Arsenic Vapour density

The fluoride is a colourless gas which fumes in moist air and has a pungent, unpleasant odour, recalling that of carbonyl chloride. It condenses at —30° C. to a liquid which on further cooling gives a solid of m.pt. —110° C. Its vapour density corresponds with the formula SOF2. It is soluble in arsenic chloride, ether, benzene and turpentine. 

The vapour density of arsenic varies with the temperature. At... 

Di-cobalt Tri-arsenide, Co2As3, is formed when cobalt monarsenide is heated at 400° to 600° C., or when cobalt is heated with arsenic trichloride at the same temperature. According to Beutell and Lorenz,8 it is formed when cobalt is heated in arsenic vapour at 345° to 365° C., but it slowly undergoes decomposition below 400° C. to form the di-arsenide, CoAs2. It also decomposes when heated above 600° C. The density is 7-35 at 0° C. 

The arsenide Cu5As.2 has been prepared by passing a current of carbon dioxide and arsenic vapour over finely divided copper heated to the temperature of boiling sulphur 11 by the action of copper on arsenic trichloride or on arsenic dissolved in hydrochloric acid 12 and by the action of cuprous chloride on arsenic. Lustrous regular crystals of density 7-56 are obtained. These tarnish on exposure to air. When heated it loses arsenic and yields Cu3As, which at a higher temperature also decomposes. Cu5As2 dissolves in nitric acid. It is readily attacked by chlorine or bromine.13... 

The product, of density 7-22, which results when iron is heated in arsenic vapour at 395° to 415° C.11 agrees in composition with the formula Fe2As3. The existence of such an arsenide has not been confirmed, however, although some forms of lollingite approach this composition. 

Arsenic pentafluoride is a colourless gas at ordinary temperature. It condenses to a pale yellow liquid of boiling point -52-8° C. and freezes to a white solid of melting point -79-8° C. The vapour density corresponds with a mol. wt. 169-5 (AsF6 =169-9). The density curve of the liquid is represented by... 

The vapour density of arsenic trichloride was found by Dumas 5 to be 6-301 (air = l), which value agrees with that required by the formula AsCl3 (=6-27). 

Tri-cobalt Di-arsenide, Co3As2, may be prepared by the action of arsenic chloride on metallic cobalt at 800-1400° C. or by heating mixtures of arsenic and cobalt in hydrogen or carbon monoxide at this temperature. It is also formed when powdered cobalt is heated in hydrogen containing arsenic vapour, and when cobalt arsenate or arsenite is reduced by hydrogen at 900° C. Its density is 7-82, and it loses arsenic when strongly heated.1... 

Cobalt Arsenide or Cobalt Monarsenide, CoAs, is obtained when the previous compound is heated from 600-800° C., and when cobalt is heated to 275-335° C. in arsenic vapour. It is a grey crystalline powder, of density 7-62, which tarnishes slightly in the air.1... 

A substance having the composition required for a Cobalt Sesqui-arsenide, Co2As3, is formed at 400-600° C., and this, at temperatures below 400° C., is slowly converted into Cobalt Di-arsenide, CoAs2. This substanc e occurs in nature as the minerals smaltite and safflorite, the former being an important ore of cobalt. It may also be formed by heating cobalt in arsenic vapour from 385-405° C.2 Its density is 6-97. It is grey in colour, slightly oxidised by air, and decomposes above 400° C. 

Iron sesqui-arsenide, Fe2As3, results when iron is heated in arsenic vapour at 395° to 415° C.7 Density 7 22. 

Mitscherlich measured vapour densities at higher temperatures, finding abnormally high values for sulphur, phosphorus, and arsenic, and the density of phosphorus pentachloride only half the normal value (see p. 219). He described the toxicological detection of white phosphorus by distillation in steam and the glow seen in the condenser. His researches on benzene and its derivatives (see p. 331), on etherification and contact action (see p. 262) and affinity (see p. 617) are described elsewhere. 

