with c = 5.96 and 



c= 0.00220 7 ' 



^65 



77,938 — r. =464 — 

 0' * ^>» 



= 60. 

 As a matter of fact, the specific iieat has l)een determined here 

 at constant pressure and not at constant vohime. In the foregoing 

 calcuUition, the difference of the specific heats c„ and Cj„ given by 



— c, 



Ac; i\ 



lias been neglected. Indeed, A is about 7,2 . 10— ^ and c^, and Tare 



both small. 



Using Dp:bije's formula, we can compare our results with 



those of PoLLiTZER ^) at somewhat higher temperatures. For this 



purpose we calculate a value of 6 agreeing as well as possible 



c 

 with Pollitzer's figures of — , we find then 110. In fig. 4 c,- is 



plotted as a function of T according to Debfje ; the values, deter- 

 mined experimentally, are indicated by circles. 



The accordance at helium temperatures is bad, as could be 

 expected in consequence of the difference between the value of 

 used in the calculation, and the one deduced from our experiments. 



6.- 



s,^ 



i.p 



tt.y 



A25 



S<i 



ioo no 



Fiff. 4. 



1) See F. PoLLiTZER. Zeitschr. f. Elektrochein. 1911. p. 5. 



