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molecules

molecules Sentence Examples

  • The organism is made up of molecules which are analogous to them.

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  • equal changes in temperature and pressure occasion equal changes in equal volumes of all gases and vapours - Avogadro deduced the law: Under the same conditions of temperature and pressure, equal volumes of gases contain equal numbers of molecules; and he showed that the relative weights of the molecules are determined as the ratios of the weights of equal volumes, or densities.

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  • He established the existence of molecules and atoms as we have defined above, and stated that the number of atoms in the molecule is generally 2, but may be 4, 8, &c. We cannot tell whether his choice of the powers of 2 is accident or design.

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  • This investigator held that the decomposition of the sugar molecules takes place outside the cell wall.

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  • Assuming that the molecules are spherical, R.

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  • The preference exhibited by yeast cells for sugar molecules is shared by mould fungi and soluble enzymes in their fermentative actions.

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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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  • 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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  • When nitric peroxide, N204, is converted into gas, it decomposes, and at about 180° C. its vapour entirely consists of molecules of the composition N02; while at temperatures between this and o C. it consists of a mixture in different proportions of the two kinds of molecules, N 2 O 4 and N02.

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  • they appear to differ in character; but if they are correctly represented by molecular equations, or equations which express the relative number of molecules which enter into reaction and which result from the reaction, it will be obvious that the character of the reaction is substantially the same in both cases, and that both are instances of the occurrence of what is ordinarily termed double decomposition H2 + C12 = 2HC1 Hydrogen.

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  • We may here mention the synthesis of oxyuvitic ester (5-methyl-4-oxy-I-3-benzene dicarboxylic ester) by the condensation of two molecules of sodium acetoacetic ester with one of chloroform (Ann., 1883, 222, p. 249).

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  • The following table gives a comparative view of the specific heats and the ratio for molecules of variable atomic content.

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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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  • 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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  • He showed that the heat motion of particles, which is too small to be perceptible when these particles are large, and which cannot be observed in molecules since these themselves are too small, must be perceptible when the particles are just large enough to be visible and gave complete equations which enable the masses themselves to be deduced from the motions of these particles.

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  • But Buffon further imagined that innumerable "molecules organiques " are dispersed throughout the world, and that alimentation consists in the appropriation by the parts of an.

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  • Thus the thio-alcohols or mercaptans (q.v.) contain the group - CH2 SH; and the elimination of the elements of sulphuretted hydrogen between two molecules of a thio-alcohol results in the formation of a thio-ether or sulphide, R 2 S.

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  • In such experiments the molecular energy of a gas is converted into work only in virtue of the molecules being separated into classes in which their velocities are different, and these classes then allowed to act upon one another through the intervention of a suitable heat-engine.

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  • the force which holds chemically dissimilar substances together (and also similar substances as is seen in di-, tri-, and poly-atomic molecules), was introduced by Hermann Boerhaave, and made more precise by Sir Isaac Newton.

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  • This diminution implies an association of molecules, the surface containing fewer molecules than it is supposed to.

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  • In such experiments the molecular energy of a gas is converted into work only in virtue of the molecules being separated into classes in which their velocities are different, and these classes then allowed to act upon one another through the intervention of a suitable heat-engine.

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  • the force which holds chemically dissimilar substances together (and also similar substances as is seen in di-, tri-, and poly-atomic molecules), was introduced by Hermann Boerhaave, and made more precise by Sir Isaac Newton.

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  • In the experiment imagined by Lord Rayleigh a porous diaphragm takes the place of the partition and trap-doors imagined by Clerk Maxwell, and the molecules sort themselves automatically on account of the difference in their average velocities for the two gases.

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  • The " molecules organiques " are physical equivalents of Leib nitz's " monads."

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  • Considering derivatives primarily concerned with transformations of the hydroxyl group, we may regard our typical acid as a fusion of a radical R CO - (named acetyl, propionyl, butyl, &c., generally according to the name of the hydrocarbon containing the same number of carbon atoms) and a hydroxyl group. By replacing the hydroxyl group by a halogen, acid-haloids result; by the elimination of the elements of water between two molecules, acid-anhydrides, which may be oxidized to acid-peroxides; by replacing the hydroxyl group by the group. SH, thio-acids; by replacing it by the amino group, acid-amides (q.v.); by replacing it by the group - NH NH2, acid-hydrazides.

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  • A historic example is that of the condensation of three molecules of acetone, CH 3 CO CH 3, in the presence of sulphuric acid, to s-trimethylbenzene or mesitylene, C 6 H 3 (CH 3) 3, first observed in 1837 by R.

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  • 4]-trimethylbenzene or pseudocumene; and of the condensation product of two molecules of isovaleryl aldehyde with one of acetone, C 3 H 7 CH 2 CH:C(C 3 H 7) CH:CH CO.

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  • The conceptions of "element," "compound" and "mixture" became more precise than they had been hitherto; in an element all the atoms are alike, in a compound all the molecules are alike, in a mixture there are different kinds of molecules.

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  • necessary to determine the specific gravities of the various gases referred to some one of them, say hydrogen; the numbers so obtained giving the weights of the molecules referred to that of the hydrogen molecule.

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  • Hence when useful work can be obtained from a system by simply connecting visible portions of it by a train of mechanism, such energy is more readily recognized than is that which would compel us to control the behaviour of molecules before we could transform it into useful work.

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  • Hence when useful work can be obtained from a system by simply connecting visible portions of it by a train of mechanism, such energy is more readily recognized than is that which would compel us to control the behaviour of molecules before we could transform it into useful work.

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  • Of these, undoubtedly the simplest are the ethers (q.v.), formed by the elimination of the elements of water between two molecules of the same alcohol, " simple ethers," or of different alcohols, " mixed ethers."

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  • From our standpoint, the plant wastes all the rest of its energy on riotous living: growing roots and leaves, soaking up water, separating carbon molecules from oxygen ones.

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  • According to the law of Avogadro, equal volumes of different gases under the same conditions of temperature and pressure contain equal numbers of molecules; therefore, since the density depends upon the number of molecules present in unit volume, it follows that for a comparison of the densities of gases, the determinations must be made under coincident conditions, or the observations reduced or re-computed for coincident conditions.

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  • the actual volume of the molecules; this is obvious by considering the result of making T zero in the characteristic equation.

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  • Oxygen, nitrogen, hydrogen and carbon monoxide have the value 1.4; these gases have diatomic molecules, a fact capable of demonstration by other means.

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  • According to the law of Avogadro, equal volumes of different gases under the same conditions of temperature and pressure contain equal numbers of molecules; therefore, since the density depends upon the number of molecules present in unit volume, it follows that for a comparison of the densities of gases, the determinations must be made under coincident conditions, or the observations reduced or re-computed for coincident conditions.

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  • the actual volume of the molecules; this is obvious by considering the result of making T zero in the characteristic equation.

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  • To see how this law follows from Dalton's theory let us consider his diagrams for the molecules of water, ethylene and the oxides of carbon.

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  • Dalton believed that the molecules of the elementary gases consisted each of one atom; his diagram for hydrogen gas makes the point clear.

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  • Mossotti found a relation between the dielectric constant and the space actually occupied by the molecules, viz.

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  • n is the mean number of molecules which associate to form one molecule, then by the normal equation we have y (Mnv) 3 =2.121(r -6°); if the calculated constant be K 1, then we have also y(Mv)3=K,(r-6°).

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  • - On the theory that crystal form and structure are the result of the equilibrium between the atoms and molecules composing the crystals, it is probable, a priori, that the same substance may possess different equilibrium configurations of sufficient stability, under favourable conditions, to form different crystal structures.

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  • Mossotti found a relation between the dielectric constant and the space actually occupied by the molecules, viz.

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  • To reduce these figures to a common standard, so that the volumes shall contain equal numbers of molecules, the notion of molecular volumes is introduced, the arbitrary values of the crystallographic axes (a, b, c) being replaced by the topic parameters' (x, ?i, w), which are such that, combined with the axial angles, they enclose volumes which contain equal numbers of molecules.

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  • A large number of cobalt compounds are known, of which the empirical composition represents them as salts of cobalt to which one or more molecules of ammonia have been added.

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  • The general conclusion would appear to be that, while as seen from the earth's surface much of the light from the sky is due to comparatively gross suspended matter, yet an appreciable proportion is attributable to the molecules of air themselves, and that at high elevations where the blue is purer, the latter part may become predominant.

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  • A large number of cobalt compounds are known, of which the empirical composition represents them as salts of cobalt to which one or more molecules of ammonia have been added.

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  • Because nanites are so small, they require little in the way of raw materials, just a few molecules here and there.

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  • The Daltonian would say that each of these weights represents a certain group of atoms, and that these groups can replace, or combine with, each other, to form new molecules.

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  • These natural philosophers suggested that equal volumes of all gaseous substances must contain, at the same temperature and pressure, the same number of molecules.

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  • These colour changes are connected with a dissociation of the molecules.

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  • The gradual accumulation of data referring to organic compounds brought in its train a revival of the discussion of atoms and molecules.

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  • We may suppose that in the formation of gaseous hydrochloric acid from gaseous chlorine and hydrogen, according to the equation H2 +C1 2 = HCI+HC1, a certain amount of energy is expended in separating the atoms of hydrogen in the hydrogen molecule, and the atoms of chlorine in the chlorine molecule, from each other; but that heat is developed by the combination of the hydrogen atoms with the chlorine atoms, and that, as more energy is developed by the union of the atoms of hydrogen and chlorine than is expended in separating the hydrogen atoms from each other and the chlorine atoms from one another, the result of the action of the two elements upon each other is the development of heat, - the amount finally developed in the reaction being the difference between that absorbed in decomposing the elementary molecules and that developed by the combination of the atoms of chlorine and hydrogen.

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  • In the formation of gaseous hydrobromic acid from liquid bromine and gaseous hydrogen H2+Br2=HBr+HBr, in addition to the energy expended in decomposing the hydrogen and bromine molecules, energy is also expended in converting the liquid bromine into the gaseous condition, and probably less heat is developed by the combination of bromine and hydrogen than by the combination of chlorine and hydrogen, so that the amount of heat finally developed is much less than is developed in the formation of hydrochloric acid.

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  • Certain a-diketones condense to form benzenoid quinones, two molecules of the diketone taking part in the reaction; thus diacetyl, CH 3 CO CO CH 3, yields p-xyloquinone, C 6 H 2 (CH 3) 2 0 2 (Ber., 1888, 21, p. 1411), and acetylpropionyl, CH 3 CO CO C 2 H 5, yields duroquinone, or tetramethylquinone, C 6 (CH 3) 4 0 2, Oxymethylene compounds, characterized by the grouping > C:CH(OH), also give benzene derivatives by hydrolytic condensation between three molecules; thus oxymethylene acetone, or formyl acetone, CH 3 CO.