Dumas determined the vapour densities of mercury, phosphorus, arsenic hydride, and stannic and titanium chlorides, the last two being redetermined in 1830, and the vapour density of phosphorus again (with those of iodine and sulphur), and again in 1832. The vapour density of phosphorus was 4-355 or 4 420 (air = i) and that of sulphur at 493° 6 495, at 506 " 6 512, at 524° 6 617 and 6 581. The vapour density of phosphorus, he found, corresponded with four times, that of sulphur with six times, and that of mercury with half, the chemical atomic weights. Since Dumas thought that the molecules of all elementary gases contain two atoms, he was unable to resolve these difficulties. 

A modification of Dumas vapour density method was used by Mitscherlich, who measured higher temperatures (270°-700°) with an air thermometer, the cylindrical glass tube containing the substance being put inside an iron tube heated in a charcoal furnace. For 300" a metal bath was used. He determined the vapour densities of bromine, sulphur, phosphorus, arsenic, mercury, sulphur trioxide, phosphorus pentachloride, antimony pentachloride, calomel and other mercury salts, and arsenious oxide. Sodium and potassium vapours attacked glass. He used H2 = i as unit with H = i the number of atoms in an equal volume found were i for mercury, 2 for bromine, 6 for sulphur, 4 for phosphorus and arsenic. The densities of phosphorus pentachloride and of antimony pentachloride were half the normal values. Mitscherlich did not appreciate the consequences of Avogadro s hypothesis e.g. he says i vol. of... 

Johann Heinrich Biltz (Berlin, 26 May 1865-Breslau, 29 October or 2 November 1943), a pupil of Victor Meyer, professor in Breslau (1911), determined the vapour densities of stannous chloride, cuprous and silver chlorides, phosphorus, sulphur, selenium, tin, arsenic, antimony and bismuth, detecting the molecule Sg. His later work was largely on organic chemistry. His brother Eugen Wilhelm Biltz (Berlin, 8 March 1877-Heidelberg, 13 November 1943) was professor in Gottingen (1900), Clausthal (1908), and Hannover. He published an immense number of papers, on colloids, the conductivities of fused salts, the compounds of ammonia with salts, compounds of beryllium and other rarer metals, sulphides, phosphides and tellurides, etc., and the molecular volumes of solid compounds. ... 

Barium Arsenide, Ba3As2.—By passing arsine over barium oxide at red heat Soubeiran 4 obtained a mixture of arsenide and arsenite. Lebeau 6 prepared the pure arsenide by reduction of barium arsenate with carbon in an electric furnace. Barium arsenide is very similar in properties to the arsenides of calcium and strontium it is slightly darker in colour, more readily fusible and more reactive chemically. Its density at 15° C. is 4-1. It burns spontaneously in fluorine, chlorine or bromine vapour. In oxygen it burns at about 300° C. and in sulphur vapour at dull red heat. 

Nickel Monarsenide, NiAs, is formed when reduced nickel is heated at 400° to 800° C. in arsenic chloride vapour.10 It is identical with the mineral niccolite or nickeline (p. 12), and has, like it, a red colour. Its density is 7-57 at 0° C. When heated it commences to lose arsenic at... 

Because of its high vapour tension as well as its low density it is difficult to maintain a high concentration of hydrocyanic acid in an open place. As the toxic action is considerably reduced by dilution, numerous artifices were used during the war to render this gas more persistent. Lebeau, in France, suggested mixing it with the smoke-producing chlorides, as stannic, titanium or arsenic chloride. The result was that the already low stability of the hydrocyanic acid was still further reduced. Then it was proposed to add a proportion of chloroform to the mixture, this forming the mixture termed " Vincennite by the French. It consisted of 50% hydrocyanic acid, 30% arsenic trichloride, 15% stannic chloride and 5% chloroform. 

Arsenic and Arsenides.—Vapour-pressure and density measurements on the element up to 77 atm and 1400 K have led to the following thermodynamic... 

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