Arsenic disulphide

Many other methods of preparation have been employed. For example, the triiodide is formed when arsenious oxide,5 or a mixture of this oxide with sulphur,6 is heated in iodine vapour or when arsenious oxide is heated with iodine,7 hydriodic acid,8 a mixture of potassium iodide and acetic acid,9 or a mixture of potassium iodide and potassium hydrogen sulphate.10 When arsenic disulphide and iodine, in the proportions 1 As Ss 3la, are heated together, arsenic triiodide is formed.11 When arsenic trisulphide is fused with an excess of iodine, the product is soluble in carbon disulphide and the solution on evaporation deposits arsenic triiodide, then a sulphiodide and finally sulphur with excess of sulphide the product is the sulphiodide, AsS2I. If a solution of iodine in carbon disulphide is added to arsenic di- or tri-sulphide, the triiodide and sulphur are formed. The triiodide is also produced when a mixture of the trisulphide and mercuric iodide is heated 12. when hydriodic... 

Arsenic disulphide is reduced to arsenic when heated in hydrogen the reaction, which is reversible,... 

Arsenic Subsulphide—Tetrarsenic Trisulphide—Arsenic Disulphide—Arsenio Trisulphide Colloidal Arsenic Trisulphide—Arsenic Pentasulphide—Thio-arsenates—Oxythioarsenates—Sulphato-eompounds of Arsenic. 

Arsenic disulphide A82 2 A vnlc bisulphide realqar red sulphide of arsenic red sulphuret of arsenic auldhide of arsenic sulnhuret of arsenic. 

Arsenic disulphide—Jiedstdphide of arsenic Beatgar—Bed orpiment Bttby sulphur—Sandarach—As,S,—214—occurs in nature in trancuucent, ruby red ciy siala It is also prepared by beating a mixture of As,0, and S OS so obtained it appears in brick-red masses. 

Arsenical pesticides, those based on arsenic, such as arsenic disulphide, a rodenticide. 

When sulphur is melted viscosity changes occur as the temperature is raised. These changes are due to the formation of long-chain polymers (in very pure sulphur, chains containing about 100 (X)0 atoms may be formed). The polymeric nature of molten sulphur can be recognised if molten sulphur is poured in a thin stream into cold water, when a plastic rubbery mass known as plastic sulphur is obtained. This is only slightly soluble in carbon disulphide, but on standing it loses its plasticity and reverts to the soluble rhombic form. If certain substances, for example iodine or oxides of arsenic, are incorporated into the plastic sulphur, the rubbery character can be preserved. 

Arsenic exhibits allotropy, which is characteristic of non-metals the usual, more stable, metallic form resembles the typical metals in appearance and in being a fairly good conductor of electricity. Under atmospheric pressure it begins to volatilise at about 450° C. and passes into a vapour containing complex molecules, As4, which at higher temperatures dissociate to As2 this complexity is not unusual in non-metals. The yellow allotrope, which is stable at low temperatures, resembles white phosphorus in being soluble in carbon disulphide—a property which emphasises the non-metallic character of this variety. The reactivity of the allotropes, as in the case of phosphorus, differs considerably. 

The solubility of yellow arsenic in carbon disulphide is as follows 7... 

Stable sols of arsenic in glacial acetic acid have been prepared 6 by dissolving yellow arsenic (012 g.) in carbon disulphide (383 ml.) and pouring the solution into pure anhydrous glacial acetic acid (667 ml.). The stability of the sols, which are yellow in colour, is decreased on addition of a protective colloid (0-1 g. per 1.), and also on attempting to remove carbon disulphide by dialysis or by heating. 

As already described, other crystalline forms of arsenic besides the rhombohedral are known or suspected to exist. The crystals of the yellow allotrope belong to the cubic system, while native arsenolamprite (p. 8) contains crystals belonging to the rhombic, or possibly to the monoclinic, system. Yellow arsenic is soluble in carbon disulphide. 

By direct action of chlorine on arsenic. When powdered arsenic is sprinkled into chlorine gas,1 or into liquid chlorine near its boiling point,2 union occurs with incandescence and a white cloud of the trichloride is formed. If the gas is passed over arsenic in a tube connected with a receiver immersed in a freezing mixture, the powder which condenses is yellow, owing to excess of chlorine the latter may be removed by distillation from powdered arsenic. The reaction is accelerated by the addition of a trace of bromine or of alkali halide.3 When chlorine is passed into a solution of yellow arsenic in carbon disulphide, brown arsenic is first precipitated, which is then converted to arsenic trichloride.4... 

Arsenic Pentachloride ( ), AsC15.—By the action of chlorine on arsenic trichloride at a low temperature Baskerville and Bennett 1 obtained a greenish-yellow liquid which they believed to be arsenic pentachloride. Pure solid arsenic trichloride was placed in a vessel surrounded by carbon dioxide snow and saturated with chlorine, the temperature being -88° C. The liquid approximated in composition to AsCIj. It was soluble in carbon disulphide and in ether, and the ether solution, on evaporation at -80° C., left yellow crystals which readily decomposed with slight rise in temperature. The formation of this compound has not been confirmed, however, and its existence is doubtful. 

The bromide may also be prepared (1) by adding arsenic powder to a mixture of carbon disulphide and bromine (2 1 by weight) and agitating the liquid until decolorised 3 on evaporation, crystals of the bromide remain (2) by heating a mixture of arsenious oxide, potassium bromide and acetic acid at 100° C. 4 (3) by heating a mixture of arsenious oxide and sulphur in a current of bromine vapour.5... 

Arsenic tribromide dissolves in many organic liquids,15 such as carbon disulphide, methylene iodide16 and benzene in the last named the decomposition voltage is 0-50 volt.17 In solutions in diethyl ether18 the electrical conductance at 18° C. rapidly increases with increase in the bromide concentration up to 95 per cent., after which it quickly falls to... 

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