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vapour

vapour

vapour Sentence Examples

  • It is very volatile, the vapour being heavy and very inflammable.

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  • The freezing points and vapour pressures of solutions of sugar are also in conformity with the theoretical numbers.

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  • Either they are placed in a leaden cupboard into which the vapour is introduced, or they are dipped for a few seconds in a mixture of one part of chloride of sulphur and forty parts of carbon disulphide or purified light petroleum.

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  • The platinum is maintained at a bright red heat, either by a gas flame or by an electric furnace, and the vapour is passed over it by leading in a current of oxygen.

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  • The platinum is maintained at a bright red heat, either by a gas flame or by an electric furnace, and the vapour is passed over it by leading in a current of oxygen.

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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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  • Schwanert, Ann., 1860, 116, p. 2 57); by passing the vapour of dietbylamine through a redhot tube; by distilling succinimide with zinc dust (C. A.

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  • Thermodynamic theory also indicates a connexion between the osmotic pressure of a solution and the depression of its freezing point and its vapour pressure compared with those of the pure solvent.

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  • Its vapour possesses a characteristic smell, somewhat resembling that of ozone.

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  • It possesses an extremely pungent smell, and its vapour is extremely irritating to the eyes.

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  • It possesses an extremely pungent smell, and its vapour is extremely irritating to the eyes.

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  • Cadmium vapour decomposes water at a red heat, with liberation of hydrogen, and formation of the oxide of the metal.

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  • The entry of gases into, and exit from, the cells, as well as the actual exhalation of watery vapour from the latter, take place in the intercellular space system of which the stomata are the outlets.

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  • The mercury vapour then possesses a unilateral conductivity, and can be used to filter off all those oscillations in a train which pass in one direction and make them readable on an ordinary galvanometer.

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  • A theory that has received much support in the past attributes the reflections to thin bubbles of water, similar to soap-bubbles, in which form vapour was supposed to condense.

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  • In order to make spongy or porous rubber, some material is incorporated which will give off gas or vapour at the vulcanizing temperature, - such as carbonate of ammonia, crystallized alum, and finely ground damp sawdust.

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  • In order to make spongy or porous rubber, some material is incorporated which will give off gas or vapour at the vulcanizing temperature, - such as carbonate of ammonia, crystallized alum, and finely ground damp sawdust.

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  • 2, A), which has distinct upper and lower faces, are placed mainly or exclusively on the lower side of the leaf, where the water vapour that escapes from them, being lighter than air, cannot pass away from the surface 01 the leaf, but remains in contact with it and thus tends to check further transpiration.

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  • A battery with a sufficient number of cells is connected to these two electrodes so as to pass a current through the mercury vapour, negative electricity proceeding from the mercury cathode to the iron anode.

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  • The next following instalments of vapour, getting diffused throughout a large mass of relatively cold gas, condense into a kind of "snow," known in commerce and valued as "flowers of sulphur" (fibres sulphuris).

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  • In this patent, the distillation is described as being conducted in a vessel having a loaded valve or a partially closed stop-cock, through which the confined vapour escapes under any desired pressure.

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  • Carbon monosulphide, CS, is formed when a silent electric discharge is passed through a mixture of carbon bisulphide vapour and hydrogen or carbon monoxide (S.

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  • This arrangement is a method of checking transpiration by creating a still atmosphere above the pore of the stoma, so that water vapour collects in it and diminishes the further outflow of vapour.

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  • The chamber has a safety value at the top of its vault, which is so balanced that the least surplus pressure from within sends it up. The first puff of sulphur vapour which enters the chamber takes fire and converts the air of the chamber into a mixture of nitrogen and sulphur dioxide.

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  • Biltz (Ber., 1888, 21, p. 2013; 1901, 34, p. 2490) showed that the vapour density decreased with the temperature, and also depended on the pressure.

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  • Such a reduction of temperature is brought about along the greater part of the coasts of India and of the BurmoSiamese peninsula by the interruption of the wind current by continuous ranges of mountains, which force the mass of air to rise over them, whereby the air being rarefied, its specific capacity for heat is increased and its temperature falls, with a corresponding condensation of the vapour originally held in suspension.

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  • Potassium, when heated, burns in the vapour of carbon bisulphide, forming potassium sulphide and liberating carbon.

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  • This arrangement is a method of checking transpiration by creating a still atmosphere above the pore of the stoma, so that water vapour collects in it and diminishes the further outflow of vapour.

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  • Potassium, when heated, burns in the vapour of carbon bisulphide, forming potassium sulphide and liberating carbon.

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  • With Sydney Young and others he investigated the critical state and properties of liquids and the relationship between their vapour pressures and temperature, and with John Shields he applied measurements of the surface tension of liquids to the determination of their molecular complexity.

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  • But these protective layers are in the main impermeable by gases and by either liquid or vapour, and prevent the access of either to the protoplasts which need them.

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  • Again, when tungsten hexachloride is converted into vapour it is decomposed into chlorine and a pentachloride, having a normal vapour density, but as in the majority of its compounds tungsten acts as a hexad, we apparently must regard its pentachloride as a compound in which an odd number of free affinities are disengaged.

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  • If the gas be mixed with the vapour of carbon disulphide, the mixture burns with a vivid lavender-coloured flame Nitric oxide is soluble in solutions of ferrous salts, a dark brown solution being formed, which is readily decomposed by heat, with evolution of nitric oxide.

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  • It gives rise to various decomposition products such as pyridine, picoline, &c., when its vapour is passed through a red-hot tube.

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  • A mixture of carbon bisulphide vapour and sulphuretted hydrogen, when passed over heated copper, gives, amongst other products, some methane.

