Cupric iodide

Ammino-cupric Iodides.—A solution of ammonia in water docs not dissolve cuprous iodide, but if air be allowed access to the mixture a blue solution is formed, and if the solution be cooled colourless crystals of diammino-cupric iodide separate. From the mother-liquor hydrated tetrammino-eupric iodide may be precipitated by means of alcohol. 

Tetrammino-cupric Iodide is produced by adding potassium-iodide solution to an aqueous ammoniacal solution of cupric sulphate and then saturating the mixture with ammonia gas at 0° C.3... 

Tetrammino-cupric Iodide Monohydrate, [Cu(NH3)4]I2.H20, crystallises in dark blue tetrahedra and decomposes rapidly in air, with loss of ammonia and formation of a dark brown compound. If the solution of the salt in ammonia be warmed it changes in colour, and, on cooling, crystals of decammino-tricupric iodide, [Cu3(NII3 separate. This substance on heating is transformed into diammino-eupric iodide. 

A polyiodide, tetrammino-cupric polyiodide, [Cu(NTI3)4]I24l2, is also known. It separates from a solution of tetrammino-cupric iodide in ammonia and excess of iodine as a blackish-brown crystalline mass.1... 

Cul2 (aq.). The value for aqueous cupric iodide is obtained from the ions. 

Cupric iodide is very unstable, and readily yields up iodine, forming cuprous iodide. On mixing cupric chloride with potassium iodide, the cuprous iodide is precipitated + + +- + + -... 

State of Polarization of Anions and Equilibria. The mutual electronic interaction in the cupric halides increases from the fluoride (white) to the chloride (yellow) and reaches a maximum for the bromide (deep red). The nonexistence of the cupric iodide has been explained by Fajans (10) as the result of the change of the continuous polarization into a discontinuous quantum change of the electrons ... 

Cupric iodide.—The iodide is formed in solution by the interaction of cuprous iodide and iodine solution, but it has not been isolated in the solid state, as it decomposes readily into cuprous iodide and iodine.12 The solution is greenish-blue. Ammonia converts cupric iodide into a stable cuprammonium salt, CuI2,4NH8,H20, prepared more readily by exposure of ammoniacal cuprous iodide to air. A compound of the formula 2CuI,CuI2,4NH3 is also known, and crystallizes in brilliant-green needles, insoluble in water, but soluble in an aqueous solution of ammonia. 

Cupric bromide, CiiBr., is a black solid obtained by reaction of copper and bromine or by solution of cupric oxide, CuO, in hydro bromic acid. It is interesting that cupric iodide, Culo, does not exist when a solution containing cupric ion is added to an iodide solution there occurs an oxidation-reduction reaction, with precipitation of (uprous iodide, Cul ... 

The oxidizing action of cupric compounds is exemplified in the action between a soluble cupric salt and potassium iodide, where cuprous iodide and iodine are formed instead of cupric iodide. 

This method is also suitable for the synthesis of steric-hindered dialkyl arylphosphonates. The yields of dialkyl arylphosphonates are, however, lower than in the case where cupric iodide is used as a catalyst. 

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