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  • 2 3, p. 2 377) investigated the condensation of pyroracemic acid, CH 3 CO 000H, with various aliphatic aldehydes, and obtained from two molecules of the acid and one of the aldehyde in the presence of baryta water alkylic isophthalic acids: with acetaldehyde [1.3.51-methylisophthalic acid or uvitic acid, C 6 H 3 CH 3 (000H) 2, was obtained, with propionic aldehyde [1.3.

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  • It is found that mercury vapour, helium, argon and its associates (neon, krypton, &c.) have the value 1.67; hence we conclude that these gases exist as monatomic molecules.

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  • Hence it may be inferred that this value is typical for diatomic molecules.

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  • It is remarkable that a great many polymorphous substances assume more symmetrical forms at higher temperatures, and a possible explanation of the increase in density of such compounds as silver iodide, &c., may be sought for in the theory that the formation of a more symmetrical configuration would involve a drawing together of the molecules, and consequently an increase in density.

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  • Hofmann and Schotensack decompose a mixture of phenol (3 molecules) and sodium carbonate (4 mols.) with carbonyl chloride at 140-zoo° C. When 90% of the phenol has distilled over, the residue is dissolved and hydrochloric acid added, any phenol remaining is blown over in a current of steam, and the salicylic acid finally precipitated by hydrochloric acid.

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  • The general trend of these researches lies in the study of the decomposition or " breaking down " products of the albumin molecules; once these are accurately determined, the synthesis of an albumin is but a matter of time.

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  • Thus, if the molecule of a substance in solution is represented by AB, Grotthus considered a chain of AB molecules to exist from one electrode to the other.

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  • A freedom of interchange is thus indicated between the opposite parts of the molecules of salts in solution, and it follows reasonably that with the solution of a single salt, say sodium chloride, continual interchanges go on between the sodium and chlorine parts of the different molecules.

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  • He pointed out that it followed that the electric forces did not cause the interchanges between the opposite parts of the dissolved molecules but only controlled their direction.

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  • Interchanges must be supposed to go on whether a current passes or not, the function of the electric forces in electrolysis being merely to determine in what direction the parts of the molecules shall work their way through the liquid and to effect actual separation of these parts (or their secondary products) at the electrodes.

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  • No work is done in separating the parts of the molecules from each other.

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  • This result again indicates that the parts of the molecules are effectively separate from each other, the function of the electric forces being merely directive.

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  • On the right, towards which the faster ion travels, five molecules of salt are left, being a loss of two from the original seven.

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  • On the left, towards which the slower ion moves, only three molecules remain - a loss of four.

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  • For instance, to take the two solutions to which we have already referred, we have of ions between molecules at the instants of molecular collision only; during the rest of the life of the ions they were regarded as linked to each other to form electrically neutral molecules.

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  • It is possible that in complicated organic substances we might have two kinds of dissociation, electrical and non-electrical, occurring simultaneously, while the possibility of the association of molecules accompanied by the electrical dissociation of some of them into new parts should not be overlooked.

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  • Solid copper chloride is brown or yellow, so that its concentrated solution, which contains both ions and undissociated molecules, is green, but changes to blue as water is added and the ionization becomes complete.

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  • Thus para-nitrophenol has colourless molecules, but an intensely yellow negative ion.

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  • Let x be the number of molecules which dissociate per second when the number of undissociated molecules in unit volume is unity, then in a dilute solution where the molecules do not interfere with each other, xp is the number when the concentration is p. Recombination can only occur when two ions meet, and since the frequency with which this will happen is, in dilute solution, proportional to the square of the ionic concentration, we shall get for the number of molecules re-formed in one second ye where q is the number of dissociated molecules in one cubic centimetre.

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  • If µ be the molecular conductivity, and its value at infinite dilution, the fractional number of molecules dissociated is k /µop, which we may write as a.

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  • The number of undissociated molecules is then I - a, so that if V be the volume of the solution containing I gramme-molecule of the dissolved substance, we get q= and p= (I - a)/V, hence x(I - a) V =yd/V2, and constant = k.

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  • Van 't Hoff's formula is equivalent to taking the frequency of dissociation as proportional to the square of the concentration of the molecules, and the frequency of recombination as proportional to the cube of the concentration of the ions.

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  • An explanation of the failure of the usual dilution law in these cases may be given if we remember that, while the electric forces between bodies like undissociated molecules, each associated with equal and opposite charges, will vary inversely as the fourth power of the distance, the forces between dissociated ions, each carrying one charge only, will be inversely proportional to the square of the distance.

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  • The forces between the ions of a strongly dissociated solution will thus be considerable at a dilution which makes forces between undissociated molecules quite insensible, and at the concentrations necessary to test Ostwald's formula an electrolyte will be far from dilute in the thermodynamic sense of the term, which implies no appreciable intermolecular or interionic forces.

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  • As the concentration is increased and un-ionized molecules are formed, a change in temperature begins to affect the ionization as well as the fluidity.

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  • In the case of weaker acids, the dissociation of which is less complete, divergences from this constant value will occur, for some of the molecules have to be separated into their ions.

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  • According to the molecular theory, diffusion is due to the motion of the molecules of the dissolved substance through the liquid.

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  • When the dissolved molecules are uniformly distributed, the osmotic pressure will be the same everywhere throughout the solution, but, if the concentration vary from point to point, the pressure will vary also.

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  • In the case of nonelectrolytes and of all non-ionized molecules this analogy completely represents the facts, and the phenomena of diffusion can be deduced from it alone.

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  • The specific rotation also varies with the concentration; this is due to the dissociation of complex molecules into simpler ones, a view confirmed by cryoscopic measurements.

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  • The properties of caoutchouc clearly show, however, that its actual molecular structure is considerably more complex than is represented by the empirical formula, and that it is to be regarded as the polymer of a terpene or similar hydrocarbon and composed of a cluster of at least ten or twenty molecules of the formula C5H8.

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  • Caoutchouc, like other "unsaturated" molecules, forms compounds with chlorine, bromine, iodine and sulphur.

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  • Tschermak, in 1878, regarded them as isomorphous mixtures of the following fundamental molecules: H 2 KA1 3 (SiO 4) 3, corresponding with muscovite; Mg 6 Si 3 0 12, a hypothetical polymer of olivine; and H4S15012, a hypothetical silicic acid.

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  • This result he considered to be due, not to any removal of impurities, but to an actual splitting-up of the yttrium molecule into its constituents, and he ventured to draw the provisional conclusion that the so-called simple bodies are in reality compound molecules, at the same time suggesting that all the elements have been produced by a process of evolution from one primordial stuff or "protyle."

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  • According to this theory the molecules of any magnetizable substance are little permanent magnets the axes of which are, under ordinary conditions, disposed in all possible directions indifferently.

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  • The process of magnetization consists in turning round the molecules by the application of magnetic force, so that their north poles may all point more or less approximately in the direction of the force; thus the body as a whole becomes a magnet which is merely the resultant of an immense number of molecular magnets.

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  • of a crowd of small compass needles (representative of magnetic molecules) is proportional to the 1.6th power of the aggregate maximum magnetic moment before or after completion of the cycle.

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  • The width of the gap may be diminished until it is no greater than the distance between two neighbouring molecules, when it will cease to be distinguishable, but, assuming the molecular theory of magnetism to be true, the above statement will still hold good for the intermolecular gap. The same pressure P will be exerted across any imaginary section of a magnetized rod, the stress being sustained by the intermolecular springs, whatever their physical nature may be, to which the elasticity of the metal is due.

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  • Weber's theory, the molecules of a ferromagnetic metal are small permanent magnets, the axes of which under ordinary conditions are turned indifferently in every direction, so that no magnetic polarity is exhibited by the metal as a whole; a magnetic force acting upon the metal tends to turn the axes of the little magnets in one direction, and thus the entire piece acquires the properties of a magnet.

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  • If, however, the molecules could turn with perfect freedom, it is clear that the smallest magnetizing force would be sufficient to develop the highest possible degree of magnetization, which is of course not the case.

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  • This represents the condition of the molecules in unmagnetized iron.

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  • Supposing Ewing's hypothesis to be correct, it is clear that if the magnetization of a piece of iron were reversed by a strong rotating field instead of by a field alternating through zero, the loss of energy by hysteresis should be little or nothing, for the molecules would rotate with the field and no unstable movements would be possible.'

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  • The fact being established that magnetism is essentially a molecular phenomenon, the next step is to inquire what is the constitution of a magnetic molecule, and why it is that some molecules are ferromagnetic, others paramagnetic, and others again diamagnetic. The best known of the explanations that have been proposed depend upon the magnetic action of an electric current.

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  • To account for diamagnetism, Weber supposed that there exist within the molecules of diamagnetic substances certain channels around which an electric current can circulate without any resistance.

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  • The strength of the induced current is - HScosO/L, where 0 is the inclination of the axis of the circuit to the direction of the field, and L the coefficient of self-induction; the resolved part of the magnetic moment in the direction of the field is equal to - HS 2 cos 2 6/L, and if there are n molecules in a unit of volume, their axes being distributed indifferently in all directions, the magnetization of the substance will be-3nHS 2 /L, and its susceptibility - 3S 2 /L (Maxwell, Electricity and Magnetism, § 838).

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  • If the structure of the molecule is so perfectly symmetrical that, in the absence of any external field, the resultant magnetic moment of the circulating electrons is zero, then the application of a field, by accelerating the right-handed (negative) revolutions, and retarding those which are left-handed, will induce in the substance a resultant magnetization opposite in direction to the field itself; a body composed of such symmetrical molecules is therefore diamagnetic. If however the structure of the molecule is such that the electrons revolving around its atoms do not exactly cancel one another's effects, the molecule constitutes a little magnet, which under the influence of an external field will tend to set itself with its axis parallel to the field.

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  • Ordinarily a substance composed of asymmetrical molecules is paramagnetic, but if the elementary magnets are so conditioned by their strength and concentration that mutual action between them is possible, then the substance is ferromagnetic. In all cases however it is the diamagnetic condition that is initially set up - even iron is diamagnetic - though the diamagnetism may be completely masked by the superposed paramagnetic or ferromagnetic condition.

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  • It crystallizes in prisms with four molecules of water; when.

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  • The acid salts are obtained by the addition of one molecule of alkali to two molecules of the acid in concentrated alcoholic solution at a low temperature.

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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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  • A process of waste resulting from the decomposition of the molecules of the protoplasm, in virtue of which they break up into more highly oxidated products, which cease to form any part of the living body, is a constant concomitant of life.

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  • In either case, the addition of molecules to those which already existed takes place, not at the surface of the living mass, but by interposition between the existing molecules of the latter.

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

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  • Fraser proved that by substitution of molecules in certain compounds a stimulant could be converted into a sedative action; thus by the addition of the methyl group CH 2 to the molecule of strychnine, thebaine or brucine, the tetanizing action of these drugs is converted into a paralysing action.

