Potassium chromic sulphates

SYNS CHROME ALUM CHROME POTASH ALUM CHROMIC POTASSIUM SULFATE CHROMIC POTASSIUM SULPHATE CHROMIUM POTASSIUM SULFATE (1 1 2) CHROMIUM POTASSIUM SULPHATE CRYSTAL CHROME ALUM POTASSIUM CHROMIC SULPHATE POTASSIUM CHROMIUM ALUM POTASSIUM DISULPHATOCHROMATE(III) SULFURIC ACID, CHROMIUM (3+) POTASSIUM SALT (2 1 1)... 

Potassium Chromic Sulphates.—Several have been described K2S04.Cr2(S04)3.H2S04 Cr2(S04)3.3KaS04 and Cr2(S0.j)3.Cr203. 

Basicity chrome alum CCRIS 7532 Chrome alum Chrome potash alum Chromic potassium sulfate Chromic potassium sulphate Chromium potassium bis(sulphate) Chromium potassium sulfate (1 1 2) Chromium potassium sulfate (CrK(S04)2) Chromium potassium sulphate Chromium(lll) potassium sulfate Crystal Chrome Alum EINECS 233401-6 Potassium chromic sulfate Potassium chromic sulphate Potassium chromium alum Potassium chromium disulfate (KCr(S04)2) Potassium disulphatochromate (III) Sulfuric acid, chromium(3 ) potassium salt (2 1 1). Mordant for dyeing fabrics uniformly [dodecahydratej mp = 89° d = 1.83 soluble in 4 parts H2O. 

Hexaethylenediamino-hexol-tetrachromic Sulphate, [Cr4(OH)6en6](SO4)3.10H2O, is prepared from partially dehydrated chromic alum. The bluish-grey powder obtained is heated with ethylene-diamine monohydrate on a water-bath till a red-coloured mass is produced, which consists of a mixture of potassium sulphate, luteo-chromic sulphate, and the sulphate of the hexol compound, and from the mixture the latter compound is obtained by dissolving out the more soluble salts with water. The crude, difficultly soluble sulphate is purified by dissolving in dilute sulphuric acid and reprecipitating with excess of ammonia. It crystallises in small needles which are almost insoluble in water and soluble in dilute acids. 

The halogenates of chromium, uranium, and manganese.—The double decomposition of chrome alum and barium chlorate, or a soln. of chromic sulphate and potassium chlorate, furnishes a violet liquid containing chromium chlorate,134 which becomes green at 65°. Even at ordinary temp, the soln. smells of chlorine at 100°, chlorine gas is given off and the liquid becomes reddish-yellow—it contains chromic... 

The preparation of potassium dichromate (Preparation 61) illustrated how chromic oxide, Cr203, can be oxidized to a chromate in which chromium exists as Cr03. For the preparation of chromic alum, it might seem as if chromic oxide or the natural chromite should yield chromic sulphate directly on treatment with sulphuric acid. This is impossible, however, because both of these substances are very resistant to the action of acids. Practically, they yield only to the action of alkaline oxidizing agents, which convert them into a chromate. Therefore potassium, or sodium, dichromates are always the products made directly from the mineral, and these serve as the materials from which other compounds of chromium are prepared. To make chromic alum from potassium dichromate it is necessary to reduce the chromium to the state of oxidation in which it originally existed in the mineral, and to add sufficient sulphuric acid to form the sulphates of potassium and... 

Similarly potassium bichromate is reduced to chromic sulphate in accordance with the equation —... 

Chromium in its Compounds is sometimes metallic and sometimes non-metallic toward the other components. Thus, in chromium trioxide, CrOg, the anhydride of the hypothetical chromic acid, H2Cr04, chromium acts as a non-metal, just like sulphur in sulphuric acid hence in chromates the chromium is acidic, or non-metallic, in its chemical relations with the other elements. In chromic compounds, however, chromium acts as a metal. Thus chromium hydroxide, Cr(OH)3, is analogous to aluminium hydroxide chrome alum is potassium chromium sulphate, and is analogous to aluminium alum. The two classes pass into each other by appropriate operations,... 

Chromic oxide jellies may be formed by adding sodium or potassium hydroxide or ammonia to a solution of chromic sulphate or chloride containing sodium acetate or by adding sodium or potassium hydroxide, hut not ammonia, to a solution of chrome alum. The jelly is violet if prepared by the addition of ammonia or of a slight excess of the alkali metal hydroxide if the latter is added in larger quantity the jelly is green. The jellies dissolve in hydrochloric acid, but re-form on neutralising the solution if sufficient sodium acetate is present. 

Potassium dichromate will oxidize oxalic acid, C2H204,2H20, in sulphuric acid solution to water and carbon dioxide. Upon evaporating the resulting solution of potassium and chromic sulphates, a double compound of these salts with twenty-four molecules of water of crystallization, which belongs to the class of alums, separates out in well-defined crystals. If the solution is heated, however, a green compound of very different properties is formed and no crystals can be obtained. 

X 10 ii per cent. C. F. Schonbein, N. Bunge, Z. Roussin, and C. W. Vincent prepared a mercury-chromium alloy or chromium amalgam, by the action of potassium or sodium amalgam on a cone. soln. of chromic chloride and H. Moissan obtained the amalgam by a similar process, as well as by the action of sodium amalgam on chromous chloride, bromide, or iodide. R. Myers obtained it by the electrolysis of a soln. of chromic sulphate in dil. sulphuric acid using a platinum anode, and mercury cathode J. Feree found that with a soln. of chromic chloride the yield is poor. 

Schumann i made some observations on the relative affinities of chromium and the metals for sulphur and oxygen. According to A. Moberg, when chromous chloride is treated with ammonium sulphide, a black precipitate—presumably chromous sulphide or chromium monosulphide, CrS—is formed E. M. P ligot obtained it by the use of potassium sulphide and observed that the precipitate is insoluble in an excess of the precipitant. M. Traube observed that the sulphide occurs among the products of the reduction of chromic sulphate heated in hydrogen. 

M. Traube showed that the black product is a mixture of chromic sulphide and oxide. M. Traube obtained some sulphide by heating acid chromic sulphate in dry hydrogen sulphide A. Moulot heated the sulphate mixed with potassium polysulphide and K. Bruckner, with sulphur. H. Moissan heated chromic oxalate in hydrogen sulphide and R. Schneider heated the higher chromium sulphides—e-5 . Cr4S7=2Cr2S3+S. 

A. Recoura obtained potassium chromitetrasulphate, K2[Cr2(S04)4], by evaporating on the water-bath a mol of green chromic sulphate with a mol of potassium sulphate and the tetrahydrate, K2[Cr2(S04)4].4H20, by dehydrating chrome-alum slowly at 110°. The former compound is dark green, and it is soluble in water. 

CAUTION. Ethers that have been stored for long periods, particularly in partly-filled bottles, frequently contain small quantities of highly explosive peroxides. The presence of peroxides may be detected either by the per-chromic acid test of qualitative inorganic analysis (addition of an acidified solution of potassium dichromate) or by the liberation of iodine from acidified potassium iodide solution (compare Section 11,47,7). The peroxides are nonvolatile and may accumulate in the flask during the distillation of the ether the residue is explosive and may detonate, when distilled, with sufficient violence to shatter the apparatus and cause serious personal injury. If peroxides are found, they must first be removed by treatment with acidified ferrous sulphate solution (Section 11,47,7) or with sodium sulphite solution or with stannous chloride solution (Section VI, 12). The common extraction solvents diethyl ether and di-tso-propyl ether are particularly prone to the formation of peroxides. 

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