Formic aldehyde methanol, HCHO3, made by oxidation of synthetic methanol or low-boiling petroleum gases such as propane or butane. Available commercially as a 37-50 percent aqueous solution which may contain up to 15 percent methanol to inhibit polymerization. Commercial grades are called formalin. An effective preservative, disinfectant, and sanitizing agent, although it is not a sterilizer, because formaldehyde does not kill completely all microorganisms. Is not typically used to sanitize drinking water treatment equipment because of personal hazards associated with it i.e., toxic by inhalation, strong irritant, and a carcinogen.