Calcium carbide 75-20-7

  Chemically pure calcium carbide is almost a colorless and transparent crystal. Ultra-pure calcium carbide is a large sky blue crystal, the same color as quenched steel. Industrial calcium carbide is divided into gray, brown or black according to its purity. Its crystal cross section is gray and purple when the purity is high. The new cross-section of calcium carbide has a shiny surface. When exposed to the air, it will lose its luster and become gray-white due to the absorption of moisture in the air. Calcium carbide is actually an impure calcium carbide, containing lime and a small amount of silica, alumina, calcium sulfide, calcium phosphide and other impurities. The chemical composition of calcium carbide with a CaC2 content of 85% is: CaC2 85.17%, CaO10.60%, SiO22.34%, (Fe2O3Chemicalbook+Al2O3)2.55%, MgO0.15%. Its density decreases as the CaC2 content increases. Its melting point changes with the content of CaC2. The melting point of pure CaC2 is 2300℃; industrial calcium carbide generally contains 80% CaC2, and its melting point is about 2000℃; the melting point of calcium carbide containing 269% CaC2 is the lowest, 1750℃; when the CaC2 content is further reduced, the melting point On the contrary, it rose again, and then dropped to 1800℃ (equivalent to 35.6% CaC2). There is a maximum temperature point of 1980℃ (equivalent to 352.5% CaC2) between 1750℃ and 1800℃. When CaC2 is lower than 35.6 %, its melting point rises again.