Copper benzoate

Copper benzoate is the chemical compound with the formula Cu(C6H5CO2)2. This coordination complex derived from the cupric ion and the conjugate base of benzoic acid. Because copper emits blue when heated in a flame, this salt has found some use as a source of blue light in fireworks.

Preparation
Preparation is easily done by mixing aqueous solutions of sodium benzoate or potassium benzoate and copper sulfate. Solid copper benzoate forms as a bluish-green precipitate and can be collected by filtration. The equations for these reactions are:
 * CuSO4 + 2KC6H5CO2 → Cu(C6H5CO2)2 + K2SO4


 * CuSO4 + 2NaC6H5CO2 →  Cu(C6H5CO2)2 + Na2SO4