![]() ![]() Chromic oxide is a bright green hygroscopic powder with melting point of 2435☌, boiling point of 4000☌ and specific gravity of 5.2. Properties vary widely depending on the particular compound. Synonyms: Chromic ion, Chromium ion, Trivalent chromiumĬhromium sulfate (CASR# 1) Physical propertiesĬhromium is a white, hard, lustrous and brittle metal that is extremely resistant to ordinary corrosive agents. Chromic sulfate is used in tanning, green paints, inks and text dyes and in ceramics. Chromium (III) nitrate is used in the preparation of chrome catalysts, in textile printing operations, and as a corrosion inhibitor. Chromium (III) acetate is used to fix certain textile dyes, to harden photographic emulsions and as a catalyst. More specifically, chromium (III) oxide is used as a paint pigment, a fixative for certain textile dyes and as a catalyst. Chromium (III) compounds are employed as pigment, as catalyst, as tanning agent in the tanning industry, in the production of pure chromium metal and chromium (VI) compounds, and in the production of refractory bricks. More applications are in the photographic industry (sensitiser), in industrial water treatment (including treatment of cooling tower water), as medicinal astringents and antiseptics, and in nuclear and high temperature research. protective coatings for automotive and equipment accessories), as dyes, as inorganic paint pigments, for leather tanning, as fungicides and wood preservatives, and as catalysts. Chromium compounds are used for chrome plating (e.g. You can also recycle the chromium ions.Chromium metal is used as an alloying element to harden steel and to manufacture stainless steel. A clean plastic bottle is a good storage bottle.Ĭhromium(III) can be harmful to marine life, so water-soluble compounds of trivalent chromium should be precipitated as chromium(III) hydroxide before being disposed of in the trash. Grow crystals of chrome alum, a double saltĬontact with solutions of chromium(III) sulfate or inhalation of particles may cause irritation, but overall this compound is relatively non-toxic.Ĭhromium(III) sulfate is relatively stable and has low reactivity, but should be kept away from temperatures greater than 40 ☌ when in the presence of moisture to avoid complex formation.It should be noted, however, that many grades of chromium(III) oxide are not reactive enough, often as a result of being calcined, to respond to treatment with acid. ![]() To extract the chromium(III) from solution, the reaction products must be treated with bases to precipitate chromium(III) hydroxide.Ĭhromium(III) sulfate can be more directly produced by the action of cold, dilute sulfuric acid on chromium(III) hydroxide or chromium(III) oxide. If the temperature of the reaction is kept low enough, the presence of chromium(III) sulfate will be indicated by a blue or blue-violet color to the end product, rather than a green color produced when the temperature is too high. The Jones oxidation, which uses a solution of potassium dichromate or sodium dichromate acidified with sulfuric acid to oxidize alcohols, produces chromium(III) sulfate as a byproduct, along with sodium or potassium sulfate. Its use as a tanning chemical has largely been superseded by chrome alum and other agents. Purer samples can be dried to form a lighter-colored powder.Ĭhromium(III) sulfate is readily soluble in water and some lower alcohols.Ĭhromium sulfate, for the most part, can only be purchased from online suppliers. Recently prepared samples or those that have been subjected to heat may contain a deep green-colored sulfato complex and are hygroscopic as a result. Strong oxidizers such as hypochlorite can oxidise the aqueous Cr(III) to chromate (CrO 4 2-).Ĭhromium(III) sulfate most often appears as a blue-grey or violet-grey amorphous solid. If the base used is a carbonate or bicarbonate, this reaction is accompanied with the release of carbon dioxide, in a manner similar to iron, which does not form carbonates. Treatment of chromium(III) sulfate with bases produces chromium(III) hydroxide. Freshly prepared chromium sulfate often contains traces of this coloration, with some samples even appearing green rather than blue, but is otherwise usable.Ī solution of both chromium(III) sulfate and potassium sulfate will yield crystals of chrome alum on partial evaporation. Solutions of chromium(III) sulfate turn from blue to green upon heating, indicating the formation of a less reactive "sulfato-complex" that may take days or weeks to revert. ![]()
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