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  • Now, what is remarkable in these and many other reactions is not only that effects apparently very opposite may result from minute differences of molecular construction, but also that, whatever the construction, agents, not wholly indifferent to the body or part, tend to anchor themselves to organic molecules in some way akin to them.

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  • On the other hand, the reagents by which such modifications are apt to be produced are not necessarily simple; many of them likewise are known to be of very high degrees of complexity, approaching perhaps in complexity the molecules to which they are akin.

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  • Of such probably are the toxins and antitoxins of certain infections, which, anchoring themselves not by any means indiscriminately, but to particular and concerted molecules, by such anchorage antagonize them or turn them to favourable or unfavourable issues.

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  • The first term includes simple sugars containing two to nine atoms of carbon, which are known severally as bioses, trioses, tetroses, pentoses, hexoses, &c.; whilst those of the second group have the formula C12H22011 and are characterized by yielding two monosaccharose molecules on hydrolysis.

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  • - Fischer found that if one molecule of phenylhydrazine acted upon one molecule of an aldose or ketose a hydrazone resulted which in most cases was very soluble in water, but if three molecules of the hydrazine reacted (one of which is reduced to ammonia and aniline) insoluble crystalline substances resulted, termed osazones, which readily characterized the sugar from which it was obtained.

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  • On reduction it yields an inactive mixture of galactonic acids, some molecules being attacked at one end, as it were, and an equal number of others at the other.

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  • The disaccharoses have the formula C12H22011 and are characterized by yielding under suitable conditions two molecules of a hexose: C12H22011+H20=C6H1206+C6H1206.

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  • Those substituted in the benzene nucleus are obtained by condensing two molecules of a substituted benzyl and benzal chlorides.

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  • The salt crystallizes out on cooling with 7 molecules of water, forming colourless orthorhombic prisms, usually small and needle-shaped.

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  • At Ioo° C. the crystals lose 6 of their molecules of water; the remaining molecule goes off at 250°, a temperature which lies close to that at which the salt begins to decompose.

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  • This view, which was specially supported by Gay-Lussac and Leopold Gmelin and accepted by Berzelius, necessitated that all acids were monobasic. The untenability of this theory was proved by Thomas Graham's investigation of the phosphoric acids; for he then showed that the ortho- (ordinary), pyroand metaphosphoric acids contained respectively 3, 2 and I molecules of " basic water " (which were replaceable by metallic oxides) and one molecule of phosphoric oxide, P2 05.

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  • In the cases of aluminium dissolved in tin and of mercury or bismuth in lead, it is at least probable that the molecules in solution are Al 2j Hg 2 and Bit respectively, while tin in lead appears to form a molecule of the type Sn4.

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  • It mixes with water in all proportions, the mixing being attended by a contraction in volume and a rise in temperature; the maximum contraction corresponds to a mixture of 3 molecules of alcohol and I of water.

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  • p. 211, Paris, 1869) proposed an equation of the form (p+po)(v - b) =RO, in which the effect of the size of the molecules is represented by subtracting a quantity b, the " covolume," from the volume occupied by the gas, and the effect of the mutual attractions of the molecules is represented by adding a quantity po, the internal pressure, to the external pressure, p. This type of equation, was more fully worked out by van der Waals, who identified the internal pressure, po, with the capillary pressure of Laplace, and assumed that it varied directly as the square of the density, and could be written a/v 2 .

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  • (17) in which c is a small quantity (expressing the defect from the ideal volume V =Re/p due to co-aggregation of the molecules) which varies inversely as the nth power of 0, but is independent of p to a first approximation at moderate pressures.

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  • According to van der Waals, assuming spherical molecules, it should be four times; according to O.

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  • In the case of imperfect gases, all the available experimental evidence shows that the specific volume tends towards its ideal value, V =Re/p, in the limit, when the pressure is indefinitely reduced and the molecules are widely separated so as to eliminate the effects of their mutual actions.

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  • The energy is less than that of an ideal gas by the term npc. If we imagine that the defect of volume c is due to the formation of molecular aggregates consisting of two or more single molecules, and if the kinetic energy of translation of any one of these aggregates is equal to that of one of the single molecules, it is clear that some energy must be lost in co-aggregating, but that the proportion lost will be different for different types of molecules and also for different types of co-aggregation.

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  • If two monatomic molecules, having energy of translation only, equivalent to 3 degrees of freedom, combined to form a diatomic molecule with 5 degrees of freedom, the energy lost would.

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    0
  • If two diatomic molecules, having each 5 degrees of freedom, combine to form a molecule with 6 degrees of freedom, we should have n = 2, or the energy lost would be 2pc per unit mass.

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    0
  • If the molecules and molecular aggregates were more complicated, and the number of degrees of freedom of the aggregates were limited to 6, or were the same as for single molecules, we should have n-= so/R.

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  • The loss of energy could not be greater than this on the simple kinetic theory, unless there were some evolution of latent heat of co-aggregation, due to the work done by the mutual attractions of the co-aggregating molecules.

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  • It is not necessary to suppose that the co-aggregated molecules are permanently associated.

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  • b, Covolume of molecules of gas.

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    0
  • it, Mean velocity of gaseous molecules.

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  • In air of considerable density the mean free path of a molecule, between its collisions with other molecules, is exceedingly small, and any such increase of gaseous pressure in front of the black surface would be immediately neutralized by flow of the gas from places of high to places of low pressure.

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  • The general nature of the phenomena is thus easily understood; but it is at a maximum at pressures comparable with a millimetre of mercury, at which the free path is still small, the greater number of molecules operating in intensifying the result.

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  • The hypothesis that the state was steady, so that interchanges arising from convection and collisions of the molecules produced no aggregate result, enabled him to interpret the new constants involved in this law of distribution, in terms of the temperature and its spacial differential coefficients, and thence to express the components of the kinetic stress at each point in the medium in terms of these quantities.

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  • As far as the order to which he carried the approximations - which, however, were based on a simplifying hypothesis that the molecules influenced each other through mutual repulsions inversely as the fifth power of their distance apart--the result was that the equations of motion of the gas, considered as subject to viscous and thermal stresses, could be satisfied by a state of equilibrium under a modified internal pressure equal in all directions.

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  • Reynolds, in his investigation, introducing no new form of law of distribution of velocities, uses a linear quantity, proportional to the mean free path of the gaseous molecules, which he takes to represent (somewhat roughly) the average distance from which molecules directly affect, by their convection, the state of the medium; the gas not being uniform on account of the gradient of temperature, the change going on at each point is calculated from the elements contributed by the parts at this particular distance in all directions.

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  • Dittmar showed that the average proportion of the salts in ocean water of 35 parts salts per thousand was as follows (calculated as parts per 'thousand of the sea-water, as percentage of the total"salts and per hundred molecules of magnesium bromide) :- The Salts in Ocean Water.

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  • There must be considerable dissociation of molecules, and as a first approximation it may be taken that of io molecules of most of the components about 9 (or in the case of magnesium sulphate 5) have been separated into their ions, and that it is only during slow concentration as in a natural saline that the ions combine to produce the various salts in the proportions set out in the above table.

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  • The doctrine that matter can be divided into, or regarded as composed of, discrete particles (termed " atoms " by early writers, and " molecules " by modern ones) has at all times played an important part in metaphysics and natural science.

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  • For instance, if oxygen and hydrogen combine to form water, we have no experimental evidence that the molecule of oxygen is not in the very same place with the two molecules of hydrogen.

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  • It ought accordingly to be possible to explain all the non-electrical and non-chemical properties of matter by treating matter as an aggregation of molecules.

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  • 18 9 0 [5], 3 0, p. 474) has pointed out that the earliest known attempt to estimate the size of molecules, made by Thomas Young in 1805, was based upon the consideration of phenomena of the kind just mentioned.

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  • The best estimates which we now possess of the sizes of molecules are provided by calculations based upon the kinetic theory of gases.

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  • In the following table are given the values of the diameters of the molecules of six substances with which it is easy to experiment in the gaseous state, these values being calculated in different ways from formulae supplied by the kinetic theory.

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  • better need not cause surprise when it is stated that the quantities are calculated on the hypothesis that the molecules are spherical in shape.

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  • An essential feature of the modern view of the structure of matter is that the molecules are supposed to be in rapid motion relatively to one another.

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  • That the distances traversed by the molecules of a solid are very small in extent is shown by innumerable facts of everyday observation, as for instance, the fact that the surface of a finely-carved metal (such as a plate used for steel engraving) will retain its exact shape for centuries, or again, the fact that when a metal body is coated with gold-leaf the molecules of the gold remain on its surface indefinitely: if they moved through.

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  • any but the smallest distances they would soon become mixed with the molecules of the baser metal and diffused through its interior.

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  • Thus the molecules of a solid must make only small excursions about their mean positions.

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  • In a gas the state of things is very different; an odour is known to spread rapidly through great distances, even in the stillest air, and a gaseous poison or corrosive will attack not only those objects which are in contact with its source but also all those which can be reached by the motion of its molecules.

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  • As a preliminary to examining further into the nature of molecular motion and the differences of character of this motion, let us try to picture the state of things which would exist in a mass of solid matter in which all the molecules are imagined to be at rest relatively to one another.

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  • The fact that a solid body in its natural state is capable both of compression and of dilatation indicates that the molecules of the body must not be supposed to be fixed rigidly in position relative to one another; the further fact that a motion of either compression or of dilatation is opposed by forces which are brought into play in the interior of the solid suggests that the position of rest is one in which the molecules are in stable equilibrium under their mutual forces.

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  • originally impinged on that at rest is now represented by the energy, kinetic and potential, of the small motions of the individual molecules.

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  • Thus the molecular theory of matter, as we have now pictured it, leads us to identify heat-energy in a body with the energy of motion of the molecules of the body relatively to one another.

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  • A body in which all the molecules were at rest relatively to one another would be a body devoid of heat.

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  • The molecules of the two surface-layers will exert forces upon one another, so that, when the rubbing takes place, each layer will set the molecules of the other into motion, and the energy of rubbing will be used in establishing this heat-motion.

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  • At first the heat-motion will be confined to molecules near the rubbing surfaces of the two bodies, but, as already explained, these will in time set the interior molecules into motion, so that ultimately the heat-motion will become spread throughout the whole mass.

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  • When the molecules are oscillating about their equilibrium positions, there is no reason why their mean distance apart should be the same as when they are at rest.

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  • Suppose for instance that two molecules, when at rest in equilibrium, are at a distance a apart.

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  • A body made up of molecules of this kind will expand on heating.

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  • As the temperature of a body increases the average energy of the molecules will increase, and therefore the range of their excursions from their positions of equilibrium will increase also.