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  • The fouling of the air that results from the steam-engine, owing to the production of carbonic acid gas and of sulphurous fumes and aqueous vapour, is well known, and its use is now practically abandoned for underground working.

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  • steam, vapour, smoke, cf.

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  • The free acid, which is obtained by treating the salts with acids, is an oily liquid smelling like prussic acid; it is very explosive, and the vapour is poisonous to about the same degree as that of prussic acid.

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  • For Heraclitus the soul approaches most nearly to perfection when it is most akin to the fiery vapour out of which it was originally created, and as this is most so in death, "while we live our souls are dead in us, but when we die our souls are restored to life."

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  • We can calculate the heat of formation from its ions for any substance dissolved in a given liquid, from a knowledge of the temperature coefficient of ionization, by means of an application of the well-known thermodynamical process, which also gives the latent heat of evaporation of a liquid when the temperature coefficient of its vapour pressure is known.

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  • In contact with a solvent a metal is supposed to possess a definite solution pressure, analogous to the vapour pressure of a liquid.

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  • We can calculate the heat of formation from its ions for any substance dissolved in a given liquid, from a knowledge of the temperature coefficient of ionization, by means of an application of the well-known thermodynamical process, which also gives the latent heat of evaporation of a liquid when the temperature coefficient of its vapour pressure is known.

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  • There is also a natural vapour bath (80°-95° F.) in the Grotta Giusti (so-called from the satirist Giuseppe Giusti, a native of the place), at Monsummano near by, discovered in 1849.

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  • An objectionable feature of the system of allowing the vapour to escape from the still to the condenser through a loaded valve, viz: the irregularity of the distillation, is thus removed, and the benefits of regular vaporization and condensation under high pressure are obtained.

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  • It may be more conveniently prepared by passing the vapour of sulphur over red hot charcoal, the unccndensed gases so produced being led into a tower containing plates over which a vegetable oil is allowed to flow in order to absorb any carbon bisulphide vapour, and then into a second tower containing lime, which absorbs any sulphuretted hydrogen.

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  • The binary conception of compounds held by Berzelius received apparent support from the observations of Gay Lussac, in 1815, on the vapour densities of alcohol and ether, which pointed to the conclusion that these substances consisted of one molecule of water and one and two of ethylene respectively; and from Pierre Jean Robiquet and Jean Jacques Colin, showing, in 1816, that ethyl chloride (hydrochloric ether) could be regarded as a compound of ethylene and hydrochloric acid.

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  • At the critical point liquid and vapour become identical, and, consequently, as was pointed out by Frankenheim in 1841, the surface tension is zero at the critical temperature.

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  • We may evaporate some of the solvent from the solution which has become weaker and thus reconcentrate it, condensing the vapour on the solution which had become stronger.

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  • The amount of watery vapour in the air passing through a stoma has no effect upon it, as the surfaces of the guard cells abutting on the air chamber are strongly cuticularized, and therefore impermeable.

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  • It seemed to Herschel that he was thus able to view the actual changes by which masses of phosphorescent or glowing vapour became actually condensed down into stars.

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  • The heated body of air carried from the Indian Ocean over southern Asia by the south-west monsoon comes up highly charged with watery vapour, and hence in a condition to release a large body of water as rain upon the land, whenever it is brought into circumstances which reduce its temperature in a notable degree.

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  • A sublimate may be formed of: sulphur - reddish-brown drops, cooling to a yellow to brown solid, from sulphides or mixtures; iodine - violet vapour, black sublimate, from iodides, iodic acid, or mixtures; mercury and its compounds - metallic mercury forms minute globules, mercuric sulphide is black and becomes red on rubbing, mercuric chloride fuses before subliming, mercurous chloride does not fuse, mercuric iodide gives a yellow sublimate; arsenic and its compounds - metallic arsenic gives a grey mirror, arsenious oxide forms white shining crystals, arsenic sulphides give reddish-yellow sublimates which turn yellow on cooling; antimony oxide fuses and gives a yellow acicular sublimate; lead chloride forms a white sublimate after long and intense heating.

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  • A mixture of carbon bisulphide vapour and nitric oxide burns with a very intense blue-coloured flame, which is very rich in the violet or actinic rays.

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  • The whole is enclosed in a jacket connected with a boiler containing a liquid, the vapour of which serves to keep the inner tube at any desired temperature.

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  • If the plants are subjected to some process, before mounting, by which injurious organisms are destroyed, such as exposure in a closed chamber to vapour of carbon bisulphide for some hours, the presence of pieces of camphor or naphthalene in the cabinet will be found a sufficient preservative.

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  • If the plants are subjected to some process, before mounting, by which injurious organisms are destroyed, such as exposure in a closed chamber to vapour of carbon bisulphide for some hours, the presence of pieces of camphor or naphthalene in the cabinet will be found a sufficient preservative.

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  • By passing the vapour of this compound through a red-hot tube, it yields the isomeric a0- pyridylpyrrol, the potassium salt of which with methyl iodide gives a substance methylated both in the pyridine and pyrrol nuclei.

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  • The cadmium molecule, as shown by determinations of the density of its vapour, is monatomic. The metal unites with the majority of the heavy metals to form alloys; some of these, the so-called fusible alloys, find a useful application from the fact that they possess a low melting-point.

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  • News, 1891, 63, p. 1); just above the boiling point the vapour is orange-yellow, but on continued heating it darkens, being deep red at 50o; at higher temperatures it lightens, becoming straw-yellow at 650°.

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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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  • By passing the vapour of this compound through a red-hot tube, it yields the isomeric a0- pyridylpyrrol, the potassium salt of which with methyl iodide gives a substance methylated both in the pyridine and pyrrol nuclei.

