bsö 



Fig. 2. 



Dewar, Olszkwski and Bulle)') it is seen, that tlie formula, as was 

 (o be expected, does not iiold up to the ciilieal temperature and 

 that the curve which gives the dependence of H on (lie temperature 

 has its concave side towards the temperature-axis. Tiie difference 

 ^/i— Ü extiap. — Tk for hjdrogen amounts to 



Ï'^=0ex1rap. — 1\=- 3.87. 



If T/A=uextiap. — Tk is divided by tlie critical tenijjeralui'e the 



3.87 



positive value r= 0.125 is obtained. For methvl-chloride •) and 



^ 3.21 ' 



ethylether') similar values are obtained''). 



Surf ( tee-tension . From the capillary rise the surface-tension i|v is 



found by means of the following formula : 



n = 



2ip, 



c,\r R-rJ 



(^liq — Cvap.) 



The densities for liquid hydrogen are taken from the observations 

 by H. Kamerllnüh Onnes and C. A. Crommeijn fComm. No. 137^). 



1) F. BuLLE. Phypik. Zeit.'^clir. p. SOU, XIV, 1913. 



-) According lo measurements by J. Verschaffelt; comp, A. v- Eldik, 

 Comm. N". 39, p. 14. 



S) E. C. DE Vries, Comm. W. 6. 



*) The corresponding figures (deduced, however, from not-corresponding tem- 

 perature ranges) are 0.Ü3S and 0.017 respectively. 



