In a 5-l. crock or battery jar, provided with a powerful mechanical stirrer, are placed 3.5 l. of water and 249 g. (165 cc., 2.16 moles) of thiophosgene (p. 506) (Note 1). To the vigorously stirred (Note 2) mixture is added slowly 255 g. (2 moles) of p-chloroaniline during about one-half hour. The stirring is continued for about an additional one-half hour. The dark brown oil is separated, washed with 50 cc. of 10 per cent hydrochloric acid, and placed in a flask for steam distillation.

The flask is immersed in an oil bath heated to 120° and dry steam is then passed through the reaction mixture. The first few cubic centimeters of distillate contain the excess of thiophosgene and are discarded. The isothiocyanate passes over with the water as an oil that solidifies on cooling. The steam distillation requires about four hours. The crude material is crystallized from two parts of ethyl alcohol at 50°, from which it separates as white needles melting at 44–45°. The yield is 245–275 g. (72–81 per cent of the theoretical amount) (Note 3).