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    0
  • When the body is in this state the relative positions of the molecules are not permanently fixed, so that the body is no longer of unalterable shape: it has, assumed a plastic or molten condition.

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  • The substance attains to a perfectly liquid state as soon as the energy of motion of the molecules is such that there is a constant rearrangement of position among them.

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  • A molecule escaping from its original position in a body will usually fall into a new position in which it will be held in equilibrium by the forces from a new set of neighbouring molecules.

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  • The body is continually losing mass by the loss of individual molecules in this way, and this explains the process of evaporation.

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  • Moreover, the molecules which escape are, on the whole, those with the greatest energy.

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  • The average energy of the molecules of the liquid is accordingly lowered by evaporation.

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  • number of collisions with other free molecules and with the sides of the vessel, fall back again into the liquid.

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  • When a stage is reached such that the number of molecules lost to the liquid by evaporation is exactly equal to that regained by condensation, we have a liquid in equilibrium with its own vapour.

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  • If the whole liquid becomes vaporized before this stage is attained, a state will exist in which the vessel is occupied solely by free molecules, describing paths which are disturbed only by encounters with other free molecules or the sides of the vessel.

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  • It follows that the average distance apart of the molecules in the gaseous state is roughly ten times as great as in the solid or liquid state, and hence that in the gaseous state the molecules are at distances apart which are large compared with their linear dimensions.

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  • (If the molecules of air at normal temperature and pressure were arranged in cubical order, the edge of each cube would be about 2.9 X I o - ' cms.; the average diameter of a molecule in air is 2.8X Io - 8 cms.) Further and very important evidence as to the nature of the gaseous state of matter is provided by the experiments of Joule and Kelvin.

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  • In terms of the molecular theory this indicates that the total energy of the gas is the sum of the separate energies of its different molecules: the potential energy arising from intermolecular forces between pairs of molecules may be treated as negligible when the matter is in the gaseous state.

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  • A number of molecules moving in obedience to dynamical laws will pass through a series of configurations which can be theoretically determined as soon as the structure of each molecule and the initial position and velocity of every part of it are known.

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  • It is accordingly clear that there can be no property common to all systems, but it can be shown that when the system contains a gas (or any other aggregation of similar molecules) as part of it there are properties which are common to all possible states, except for a number which form an insignificant fraction of the whole.

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  • The second line in E2 will represent the energy (or part of the energy) of s' similar molecules of the second kind, and so on.

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  • It is not at present necessary to suppose that the molecules are those of substances in the gaseous state.

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  • are very large, then, for all states except an infinitesimal fraction of the whole number, the values of u, v, w lie within ranges such that (i) the values of u (and similarly of v, w) are distributed among the s molecules of the first kind according to the law of trial and error; and similarly of course for the molecules of other kinds: (ii) E2mu2 E2mv 2 E2mw2 ?2aie12 s S s s s s - s E s' S' s' - - s' ' See Jeans, Dynamical Theory of Gases (1904), ch.

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  • If each of the fractions (3) is put equal to i/4h, it is readily found, from the first property of the normal state, that, of the s molecules of the first kind, a number sal (h3m3 /13)e hm (u2+v2+w2)dudvdw (4) Velocities.

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  • have velocities of which the components lie between u and u+du, v and v+dv, w and w+dw, while the corresponding number of molecules of the second kind is, similarly, s' y (h3m'3/73)e hm'(u2-1-v2+"' 2)dudvdw.

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  • (5) If c is the resultant velocity of a molecule, so that c 2 =u2+v2+w2, it is readily found from formula (4) that the number of molecules of the first kind of which the resultant velocity lies between c and c+dc is 4lrs1,l (h 3 rn 3 17r 3)e hmc2 c 2 dc. (6) These formulae express the " law of distribution of velocities " in the normal state: the law is often called Maxwell's Law of Distribution.

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  • If 2mu 2 denote the mean value of 2mu 2 averaged over the s molecules of the first kind, equations (3) may be written in the form Z mu g = 2 mv 2 = 2 mw 2 = 2x,0 2 1 =.

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  • (8) When a system is composed of a mixture of different kinds of molecules, the fact that h is the same for each constituent [cf.

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  • A simple approximate calculation of the pressure exerted by a gas on its containing vessel can be made by supposing that the molecules are so small in comparison with their distances apart that they may be treated as of infinitesimal size.

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  • Let a mixture of gases contain per unit volume v molecules of the first kind, v' of the second kind, and so on.

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  • The number of molecules of the first kind of gas, whose components of velocity lie within the ranges between u and u+du, v and v+dv, w and w+dw, will, by formula (5), be v?l (h 3 m 3 /7 3)e hm (u2+v2+w2)dudvdw (9) per unit volume.

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  • Each of the molecules enumerated in expression (9) will move parallel to the edge of this cylinder, and each will describe a length equal to its edge in time dt.

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  • Thus each of these molecules which is initially inside the cylinder, will impinge on the area dS within an interval dt.

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  • The cylinder is of volume u dt dS, so that the product of this and expression (9) must give the number of impacts between the area dS and molecules of the kind under consideration within the interval dt.

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  • Thus the contribution to the total impulsive pressure exerted on the area dS in time dt from this cause is mu X udtdS X (11 3 m 3 /,r 3)e hm (u2+v2+w2 )dudvdw (I o) The total pressure exerted in bringing the centres of gravity of all the colliding molecules to rest normally to the boundary is obtained by first integrating this expression with respect to u, v, w, the limits being all values for which collisions are possible (namely from - co too for u, and from - oo to + oo for v and w), and then summing for all kinds of molecules in the gas.

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  • Further impulsive pressures are required to restart into motion all the molecules which have undergone collision.

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  • The aggregate amount of these pressures is clearly the sum of the momenta, normal to the boundary, of all molecules which have left dS within a time dt, and this will be given by expression (pp), integrated with respect to u from o to and with respect to v and w from - oo to +oo, and then summed for all kinds of molecules in the gas.

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  • On combining the two parts of the pressure which have been calculated, the aggregate impulsive pressure on dS in time dt is found to be dS ff f v1,1 (h 3 m 3 /7r 3)e h m(u2+v2+w2 >mu2dudvdw, where M denotes summation over all kinds of molecules.

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  • Clearly the integral is the sum of the values of mu g for all the molecules of the first kind in unit volume, thus p=v mu l +v'm'u 2 +...

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  • ..) RT The number of molecules per unit volume in a gas at normal temperature and pressure is known to be about 2.75 X 10 19.

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  • T =273, we obtain R =1.35 X Io -16 and this enables us to determine the mean velocities produced by heat motion in molecules of any given mass.

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  • For molecules of known gases the calculation is still easier.

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  • 35 X I 016 it is readily calculated that a molecule, or aggregation of molecules, of mass Io - 12 grammes, ought to have a mean velocity of about 2 millimetres a second at O.

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  • C. Such a velocity ought accordingly to be set up in a part i cle of -12 grammes mass immersed in air or liquid at 0° C., by the continual jostling of the surrounding molecules or particles.

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  • ., the total number of molecules per unit volume, is determined when p, T and the constant R are given.

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  • Hence we have Avogadro's law: Different gases, at the same temperature and pressure, contain equal numbers of molecules per unit volume.

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  • - If v is the volume of a homogeneous mass of gas, and N the total number of its molecules, N =v(v+v'+ ...), so that pv =RNT.

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  • Van der Waals, in a famous monograph, On the Continuity of the Liquid and Gaseous States (Leiden, 1873), has shown that the imperfections of equation (14) maybe traced to two_causes: (i.) The calculation has not allowed for the finite size of the molecules, and their consequent interference with one another's motion, and (ii.) The calculation has not allowed for the field of inter-molecular force between the molecules, which, although small, is known to have a real existence.

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  • To allow for the first of these two factors, Van der Waals finds that v in equation '04) must be replaced by v - b, where b is four times the aggregate space occupied by all the molecules, while to allow for the second factor, p must be replaced by p +a/v 2 .

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  • The molecules of gases for which n = o must accordingly be spherical in shape and in internal structure, or at least must behave at collisions as though they were spherical, for they would otherwise be set into rotation by the forces experienced at collisions.

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  • In the light of these results it is of extreme significance that the four gases for which n = o are all believed to be monatomic: the molecules of these gases consist of single atoms. Moreover, these four are the only monatomic gases for which the value of y is known, so that the only atoms of which the shape can be determined are found to be spherical.

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  • The kinetic energy of the molecules of these gases must contain two terms in addition to those representing translational energy.

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  • We must accordingly suppose that the molecules of gases for which n =2 are of this shape.

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  • Now this is exactly the shape which we should expect to find in molecules composed of two spherical atoms distorting one another by their mutual forces, and all gases for which n=2 are diatomic.

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  • On the other hand, the theory encounters a very serious difficulty in the fact that all molecules possess a great number of possibilities of internal motion, as is shown by the number of distinct lines in their spectra both of emission and of absorption.

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  • SAFRANINE, in chemistry, the azonium compounds of symmetrical diamino-phenazine and containing the ring system annexed: / N / or X N .% CI R C1 R They are obtained by the joint oxidation' of one molecule of a paradiamine with two molecules of a primary amine; by the condensation of para-aminoazo compounds with primary amines (0.

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  • Pyrophosphoric acid, 'H' 4 P 2 0 7, is a tetrabasic acid which may be regarded as derived by eliminating a molecule of water between two molecules of ordinary phosphoric acid; its constitution may therefore be written (HO) 2 0P O PO(OH) 2.

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  • In chemistry the term is given to chemical reactions in which a substance decomposes into two or more substances, and particularly to cases in which associated molecules break down into simpler molecules.

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  • Aqueous solutions deposit crystals containing 2, 4 or 6 molecules of water.

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  • Modern theory accepts the deduction, but ascribes the momentum to the revolving ions in the molecules of matter traversed by the light; for the magneto-optic effect is present only in material media.

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  • Long previously Lord Kelvin himself came nearer this view, in offering the opinion that magnetism consisted, in some way, in the angular momentum of the material molecules, of which the energy of irregular translations constitutes.

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  • heat; but the essential idea of moving electric ions of both kinds, positive and negative, in the molecules had still to be introduced.

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  • If the aether were itself constituted of discrete molecules, on the model of material bodies, such transparency would not be conceivable.

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  • To make room for these we have to remember that the atomic nucleus has remained entirely undefined and beyond our problem; so that what may occur, say when two molecules come into close relations, is outside physical science - not, however, altogether outside, for we know that when the vital nexus in any portion of matter is dissolved, the atoms will remain, in their number, and their atmospheres, and all inorganic relations, as they were before vitality supervened.

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  • Our direct knowledge of matter can, however, never be more than a rough knowledge of the general average behaviour of its molecules; for the smallest material speck that is sensible to our coarse perceptions contains myriads of atoms. The properties of the most minute portion of matter which we can examine are thus of the nature of averages.

