Na2Cr2O7

Sodium dichromate, with the chemical formula Na2Cr2O7, is an inorganic compound consisting of sodium ions and the dichromate anion. It appears as orange to reddish-orange crystalline solids and is highly soluble in water. It is a strong oxidizing agent and contains chromium in the hexavalent state (Cr(VI)).

In aqueous solution, chromate and dichromate species are interrelated and depend on pH. Dichromate (Cr2O7^2−) is common under acidic conditions, while chromate (CrO4^2−) dominates at higher pH. As a Cr(VI) compound, sodium dichromate can be reduced to Cr(III) in redox reactions, a property exploited in various chemical applications but also a source of toxicity.

Industrially, sodium dichromate is produced and used as an intermediate in the manufacture of sodium chromate and chromic acid. It serves as a versatile precursor for chromium-based reagents used in metal finishing, dyeing and pigment manufacturing, and as an oxidizing agent in organic synthesis. Historically, it has been employed in wood preservation and as a component of chromated metal treatments; many of these uses have been restricted or phased out due to safety and environmental concerns.

Safety and handling guidelines emphasize that sodium dichromate is toxic and carcinogenic. Proper PPE and engineering controls are required to minimize exposure, and it should be handled away from organic materials and reducing agents. Waste and spills are treated as hazardous, with Cr(VI) typically reduced to Cr(III) prior to disposal to mitigate environmental risk. Regulatory controls govern its use, handling, and disposal in many jurisdictions.