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  • Iridium sulphide, IrS, is obtained when the metal is ignited in sulphur vapour.

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  • Boron sulphide B 2 S 3 can be obtained by the direct union of the two elements at a white heat or from the tri-iodide and sulphur at 44 0 ° C., but is most conveniently prepared by heating a mixture of the trioxide and carbon in a stream of carbon bisulphide vapour.

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  • Another form of receiver can be made depending on the properties of mercury vapour.

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  • Carnelley), forming a deep yellow vapour.

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  • They are widely distributed, but are particularly abundant in certain tropical climates where active root absorption goes on while the air is nearly saturated with water vapour.

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  • It is marked by the constant and continuous absorption of a certain quantity of oxygen and bythe exhalation of a certain volume of carbon dioxide and water vapour.

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  • vapour of the atmosphere is caused in part by vertical movements of the atmosphere involving heat changes and apparently independent of the surface upon which precipitation occurs; but in greater part it is dictated by the form and altitude of the land surface and the direction of the prevailing winds, which itself is largely influenced by the land.

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  • In the winter similar consequences ensue, in a negative direction, from the prolonged loss of heat by radiation in the long and clear nights - an effect which is intensified wherever the surface is covered with snow, or the air little charged with vapour.

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  • The oxychloride, bromides, and other compounds were subsequently discovered; here we need only notice Moissan's preparation of the trifluoride and Thorpe's discovery of the pentafluoride, a compound of especial note, for it volatilizes unchanged, giving a vapour of normal density and so demonstrating the stability of a pentavalent phosphorus compound (the pentachloride and pentabromide dissociate into a molecule of the halogen element and phosphorus trichoride).

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  • From B the curve of equilibrium (BD) between rhombic and liquid sulphur proceeds; and from C (along CE) the curve of equilibrium between liquid sulphur and sulphur vapour.

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  • Among other subjects at which he subsequently worked were the absorption of gases in blood (1837-1845), the expansion of gases by heat (1841-1844), the vapour pressures of water and various solutions (1844-1854), thermo-electricity (1851), electrolysis (1856), induction of currents (1858-1861), conduction of heat in gases (1860), and polarization of heat (1866-1868).

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  • These are knocked off, ground up with water, freed from metal-particles by elutriation, and the paste of white lead is allowed to set and dry in small conical forms. The German method differs from the Dutch inasmuch as the lead is suspended in a large chamber heated by ordinary means, and there exposed to the simultaneous action of vapour of aqueous acetic acid and of carbon dioxide.

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  • It may be artificially prepared by leading sulphur vapour over lead, by fusing litharge with sulphur, or, as a black precipitate, by passing sulphuretted hydrogen into a solution of a lead salt.

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  • By passing acrolein vapour into ammonia, acrolein ammonia, C 6 H 9 NO, is obtained.

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  • 1825) he devised a method for determining vapour densities at temperatures up to 1400° C., and, partly with F.

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  • Columbium trichloride, CbC1 3, is obtained in needles or crystalline crusts, when the vapour of the pentachloride is slowly passed through a red-hot tube.

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  • Columbium oxysulphide, CbOS 3, is obtained as a dark bronze coloured powder when the pentoxide is heated to a white heat in a current of carbon bisulphide vapour; or by gently heating the oxychloride in a current of sulphuretted hydrogen.

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  • Both men and women avoided washing, but there was something of the nature of a vapour bath, with which Herodotus has confused a custom of using the smoke of hemp as a narcotic. The women daubed themselves with a kind of cosmetic paste.

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  • The hot vapour produced combines with the oxygen of the air into white oxide, Sn02.

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  • The vapour density below 700° C. corresponds to Sn2C14, above Soo° C. to nearly SnCl 2.

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  • The vapour mixed with oxygen or air is violently explosive.

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  • A little vapour is given off at ordinary temperatures and pressures, and when under a few millimetres pressure only it rapidly vaporizes below Ioo° C. The freezing-point is uncertain, owing perhaps to the existence of two modifications, as suggested by Kast (Zeits.

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  • Its vapour produces violent headache, and the same effect is often caused by handling compositions containing it.

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  • Formic acid yields acridine, and the higher homologues give derivatives substituted at the meso carbon atom, N N +[[Hcooh-C 6 H 5 /Inc6h5->C6h4 C6h4 Cho Ch N N +Ch 3 000h->C 6 H 5 /IC 6 H 5 --C 6 H 4 C6h4 Coch 3 C]](CH3) Acridine may also 1:e obtained by passing the vapour of phenylortho-toluidine through a red-hot tube (C. Graebe, Ber., 1884, 17, p. 1 37 0); by condensing diphenylamine with chloroform, in presence of aluminium chloride (0.

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  • Its vapour is spontaneously inflammable when exposed to air.

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  • The hexachloride, Si 2 C1 61 is formed when silicon chloride vapour is passed over strongly heated silicon; by the action of chlorine on the corresponding iodocompound, or by heating the iodo-compound with mercuric chloride (C. Friedel, Comptes rendus, 18 7 1, 73, P. 497).

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  • Silicon tetraiodide, Si14, is formed by passing iodine vapour mixed with carbon dioxide over strongly-heated silicon (C. Friedel, Comptes rendus, 1868, 67, p. 98); the iodo-compound condenses in the colder portion of the apparatus and is purified by shaking with carbon bisulphide and with mercury.

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  • It crystallizes in octahedra which melt at 120.5° C. and boil at 290° C. Its vapour burns with a red flame.

