Na2C2O42H2O

Sodium oxalate dihydrate, with the chemical formula Na2C2O4·2H2O, is the hydrated form of sodium oxalate. Sodium oxalate itself is an ionic compound composed of sodium cations (Na+) and oxalate anions (C2O4^2-). In the dihydrate form, two water molecules are incorporated into the crystal lattice for each formula unit of sodium oxalate. This compound typically appears as white, crystalline solid.

Na2C2O4·2H2O is soluble in water, forming a neutral solution. The anhydrous form, Na2C2O4, can be obtained by heating the dihydrate, which drives off the water molecules. Sodium oxalate is a relatively strong reducing agent and can react with oxidizing agents. It is also known for its ability to precipitate calcium ions from solution, forming insoluble calcium oxalate. This property is utilized in various analytical chemistry procedures.

Historically, sodium oxalate has been used in various applications, including as a mordant in dyeing, in photography, and as a cleaning agent. It is also a component in some analytical standards for titrations. Due to its toxicity, particularly its ability to chelate calcium and cause kidney damage, caution should be exercised when handling sodium oxalate and its hydrates.