Sodium cyanide is a poisonous compound with the formula NaCN. It is a white, water-soluble solid. Cyanide has a high affinity for metals, which leads to the high toxicity of this salt. Its main application, in gold mining, also exploits its high reactivity toward metals. It is a moderately strong base. When treated with acid, it forms the toxic gas hydrogen cyanide:

NaCN + H2SO4 → HCN + NaHSO4