advantages over conventional nitrogen fertilizers. However, the large-scale implementation of ammonia synthesis via the Haber process became a serious competitor to the very energy-intensive Frank Caro process. As urea (formed via the Haber–Bosch process) was significantly more nitrogen-rich (46% compared to ca. 20% nitrogen content) cheaper and faster acting, the role of calcium cyanamide was gradually reduced to a multifunctional nitrogen fertilizer in niche applications. Other reasons for its loss of popularity were its dirty-black color, dusty appearance and irritating properties, as well as its inhibition of an alcohol-degrading enzyme which causes temporary accumulation of acetaldehyde in the body leading to dizziness, nausea, and alcohol flush reaction when alcohol is consumed around the time of bodily exposure. Production Calcium cyanamide is prepared from calcium carbide. The carbide powder is heated at about 1000 °C in an electric furnace into which nitrogen is passed for several hours. The product is cooled to ambient temperatures and any unreacted carbide is leached out cautiously with water. CaC2 + N2 → CaCN2 + C (ΔH = –69.0 kcal/mol at 25 °C) It crystallizes in hexagonal crystal system with space group R3m and lattice constants a = 3.67 Å, c = 14.85 Å. Uses The main use of calcium cyanamide is in agriculture as a fertilizer. In contact with water, it decomposes and liberates ammonia: CaCN2 + 3 H2O → 2 NH3 + CaCO3 It was used to produce sodium cyanide by fusing with sodium carbonate: CaCN2 + Na2CO3 + 2 C → 2 NaCN + CaO + 2 CO Sodium cyanide is used in cyanide process in gold mining. It can also be used in the preparation of calcium cyanide and melamine. Through hydrolysis in the presence of carbon dioxide, calcium cyanamide produces cyanamide: CaCN2 + H2O + CO2 → CaCO3 + H2NCN The conversion is conducted in slurries. For this reason, most commercial calcium cyanamide is sold as an aqueous solution. Thiourea can be produced by the reaction of hydrogen sulfide with calcium cyanamide in the presence of carbon dioxide. Calcium cyanamide is also used as a wire-fed alloy in steelmaking to introduce nitrogen into the steel. Safety The substance can cause alcohol intolerance, before or after the consumption of alcohol. References External links Bioassay of Calcium Cyanamide for Possible Carcinogenicity (CAS No. 156-62-7) Calcium compounds Cyanamides Inorganic fertilizers