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  • Silicon nitrogen hydride, SiNH, is a white powder formed with silicon amide when ammonia gas (diluted with hydrogen) is brought into contact with the vapour of silicon chloroform at -10° C. Trianilino silicon hydride, SiH (NHC 6 H 5) 3, is obtained by the action of aniline on a benzene solution of silicon chloroform.

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  • Silicon sulphide, SiS 2, is formed by the direct union of silicon with sulphur; by the action of sulphuretted hydrogen on crystallized silicon at red heat (P. Sabatier, Comptes rendus, 1880, 90, p. 819); or by passing the vapour of carbon bisulphide over a heated mixture of silica and carbon.

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  • Silver vapour is blue, potassium vapour is green, many others (mercury vapour, for instance) are colourless.

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  • In the oxyhydrogen flame silver boils, forming a blue vapour, while platinum volatilizes slowly, and osmium, though infusible, very readily.

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  • Sulphur.-Amongst the better known metals, gold and aluminium are the only ones which, when heated with sulphur or in sulphur vapour remain unchanged.

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  • The metals of the alkalis and alkaline earths, also magnesium, burn in sulphur vapour as they do in oxygen.

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  • It may be solidified to rhombic crystals which melt at 5.4° C. (Mansfield obtained perfectly pure benzene by freezing a carefully fractionated sample.) It boils at 80 4°, and the vapour is highly inflammable, the flame being extremely smoky.

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  • Passed through a red-hot tube, benzene vapour yields hydrogen, diphenyl, diphenylbenzenes and acetylene; the formation of the last compound is an instance of a reversible reaction, since Berthelot found that acetylene passed through a red-hot tube gave some benzene.

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  • A certain critical temperature is observed in a gas, above which the liquefaction is impossible; so that the gaseous state has two subdivisions into (i.)a true gas, which cannot be liquefied, because its temperature is above the critical temperature, (ii.) a vapour, where the temperature is below the critical, and which can ultimately be liquefied by further lowering of temperature or increase of pressure.

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  • Evaporation of the Juice to Syrup. - The third operation is the concentration of the approximately pure, but thin and watery, juice to syrup point, by driving off a portion of the water in vapour through some system of heating and evaporation.

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  • But this competition among inventors, whatever the incentive, has not been without benefit, because to-day, by means of very simple improvements in details, such as the addition of circulators and increased area of connexions, what may be taken to be the standard type of multiple-effect evaporator (that is to say, vertical vacuum pans fitted with vertical heating tubes, through which passes the liquor to be treated, and outside of which the steam or vapour circulates) evaporates nearly double the quantity of water per square foot of heating surface per hour which was evaporated by apparatus in use so recently as 1885 - and this without any increase in the steam pressure.

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  • A fan blast enters the lower end, and, passing out at the upper end, carries off the vapour produced by the drying of the sugar, and at the same time assists the evaporation.

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  • On passing the vapour through red-hot tubes it yields anthracene and toluene.

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  • The ore, even if it is not blende, must be roasted or calcined in order to remove all volatile components as completely as possible, because these, if allowed to remain, would carry away a large proportion of the zinc vapour during the distillation.

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  • The zinc vapour produced descends through the pipe and condenses into liquid zinc, which is collected in a ladle held under the outlet end of the pipe.

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  • After a time the flame becomes dazzling white, showing that zinc vapour is beginning to escape.

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  • When hydraulic pressure to the amount of 2000 to 3000 lb per square inch is applied, the saving is unquestioned, since less time is required to dry the pressed retort, its life in the furnaces is longer, its absorption of zinc is less, and the loss of zinc by passage through its walls in the form of vapour is reduced.

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  • It fuses at 415° C. and under ordinary atmospheric pressure boils at 1040° C. Its vapour density shows that it is monatomic. The molten metal on cooling deposits crystals belonging to the hexagonal system, and freezes into a compact crystalline solid, which may be brittle or ductile according to circumstances.

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  • Zinc oxide, ZnO, is maufactured for paint by two processes - directly from the ore mixed with coal by volatilization on a grate, as in the Wetherill oxide process, and by oxidizing the vapour given off by a boiling bath of zinc metal.

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  • The temperature of the electric furnace, whether of the arc or incandescence type, is practically limited to that at which the least easily vaporized material available for electrodes is converted into vapour.

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  • Moissan showed that at this temperature the most stable of mineral combinations are dissociated, and the most refractory elements are converted into vapour, only certain borides, silicides and metallic carbides having been found to resist the action of the heat.

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  • By passing chloroform vapour over the heated dioxide the tetradiand tri-chlorides are formed, together with the free metal and a gaseous hydride, TiH 4 (Renz, Ber., 1906, 39, p. 2 49).

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  • Titanium trichloride, TiC131 forms involatile, dark violet scales, and is obtained by passing the vapour of the tetrachloride mixed with hydrogen through a red-hot tube, or by heating the tetrachloride with molecular silver to 200°.

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  • It is a heavy vapour which condenses at 7° C. to a liquid, having a pronounced fish-like smell.

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  • By this time it is heavily laden with vapour, which it continues to bear along across the continent, depositing it and supplying the sources of the Amazon and La Plata.

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  • The vaporization of a substance below its normal boiling-point can also be effected by blowing in steam or some other vapour; this operation is termed "distillation with steam."

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  • If N be the length of the unheated mercury column in degrees, t the temperature of this column (generally determined by a small thermometer placed with its bulb at the middle of the column), and T the temperature recorded by the thermometer, then the corrected temperature of the vapour is T-+o 000143 (T - t) N (T.