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  • of electric separation in the molecules, specified per unit volume.

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  • In the present case the total dielectric contribution to this current works out to be the change per unit time in the electric separation in the molecules of the element of volume, as it moves uniformly with the matter, all other effects being compensated molecularly without affecting the propagation.

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  • In the moist and plastic slate the mineral particles slowly enlarged by the addition of new crystalline molecules.

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  • This was based on the assumption that the medium in which the light is propagated is discontinuous and molecular in character, the molecules being subject to a mutual attraction.

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  • Sellmeier adopted the elastic-solid theory of the ether, and imagined the molecules to be attached to the ether surrounding them, but free to vibrate about their mean positions within a limited range.

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  • Thus the ether within the dispersive medium is loaded with molecules which are forced to perform oscillations of the same period as that of the transmitted wave.

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  • It can be shown mathematically that the velocity of propagation will be greatly increased if the frequency of the light-wave is slightly greater, and greatly diminished if it is slightly less than the natural frequency of the molecules; also that these effects become less and less marked as the difference in the two frequencies increases.

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  • It crystallizes from water in colourless rhombic prisms, containing four molecules of water of crystallization, and possesses a very acid reaction.

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  • The salt crystallizes in large yellow plates, containing three molecules of water of crystallization.

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  • The green salt appears to dissociate in aqueous solution into two ions, namely CrC1 2 (OH 2) 4 and one chlorine ion, since practically only one-third of the chlorine is precipitated by silver nitrate solution at o° C. Two of the six water molecules are easily removed in a desiccator, and the salt formed, CrC13.4H20, resembles the original salt in properties, only one-third of the chlorine being precipitated by silver nitrate.

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  • It is only recently that owing to the introduction of carbon tubes heated electrically the excitement of the luminous vibrations of molecules by temperature alone has become an effective method for the study of their spectra even in the case of metals.

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  • When we are trying to bring radiation into connexion with temperature, we must therefore take a sufficiently large group of molecules and compare their average energies with the average radiation.

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  • The question arises whether in a vacuum discharge, in which only a comparatively small proportion of the molecules are affected, we are to take the average radiation of the affected portion or include the whole lot of molecules, which at any moment are not concerned in the discharge at all.

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  • According to present ideas, the wave originates in a disturbance of electrons within the molecules.

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  • But the molecules affected by a spark discharge are not in any sense in equilibrium as regards their partition of energy and the word temperature " cannot therefore be applied to them in the ordinary sense.

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  • If all molecules moved with the velocity of mean square, the line would be drawn out into a band having on the frequency scale a width 2Nv/V, where v is now the velocity of mean square.

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  • According to Maxwell's law, however, the number of molecules having a velocity in the line of sight lying between v and vd-dv is proportional to e-1 3v2 dv, where (3 is equal to 312u 2; for v=u, we have therefore the ratio in the number of molecules having velocity u to those having no velocity in the line of sight e-0/1 2 =-- e-z = 22.

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  • In the case of hydrogen rendered luminous in a vacuum tube we may put approximately u equal to 2000 metres per second, if the translatory motion of the luminous molecules is about the same as that at the ordinary temperature.

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  • He finds a remarkable agreement between the theoretical and experimental values, which it would be important to confirm with the more suitable instruments which are now at our disposal, as we might in this way get an estimate of the energy of translatory motion of the luminous molecules.

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  • Experiments which will be discussed in § to seem to show that there is a difference in this respect between the impacts of similar and those of dissimilar molecules.

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  • - It is natural to consider the frequencies of vibrations of radiating molecules as analogous to the different notes sent out by an acoustical vibrator.

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  • According to this view the different lines are given out by different molecules, and we should have to take averages over a number of molecules to obtain the complete spectrum just as we now take averages of energy to obtain the temperature.

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  • - In many cases the spectra of molecules consist of lines so closely ruled together in groups as to give the appearance of continuous bands unless high resolving powers are employed.

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  • The facts, as quoted, point to the closeness of the packing of molecules as the factor which always accompanies and perhaps causes the widening of lines.

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  • Increased density at the same temperature means in the first place a reduction of the average distance between the molecules, but it means also a reduction in the mean free path and an increase in the number of impacts.

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  • Assuming for a moment the change to be one of density and leaving out of account the pressure shift, the cases (e) and (f) point to the fact that it is the closeness of packing of similar molecules which is effective, e.g.

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  • the number of oxygen molecules per cubic centimetre determines the width of the oxygen lines, though nitrogen molecules may be mixed with them without materially affecting the appearance.

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  • But this argument is not conclusive, for though the total number of hydrogen molecules is fixed when the gas is enclosed, yet the number of luminous molecules may vary with the condition.

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  • luminous may, if they do not contain the same vibrating system, behave like inert molecules.

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  • We have further to consider the possibility of sudden changes of phrase during an encounter between two molecules, and we can easily form an estimate of the amount of apparent widening due to this cause.

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  • Schuster suggested that the proximity of molecules vibrating in the same period might be the cause of the diminished frequency, and suggested that according to this view the shifts would be similar if the increase of density were produced by the presence of molecules of a different kind from those whose lines are being examined.

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  • If the medium which contains the vibration is divided into a sphere equal to k times the molecular vibration outside of which the effects of these molecules may be averaged up, so that its Roy.

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  • The question is complicated by the fact that in the cases which have been observed, the greater portion of the metallic vapour vibrates in an atmosphere of similar molecules, and the static energy of the field is determined by the value of K applicable to the particular frequency.

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  • It would therefore seem to be more appropriate to replace 1 - K- 1 by (2 - I)1112, where j s is the refractive index; but this expression involves the wave propagation for periods coinciding with free periods of the molecules.

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  • The explanation of these facts presents no difficulty, inasmuch as during the sudden discharge which takes place in the absence of a self-induction, the metallic molecules have not sufficient time to diffuse through the spark gap; hence the discharge is carried by the gas in which it takes place.

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  • Hemsalech 1 have measured the velocity with which the luminous molecules are projected from metallic poles when a strong spark is passed through the air interval which separates the poles.

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  • The change of frequency of oscillation of radiating molecules placed in a magnetic field, which was discovered by P. Zeeman, and the observed polarization of the components, are all beautifully explained by the theory of H.

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  • These rays are apparently the trajectories of positively charged particles having masses of the order of magnitude of the gaseous molecules.

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  • Thompson and others have shown however that they contain both neutral and charged molecules in a relative proportion which adjusts itself continuously, so that even neutral molecules may partake of the translatory motion which they gained while carrying a charge.

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  • Applying the reasoning to the case of a homogeneous radiation traversing an absorbing medium, we realize that the mutual disturbances of the molecules by collision or otherwise must bring in the free period of the molecule whatever the incident radiation may be.

    0
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  • This is used as the sulphate, which has the empirical formula of (C15H21N302)2, H 2 SO 4, plus an unknown number of molecules of water.

    0
    0
  • When heated to 100° C., it loses five molecules of water of crystallization, and at a higher temperature loses the remainder of the water and also ammonia, leaving a residue of magnesium pyrophosphate, Mg 2 P 2 0 7.

    0
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  • Tschelinzeff (Ber., 1906, 39, p. 773) considers that they contain two molecules of ether.

    0
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  • With unsaturated alkyl halides the products are only slightly soluble in ether, and two molecules of the alkyl compound are brought into the reaction.

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  • He supposes that aesthesis and tropesis, as rudimentary sensation and will, are the very causes of condensation; that they belong to pyknatoms, to ponderables and imponderables, to chemical atoms and molecules.

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  • If he has any originality, it consists in substituting for the association of ideas the " economy of thinking," by which he means that all theoretical conceptions of physics, such as atoms, molecules, energy, &c., are mere helps to facilitate our consideration of things.

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  • According to him, whatever inferences we make, certain or uncertain, are mere economies of thought, adapting ideas to sensations, and filling out the gaps of experience by ideas; whatever we infer, whether bodies, or molecules, or atoms, or space of more than three dimensions, are all without distinction equally provisional conceptions, things of thought; and " bodies or things are compendious mental symbols for groups of sensations - symbols which do not exist outside thought."

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  • van't Hoff in 1885, who showed that Pfeffer's results indicated that osmotic pressure of a dilute solution conformed to the well-known laws of gas pressure, and had the same absolute value as the same number of molecules would exert as a gas filling a space equal to the value of the solvent.

    0
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  • At B we have the non-variant cryohydric point at which ice, the hydrate Fe2C16 12H20, the saturated solution and the vapour are in equilibrium at 55° C. As the proportion 26 of salt is increased, the melting point of the con glomerate rises, till, at the -40 maximum point C, we have the pure compound the hydrate with twelve molecules ¦¦ 0.b, E, ?

    0
    0
  • The density of the liquid is MN/V, where N is the number of solvent molecules, and V the total volume of the liquid.

    0
    0
  • Substituting these values, we find that the relative lowering of vapour pressure in a very dilute solution is equal to the ratio of the numbers of solute and solvent molecules, or (p - p')/p = n/N.

    0
    0
  • At the limit of dilution, when the concentration of a solution approaches zero, we have seen that thermodynamical theory, verified by experiment, shows that the osmotic pressure has the same value as the gas pressure of the same number of molecules in the same space.

    0
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  • The variation of gases from Boyle's law is represented in the equation of Van der Waals by subtracting a constant b from the total volume to represent the effect of the volume of the molecules themselves.

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  • Callendar is to trace the effect of possible combination of molecules of solute with molecules of the solvent.

    0
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  • These combined solvent molecules are thus removed from existence as solvent, the effective volume of which is reduced to that of the remaining free molecules of solvent.

    0
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  • The greater the number of water molecules attached to one sugar molecule, the less the residual volume, and the greater the theoretical pressure.

    0
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  • Callendar finds that five molecules of water in the case of cane-sugar or two molecules in the case of dextrose are required to bring the curves into conformity with the observations of Berkeley and Hartley, which in fig.

    0
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  • If each molecule of the solute combines with a certain number of molecules of the solvent in such a way as to render them inactive for evaporation, we get a lowering of vapour pressure.

    0
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  • Let us assume that the ratio p/p' of the vapour pressures of the solvent and solution is equal to the ratio of the number of free molecules of solvent to the whole number of molecules in the solution.

    0
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  • If there are n molecules of solute to N of solvent originally, and each molecule of solute combines with a molecule of solvent, we get for the ratio of vapour pressures p/p'=(N - an)/(N - an+n), while the relative lowering of vapour pressure is (p - p')/p=n/(N - an).

    0
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  • On the lines of Poynting's theory of solution, each ion in electrolytes must combine with one or more molecules of solvent.

    0
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  • In yet other solutions, the particles are smaller again, and seem to approach in size the larger molecules of crystalloid substances.

