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It is the acidic anhydride of chromic acid, and is sometimes marketed under the same name. [6] This compound is a dark-purple solid under anhydrous conditions and bright orange when wet. The substance dissolves in water accompanied by hydrolysis. [clarification needed] Millions of kilograms are produced annually, mainly for electroplating. [7]
Chromium(VI) compounds in solution can be detected by adding an acidic hydrogen peroxide solution. The unstable dark blue chromium(VI) peroxide (CrO 5) is formed, which can be stabilized as an ether adduct CrO 5 ·OR 2. [6] Chromic acid has the hypothetical formula H 2 CrO 4. It is a vaguely described chemical, despite many well-defined ...
Further condensation reactions can occur in strongly acidic solution with the formation of trichromates, Cr 3 O 2− 10, and tetrachromates, Cr 4 O 2− 13. [2] All polyoxyanions of chromium(VI) have structures made up of tetrahedral CrO 4 units sharing corners. [3] The hydrogen chromate ion, HCrO 4 −, is a weak acid: HCrO − 4 ⇌ CrO 2−
Chromic acid is an intermediate in chromium plating, and is also used in ceramic glazes, and colored glass. Because a solution of chromic acid in sulfuric acid (also known as a sulfochromic mixture or chromosulfuric acid) is a powerful oxidizing agent, it can be used to clean laboratory glassware, particularly of otherwise insoluble organic ...
Although insoluble in water, it reacts with acid to produce salts of hydrated chromium ions such as [Cr(H 2 O) 6] 3+. [10] It is also attacked by concentrated alkali to yield salts of [Cr(OH) 6] 3−. When heated with finely divided carbon or aluminium, it is reduced to chromium metal: Cr 2 O 3 + 2 Al → 2 Cr + Al 2 O 3
The mechanism of this process likely depends on the acidity of the chromium reagent. Acidic reagents such as PCC may cause ionization and recombination of the chromate ester (path A), while the basic reagents (Collins) likely undergo direct allylic transposition via sigmatropic rearrangement (path B).
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CrO3 dissolves in water to make a solution containing H+ and CrO4-- ions, which is a dilute solution of chromic acid. Interestingly, CrO3 shows acid properties without water being present e.g. CaO + CrO3 --> CaCrO4. It is an example of a "Lewis acid" which meets the (broader) definition of an acid suggested by the chemist G.N.Lewis in the 1920s.