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  • Of other common types of condenser, we may notice the "spiral" or "worm" type, which consists of a glass, copper or tin worm enclosed in a vessel in which water circulates; and the ball condenser, which consists of two concentric spheres, the vapour passing through the inner sphere and water circulating in the space between this and the outer (in another form the vapour circulates in a shell, on the outside and inside of which water circulates).

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  • The success of the operation depends upon two factors: (I) that the heating be careful, slow and steady, and (2) that the column attached to the flask be efficient to sort out, as it were, the most volatile vapour.

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  • Three types of columns are employed: (I) the elongation is simply a straight or bulb tube; (2) the column, properly termed a "dephlegmator," is so constructed that the vapours have to traverse a column of previously condensed vapour; (3) the column is encircled by a jacket through which a liquid circulates at the same temperature as the boiling-point of the most volatile component.

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  • When the components are completely immiscible, the vapour pressure of the one is not influenced by the presence of the other.

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  • The composition of the distillate is determinate (by Avogadro's law) if the molecular weights and vapour pressure of the components at the temperature of distillation be known.

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  • If M 1, M2, and P 1, P 2 be the molecular weights and vapour pressures of the components A and B, then the ratio of A to B in the distillate is M 1 P 1 /M 2 P 2.

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  • In general, when the substance to be distilled has a vapour pressure of only 10 mm.

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  • A dissolved in B and B dissolved in A, since both of these solutions emit vapours of the same composition (this follows since the same vapour must be in equilibrium with both solutions, for if it were not so a cyclic system contradicting the second law of thermodynamics would be realizable).

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  • The composition of the vapour, however, would not be the same as that of either layer.

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  • (i.) If the vapour of A be readily soluble in the liquid B, and the vapour of B readily soluble in the liquid A, there will exist a mixture of A and B which will have a lower vapour pressure than any other mixture.

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  • The vapour pressure composition curve will be convex to the axis of compositions, the maximum vapour pressures corresponding to pure A and pure B, and the minimum to some mixture of A and B.

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  • On distilling such a mixture under constant pressure, a mixture of the two components (of variable composition) will come over until there remains in the distilling flask the mixture of minimum vapour pressure.

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  • (ii.) If the vapours be sparingly soluble in the liquids there will exist a mixture having a greater vapour pressure than that of any other mixture.

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  • The vapour pressure-composition curve will now be concave to the axis of composition, the minima corresponding to the pure components.

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  • The vapour tension may approximate to a linear function of the composition, and the curve will then be practically a straight line.

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  • 4 let AB be the axis of composition, AP be the vapour pressure of pure A, BQ the vapour pressure of pure B.

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  • For immiscible liquids the vapour pressure curve is the horizontal line ab, described so that aP = QB and bQ=AP. For partially miscible liquids the curve is Pa i b i Q.

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  • Sidney Young has suggested conducting the operation in a current of carbon dioxide which sweeps out the vapours as they are evolved, and also heating in a vapour bath, e.g.

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  • It oxidizes rapidly when exposed to air, and burns when heated in air, oxygen, chlorine, bromine or sulphur vapour.

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  • Other methods consist in determining the vapour tension by means of the vaporimeter of Geissler, or the boiling point by the ebullioscope.

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  • The isothermals are approximately equilateral hyperbolas (pv= constant), with the axes of p and v for asymptotes, for a gas or unsaturated vapour, but coincide with the isopiestics for a saturated vapour in presence of its liquid.

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  • Clausius (1850), applying the same assumption, deduced the same value of F'(t), and showed that it was consistent with the mechanical theory and Joule's experiments, but required that a vapour like steam should deviate more considerably from the gaseous laws than was at that time generally admitted.

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  • saturated vapour), in which it occupies a volume v", the line BC represents the change of volume (v" - v').

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  • In the case of an ideal gas, dp/d9 at constant volume =R/v, and dvld6 at constant pressure =R/p; thus we obtain the expressions for the change of entropy 0-4)0 from the state poeovo to the state pev, log e e/eo+R logev/vo =S log e 9/00-R (32) In the case of an imperfect gas or vapour, the above expressions are frequently employed, but a more accurate result may be obtained by employing equation (17) with the value of the specific heat, S, from (29), which gives the expression 4-¢o = Sologe0/00 - R logep/po-n(cp/B-copo/Bo)

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  • The simplest case to consider is that of equilibrium between solid and liquid, or liquid and vapour.

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  • Writing formulae (3r) and (33) for the energy and entropy with indeterminate constants A and B, instead of taking them between limits, we obtain the following expressions for the thermodynamic functions in the case of the vapour: " =Solog e 0 - R log e p - ncp/D+A".

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  • Neville determined it to be 1061 7° C.; Daniel Berthelot gives 1064° C., while Jaquerod and Perrot give 1066.1-1067.4° C. At still higher temperatures it volatilizes, forming a reddish vapour.

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  • Related to the determination of the density of a gas is the determination of the density of a vapour, i.e.

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  • This subject owes its importance in modern chemistry to the fact that the vapour density, when hydrogen is taken as the standard, gives perfectly definite information as to the molecular condition of the compound, since twice the vapour density equals the molecular weight of the compound.

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  • In 1826 Dumas devised a method suitable for substances of high boiling-point; this consisted in its essential point in vaporizing the substance in a flask made of suitable material, sealing it when full of vapour, and weighing.

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  • Troost made it available for specially high temperatures by employing porcelain vessels, sealing them with the oxyhydrogen blow-pipe, and maintaining a constant temperature by a vapour bath of mercury (3500), sulphur (4400), cadmium (860°) and zinc (1040°).

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  • The vessel is then lowered into a jacket containing vapour at a known temperature which is sufficient to volatilize the substance.

