GEOPHYSICAL LABORATORY. 161 



tion a cylinder of the solid, surrounded by a liquid such as kerosene, was in- 

 closed in a tliick-walled steel bomb fitted with a movable leak-proof piston, 

 and pairs of simultaneous readings were taken of (1) the displacement of 

 the piston, i.e., the volume-change, and (2) the pressure. The piston 

 displacement was measured to within 0.01 mm. by means of a dial micro- 

 meter. In measuring the pressure, advantage was taken of the change of 

 resistance under pressure of a "therlo" wire, and in order to determine 

 the pressure to within 1 megabar the resistance change was measured with a 

 type of Wheatstone bridge having no movable contacts. The P-AV 

 graphs, which show the relation between volume-change and pressure, were 

 found to be nearly straight Hues; however, the more compressible metals 

 exhibit a slight but unmistakable curvature, such that the graphs are con- 

 cave toward the pressure axis. From this curvature a rough estimate was 

 obtained of the change of compressibihty between and 10,000 megabars of 

 all the soKds examined (except gold, copper, silver, aluminum, and brass, for 

 wliich the compressibiitiy is independent of pressure within the error of 

 experiment). 



(9) Some phj'sical constants of mustard "sas." L. H. Adams and E. D. Williamson. 



J. Wash. Acad. Sci., 9, 30-35 (1919). 



For military purposes it was desired to know the compressibihty of the 

 liquid 2, 2-dichloroethylsulphide, commonly known as mustard gas. With 

 the apparatus already used for the determination of the compressibihty of 

 various rocks, metals, and other solids, it was a comparatively simple matter 

 to make the requisite measurements. At the same time, certain other prop- 

 erties of this interesting substance were determined from its behavior under 

 hydrostatic pressure. The compressibilitv (pres.sure being expressed in mega- 

 bars) was found to be 49.6X10-^ and 23.9 XlO'^ at pressures of 1 and 2,000 

 megabars respectively, values which are about identical with those for water. 

 From the measured change of volume upon melting and the slope of the cm've 

 of melting temperatures under various pressures, the latent heat of fusion was 

 calculated and found to be 25 calories per gram. 



(10) Note on the Bucher cyanide process for the fixation of nitrogen. Eugen Posnjak and 



H. E. Merwin. J. Wash. Acad. Sci., 9, 28-30 (1919). 



In the course of an investigation of the Bucher cyanide process undertaken 

 by the Laboratory at the request of the Nitrate Division of the Ordnance 

 Department of the Army, it was found by means of microscopical examinations 

 that the nitrogen-bearing constituent of some of the crude technical products 

 manufactured by this process consisted principally of some other substance 

 than ordinaiy sodium cyanide. Further experiments substantiated the 

 microscopical evidence. The investigation of the chemical nature of the 

 substance in question is being continued. 



(11) An apparatus for growing crystals under controlled conditions. J. C. Hostetter. 



J. Wash. Acad. Sci., 9, 85-94 (1919). 



Crystals, to be suitable for the study of the effects of pressure, must be 

 perfectly developed and of comparatively large size. For the growth of such 

 crystals apparatus is necessary in wliich all variables affecting rate of growth 

 are controlled, and the device described here fulfills these conditions. Essen- 

 tially, the apparatus consists of two thermostats connected in such a manner 

 that solution may be continually pumped from one, containing feeding 

 crystals held at a certain temperature, into the second, which is maintained 

 at a lower temperature than the first and which contains the crystals to be 

 grown. Crystals of potassium alum and sodium chlorate grown in this 

 apparatus have been used for pressure studies, the results of wliich v.ill be 

 pubhshed later. 



