th century had to thank it for their early training.

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  • Apart from Liebig's labours for the improvement of chemical teaching, the influence of his experimental researches and of his contributions to chemical thought was felt in every branch of the science.

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  • In regard to methods and apparatus, mention should be made of his improvements in the technique of organic analysis, his plan for determining the natural alkaloids and for ascertaining the molecular weights of organic bases b y means of their chloroplatinates, his process for determining the quantity of urea in a solution - the first step towards the introduction of precise chemical methods into practical medicine - and his invention of the simple form of condenser known in every laboratory.

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  • In animal physiology he set himself to trace out the operation of determinate chemical and physical laws in the maintenance of life and health.

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  • Vegetable physiology he pursued with special reference to agriculture, which he held to be the foundation of all trade and industry, but which could not be rationally practised without the guidance of chemical principles.

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  • Rejecting the old notion that plants derive their nourishment from humus, he taught that they get carbon and nitrogen from the carbon dioxide and ammonia present in the atmosphere, these compounds being returned by them to the atmosphere by the processes of putrefaction and fermentation - which latter he regarded as essentially chemical in nature - while their potash, soda, lime, sulphur, phosphorus, &c., come from the soil.

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  • von Hofmann, which is the Faraday lecture delivered before the London Chemical Society in March 1875, and is reprinted in Hofmann's Zur Erinnerung an vorangegangene Freunde; also W.

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  • The present article, as explained under Electrochemistry, treats only of those processes in which electricity is applied to the production of chemical reactions or molecular changes at furnace temperatures.

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  • In these processes the electric current is used solely to generate heat, either to induce chemical reactions between admixed substances, or to produce a physical (allotropic) modification of a given substance.

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  • From 1796 to 1800 he was sub-editor of the Encyclopaedia Britannica, in succession to his elder brother, JAMES THOMSON (1768-1855), who filled that position in 1795-1796, and who in 1805 was ordained to the parish of Eccles, Berwickshire; and the chemical and mineralogical articles which he contributed to the supplement to the third edition formed the basis of his System of Chemistry, the first edition of which was published in 1802 and the seventh in 1831.

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  • (0 = 16)], a metallic chemical element.

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  • In its chemical relations, titanium is generally tetravalent, and occurs in the same sub-group of the periodic classification as zirconium, cerium and thorium.

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  • The subject is here treated under the following subdivisions: (I) ordinary distillation, (2) distillation under reduced pressure, (3) fractional distillation, (4) distillation with steam, (5) theory of distillation, (6) dry distillation, (7) distillation in chemical technology and (8) commercial distillation of water.

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  • Distillation in Chemical Technology.

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  • STRONTIUM [[[Symbol]] Sr, atomic weight 87.62 (0 = 16)], a metallic chemical element belonging to the alkaline earth group. It is found in small quantities very widely distributed in various rocks and soils, and in mineral waters; its chief sources are the minerals strontianite, celestine and barytocelestine.

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  • Corn and saw mills, distilleries, chemical factories, breweries, candle-works, ink-works, foundries, agricultural machine and automobile works, have been established and are flourishing.

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  • Kopp devoted himself especially to physico-chemical inquiries, and in the history of chemical theory his name is associated with several of the most important correlations of the physical properties of substances with their chemical constitution.

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  • The action of lithontriptic medicines,, especially lime-water, was one of the questions of the day, and through his investigations of this subject Black was led to the chemical discoveries associated with his name.

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  • &KTis, ray, p rpov, measure), an instrument for measuring the heating and chemical effects of light.

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  • The word actinometer is now usually applied to instruments for measuring the actinic or chemical effect of luminous rays; their action generally depends upon photochemical changes.

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  • The other volumes dealt with (a) iron and steel, (b) copper and brass, their smelting, conversion and assaying, and chemical experiments thereon.

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  • The convenience also with which the energy of waterfalls can be converted into electric energy has led to the introduction of chemical industries into countries and districts where, owing to the absence of coal, they were previously unknown.

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  • The current, by endosmosis, favours the passage of the solution into the hide-substance, and at the same time appears to assist the chemical combinations there occurring; hence a great reduction in the time required for the completion of the process.

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  • p. 375) applied in Russia to the manufacture of alcohol, by a series of chemical reactions starting from the production of acetylene by the action of water upon calcium carbide.

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  • Among the most representative are: the Popular Science Monthly, New York; the monthly Boston Journal of Education; the quarterly American Journal of Mathematics, Baltimore; the monthly Cassier's Magazine (1891), New York; the monthly American Engineer (1893), New York; the monthly House and Garden, Philadelphia; the monthly Astrophysical Journal, commenced as Sidereal Messenger (1882), Chicago; the monthly American Chemical Journal, Baltimore; the monthly American Naturalist, Boston; the monthly American Journal of the Medical Sciences, Philadelphia; the monthly Outing, New York; the weekly American Agriculturist, New York; the quarterly Metaphysical Magazine (1895) New York; the bi-monthly American Journal of Sociology, Chicago; the bi-monthly American Law Review, St Louis; the monthly Banker's Magazine, New York; the quarterly American Journal of Philology (1880), Baltimore; the monthly Library Journal (1876), New York; the monthly Public Libraries, Chicago; Harper's.