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  • It is necessary to determine the pressure exerted on the vapour by the mercury in the narrow limb; this is effected by opening the capillary and inclining the tube until the mercury just reaches the top of the narrow tube; the difference between FIG.

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  • the height of the mercury in the wide tube and the top of f he narrow tube represents the pressure due to the mercury column, and this must be added to the barometric pressure in order to deduce the total pressure on the vapour.

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  • It consists in determining the air expelled from a vessel by the vapour of a given quantity of the substance.

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  • To use the apparatus, the long tube is placed in a vapour bath (c) of the requisite temperature, and after the air within the tube is in equilibrium, the delivery tube is placed beneath the surface of the water in a pneumatic trough, the rubber stopper pushed home, and observation made as to whether any more air is being expelled.

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  • The vapour density is calculated by the following formula: D - W(1 +at) X587,780 (p-s) V in which W =weight of substance taken, V =volume of air expelled, a= 1/273 = .003665, t and p = temperature and pressure at which expelled air is measured, and s= vapour pressure of water at 1°.

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  • Vapour baths of iron are used in connexion with boiling anthracene (335°), anthraquinone (368°),sulphur(444°),phosphoruspentasulphide(518°); molten lead may also be used.

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  • For higher temperatures the bulb of the vapour density tube is made of porcelain or platinum, and is heated in a gas furnace.

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  • 6) consists of a barometer tube, containing mercury and standing in a bath of the same metal, surrounded by a vapour jacket.

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  • The vapour is circulated through the jacket, and the height of the mercury read by a cathetometer or otherwise.

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  • The vapour tension of mercury need not be taken into account when water is used in the jacket.

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  • The principle of this method is as follows: - In the ordinary air expuls i on method, the vapour always mixes to some extent with the air in the tube, and this involves a reduction of the pressure of the vapour.

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  • When the volatilization is quite complete, the level is accurately adjusted, and the difference of the levels of the mercury gives the pressure exerted by the vapour.

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  • Travers, The Experimental Study of Gases (1901); and vapour density determinations in Lassar-Cohn's Arbeitsmethoden fur organisch-chemische Laboratorien (1901), and Manual of Organic Chemistry (1896), and in H.

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  • This hypothesis, however, does not accord with the theory of the development of the earth from the state of a sphere of molt s en rock surrounded by an atmosphere of gaseous metals by which the first-formed clouds of aqueous vapour must have been absorbed.

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  • Further Physical Properties of Sea-water.---The laws of physical chemistry relating to complex dilute solutions apply to seawater, and hence there is a definite relation between the osmotic pressure, freezing-point, vapour tension and boiling-point by which when one of these constants is given the others can be calculated.

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  • The relation of the elevation of the boiling-point (t°) to the osmotic pressure (P) is very simply derived from the formula t=o 02407P 0, while the reduction of vapour pressure proportional to the concentration can be very easily obtained from the elevation of the boiling-point, or it may be obtained directly from tables of vapour tension.

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  • The elevation of the boilingpoint is of little practical importance, but the reduction of vapour pressure means that sea-water evaporates more slowly than fresh water, and the more slowly the higher the salinity.

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  • For its complete combustion a volume of acetylene needs approximately twelve volumes of air, forming as products of combustion carbon dioxide and water vapour.

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  • When, however, the air is present in much smaller ratio the combustion is incomplete, and carbon, carbon monoxide, carbon dioxide, hydrogen and water vapour are produced.

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  • Under the same conditions it becomes incandescent in the vapour of sulphur, yielding calcium sulphide and carbon disulphide; the vapour of phosphorus will also unite with it at a red heat.

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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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  • „ air 15° C = 49,800 „ „ „ mercury vapour at o° „ C = 18,500 „ and other velocities can readily be calculated.

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  • There are many thousands of lines in the mercury spectrum, so that from this evidence it would appear that for mercury vapour n ought to be very great, and y almost equal to unity.

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  • Whilst alcohol is applied in motor engines in a similar manner to petrol, its vapour mixed with a proper proportion of air being drawn into the cylinder where it is compressed and ignited, it cannot be used with maximum efficiency by itself in engines such as are fitted to modern motors because it requires a higher degree of compression than petrol engines are usually designed to stand, and also because, unless special arrangements are made, a motor engine will not start readily from the cold with alcohol alone.

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  • The tetroxide, 0s04, can be easily reduced to the metal by dissolving it in hydrochloric acid and adding zinc, mercury, or an alkaline formate to the liquid, or by passing its vapour, mixed with carbon dioxide and monoxide, through a red-hot porcelain tube.

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  • It is obtained as a yellowish coloured mass and can be sublimed in the form of needles which melt at 40° C. It possesses an unpleasant smell and its vapour is extremely poisonous.

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  • Water vapour is always present; the amount is determined by instruments termed hygrometers.

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  • This circumstance appeared so anomalous that some astronomers doubted whether the surviving lines were really due to calcium; but Sir William and Lady Huggins (née Margaret Lindsay Murray, who, after their marriage in 1875, actively assisted her husband) successfully demonstrated in the laboratory that calcium vapour, if at a sufficiently low pressure, gives under the influence of the electric discharge precisely these lines and no others.

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  • Ruapehu (9100 ft.) is intermittently active, and Ngauruhoe (75 1 5 ft.) emits vapour and steam incessantly.

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  • Kundt's dust-tube may also be employed for the determination of the ratio of the specific heats of a gas or vapour.

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  • Kundt and Warburg applied the method to find y for mercury vapour (Pogg.

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  • When the wire was heated by an electric current a fine line of vapour descended from each drop. The pipe was closed at the centre by a membrane which prevented a through draught, yet permitted the vibrations, as it was at a node.

