[MILLER] CHEMICAL LABORATORY RESEARCHES 49 



The following experiments are, I think, conclusive. Water, 

 freed from motes by distillation without ebullition, w'as passed 

 through a flattened capillary under the ultra-microcsope. From the 

 dimensions of the field of view, the depth of focus and the speed of 

 the motes, it was easy to determine roughly the number of motes 

 per cubic centimetre. Ordinary distilled water showed about 20,000. 

 Wolski found 29,000, so it is evident that he and I are looking at the 

 same thing. The light scattering of this water was 0.7 (benzene = 1). 

 After two distillations the number of motes was about 1,000 and the 

 scattering 0.12; after eight distillations no particles were seen and 

 the scattering was 0.07. These results show that distillation removes 

 the ultra-microscopic particles just as Wolski's filter does, but that 

 the liquid still scatters light as was shown in 1913. 



The Pressure-Volume Relations of Superheated Liquids 



By K. L. WiSMER 



Presented by Professor F. B. Kenrick, F.R.S.C. 



Unusual conditions were imposed on these experiments by the 

 fact that under extreme superheating liquids can be kept for only 

 a few seconds before explosion takes place. Bulbs of the liquid were 

 first heated to about 170° at a pressure of 30 atmospheres (a treat- 

 ment w^hich favoured subsequent superheating) and were then trans- 

 ferred to another thermostat at the temperature to be investigated, 

 say 130°. The pressure was then suddenly lowered and in the brief 

 interval of time before explosion took place the pressure and the 

 position of a mercury meniscus outside the thermostat were noted. 

 Manipulation of the bulb was made possible by the use of a long 

 flexible capillary glass tube to connect it with the manometer and 

 pressure machine. 



The pressure-volume relations were determined for liquid ether 

 at 121°, 128° and 134° for pressures from above 30 atmospheres to 

 as low as 1 atmosphere. Similar measurements were made with 

 ethyl chloride at 99°, 110° and 117°. In both cases the p-v curve is 

 almost a straight line and shows no sign of more rapid cur\àng as 

 the limit of superheating is reached although in both cases the temper- 

 atures reached at atmospheric pressure are much above the maximum 

 temperatures possible, calculated from van der Waals' equation. 



