314 



Mr. J. B. Hannay. 



In drawing out the above tables (which may exhibit slight irregu- 

 larities) recourse was made to a large number of quite separate 

 observations, as full series are often difficult to obtain, owing to some 

 failure in the apparatus when it has been in use for some time at high 

 pressures. 



Hitherto only one liquid — alcohol — had been used in these experi- 

 ments, so it was determined to try the same experiments with other 

 liquids, and those chosen were carbon disulphide, carbon tetrachloride, 

 and methyl alcohol. 



The carbon disulphide was digested over sodium for some time and 

 distilled off pure quick-lime. This gives a liquid having no offensive 

 odour and quite colourless. It was distilled into an apparatus similar 

 to that used for alcohol, and preserved under a bell-jar over oil of 

 vitriol. Four sets of observations were done in order to determine 

 the critical temperature and pressure accurately; in all 163 experi- 

 ments. The results are as follows : — 



Mean temperature corrected 2 77° '68. 



Probable error of mean o, 16. 



Mean pressure corrected 78*14 atmos. 



Probable error 0*07 „ 



The apparatus was now arranged so that the critical temperature 

 could be observed under pressure with hydrogen with the following 

 results : — 



Mean temperature corrected 2 74° ■ 93. 



Probable error o, 09. 



Mean pressure corrected 17154 atmos. 



Probable error 0*07 „ 



For these numbers sixty-two experiments were done. 

 Nitrogen was then substituted for the hydrogen, and the experi- 

 ments conducted as before. Forty-one determinations were made to 



obtain the following means : — 



Mean temperature corrected 273°'12. 



Probable error 0°'19. 



Mean pressure corrected 141 "45 atmos. 



Probable error 0*16 „ 



Here we see that while the pressure of the nitrogen on the carbon 

 disulphide is much lower, the temperature at which the meniscus 

 disappears is also lower. This is likely owing to the greater solubility 

 of the nitrogen in the liquid, as the density makes it approach much 

 nearer to the density of the disulphide than hydrogen. 



A third series was conducted with hydrogen, using, however, a 

 much lower pressure : — - 



