Ammonium Tetrachromate

Ammonium nitrate, 4522 Ammonium permanganate, 4518 Ammonium tetrachromate(2—), 4253 Ammonium tetranitroplatinate(II), 4578 Ammonium trichromate (2—), 4252 Anilinium nitrate, 2379... 

List of Tetrachromates Ammonium Tetrachromate, (NH4)2Cr40)3, mw 452.12 brn-red hygroscopic crysts, less stable than Amm trichromate mp - blackens at 160°, melts at 170° and decomp spontaneously giving off nitrous fumes. Can be prepd by evapg, in cold over coned sulfuric acid, a soln of Amm trichromate in nitric acid, d 1.39(Refs 1 2). 

Ammonium nitrate, 4517 Ammonium permanganate, 4513 Ammonium tetrachromate(2—), 4247 Ammonium tetranitroplatinate(II), 4573 Ammonium trichromate(2—), 4246 Anilinium nitrate, 2372... 

The results are shown respectively in Fig. 29. The region above the line abedef refers to unsaturated soln. eib represents soln. in equilibrium with solid chromium trioxide -, he, with solid ammonium tetrachromate cd, with solid trichromate de, with solid dichromate and ef, with solid monochromate. Ammonia was here selected as one of the componente because (NH4)20 is not stable. 

G. N. Wyrouboff 1 reported ammonium tetrachromate, (NH4)2Cr40i3, to be formed by crystallization from a soln. of ammonium dichromate in hot nitric acid of sp. gr. 1 41. E. Jager and G. Krliss could not obtain the salt in this way, "but... 

Chromium(vi) does not give rise to the extensive and complex series of polyacids and polyanions characteristic of the somewhat less acidic oxides of Vv, Movl and WVI. The reason for this is perhaps the greater extent of multiple bonding, Cr=0, for the smaller chromium ion. Other than the chromate and dichromate ions there is no oxo acid or anion of major importance, although trichromates, M2Cr3O10, and tetrachromates, M2Cr4013, have been reported. The dichromate ion in the ammonium salt has the structure shown in Fig. 25-C-2. 

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