TriChromate, potassium

Barium Potassium Trichromate, 2BaCr30io- 2Clr30]o-3H20, is formed when a potassium salt is added to a chromic acid solution of barium dichromate and the mixture concentrated it crystallises in brownish-red needles, which are very deliquescent and ai-e decomposed by water. 

Potassium Trichromate, EgCrgOio, obtained by dissolving the dichromate in nitric acid, of density 1-19, or by interaction of potassium dichromate with chromium trioxide or chromic acid, as red monoclinic crystals,of density 2-649, which melt at 250° C., and are decomposed by water with formation of dichromate and chromic acid. ... 

G. Kriiss obtained the trichromate by evaporating over sulphuric acid a soln. of potassium dichromate in chromic acid F. A. H. Schreinemakers, and I. Koppel and E. Blumenthal studied the conditions of equilibrium, and the results are summarized in Figs. 36 to 41. Potassium trichromate furnishes deep red, prismatic crystals and F. Bothe reported that the monoclinic prisms have the axial ratios a 6 c=0-8437 1 0-8318, and j8=101° 0 the (OlO)-cleavage is distinct. F. Bothe gave 3-613 for the sp. gr. H. G. F. Schroder, 2-676-2-702 L. Pla air and J. P. Joule, 2-655 and E. Jager and G. Kriiss, 2-667 at 10°—crystallized from chromic acid—-and 2-648 at 11°—crystallized from nitric acid. The hardness is... 

Potassium Tetrachromate, KaCrjO, is prepared similarly to the trichromate (the nitric acid used haring density 1-41), and has similar properties. The crystals belong to the monoclinic system. ... 

The results are plotted in Fig. 36 where the solubility curve ah has the solid phase CrOs he, potassium tetraohromate cd, trichromate de, dichromate ... 

C. Schmidt used cone, nitric acid, but G. N. Wyroubofi said that if the nitric acid be too cone.—-over 1-41 sp. gr.—-some tetrachromate is formed. H. Eeinsch, and C. J. B. Karsten observed the tendency of potassium nitrate to crystallize out with the trichromate in nitric acid soln. -, and L. Darmstadter mistook the impure product for nitrochromate. M. Siewert separated the product from potassium nitrate by fractional crystallization. C. von Hauer, M. Siewert, and E. Jager and... 

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... 

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