Chromium sulphates

Various chromium-complex dyes were prepared recently by reacting ammonium chromium sulphate with a series of chelatable o,o -dihydroxyazopyridone structures (Scheme 5.9). Elemental analyses corresponded to a 1 2 metal-dye ligand ratio (5.35). The... 

Chromiummetal reacts with bromine in DMF solution to afford [Cr(DMF) ]-(Br3)3 which has been characterized by magnetic and spectral studies. The compound Cr2(S04)3,12C0(NH2)2,6H20 has been identified in the urea-chromium sulphate-water ternary system at 25 and the greater thermal... 

Prepare 20 ml of a solution of the obtained compound saturated at room temperature. Pour 3 ml of the solution into each of three test tubes. Add to the first tube 1 ml of a 1 N sulphuric acid solution, one drop of silver nitrate, and one drop of a 1 N manganese sulphate solution. Heat the tube. Add to the second tube 1 ml of a 1 A chromium sulphate solution and 2 ml of a 1 A sodium hydroxide solution. Pour into the third tube 1 ml of a 1 A sodium hydroxide solution and 1 ml of a 1 A manganese sulphate solution. Comment on your observations. Write the equations of the reactions. 

From this equation it can be seen that during the regeneration of chromium lyes sulphuric acid, which has been fixed in the form of chromium sulphate during the oxidation of organic compounds, is freed again. 

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,... 

Chromium also occurs in the folio-wing minerals dauhreelite, FeS.CrjSg, massive, brittle, non-magnetic, density 5-01,- redingfonitc, a hydrated chromium sulphate tarapacite, essentially a chromate of potassium and chrome-diopside, a pyroxene from Kimberley. 

When potassium hydroxide is added to solutions containing ferric chloride and chromium sulphate in A arying proportions, the iron is not... 

Violet Chromium Sulphates.—Chromic sulphate can be obtained in aqueous solution by dissolving chromic hydroxide (dried at 100° C.) in the calculated quantity of warm sulphuric acid, allowing the green solution to stand for a week, when it becomes blue in colour (although... 

Green Chromium Sulphates.—When the solid violet salt is heated above 90° C. a green amorphous mass is obtained. Contrary to the opinion of Wjwouboff, Colson considers that this substance may be regarded as a condensed sulphate for example,... 

Compounds of the green chromium sulphate with chromic acid have been prepared, viz. H2[Cr04.Cr2(S04)3], H4[(Cr04),.Cr2(S04)3], and... 

Chromium Chlorsulphates may be prepared either by the action of sulphuric acid on chromic chloride, or by the interaction of hydrochloric acid -with chromium sulphate. Isomeric modifications of these salts exist, for it has been shown that in certain cases the — SO4, and in others the —Cl, is ionised. 

Attempts of Sargeson and coworkers [158] to cross-link the chromium(III) tris-ethylenediaminate have not been successful because of rapid dissociation of intermediate imine species. However, Endicott and coworkers [159] have managed to synthesize chromium(III) sepulchrate, not isolating its tris-ethylenediaminate, upon heating of anhydrous chromium sulphate with concentrated aqueous ethylenediamine for several hours followed by the addition of formaldehyde and ammonia with constant heating. The... 

The concentration of the initial chromium sulphate solution for practical tanning is around 15-20% (w/w), which should be diluted for analysis. Pipette 10 ml of the initial chromium sulphate solution into a 11 volumetric bottle. Dilute the solution with distilled water to the 11 mark. Pipette 100 ml (Vp of the diluted solution into a 250 ml triangular beaker. Add 5 ml of hydrogen peroxide (around 33% w/w of... 

H.OJ and 5 ml of 10% potassium hydroxide (or sodium hydroxide). Boil the solution gently for 1 h to oxidize Cr to C.f + and to get rid of excess peroxide. Add 10 ml of 6 N H,SO to acidify the solution. After standing in the dark for 5 min, add 20 ml of 10% (w/w) potassium iodide. The solution turns to a dark reddish brown owing to the formation of iodine. Titrate the iodine in the solution with 0.1 N standard solution of sodium thiosulphate until the colour of the solution turns to yellow. Add 1-2 ml of starch solution (1% w/w) as an indicator. The colour of the solution turns to dark blue. Continue titration until the colour just disappears. Record the volume of the standard solution of sodium thiosulphate used (V ). The concentration C (g 1 ) of initial chromium sulphate solution can be calculated by the following equation ... 

As we can see, titration of the chromium sulphate and preparation of the standard sodium thiosulphate solution are relatively long procedures. By means of AAA, the test for chromium can be simplified. 

Sulphate of chromium CrS04.7H2O Chromium sulphate. 

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