When treated with water, chloral evolves heat and unites with the water to form a crystalline hydrate, CC13CH(0H)2.

The quantity of water necessary for this change is added slowly, to avoid too much development of heat. One hundred parts of chloral require 12 2 parts of water, and yield 112 2 parts of the hydrate. To obtain the purest product, the solid thus obtained is recrystallised from benzene, chloroform, carbon disulphide, or petroleum ether as already described. A mixture of ethylene chloride and ethidene chloride, obtained as a by-product in the manufacture, has also been used for recrystallising the product. In order to get the hydrate in the form of cubes or plates rather more than the calculated theoretical quantity of water is added to the chloral, slowly and with energetic shaking, which is continued until the milky, syrupy mass has quite cooled down and set; this treatment obviates the formation of lumpy masses. The product is z spread on porcelain plates, cut into cubes, and dried in a drying-chamber over sulphuric acid.