Kaliumchromat

Kaliumchromat, or potassium chromate, is an inorganic salt with the formula K2CrO4. It contains the chromate anion CrO4^2− and chromium in the +6 oxidation state. At room temperature it forms yellow to orange-yellow crystalline solids that are highly soluble in water. In aqueous solution, chromate equilibrates with dichromate depending on pH: acidic conditions favor conversion to dichromate (Cr2O7^2−).

Preparation and occurrence: Potassium chromate is produced industrially as an intermediate in chromium chemistry. It can be prepared by neutralizing chromic acid or by reactions involving potassium hydroxide with dichromate salts. It also occurs as a historical pigment and as a lab reagent.

Uses: Historically it has been used as a pigment (chrome yellow) and as a qualitative inorganic-analysis reagent. In analytical chemistry, chromate ions are employed to detect certain cations; for example, lead ions form a yellow precipitate of lead chromate (PbCrO4) with chromate solutions, and silver ions can form silver chromate under specific conditions. Potassium chromate also serves as a source of chromate in some coatings and industrial processes that involve chromium(VI) species, though many uses are now restricted due to safety concerns.

Safety and handling: Potassium chromate is a chromium(VI) compound, which is toxic, carcinogenic, and a strong oxidizer. It can irritate skin, eyes, and the respiratory tract. Handling requires appropriate personal protective equipment and good ventilation, with dust control. It should be stored away from reducing agents and incompatible materials and disposed of as hazardous waste in accordance with local regulations. Environmental release poses risks to aquatic life, and chromium(VI) compounds are subject to strict regulatory controls in many jurisdictions.