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  • The filtrate, now containing roughly two molecules of alumina to one of soda, is concentrated to the original gravity of 1.45, and employed instead of fresh caustic for the attack of more bauxite; the precipitate is then collected, washed till free from soda, dried and ignited at about looo C. to convert it into a crystalline oxide which is less hygroscopic than the former amorphous variety.

    0
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  • Potassium aluminate, K 2 Al 2 0 4, is obtained in solution by dissolving aluminium hydrate in caustic potash; it is also obtained, as crystals containing three molecules of water, by fusing alumina with potash, exhausting with water, and crystallizing the solution in vacuo.

    0
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  • Its vapour density at temperatures above 750 corresponds to the formula AlCl 3 j below this point the molecules are associated.

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  • de Phys., 1811), in which he enunciated the hypothesis known by his name (Avogadro's rule) that under the same conditions of temperature and pressure equal volumes of all gases contain the same number of smallest particles or molecules, whether those particles consist of single atoms or are composed of two or more atoms of the same or different kinds.

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  • It ascends the flow pipe by convection, where its onward journey would speedily end if it were not for the driving force of other molecules of water following, and the suction set up by the gravitation into the boiler of the cooled water by the return pipe.

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  • so to break up its molecules that, apart from small quantities used for its own substance, masses of it out of all proportion to the mass of yeast used become resolved into other bodies, such as carbon dioxide and alcohol, the process requiring little or no oxygen.

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  • typical graphitic cast iron results; or, as usually happens, certain molecules may follow one diagram while the rest follow the other diagram, so that cast iron which has both cementite and graphite results, as in most commercial grey cast iron, and typically in " mottled cast iron," in which there are distinct patches of grey and others of white cast iron.

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  • that to which the metal, in which by suitable thermal treatment the iron molecules have been brought to the allotropic -y or 1 3 state or a mixture of both, can be heated without losing its hardness through the escape of that iron into the a state.

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  • Traube, Ber., 1882, 15, p. 659); in the oxidation of zinc, lead and copper in presence of water, and in the electrolysis of sulphuric acid of such strength that it contains two molecules of water to one molecule of sulphuric acid (M.

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  • the molecules, are identical, and so the molecule of both butylene and isobutylene is indicated by the same chemical symbol C4118, expressing that each molecule contains, in both cases, four atoms of carbon (C) and eight of hydrogen (H).

    0
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  • An early step accomplished by Ostwald in this direction is to define ozone in its relation to oxygen, considering the former as differing from the latter by an excess of energy, measurable as heat of transformation, instead of defining the difference as diatomic molecules in oxygen, and triatomic in ozone.

    0
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  • The third most valuable indication which molecular structure gives about these isomers is how to prepare them, for instance, that normal hexane, represented by CH 3 CH 2 CH 2 CH 2 CH 2 CH3, may be obtained by action of sodium on propyl iodide, CH 3 CH 2 CH 2 I, the atoms of iodine being removed from two molecules of propyl iodide, with the resulting fusion.

    0
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  • In this equation a relates to molecular attraction; and it is not improbable that in isomeric molecules, containing in sum the same amount of the same atoms, those mutual attractions are approximately the same, whereas the chief difference lies in the value of b, that is, the volume occupied by the molecule itself.

    0
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  • Conduction, however, is generally understood to include diffusion of heat in fluids due to the agitation of the ultimate molecules, which is really molecular convection.

    0
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  • This, however, is merely transferring the properties of matter in bulk to its molecules.

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  • It is much more probable that heat is really the kinetic energy of motion of the molecules, and is passed on from one to another by collisions.

    0
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  • On the kinetic theory the molecules of a gas are relatively far apart and there is nothing analogous to friction between two adjacent layers A and B moving with different velocities.

    0
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  • There is, however, a continual interchange of molecules between A and B, which produces the same effect as viscosity in a liquid.

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  • on the " mean free path "), and (3) on the average velocity of translation of the molecules, which varies as the square root of the temperature.

    0
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  • Similarly if A is hotter than B, or if there is a gradient of temperature between adjacent layers, the diffusion of molecules from A to B tends to equalize the temperatures, or to conduct heat through the gas at a rate proportional to the temperature gradient, and depending also on the rate of interchange of molecules in the same way as the viscosity effect.

    0
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  • This, at first sight, paradoxical result is explained by the fact that the mean free path of each molecule increases in the same proportion as the density is diminished, so that as the number of molecules crossing each square centimetre decreases, the distance to which each carries its momentum increases, and the total transfer of momentum is unaffected by variation of density.

    0
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  • If the effects depended merely on the velocity of translation of the molecules, both conductivity and viscosity should increase directly as the square root of the absolute temperature; but the mean free path also varies in a manner which cannot be predicted by theory and which appears to be different for different gases (Rayleigh, Proc. R.S., January 1896).

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  • Certain it is that in the course of the waking day a great number of stimuli play on the sense organs, and through these produce disintegration of the living molecules of the central nervous system.

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  • It acts as a powerful oxidizing agent, both in acid and alkaline solution; in the first case two molecules yield five atoms of available oxygen and in the second, three atoms: 2KMnO 4 +3H 2 SO 4 = K2S04+2MnS04+3H20+50; 2KMnO 4 +3H 2 O =2Mn02 H20+2KHO+30.

    0
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  • The simple nature of the alkalies Lavoisier considered so doubtful that he did not class them as elements, which he conceived as substances which could not be further decomposed by any known process of analysis - les molecules simples et indivisibles qui composent les corps.

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  • They may be regarded as the anhydrides of the alcohols, being formed by elimination of one molecule of water from two molecules of the alcohols; those in which the two hydrocarbon radicals are similar are known as simple ethers, and those in which they are dissimilar as mixed ethers.

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  • This Effect Is Probably Due, As Suggested By Rowland, To The Presence Of A Certain Proportion Of Ice Molecules In The Liquid, Which Is Also No Doubt The Cause Of The Anomalous Expansion.

    0
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  • They Also Indicate That It Is Much Larger, And Increases Considerably With Rise Of Temperature, In The Case Of More Condensible Vapours, Such As C1 2J Br 2, Or More Complicated Molecules, Such As Co 2, N 2 0, Nh 3, C 2 H 4.

    0
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  • According To The Elementary Kinetic Theory Of An Ideal Gas, The Molecules Of Which Are So Small And So Far Apart That Their Mutual Actions May Be Neglected, The Kinetic Energy Of Translation Of The Molecules Is Proportional To The Absolute Temperature, And Is Equal To 3/2 Of Pv, The Product Of The Pressure And The Volume, Per Unit Mass.

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  • If The Molecules Are Supposed To Be Like Smooth, Hard, Elastic Spheres, Incapable Of Receiving Any Other Kind Of Energy Except That Of Translation, The Specific Heat At Constant Volume Would Be The Increase Per Degree Of The Kinetic Energy Namely 3Pv/20=3R/2, That At Constant Pressure Would Be 5R/2, And The Ratio Of The Specific Heats Would Be 5/3 Or 1.666.

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  • Boltzmann Suggested That A Diatomic Molecule Regarded As A Rigid Dumb Bell Or Figure Of Rotation, Might Have Only Five Effective Degrees Of Freedom, Since The Energy Of Rotation About The Axis Of Symmetry Could Not Be Altered By Collisions Between The Molecules.

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  • Since Much Smaller Values Are Found For More Complex Molecules, We May Suppose That, In These Cases, The Energy Of Rotation Of A Polyatomic Molecule May Be Greater Than Its Energy Of Translation, Or Else That Heat Is Expended In Splitting Up Molecular Aggregates, And Increasing Energy Of Vibration.

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  • For More Complex Molecules The Radiative And Absorptive Powers Are Known To Be Much Greater.

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  • When heated to 100° C. it loses four molecules of ammonia.

    0
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  • Two hydrated forms have been described, one containing three molecules of water and the other half a molecule.

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  • It forms hydrates containing one, two, five, six and seven molecules of water.

    0
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  • It loses four molecules of water of crystallization when heated to 100° C. and becomes anhydrous at about 300° C. The hexahydrate is dimorphous, a tetragonal form being obtained by crystallization of a solution of the heptahydrate between 20° and 30° C., and a monoclinic form between 50° and 70° C. Nickel sulphate combines with many metallic sulphates to form double salts, and also forms addition compounds with ammonia aniline and hydroxylamine.

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  • For example, from the evidence of molar changes due to the obvious parts of bodies, science first comes to believe in molecular changes due to imperceptible particles, and then tries to conceive the ideas of particles, molecules, atoms, electrons.

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  • Raoult (Comptes Rendus, 1886-87) employed other solvents besides water, and showed that the relative lowering for different solvents and different dissolved substances was the same in many cases for solutions in which the ratio of the number of gramme-molecules n of the dissolved substance to the number of molecules N of the solvent was the same, or that it varied generally in proportion to the ratio n/N.

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  • The most important apparent exceptions to Raoult's law in dilute solutions are the cases, (I) in which the molecules of the dissolved substance in solution are associated to form compound molecules, or dissociated to form other combinations with the solvent, in such a way that the actual number of molecules n in the solution differs from that calculated from the molecular weight corresponding to the accepted formula of the dissolved substance; (2) the case in which the molecules of the vapour of the solvent are associated in pairs or otherwise so that the molecular weight m of the vapour is not that corresponding to its accepted formula.

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  • p. 631) showed how to calculate the effective number of molecules n" = (1 +ek/ko)n,from the molecular conductivity k of the solution and its value ko at infinite dilution, for an electrolyte giving rise to e +I ions.

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  • Thus for calcium chloride the depression of the freezing-point, when n =7, N= l oo, is nearly 60° C. At this point n" = Jo nearly, and the depression should be only 10 4° C. These and similar discrepancies have been very generally attributed to a loose and variable association of the molecules of the dissolved substance with molecules of the solvent, which, according to H.

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  • 1905, 33, p. 584), may vary all the way from a few molecules of water up to at least 30 molecules in the case of CaC1 2, or from 12 to 140 for glycerin.

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  • It is assumed that each molecule of solute combines with a molecules of solvent according to the ordinary law of chemical combination, and that the number a, representing the degree of hydration, remains constant within wide limits of temperature and concentration.

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  • In this case the ratio of the vapour-pressure of the solution p" to that of the solvent p' should be equal to the ratio of the number of free molecules of solvent N - an to the whole number of molecules N - an+n in the solution.

    0
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  • The explanation of this relation is that each of the n compound molecules counts as a single molecule, and that, if all the molecules were solvent molecules, the vapour-pressure would be p', that of the pure solvent.

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  • It appears that the relatively enormous deviations of CaC1 2 from Raoult's law are accounted for on the hypothesis that a=9, but there is a slight uncertainty about the degree of ionization of the strongest solutions at-50° C. Cane-sugar appears to require 5 molecules of water of hydration both at o° C. and at loo° C., whereas KC1 and NaCI take more water at loo° C. than at o° C. The cases considered by Callendar (loc. cit.) are necessarily limited, because the requisite data for strong solutions are comparatively scarce.

