166 Journal of the Mitchele Society. [DA 



being kept constant. A liquid cannot exist above its critic 

 temperature, and above that point the liquid and its vap 

 are identical. The critical temperature therefore mar 



SP 



the limit for which the y= of equation 12 can be obtain* 



but just at that point the «t=- of the liquid and the j-n\ °f 



vapor at constant volume must be identical. That the - 



obtained from the Biot formula could not in the nature of t 

 case be accurate at or near the critical temperature we ha 

 already pointed out (second paper, p. 395). That the var 

 tion we were there led to expect is quantitively equal to t 

 actual variation as found for equation 13 we have subs 

 quently shown (p. 146). It remains to be seen if u #" of equ 



4ion 13 corresponds to the function =^-77 — , T .„. — ^ — , _„, 



r W/3 -f V"3 zr/3 _j- YVzv 



equation 12. 



At the critical temperature v = V, and therefore we ha 

 at that point, 



[14] a = -^-. 



Choosing- isopentane as being- one of the most careful 

 measured substances, we found for // the value 105.4 (Tat 

 25) and V is 4.266. "0" therefore becomes 159,400. T 

 values given by Dr, Young 1 at volume 4.3 are 157,880 fr< 

 drawn isochors, and 162,890 when calculated from soi 

 values of b. The agreement in this instance is therefore 

 be regarded as perfect. 



That the laws of attraction we have assumed enable t] 

 constants of the equation of Ramsay and Young at one poij 

 to be foreseen and calculated is proof of the most convincii 

 nature that the theory of the attraction outlined is correc 

 We are led to believe that, properly modified, the same consi 

 erations will elsewhere be successful in a further calculate 

 iProc. Phys. Soc, 1894-95, p. 654. 



