Arsenic triiodide, preparation

Arsenic triiodide, preparation of, 7 15 Arsenic(V), C-containing compounds, 28 204-216... 

Arsenic triiodide is prepared by treating elemental arsenic with a solution of iodine in carbon disulfide. Alternatively, it can be precipitated out from a hot solution of arsenic trioxide or arsenic trisulfide in hydrochloric acid on treatment with potassium or sodium iodide. Also, it is made by the reaction of arsenic trichloride with potassium iodide. 

Triphenylarsine has been prepared by the action of arsenic triiodide or arsenic trichloride on phenylinagnesium Ijromide... 

Ammino-arsenic Tri-iodides.—Several compounds of arsenic tri-iodide have been prepared. Bamberger and Philipp 4 obtained a compound, [As4(NII3)9JI, by passing dry ammonia gas into arsenic triiodide in ether, when a bulky white precipitate was produced. On heating to 50° C. it loses ammonia, and is completely decomposed at higher temperatures. Arsenic tri-iodide absorbs ammonia, slowly at first, and then more rapidly towards the point of saturation. The compound produced is a tetrammino-derivative.1... 

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 triiodide has been prepared by direct union of the elements with or without a solvent,1 by the reaction of iodine with arsenic trioxide2 or sulfide,3 and by the reaction of aqueous solutions of an arsenic compound and an iodide.4 The last mentioned furnishes the most convenient method of obtaining the material in pure form. 

The compound AS2I4 is synthesized by reaction of arsenic metal with arsenic triiodide. If a solid cubic block of arsenic (d = 5.72 g/cm ) that is 3.00 cm on edge is allowed to react with 1.01 X lO " molecules of arsenic triiodide, what mass of AS2I4 can be prepared If the percent yield of AS2I4 was 75.6%, what mass of AS2I4 was actually isolated ... 

Arsenic triiodide [7784-45-4] M 455.6, m 146", b 400"/atm, d 4 4.688. It crystallises from acetone and sublimes below 100°. It is very slowly hydrolysed by H2O (much more slowly than the chloride). POISONOUS. [Schenk in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 597-598 1963.]... 

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