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  • The vapour line, therefore, merely vibrated to and fro when the pipe was sounded.

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  • The extent of vibration at different parts of the pipe was studied through a glass side wall, a stroboscopic method being used to get the position of the vapour line at a definite part of the vibration.

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  • Montaigne is far too much occupied about all sorts of the minutest details of human life to make it for a moment admissible that he regarded that life as a whole but as smoke and vapour.

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  • Heated in chlorine or with bromine, it yields carbon and calcium chloride or bromide; at a dull red heat it burns in oxygen, forming calcium carbonate, and it becomes incandescent in sulphur vapour at 500°, forming calcium sulphide and carbon disulphide.

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  • Calcium phosphide, Ca 3 P 2, is obtained as a reddish substance by passing phosphorus vapour over strongly heated lime.

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  • The pure acid thus obtained is a most dangerous substance to handle, its vapour even when highly diluted with air having an exceedingly injurious action on the respiratory organs, whilst inhalation of the pure vapour is followed by death.

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  • Soc., 1889, 55, p. 163) determined the vapour density of hydrofluoric acid at different temperatures, and showed that there is no approach to a definite value below about 88° C. where it reaches the value 10.29 corresponding to the molecular formula HF; at temperatures below 88° C. the value increases rapidly, showing that the molecule is more complex in its structure.

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  • The salt volatilizes (mostly in the form of a mixed vapour of the two components, which reunite on cooling), and condenses in the dome in the form of a characteristically fibrous and tough crust.

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  • On heating it melts at 95.6° (Bunsen) to a liquid resembling mercury, and boils at 877.5° (Ruff and Johannsen, Ber., 1905, 38, p. 3601), yielding a vapour, colourless in thin layers but a peculiar purple, with a greenish fluorescence, when viewed through thick layers.

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  • (For the optics of sodium vapour see R.

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  • But in consequence of the humidity of the climate of England it is better to suppose the air to be (on the average) two-thirds saturated with aqueous vapour, and then the standard temperature will be reduced to 60° F., so as to secure the same standard density; the density of the air being reduced perceptibly by the presence of the aqueous vapour.

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  • Propylene, C 3 H 6, may be obtained by passing the vapour of trimethylene through a heated tube (S.

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  • Isobutylene, (CH 3) 2 C:CH 2, is formed in the dry distillation of fats, and also occurs among the products obtained when the vapour of fusel oil is led through a heated tube.

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  • It burns when heated in an atmosphere of oxygen, forming carbon dioxide, and when heated in sulphur vapour it forms carbon bisulphide.

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  • This fact, coupled with the determination of the vapour density of the gas, establishes the molecular formula CO.

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  • Its vapour density is 3.46 (air = I).

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  • Suppl., 5, p. 236) by passing carbon monoxide and sulphur vapour through a tube at a moderate heat.

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  • Its Vapour Density Is 2.1046 (Air= I).

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  • It fuses at 62.5°C. (Bunsen) and boils at 667°, emitting an intensely green vapour.

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  • The reaction may be written 2K+ 211 2 0= 2K0H+H2, and the flame is due to the combustion of the hydrogen, the violet colour being occasioned by the potassium vapour.

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  • The liquors after a concentration in iron vessels are now evaporated in a silver dish, until the heavy vapour of the hydrate is seen to go off.

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  • At a white heat the vapour breaks down into potassium, hydrogen and oxygen.

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  • It forms colourless cubes which are readily soluble in water, melt at 685°, and yield a vapour of normal density.

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  • Poas (8895), the scene of a violent eruption in 1834, begins a fresh series of igneous peaks, some with flooded craters, some with a constant escape of smoke and vapour.

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  • The magma, or molten lava in the interior of the earth, may be regarded as a mutual solution of various mineral silicates, charged with highly-heated vapour, sometimes to the extent of supersaturation.

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  • P. Leroux discovered that iodine vapour refracted the red rays more than the violet, the intermediate colours not being transmitted; and in 1870 Christiansen found that an alcoholic solution of fuchsine refracted the violet less than the red, the order of the successive colours being violet, red, orange, yellow; the green being absorbed and a dark interval occurring between the violet and red.

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  • Kundt, is that exhibited by the vapour of sodium.

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  • It has not been found practicable to make a prism of this vapour in the ordinary way by enclosing it in a glass vessel of the required shape, as sodium vapour attacks glass, quickly rendering it opaque.

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  • But the best way of exhibiting the effect is by making use of a remarkable property of sodium vapour discovered by R.

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  • The sodium vapour in the middle is very dense on the heated side, the density diminishing rapidly towards the upper part of the tube, so that, although not prismatic in form, it refracts like a prism owing to the variation in density.

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  • Thus if a horizontal slit is illuminated by an arc lamp, and the light - rendered parallel by a collimating lens - is transmitted through the sodium tube and focused on the vertical slit of a spectroscope, the effect of the sodium vapour is to produce its refraction spec trum vertically on the slit.

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  • - Anomalous Dispersion of a small part in the neighSodium Vapour.

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  • But the light of slightly greater wave-length than the D lines, being refracted strongly downward by the sodium vapour, illuminates the.

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  • If the sodium is only gently heated, so as to produce a comparatively rarefied vapour, and a grating spectroscope employed, the spectrum obtained is like that shown in fig.

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  • ioablis (violet-coloured), in allusion to the colour of its vapour.

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  • The specific heat of iodine vapour at constant pressure is o-03489, and at constant volume o 02697.

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  • Iodine vapour on heating passes from a violet colour to a deep indigo blue; this behaviour was investigated by V.

