Calcium Carbide

About This Product

Calcium carbide, CaC2, CAS number 75-20-7, is made by reducing lime with coke in an electric arc furnace at around 2,000 degrees Celsius. Commercial material is a hard, grey to black crystalline lump, never the pure white of the laboratory compound, because it carries free lime, carbon and other furnace residues. Its whole value rests on one reaction: with water it gives acetylene and calcium hydroxide, and it does so readily enough that the same reaction is its main hazard. Quality is therefore not quoted as a purity but as a gas yield, the litres of acetylene released per kilogram at 20 degrees Celsius and 101.3 kPa. The 295 litres per kilogram offered here is a standard commercial figure against a theoretical maximum near 350. Because atmospheric humidity alone is enough to start the reaction, carbide is packed in sealed steel drums, normally under nitrogen, and a drum that has been opened and left will both lose yield and accumulate acetylene in its head space. Lump size is specified separately and matters in use: a generator designed for 50 to 80 millimetre lumps will flood if it is charged with fines. It is used to generate acetylene for oxy-acetylene welding and cutting, as the acetylene feedstock for carbide-route vinyl chemistry, in steelmaking for desulphurisation and deoxidation, and in calcium cyanamide production. Bio Green Chem supplies calcium carbide at 295 litres per kilogram minimum gas yield in sealed 50 kg and 100 kg iron drums, with lump size agreed on the order. It is UN 1402, Class 4.3, a dangerous-when-wet solid that emits flammable acetylene on contact with water; store it dry and sealed and handle to the safety data sheet.