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  • Van't Hoff showed that the osmotic pressure P due to a number of dissolved molecules n in a volume V was the same as would be exerted by the same number of gas-molecules at the same temperature in the same volume, or that PV = ROn.

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  • The highest pressures recorded for cane-sugar are nearly three times as great as those given by van't Hoff's formula for the gas-pressure, but agree very well with the vapour-pressure theory, as modified by Callendar, provided that we substitute for V in Arrhenius's formula the actual specific volume of the solvent in the solution, and if we also assume that each molecule of sugar in solution combines with 5 molecules of water, as required by the observations on the depression of the freezing-point and the rise of the boiling-point.

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  • Employing this type of equation, all the thermodynamical properties of the substance may conveniently be expressed in terms of the diminution of volume c due to the formation of compound or coaggregated molecules, (v - b) =RO/p - co(Oo/O) n =V - c. .

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  • The approximate equation of Rankine (23) begins to be I or 2% in error at the boiling-point under atmospheric pressure, owing to the coaggregation of the molecules of the vapour and the variation of the specific heat of the liquid.

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  • It is equivalent, as Callendar (loc. cit.) points out, to supposing that the variation of the specific heat is due to the formation and solution of a mass w/(v-w) of vapour molecules per unit mass of the liquid.

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  • The salt forms large monoclinic prisms; molecules containing 25 and 21 H 2 O separate from solutions crystallized at higher temperatures.

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  • van Deventer, ibid., 1906, 3, p. 515.) It crystallizes with five molecules of water as large blue triclinic prisms. When heated to Poo°, it loses four molecules of water and forms the bluish-white monohydrate, which, on further heating to 250°-260°, is converted into the white CuSO 4.

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  • It forms dark blue prismatic crystals containing 3, 4, or 6 molecules of water according to the temperature of crystallization.

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  • pp. 268 et seq.); and conversely on boiling with dilute acids or alkalis it takes up a molecule of water and yields two molecules of gallic acid, C 7 H 6 0 5.

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  • In 1855, reviewing the various substances that had been obtained from glycerin, he reached the conclusion that glycerin is a body of alcoholic nature formed on the type of three molecules of water, as common alcohol is on that of one, and was thus led (1856) to the discovery of the glycols or diatomic alcohols, bodies similarly related to the double water type.

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  • A saturated solution of the hydroxide deposits on cooling a hydrated form Ba(OH) 2.8H 2 0, as colourless quadratic prisms, which on exposure to air lose seven molecules of water of crystallization.

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  • Borax crystallizes with ten molecules of water, the composition of the crystals being Na2B407+10H20.

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  • Various attempts have also been made to deduce these laws from particular hypotheses as to the action between the molecules of the elastic substance.

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  • The second part endeavours to deduce the facts of the elasticity of a finite portion of the substance from hypotheses as to the motion of its constituent molecules and the forces acting between them.

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  • Laplace assumed that the liquid has uniform density, and that the attraction of its molecules extends to a finite though insensible distance.

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  • The pressure at any point of the liquid arises from two causes, the external pressure P to which the liquid is subjected, and the pressure arising from the mutual attraction of its molecules.

    0
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  • If we suppose that the number of molecules within the range of the attraction of a given molecule is very large, the part of the pressure arising from attraction will be proportional to the square of the number of molecules in unit of volume, that is, to the square of the density.

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  • Lord Rayleigh has shown that the fall of surface-tension begins when the quantity of oil is about the half of that required to stop the camphor movements, and he suggests that this stage may correspond with a complete coating of the surface with a single layer of molecules.] On the Forms of Liquid Films which are Figures of Revolution.

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  • Soc., 18 93, p. 1 54) has suggested yet another source of energy, in the bombardment of these minute masses by the molecules of the environment, the velocity of which is sufficient to drive them well into the organism, and carry energy in of which they can avail themselves.

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  • It consists in all probability of disturbance, by means of the chemical affinities of the toxin, of the highly complicated molecules of living cells.

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  • In fact, organic molecules can be divided into two classes according as they give rise to anti-substances or fail to do so.

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  • The molecules which lead to the production of anti-substances are usually known as antigens, and each antigen has a specific combining affinity for its corresponding anti-substance, fitting it as a lock does a key.

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  • Kanthack and Cobbett, that in certain instances the toxin can be made to pass through a gelatine membrane, whereas the antitoxin cannot, its molecules being of larger size.

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  • This result, which is usually known now as the " Ehrlich phenomenon," was explained by him on the supposition that the " toxin " does not represent molecules which are all the same, but contains molecules of different degrees of combining affinity and of toxic action.

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  • Accordingly, the most actively toxic molecules will be neutralized first, and those which are left over, that is, uncombined with antitoxin, will have a weaker toxic action.

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  • We are probably safe in saying, however, that the molecules of a toxin are not identical but vary in the degree of their combining affinities, and also in their toxic action, and that, while in some cases the combination of anti-substances has been shown to be reversible, we are far from being able to say that this is a general law.

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  • The' side-chains constitute the means by which other molecules are added to the living molecule, e.g.

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  • It is by means of such side-chains that toxin molecules are attached to the protoplasm, so that the living molecules are brought under the action of the toxophorous groups of the toxins.

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  • Ultimately the regeneration becomes an over-regeneration and free side-chains produced in excess are set free and appear in the blood as antitoxin molecules.

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  • In other words the substances, which when forming part of the cells fix the toxin to the cells, constitute antitoxin molecules when free in the serum.

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  • Wassermann and Takaki in the case of tetanus, that there do exist in the nervous system molecules with combining affinity for the tetanus toxin.

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  • Further, these molecules in the nervous system present the same susceptibility to heat and other physical agencies as does tetanus antitoxin.

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  • There is therefore strong evidence that antitoxin molecules do exist as part of the living substance of nerve cells.

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  • The explanation is thus carried back to the complicated constitution of biogen molecules in various living cells of the body.

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  • We are, accordingly, justified in definitely concluding that their appearance in large amount in the blood, as the result of active immunization, represents an increased production of molecules which are already present in the body, either in a free condition in its fluids or as constituent elements of its cells.

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  • The phenomenon of agglutination depends essentially on the union of molecules in the bacteria - the agglutinogens - with the corresponding agglutinins, but another essential is the presence of a certain amount of salts in the fluid, as it can be shown that when agglutinated masses of bacteria are washed salt-free the clumps become resolved.

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  • Natural immunity against toxins must be taken into account, and, if Ehrlich's view with regard to toxic action be correct, this may depend upon either the absence of chemical affinity of the living molecules of the tissues for the toxic molecule, or upon insensitiveness to the action of the toxophorous group. It has been shown with regard to the former, for example, that the nervous system of the fowl, which possesses immunity against tetanus toxin, has little combining affinity for it.

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  • Pure Oxalic Acid May Also Be Used, Which, In The Presence Of Sulphuric Acid, Is Oxidized By The Standard Solution According To The Reaction: 5(H2C2042H20) 3H 2 So 4 2Kmn04 =10002 2Mns04 K2S04 18H20 The Reaction In Case Of Ferrous Sulphate Is: 10Fes04 2Kmn04 8H2S04 = 5Fe2(S04)3 K2S04 2Mns04 8H20; That Is, The Same Amount Of Potassium Permanganate Is Required To Oxidize 5 Molecules Of Oxalic Acid That Is Necessary To Oxidize I O Molecules Of Iron In The Form Of Ferrous Sulphate To Ferric Sulphate, Or 63 Parts By Weight Of Oxalic Acid Equal 56 Parts By Weight Of Metallic Iron.

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  • Hantzsch (Ann., 1882, 215, p. I; Ber., 1882, 15, p. 2914) which consists in the condensation of two molecules of aceto-acetic ester with one of an aldehyde and one of ammonia: RO 2 C CH 2 R' CHO CH 2 CO 2 R RO 2 C C CHR' C C02R CH 3 CO + NH 3 + CO CH 3 -' CH3 C-NH-C CH3 The resulting dihydro-compound is then oxidized with nitrous acid, the ester hydrolysed and the resulting acid heated with lime; carbon dioxide is eliminated and a trisubstituted pyridine of the type CH C(CH3) is obtained.

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  • It can be prepared from dibrom-menthone (obtained by brominating menthone in chloroform solution) by eliminating two molecules of hydrobromic acid.

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  • It boils at 290°, forming a colourless vapour which just about the boiling-point corresponds in density to tetratomic molecules, P4; at 1500° to 1700°, however, Biltz and Meyer detected dissociation into P2 molecules.

    0
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  • Beckmann obtained P4 molecules from the boiling-point of carbon bisulphide solutions, and Hertz arrived at the same conclusion from the lowering of the freezing-point in benzene solution; E.

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  • It is in fact an impossibility that loss should go on without regeneration, for if any part of the sun's body loses heat, it will be unable to support the pressure of neighbouring parts upon it; it will therefore be compressed, in a general sense towards the sun's centre, the velocities of its molecules will rise, and its temperature will again tend upwards.

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  • Larmor suggests is due to relaxation of the spring of the surrounding ether by reason of the crowding of the molecules; a shift of 0.17 tenth-metres would, if interpreted by Doppler's principle, have been read as a receding velocity of I I km.

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  • It crystallizes in needles, which contain two molecules of water of crystallization, and melt at 156° C. When heated above the melting-point it loses carbon dioxide and yields quinoline.

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  • C ALLOXANTIN $ H 4 N 4 0 7.3H 2 0, a product obtained by the combination of alloxan and dialuric acid, probably possessing the constitution NH - CO CO - NH O - O - H NH - C CO - NH one of the three molecules of water being possibly constitutional.

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  • The term "perfect gas" is applied to an imaginary substance in which there is no frictional retardation of molecular motion; or, in other words, the time during which any molecule is influenced by other molecules is infinitesimally small compared with the time during which it traverses its mean free path.

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  • By gently heating in a vacuum to 140°, the hepta-hydrate loses 6 molecules of water, and yields a white powder, which on heating in the absence of air gives the anhydrous salt.

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  • Ferrous chloride dissolved in strong hydrochloric acid absorbs two molecules of the gas (Kohlschiitter and Kutscheroff, Ber., 1907, 40, p. 873).

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  • In crystals the rotary property appears to be sometimes inherent in the crystalline arrangement of the molecules, as it is lost on fusion or solution, and in several cases belongs to enantiomorphous crystals, the two correlated forms of which are the one right-handed and the other left-handed optically as well as crystallographically, this being necessarily the case if the property be retained when the crystal is fused or dissolved.

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  • Substances that by reason of the structure or arrangement of their molecules rotate the plane of polarization are said to be structurally active, and the rotation produced by unit length is called their rotary power.

