English: freon, a general term for several chlorofluorocarbons and chloroethane. Include CCl3F(F- 1 1), CCl2F2(F- 12), CClF3(F- freon 13), CHCl2F (F-2 1) and chcl2 (f F2clc-cclf2 (f-114), C2H4F2(F- 152), c2clf5 (f-15), c2h3f3 (f/kloc) The freon is colorless gas or volatile liquid at room temperature, with slight fragrance, low toxicity and stable chemical properties. The most important is dichlorodifluoromethane CCl2F2(F- 12). Dichlorodifluoromethane is a colorless gas at normal temperature and pressure; Melting point-158℃, boiling point -29.8℃, density-1.486 g/cm (-30℃); Slightly soluble in water, easily soluble in ethanol and ether; Does not react with acids and bases. Dichlorodifluoromethane can be prepared by the reaction of carbon tetrachloride with anhydrous hydrogen fluoride in the presence of catalyst. The reaction products are mainly dichlorodifluoromethane, as well as CClF3 and CCLF3, and CCl2F2 can be separated by fractionation.

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