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Chromate and dichromate salts of heavy metals, lanthanides and alkaline earth metals are only very slightly soluble in water and are thus used as pigments. The lead-containing pigment chrome yellow was used for a very long time before environmental regulations discouraged its use. [ 7 ]
Sodium dichromate is the inorganic compound with the formula Na 2 Cr 2 O 7.However, the salt is usually handled as its dihydrate Na 2 Cr 2 O 7 ·2H 2 O.Virtually all chromium ore is processed via conversion to sodium dichromate and virtually all compounds and materials based on chromium are prepared from this salt. [1]
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]
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 ...
Pyridinium chlorochromate (PCC) is a yellow-orange salt with the formula [C 5 H 5 NH] + [CrO 3 Cl] −. It is a reagent in organic synthesis used primarily for oxidation of alcohols to form carbonyls. A variety of related compounds are known with similar reactivity.
The second family of reagents are salts, featuring the pyridinium cation (C 5 H 5 NH +). pyridinium dichromate (PDC) is the pyridium salt of dichromate, [Cr 2 O 7] 2-. pyridinium chlorochromate (PCC) is the pyridinium salt of [CrO 3 Cl] −. These salts are less reactive, more easily handled, and more selective than Collins reagent in ...
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 ...
Sodium chromate is converted into other hexavalent chromium compounds such as chromium trioxide and various salts of chromate and dichromate. Industrial uses of hexavalent chromium compounds include chromate pigments in dyes, paints, inks, and plastics; chromates added as anticorrosive agents to paints, primers, and other surface coatings; and ...