Cadmium and Potassium Iodide

Cadmium and potassium iodide readily acquires a slight yellowish color on keeping. 

Derivation By combining cadmium iodide and potassium iodide in solution in proportion of their combining weights, and subsequent crystallization. 

Sandri (15) reported the formation of characteristic crystals with cadmium bromide-hydrobromic acid, bismuth iodide-potassium iodide, and bismuth bromide-hydrobromic acid, with compositions CdBr2 HBr CgHgN 4H 0, HBiI CgHoN, and HBiBr CgHgN, respectively. 

Arsenic triiodide also dissolves, the saturated solution at 15° C. having density 3-661. Other soluble halides are potassium bromide, anhydrous ferric and aluminium chlorides 6 and tetramethyl ammonium iodide but the iodides of rubidium, cadmium, manganese and cobalt, also mercuric and stannic iodides, and cobalt and stannic bromides, are insoluble or only very slightly soluble in arsenic tribromide. The liquid also dissolves phosphoryl bromide and, very slightly, ammonium thiocyanate. In the mixed solutions of halides, the components may react chemically (cf. p. 106), but such is not always the case for example, with antimony tribromide a continuous series of solid solutions is formed.7... 

Potassium iodide solution, 0.1 M for cadmium determination Dissolve 1.66 g of KI in water and dilute to 100 ml prepare fresh daily. 

The selectivity of the Pb reaction with PAR can be increased by the use of cyanide, which efficiently masks Ag, Cd, Hg, Cu, Ni, Co, and Zn. Another way to improve the selectivity is to use a preliminary isolation of lead. Extraction as the iodide complex is a convenient method for its separation from interfering metals. Before this operation, Fe(III) and some other metals can be separated by extraction as thiocyanate complexes. Then potassium iodide is added, the HCl concentration adjusted, and the iodide-lead complex extracted with MIBK. Besides lead, the extract should contain only cadmium (see the procedure below). However, in the preliminary extraction from thiocyanate medium, about 15% of the lead present is also extracted [4]. 

Potassium Tetraiodocadmate. Dipotassium tetra-iodocadmate(2 —) cadmium potassium iodide potassium cadmium iodide potassium iodocadmate Marme s reagent Cdl4K2 mol wt 698.21. Cd 16.10%, I 72.70%, K 11.20%. K2[CdlJ. Dihydrate prepd from aq solns of stoichiometric amounts of Cdl2 and KI must bs recrystallized from water at low temps Croft, Phii Mag 21, 355 (1842) J. Praki Chem. 58, 399 (1856) Hittorf, Pogg Ann. 106, 525 (1859) Eder, Photagr. Milt 13, 67 (1867) Rimbach, Ber. 38. 1562 (1905). 

Samarium selenides. Reductive cleavage of ArSeSeAr by samarium is catalyzed by a great number of metal halides bismuth(III) chloride, cadmium chloride, chromium(IIl) chloride, cobalt(II) chloride, potassium iodide, and titanium(lV) chloride. The resulting samarium arylselenides readily react with various organic halides. 

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