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  • An ample supply of natural gas is utilized by its manufacturing establishments; and among its manufactures are axes, lumber, foundry and machine shop products, furniture, boilers, woollen goods, glass and chemical fire-engines.

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  • Reference should be made to the articles Chemical Action, Thermochemistry and Solutions, for the theory of the strength or avidity of acids.

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  • Digestion is quick and much accelerated by the quantity of saliva which is secreted during the progress of deglutition, and in venomous snakes probably also by the chemical action of the poison.

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  • The animal and the plant alike require food to repair waste, to build up new tissue and to provide material which, by chemical change, may liberate the energy which appears in the processes of life.

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  • It may conveniently be extended to similar mixtures of sulphur and selenium or tellurium, of bismuth and sulphur, of copper and cuprous oxide, and of iron and carbon, in fact to all cases in which substances can be made to mix in varying proportions without very marked indication of chemical action.

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  • The term "alloy" does not necessarily imply obedience to the laws of definite and multiple proportion or even uniformity throughout the material; but some alloys are homogeneous and some are chemical compounds.

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  • But it is not permissible to call brass a chemical compound, for we can largely alter its percentage composition without the substance losing the properties characteristic of brass; the properties change more or less continuously, the colour, for example, becoming redder with decrease in the percentage of zinc, and a paler yellow when there is more zinc. The possibility of continuously varying the percentage composition suggests analogy between an alloy and a solution, and A.

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  • These halts in temperature that occur during the cooling of a mixture should be carefully noted, as they give valuable information concerning the physical and chemical changes that are taking place.

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  • These uniform solid solutions must not be mistaken for chemical compounds; they can, within limits, vary in composition like an ordinary liquid solution.

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  • But the occasional or indeed frequent existence of chemical compounds in alloys has now been placed beyond doubt.

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  • The freezingpoint curve sometimes indicates the existence of chemical compounds.

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  • certainly give no indication of chemical combination.

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  • But the subject is now being vigorously studied, and, apart from its importance as a branch of descriptive chemistry, it is throwing light, and promises to throw more, on obscure parts of chemical theory.

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  • The graphical representation of the properties of alloys can be extended so as to record all the changes, thermal and chemical, which the alloy undergoes after, as well as before, solidification, including the formation and breaking up of solid solutions and compounds.

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  • If the alloy were a true chemical compound the counteracting electromotive force should not occur; experiments in this direction are much needed.

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  • Notwithstanding this permission there have been many agitations on the part of chemical manufacturers to obtain a less restricted use of absolute alcohol, and in 1905 an Industrial Alcohol Committee was appointed to receive evidence and report as to whether any modification of the present law was advisable.

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  • Dielectric constant.-Since all electric charge consists in a state of strain or polarization of the dielectric, it is evident that the physical state and chemical composition of the insulator must be of great importance in determining electrical phenomena.

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  • GOLD [[[symbol]] Au, atomic weight 1 95.7(11 = I),197 2(O =16)], a metallic chemical element, valued from the earliest ages on account of the permanency of its colour and lustre.

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  • Over 10% of copper makes the parting difficult; consequently in such alloys the percentage of copper is diminished by the addition of silver free from copper, or else the copper is removed by a chemical process.

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  • It is now generally accepted that this number, experimentally determined by Moseley for a number of elements, defines the physical and chemical properties of the particular element.

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  • To the transactions of that society he contributed papers on the Wrekin and the Shropshire coalfield, &c. Later he became secretary of the Society of Arts, and in 1841 treasurer of the Chemical Society.

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  • BISMUTH, a metallic chemical element; symbol Bi, atomic weight 208.5 (0 = 16).

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  • The wet refining process is more tedious and expensive, and is only exceptionally employed, as in the case of preparing the pure metal or its salts for pharmaceutical or chemical purposes.

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  • It is precipitated as the metal from solutions of its salts by the metals of the alkalis and alkaline earths, zinc, iron, copper, &c. In its chemical affinities it resembles arsenic and antimony; an important distinction is that it forms no hydrogen compound analogous to arsine and stibine.

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  • The principal manufactures of the town are sugar, cigars, paper, gloves, chemical products, beer and machinery.

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  • TELLURIUM [[[Symbol]] Te, atomic weight 127.5 (0=16)], a chemical element, found to a certain extent in nature in the uncombined condition, but chiefly in combination with other metals in the form of tellurides, such, for example, as sylvanite, black tellurium, and tetradymite.

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  • TANTALUM [[[symbol]] Ta, atomic weight 181 o (0=16)], a metallic chemical element, sparingly distributed in nature and then almost invariably associated with columbium.

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  • A minute fraction is always separating out of the water, and as a prodigious length of time may be accepted for the accomplishment of all the chemical and physical processes in the deep sea, we must take account of the gradual accumulation of even this infinitesimal precipitation.

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  • Chemical News (1870), vol.

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  • Such, for instance, were those of Spindler and Wrangell in the Black Sea by sinking an electric lamp, those of Paul Regnard by measuring the change of electric resistance in a selenium cell or the chemical action of the light on a mixture of chlorine and hydrogen, by which he found a very rapid diminution in the intensity of light even in the surface layers of water.

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  • The facts regarding carbonic acid in sea-water are even less understood, for here we have to do not only with the solution of the gas but also with a chemical combination.

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