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The hydrogen chromate ion may be protonated, with the formation of molecular chromic acid, H 2 CrO 4, but the pK a for the equilibrium H 2 CrO 4 ⇌ HCrO − 4 + H + is not well characterized. Reported values vary between about −0.8 and 1.6. [4] The dichromate ion is a somewhat weaker base than the chromate ion: [5]
Dichromate and chromate salts are oxidizing agents. For the tanning of leather, sodium dichromate is first reduced with sulfur dioxide. In the area of organic synthesis, [2] this compound oxidizes benzylic and allylic C-H bonds to carbonyl derivatives. For example, 2,4,6-trinitrotoluene is oxidized to the corresponding carboxylic acid. [3]
For lab and small scale preparations a mixture of chromite ore, sodium hydroxide and sodium nitrate reacting at lower temperatures may be used (even 350 C in the corresponding potassium chromate system). [2] Subsequent to its formation, the chromate salt is converted to sodium dichromate, the precursor to most chromium compounds and materials. [3]
In 2005–06, potassium dichromate was the 11th-most-prevalent allergen in patch tests (4.8%). [12] Potassium dichromate is one of the most common causes of chromium dermatitis; [13] chromium is highly likely to induce sensitization leading to dermatitis, especially of the hand and forearms, which is chronic and difficult to treat ...
The change in equilibrium is visible by a change from yellow (chromate) to orange (dichromate), such as when an acid is added to a neutral solution of potassium chromate. At yet lower pH values, further condensation to more complex oxyanions of chromium is possible. Both the chromate and dichromate anions are strong oxidizing reagents at low pH ...
Chromic acid is jargon for a solution formed by the addition of sulfuric acid to aqueous solutions of dichromate. It consists at least in part of chromium trioxide. [3] The term chromic acid is usually used for a mixture made by adding concentrated sulfuric acid to a dichromate, which may contain a variety of compounds, including solid chromium ...
Salts that produce hydroxide ions when dissolved in water are called alkali salts, and salts that produce hydrogen ions when dissolved in water are called acid salts. If the compound is the result of a reaction between a strong acid and a weak base, the result is an acid salt. If it is the result of a reaction between a strong base and a weak ...
Cadmium chromate; Caesium chromate; Calcium chromate; Chromate ester; Chromated copper arsenate; Template:Chromates and dichromates; Chrome orange; Chrome yellow; Chromic acid; Chromium(VI) oxide peroxide