102 Prof. Potter on Mr. Alexander's formula 



For the vapour of ether, taking the temperatures t° C. =0 and 

 t° C. = 100° to find the values of a and b in the formula 

 p = (a + bt) 6 , we find 



a=2-385739, 

 b= -01742984, 



which give the results in the third column of Table II. ; 

 and the second column contains M. Regnault's corresponding 

 results, from his Table at page 393, vol. ii. 



The general accordance of the second and third columns through 

 a range of 140° C, for so volatile a liquid as ether, is, I think, 

 sufficient to show that the elastic force of its vapour is repre- 

 sented by the formula p= (a -f bt) 6 : 



For the vapour of sulphur et of carbon, taking the temperatures 

 f C. =0 and t° C. = 100°, we find the values of a and b in the for- 

 mula j9= [a -f bt) 6 as follows, 



a= 2-244660, 



b= -01618729, 

 which give the results in the third column of Table III.* 

 M. Regnault's corresponding results (from his Table at page 402, 

 vol. ii.) being given in the second column 



Table III. 



Temperature Centi- 

 grade by air-thermo- 

 meter. 



j astic force of vapour 



sulphuret of carbon 



by interpolation 



formula. 



Calculation by Alex- 

 ander's formula. 





millims. 



millims. 



-20 



4730 



50-240 



-10 



79-44 



81-634 







127-91 



127910 



+ 10 



198-46 



194-245 



20 



298-03 



287-066 



30 



434-62 



414-231 



40 



61753 



585-230 



50 



857-07 



811-400 



60 



1164-51 



1106146 



70 



155209 



1485-185 



80 



2032-53 



1966-785 



90 



261908 



2572043 



100 



3325 15 



3325 144 



110 



416406 



4253-690 



120 



5148-79 



5388-924 



130 



6291-60 



6766- 143 



The general accordance of the second and third columns is 

 again sufficient to lead to the conclusion that the vapour of sul- 

 phuret of carbon has its elastic force represented by the formula 

 p = (a-\-bt) 6 . 