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  • Meyer (Be y ., 1880, 1 3, p. 394), who found that the change of colour was accompanied by a change of vapour density.

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  • Thus, the density of air being taken as unity, Victor Meyer found the following values for the density of iodine vapour at different temperatures: T° C...

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  • Hydriodic acid, HI, is formed by the direct union of its components in the presence of a catalytic agent; for this purpose platinum black is used, and the hydrogen and iodine vapour are passed over the heated substance.

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  • The usual method is to make a mixture of amorphous phosphorus and a large excess of iodine and then to allow water to drop slowly upon it; the reaction starts readily, and the gas obtained can be freed from any admixed iodine vapour by passing it through a tube containing some amorphous phosphorus.

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  • It boils at 118°, giving a vapour of abnormal specific gravity.

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  • Andrews's conception of the critical temperature of gases by defining the absolute boiling-point of a substance as the temperature at which cohesion and heat of vaporization become equal to zero and the liquid changes to vapour, irrespective of the pressure and volume.

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  • Its vapour is inflammable.

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  • It is obtained by passing ammonia gas over hot coal; by subliming a mixture of ammonium chloride and potassium cyanide; by passing a mixture of ammonia gas and chloroform vapour through a red hot tube; and by heating a mixture of ammonia and carbon monoxide: CO+2NH 3 = NH 4 NC+H 2 0.

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  • As the earth of light has five tokens (the mild zephyr, cooling wind, bright light, quickening fire, and clear water), so has the earth of darkness also five (mist, heat, the sirocco, darkness and vapour).

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  • This is consistent with Kirchhoff's law and shows that the sodium in a flame possesses the same relative radiation and absorption as sodium vapour heated thermally to the temperature of the flames.

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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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  • These lines in the case of the spark cannot be due entirely to the increased mass of vapour near the poles, but indicate a real change of spectrum probably connected with a higher temperature.

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  • In the case of some metals, notably bismuth, the velocity measured was different for different lines, which seems intelligible only on the supposition that the metal vapour consists of different vibrating systems which can differ with different velocities.

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  • Paschen proved that the emission spectra of water vapour as observed in an oxyhydrogen flame, and of carbon dioxide as observed in a hydrocarbon flame may be obtained by heating aqueous vapour and carbon dioxide respectively to a few hundred degrees above the freezing point.

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  • There is a vast amount of literature on the subject, but in spite of the difficulty of conceiving a luminous carbon vapour at the temperature of an ordinary carbon flame, the evidence seems to show that no other element is necessary for its production as it is found in the spectrum of pure carbon tetrachloride and certainly in cases where chlorine is excluded.

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  • Another much disputed spectrum is that giving the bands which appear in the electric arc; it is most frequently ascribed to cyanogen, but occasionally also to carbon vapour.

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  • In the light of our present knowledge we should look for the different behaviour in the peculiarity of the oxygen flame to ionize the metallic vapour.

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  • It is not possible here to enter into a detailed description of the phenomena of fluorescence (q.v.), though their importance from a spectroscopic point of view has been materially increased through the recent researches of Wood s on the fluorescence of sodium vapour.

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  • Formerly, on the eve of a great eruption of Mauna Loa, this crater often spouted forth great columns of flame and emitted clouds of vapour, but in modern times this action has usually been followed by a fracture of the mountain side from the summit down to a point moo ft.

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  • When magnesium is heated in fluorine or chlorine or in the vapour of bromine or iodine there is a violent reaction, and the corresponding halide compounds are formed.

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  • Magnesium sulphide, MgS, may be obtained, mixed with some unaltered metal and some magnesia, as a hard brown mass by heating magnesia, in sulphur vapour.

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  • Boric acid is easily soluble in alcohol, and if the vapour of the solution be inflamed it burns with a characteristic vivid green colour.

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  • That orthoboric acid is a tribasic acid is shown by the formation of ethyl orthoborate on esterification, the vapour density of which corresponds to the molecular formula B(0C2H5)3; the molecular formula of the acid must consequently be B(OH) 3 or H 3 B0 3.

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  • He definitely established the absorptive power of clear aqueous vapour - a point of great meteorological significance.

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  • Thus water and steam are in equilibrium with each other when the chemical potential of water substance is the same in the liquid as in the vapour.

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  • It is usual to call each part of the system of uniform composition throughout a phase; in the example given, water substance, the only component is present in two phases - a liquid phase and a vapour phase, and when the potentials of the component are the same in each phase equilibrium exists.

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  • To take the simplest case of a one component system water substance has its three phases of solid ice, liquid water and gaseous vapour in equilibrium with each other at the freezing point of water under the pressure of its own vapour.

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  • If we attempt to change either the temperature or the pressure ice will melt, water will evaporate or vapour condense until one or other of the phases has vanished.

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  • We then have water and vapour in equilibrium, and, as more heat enters, the temperature rises and the vapour-pressure rises with it.

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  • The phenomena of equilibrium can be represented on diagrams. Thus, if we take our co-ordinates to represent pressure and temperature, the state of the systems p with ice, water and vapour in equilibrium is represented by the point 0 where the pressure is that of the vapour of water at the freezing point and the temperature is the freezing point under that pressure.

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  • If all the ice be melted, we pass along the vapour pressure curve of water OA.

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  • If all the water be frozen, we have the vapour pressure curve of ice OB; while, if the pressure be raised, so that all the vapour vanishes, we get the curve OC of equilibrium between the pressure and the freezing point of water.

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  • The four phases are (I) crystals of salt, (2) crystals of ice, (3) a saturated solution of the salt in water, and (4) the vapour, which is that practically of water alone, since the salt is non-volatile at the temperature in question.

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