ADAMS AND WILI.IAMSON : PHYSICAL, CONSTANTS OF MUSTARD GAS 3 1 



and at the same time certain other properties of this substance 

 were determined from its behavior under hydrostatic pressure. 



The compound 2,2-dichloroethylsulfide^ — (C2H4C1)2S — is known 

 as mustard gas or mustard oil, and is, when pure, a colorless, 

 oily liquid which boils about 217°. The compressibility was 

 measured by the same method and using the same apparatus 

 as that already described. ^ The procedure, in brief, is as fol- 

 lows: The material to be compressed is surrounded by kero- 

 sene in the interior of a thick-walled steel cylinder, one end of 

 which is closed while the other end is fitted with a piston and 

 leak-proof packing. By means of a hydraulic press the piston 

 is forced into the cylinder, thus subjecting the kerosene and the 

 given material to hydrostatic pressure and thereby decreasing 

 the volume of each. The decrease in volume of the substance 

 for each increment of pressure is determined from a pair of read- 

 ings of pressure and corresponding piston displacement. Pres- 

 sures were measured by an electrical method, the precision be- 

 ing such that one scale division was equal to about one megabar;^ 

 the displacement of the piston was read on a dial micrometer 

 which was graduated to 0.01 mm. Temperature regulation 

 was obtained by an electric heating coil of asbestos-covered 

 "nichrome" wire wrapped around the heavy steel cyHnder and 

 covered with an insulating layer of felt. About 10 g. of the 

 material was contained in a steel capsule closed at the top and 

 terminating below in a capillary which dipped into a cup con- 

 taining mercury. Pressure could thus be transmitted through 

 the mercury seal to the interior of the capsule. 



Table i shows the results for the decrease in volume (at 3 1 . 5 °) 

 of the liquid under pressure. The second and third columns 

 of the table give for two separate runs the values of — Lv/vo 

 where Au is reckoned from the initial pressure, Po = 392 mega- 

 bars, and Vo is the volume^ of the liquid at 31.5° and atmos- 



1 Also called thiodiglycolchloride. Conf. BeiIvSTEIn, Vol. I, p. 358. Ber. Deutsch. 

 Chem. Ges. 19: 3260. 1886. 



- Joiirn. Amer. Chem. Soc. 41: January, 19 19. 



' I megabar = 10* dynes /cm^. = 1.020 kg. /cm^. = 0.987 atm. 



* This was calculated from the known density which at 20°, 25°, 30°, and 35°, 

 respectively, is 1.274, 1-269, 1.264, and 1.258. 



