Ammonium Trichromates

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

Noteworthy properties were discovered in ammonium trichromate (NH4)3Cr3O10, produced while crystallizing ammonium bichromate from nitric acid, d = 1.39 (Siewert [47]). At 190°C the compound undergoes explosive decomposition, evolving nitric oxide and nitrogen dioxide. 

List of Trichromates Ammonium Trichromate, (NH4)2Cr3010, mw 352.11 dk garnet-red, rhmb bipyramids mp-darkens at 110-20° decomp at 150-60°... 

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

L. Varenne reported crystals of the oclohydrate, CrBr3.8H20, to be formed by treating a cold, cone. soln. of potassium or ammonium trichromate with dil. hydrobromic acid, and allowing the liquor to stand at 0°. The violet crystals are a combination of the cube and octahedron. The salt loses water at 110° and becomes green at 200°, in air, it forms an oxybromide, and finally chromic oxide. A. Werner... 

Ammonium Salts Which are Explosive, examined by H.Kast and described in SS 21, 205-9(1926) and SS 22, 6-9, 30-4, 56-61, 77-80, 99-102 131-5(1925) included azide, bichromate, chlorate, nitrate, nitrite, perchlorate, permanganate and trichromate... 

The kinetics of the ammonium chromate, bichromate and trichromate decomposition were investigated by Fischbeck and Spingler [48] who measured the increase of pressure with time in an evacuated vessel. The activation energy is 40.0, 49.0 and 34.0 kcal/mole, respectively. 

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). 

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. 

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. 

M. Siewert i evaporated a soln. of ammonium dichromate in nitric acid, and obtained ntnmnniiim trichromate, (NH )2Cr30io. E. Jager and G. Kriiss recommended nitric acid of sp. gr. 1 39 but added that it is more convenient to prepare the salt from a soln. of ammonium dichromate in a cone. soln. of chromic acid. 

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