606 



boiling point and the critical point go down a little, but the change 

 is williin the limits of accuracy as previously given. Tiie conclusions 

 formerly drawn from Ihe temperature-measurements thus remain 

 valid, especially (he rapid change of the constant ƒ in van der W.\ai,s's 

 vapour-pressure law which we inferred at the time. 



With the chosen pressures in the helium-thermometer with mercury- 

 manometer the correction for B becomes of minor importance. 



At the boiling poinl of helium it is too small to have any inthience. 



^^ B 



Accoiding to Comni. N°. 119/> § 5 in po^=RT-\ we found 



V 



54021 K^ — 0.000047 and we thus have with pü°c ^ 25.5 cc. at 



J- CüiTccrrd fur B 



4°.21 K. 



T 



1 + 0.000128. 



Tt is true, that at lower temperatures, as discussed '\n ^ 1, B 

 becomes much larger. An exti'apolation according to the "mean" 

 equation of state, in itself certainly little justified, would give. 

 iii 50K. ^ 56.1 .B4.021 K. Even on this supposition an error of only 

 27o or 0,03 degrees would have to be expected from B being 

 neglected. This deviation is smaller than the uncertainty of the cor- 

 rection for the thei-mal molecular pressure. 



When the melting-point pressure in the thermometer with healed- 

 wire manometer is as low as it was taken in the above 2nd series, 

 the uncertainty regarding the last-named correction becomes predo- 

 minant. From this it appears, that a very accurate knowledge of 



1) W. H. Keesom, Suppl. N». 30, p. 12. 