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  • It is impossible within brief limits to convey more than a general idea of the work of a philosopher who published more than three hundred original papers bearing upon nearly every branch of physical science; who one day was working out the mathematics of a vortex theory of matter on hydrodynamical principles or discovering the limitations of the capabilities of the vortex atom, on another was applying the theory of elasticity to tides in the solid earth, or was calculating the size of water molecules, and later was designing an electricity meter, a dynamo or a domestic water-tap. It is only by reference to his published papers that any approximate conception can be formed of his life's work; but the student who had read all these knew comparatively little of Lord Kelvin if he had not talked with him face to face.

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  • esters formed by the union of three molecules of fatty acids with one molecule of the trihydric alcohol glycerin, whereas the waxes consist of esters formed by the union of one molecule of fatty acid with one molecule of a monohydric alcohol, such as cetyl alcohol, cholesterol, &c. Only in the case of the wax coccerin two molecules of fatty acids are combined with one molecule of a dihydric (bivalent) alcohol.

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  • He proceeded to take off on an explanatory lecture that mentioned anandamides as brain messenger molecules and details about brain chemistry.

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  • The world's smallest abacus now uses individual molecules (13 November 1996 ).

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  • Lectures will include examples of signaling molecules that mediate growth and differentiation of cells and describe how these become aberrant in disease.

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  • absorbed by other gas molecules.

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  • addition of hydrogen to unsaturated molecules reduces the number of double bonds; the triglycerides become more saturated.

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  • Her team recently announced it had created the highest density electronically addressable memory reported to date, a 64-bit memory using molecules as switches.

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  • ATP adenosine Triphosphate - a compound consisting of the nucleotide adenosine attached through its ribose group to three phosphoric acid molecules.

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  • adhesion molecules are shown.

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  • The dissociated molecules can undergo thermal reactions with neighboring surface atoms or with other adsorbates.

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  • The binding energy of a second layer of adsorbate molecules is similar to the latent heat of sublimation or vaporization of the adsorbate molecules is similar to the latent heat of sublimation or vaporization of the adsorbate.

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  • adsorption of molecules from solution.

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  • More generally, over 100 molecules are in development as apoptosis agonists, although approaching 70% of these remain in preclinical development.

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  • For simple organic molecules, including alkanes, alkenes and cycloalkanes, construct appropriate isomeric forms, given a molecular formula 11.

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  • alkane molecules usually produces a mixture of smaller molecules some of them alkenes.

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  • H that hydrocarbon molecules can be cracked to form smaller molecules including alkenes.

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  • alkene monomer molecules leads to a variety of different polymers with differing properties.

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  • Know that the cracking of hydrocarbon molecules yields alkenes.

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  • amylose molecules.

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  • Acid dye These molecules are generally sodium salts which dissociate to form the acid dye anion.

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  • atoms in the original molecules are found in the bigger one.

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  • Another 21% of the air is oxygen, with the molecules having an atomic weight of 32.

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  • bicarbonate ions immediately latch onto a section of the crocodiles ' hemoglobin molecules, forcing the hemoglobin to release its attached oxygen.

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  • binding of ligands to several Src family SH2 domains is mediated by a network of water molecules.

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  • bioactive molecules in a single step.

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  • We are developing a new method of screening potentially bioactive molecules which uses a combination of enzymes to select active structures.

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  • To complement genetic approaches we are establishing a confocal based screen for small molecules that interfere with peroxisome biogenesis.

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  • These molecules may be of different chain lengths, and may also have double bonds in some places.

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  • Researchers chemically modified adrenaline to find molecules that would have the same effect in dilating the bronchioles but without the stimulation of the heart.

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  • There, the chlorine released by CFCs destroys the ozone at the rate of 100,000 molecules of ozone per chlorine released by CFCs destroys the ozone at the rate of 100,000 molecules of ozone per chlorine atom.

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  • When a solution of the sample molecule is mixed with a metal colloid the molecules are absorbed onto the surface of the colloids.

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  • condenseis also a small amount of water vapor that respires from plants and evaporates to join other water molecules in condensing into clouds.

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  • Molecules are able to activate chloride conductance in airway cell line, primary human cell cultures and most importantly from cells with CFTR mutations.

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  • conformation of extracellular matrix molecules in aqueous solution.

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  • The two molecules are virtually identical in their molecular conformation.

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  • coulomb explosion in molecules.

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  • A large unknown area in pectin chemistry concerns the possible presence in vivo of covalent cross-links between pectic molecules.

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  • cross-links between pectic molecules.

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  • The lack of branching allows molecules to lie close together in a regular way which is almost crystalline.

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  • Here is the spectrum of cytochrome c. The absorption pattern for all three cytochrome c. The absorption pattern for all three cytochromes changes markedly when these molecules are oxidized and reduced.

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  • As mentioned above interferon gamma or molecules able to mimic or induce this cytokine may be of use in the treatment of sepsis.

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  • delaminate direct sunlight will attack the foam's molecules, weakening it, even delaminating in extreme cases.

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  • delaminate direct sunlight will attack the foam's molecules, weakening it, even delaminating in extreme cases.

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  • deoxyribose molecules.

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  • malt dextrin contains between 9 and 11 molecules of glucose in a long chain.

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  • Briefly, target molecules will be used on bone marrow stem cells in tissue culture to induce specific appropriate differentiation.

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  • For small molecules, it is possible to analyze X-ray diffraction data by means of the direct methods.

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  • diffusion of guest molecules to the host surface is insignificant with respect to the reaction rate.

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  • Each of the hydrogen atoms in each of the molecules of water in your brain is a tiny magnetic dipole.

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  • particle Size Characterization Dynamic Light Scattering (DLS) is a non-invasive method for measuring the size of molecules and particle dispersions.

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  • dissociate the molecules.

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  • dissociation of DNA molecules which in turn can lead to gene mutations.

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  • dissociation dynamics of these molecules.

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  • These molecules may be of different chain lengths, and may also have double bonds in some places.

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  • DNA molecules have two distinct strands which are held together by weak hydrogen bonds to form a double helix.

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  • Some of these molecules are remarkably durable, surviving as evidence of living tissue that has otherwise completely dispersed.

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  • The molecules which bind to these sites are called effectors.

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  • effector molecules may act by having an opposite effect.

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  • electrolytic dissociation of water molecules to hydrogen and oxygen with membrane separation.

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  • A powerful electromagnet causes the nuclei of atoms (particularly hydrogen in water molecules) to align magnetically.

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  • electrophilic addition reactions An addition reaction is a reaction in which two molecules join together to make a bigger one.

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  • A model for the separation of large DNA molecules by crossed field gel electrophoresis.

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  • Many molecules that are capable of blocking neurite elongation in vitro are present in CNS tissue.

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  • This approach has worked very well for other types of molecules studied in frog embryos.

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  • endothelium from different tissues express different patterns of adhesion molecules?

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  • energetic photons would dissociate the molecules.

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  • Also... bond enthalpy values apply to molecules in the gaseous state.

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  • Some functionally equivalent molecules can have between 30 - 50% of their amino acids different.

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  • It would also be necessary to use labeled erythrocytes again to determine if isolated molecules are B.bovis derived.

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  • When sunlight strikes methane molecules they react to form ethane molecules they react to form ethane.

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  • A prime example is provided by sugars, which can be represented as straight-chain molecules or as cyclic ethers.

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  • excitation of molecules during the reactions.

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  • This approach has, however, remained experimental, and indeed most molecules in development remain in preclinical phases.

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  • Outside the cell, collagen molecules become aligned in parallel formations, and then they link up laterally to form fibrils.

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  • The distended capillaries allow large molecules e.g. fibrinogen, red blood cells, to escape into the interstitial spaces.

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  • A myosin filament contains several hundred myosin molecules in two bundles packed end to end.

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  • New methods of introducing fluorine We continue to seek new methods of introducing fluorine to molecules.

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  • Maybe eventually, we'll also find a way to use the antifreeze molecules to prevent frostbite in humans.

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  • fullerene molecules, was able to insert one or more yttrium atoms.

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  • Glassy polymers In a glassy polymers In a glassy polymer, all the molecules are fixed firmly in position.

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  • gradient across the membrane to generate energy rich ATP molecules.

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  • The dust grains may provide the shelter for molecules to form.

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  • gramicidin molecules join end to end to span the membrane.

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  • This is the way graphene molecules were " extracted " from bulk graphite.

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  • A cholesteric (or twisted nematic) liquid crystal is chiral: the molecules have left or right handedness.

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  • DNA molecules have two distinct strands which are held together by weak hydrogen bonds to form a double helix.

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  • helix effect of the bound l-tryptophan molecules is to orient the recognition helices correctly for DNA binding.

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  • hemoglobin molecules 200 to 300 times more readily than does oxygen.

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  • heterogeneous in nature with differences occurring in their affinity and capacity for binding insulin molecules.

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  • heterogenous water molecules in the current database.

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  • histocompatibility molecules.

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  • If the surface is too sticky the component building block molecules won't circulate and find their complementary bonding partners to make the honeycomb.

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  • hydrocarbon molecules in crude oil vary in size.

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  • hydrogen bonds to water molecules (ie isolated oxygen atoms) are found, and also hydrogen bonds between water molecules.

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  • Infrared spectra show the presence of different types of water molecules and/or hydroxyl ions.

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  • In order to see some of these more clearly, 64 of the 280 water molecules have been removed from the water icosahedron.

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  • immunoglobulin molecules will be stressed.

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  • indole ring in both molecules.

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  • interacting molecules.

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  • Cell adherens junctions are points of cell-cell contact, mediated by the extracellular interactions of cadherin molecules.

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  • interpenetrateo separate interpenetrating networks, linked through the four equatorial water molecules in the hexamers.

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  • To the contrary, paraffin molecules are not polar, this is the reason why paraffin cannot respond to the microwave irradiation.

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  • isolation of conventional antibodies through to the identification of wholly new molecules or novel applications.

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  • Cell adherens junctions are points of cell-cell contact, mediated by the extracellular interactions of cadherin molecules.

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  • A high temperature from a match or spark etc., gives the reactant molecules enough kinetic energy to overcome the activation energy * .

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  • lanthanide hairpin molecules are designed for DNA intercalation.

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  • Cholesterol travels through the blood in minute packages mixed with large molecules called lipoproteins.

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  • Monday's session focused on describing the roles of signaling molecules at the synapse in regulating worm locomotion.

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  • The relation between bulk properties and the properties of individual atoms and molecules, including macromolecules.

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  • manipulation of biological molecules and organisms.

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  • mediated by the extracellular interactions of cadherin molecules.

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  • Do n't memorize the molecules, study the patterns.

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  • messenger molecules, with their synthesis or physiological activity or destruction.

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  • After all, even a cubic micron of water contains about thirty billion molecules.

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