1887.] 



On Phospho?iium Chloride. 



285 



is an unexpected result, as the substitution of a less volatile element 

 has the effect of raising the critical temperature : thus for C0 2 

 critical temperature is 31*9° and for CS 3 278°. 



I have also noticed the formation of a crystalline hydrate of 

 phosphine when the gas is liquefied in the presence of water. The 

 liquid gas floats on the surface of the water like benzene, and is 

 apparently only slightly soluble. By suddenly increasing and 

 decreasing the pressure the two liquids are mixed together, and after 

 a short time a mass of crystals is formed. 



The following table gives the results of measurements of the 

 saturated volume, maximum pressure, and liquid volume at different 

 temperatures. 



Temperature. 



Saturated 

 volume. 



Maximum 

 pressure. 



Liquid volume. 



Density of 

 the liquid. 



o 



c.c. 



atmospheres. 



c.c. 





51 -4 





0-160 



0-402 



49-4 



0*362 



62*4 



0-154 



0-417 



44-4 



0-468 



56 1 



0-137 



0-469 



39 *4 



0-553 



50-8 



0-128 



0-502 



29'4 



0-744 



41-3 



0-120 



0-536 



24-6 



0-851 



37-1 



0-118 



0-545 



18*4 





32 -6 



0-115 



0-559 



8-4 





27 -2 



0-108 



0-595 



2-4 





23-4 



0-104 



0-618 



The numbers in the column headed density are calculated by 

 dividing the whole mass in grams of the gas by the volume of the 

 liquid in cubic centimetres. The mass of the gas was O06435 gram. 



The physical constants for hydrochloric acid gas used in the 

 diagrams are calculated from Ansdell's paper ('Roy. Soc. Proc.,' 

 vol. 30, 1880). The mass of the gas* he used was 0-08531 gram ; and 

 therefore the proper reduction has been made so that the volumes in 

 the diagram may be those occupied by the molecular mass of hydro- 

 chloric acid in milligrams. 



In the first diagram I have plotted for comparison the maximum 

 pressure of the vapours at different temperatures both above and 

 below zero. In the case of PH 4 C1 the curve is drawn from my own 

 observations from the critical point to 7° ; that point is joined by a 

 dotted curve to the point corresponding to 1 atmosphere at —30°, at 

 which temperature Ogier states that the crystals are formed under 

 atmospheric pressure. The curve forHCl below zero is from numbers 

 given by Faraday (' Phil. Trans.,' 1846). The curve for PH 3 is from 



* Found by calculation from Ansdell's data. 



T 2 



