Arseni furnace

Iron Monarsenide, FeAs, may be obtained by heating iron in a current of arsenic vapour at 335° to 380° C. 2 by heating a mixture of the elements in a bomb tube at 680° C.,3 or a mixture of iron, arsenious oxide and carbon in an electric arc furnace 4 by the action of fused potassium cyanide on iron arsenate 8 by reduction of the di-arsenide at 680° C. in a current of hydrogen 3 or by dropping a solution of a ferrous salt into an atmosphere of arsine.6... 

Vitreous Arsenious Oxide from Furnaces at Wiluna... 

The ore is crushed and ground in.ball mills to pass through a 30-mesh sieve. It is mixed with suitable fluxes (limestone and quartz) and smelted in small blast-furnaces having a capacity of 25 to 30 tons per twenty-four hours. The products obtained are (i) flue dust, which is returned to the furnaces, and crude arsenious oxide, which is resublimed and sold (ii) a silicate slag, which is thrown away unless it contains more than 10 ounces of silver per ton (iii) crude silver bullion, which is mechanically detached and cupelled to a fineness of 994 before it is sold to silver refiners and (iv) a speiss of cobalt, nickel, iron, and copper arsenides, containing considerable amounts of silver. The crude silver bullion contains about three-fourths of the silver present in the ore. 

Furnace phosphoric acid is pure enough for most uses as obtained directly from the process. Food-grade applications require removal of traces of arseni-ous oxide (Table 10.6). Arsenic is present to the extent of 50-180 ppm (as AS2O3 equivalent) in the feed phosphorus because of the similarity of its chemical properties to those of phosphorus (same group in the periodic table). This ends up in the product acid on oxidation and hydration [1]. It may be removed by the addition of the requisite amount of sodium sulfide or hydrogen sulfide to the furnace acid, which precipitates it as the arsenic III and V sulfides (e.g., Eq. 10.20). 

Twelve hundred to 1500 lbs. of impure antimony are charged into the furnace, previously heated to a red heat. As soon as the metal is melted, generally in less than half an hour, 3 to 7 per cent, of soda, with which is mixed a little coke-dust or fine charcoal, is added, according to the purity of the metal After this the heat is raised to bright redness in order to fuse the soda. During the charging and the fusion, vapour of antimonious and arsenious oxides is given off. 

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... 

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