1162 



distilled from charcoal cooled in liquid air. The equilibrium-pressures 

 which were obtained at 7'=: 43°. 83 K are giveji in the above table. 

 It will be seen that pressures show a not inconsiderable systematic 

 rise as the quantity' of condensed gas increases. 



As the nature of the impurity is still uncertain it is impossible 

 in the meantime to apply collections to the pressures observed, on 

 the basis of the formulae given by Kkesom ') for the change of the 

 vapour-pressure by small admixtures. 



\0 



O,-* (Xt> 0.6 to 



III the accompanying diagram are given the reduced vapour-pressure 

 curves for oxygen, nitrogen, argon, neon, and liydrogen, all according 

 to the Leiden-observations. It is very striking that the curve for 

 hydrogen — which at these temperatures behaves as a mon-atomic 

 substance — deviates proportionately so much more strongly from that 

 of neon than the latter from that of argon, although the critical tem- 

 perature of neon is relatively low. This raises the question whether 

 an influence of the "quanta" may play a part in these deviations. 

 For this influence would be mucli smaller for neon owing to its 

 higher molecular weight than for hydrogen. 



1) Leiden Comm. N°. 79. These Proceedings IV, p. 659. 



