Dikromaatit

Dikromaatit, also known as dichromates, are salts that contain the dichromate anion Cr2O7^2-. The dichromate anion arises from dichromic acid H2Cr2O7 and in aqueous solution Cr2O7^2- predominates at neutral to basic pH, while strong acidity converts it to dichromic acid H2Cr2O7. Common examples of dichromate salts are potassium dichromate K2Cr2O7, sodium dichromate Na2Cr2O7, and ammonium dichromate (NH4)2Cr2O7. They typically form orange to yellow-orange crystalline solids and dissolve readily in water. Dichromates are strong oxidizing agents and, in acidic conditions, Cr(VI) species can oxidize a wide range of substrates, with Cr(VI) reduced to Cr(III) in the process.

Uses of dikromaatit include oxidation in organic synthesis, sanitation and passivation of laboratory glassware, and historical roles in photographic chemistry where dichromates were used to harden gelatin in negatives. They have also been employed in leather tanning, wood treatment, and as mordants in dyeing and printing.

Safety and environmental concerns are central to their handling. Dikromaatit contain hexavalent chromium, a known carcinogen and toxic substance. Exposure can cause irritation of skin, eyes, and respiratory tract. They are strong oxidizers and should be kept away from combustible materials. Waste containing dichromates must be treated as hazardous and disposed of according to regulatory requirements. If released to the environment, they can persist and should be reduced to Cr(III) prior to disposal to minimize ecological risk.