In a 1-l. three-necked flask are mixed 150 g. (1.63 moles) of β-hydroxyethyl methyl sulfide (p. 345) (Note 1) and 200 g. of dry chloroform (Note 2). The flask is placed on a steam bath and is fitted with a dropping funnel, a mechanical stirrer, and a condenser. The condenser is fitted with a trap to remove the vapors of hydrogen chloride and sulfur dioxide. A solution of 204 g. (1.7 moles) (Note 3) of thionyl chloride in 135 cc. of dry chloroform is added dropwise to the β-hydroxyethyl methyl sulfide over a period of about two hours (Note 4). The reaction mixture is stirred vigorously during this addition and for about four hours after the addition is complete. The chloroform is distilled on the steam bath and the residue is distilled under reduced pressure. The yield is 135–153 g. (75–85 per cent of the theoretical amount) of a product boiling at 55–56°/30 mm. (Note 5).