444 



calculated fioui a Wkede-Rankink-Keesom formula ') *) : 



58.40 61 



%p = 4.6063 



(1) 



The 4'^ column gives the ditferences of the observed values and 

 the values calculated from (1), the 5^^^ column the corresponding 

 differences in temperature. 



From (1) follows for the boiling point: 20.33°K. = — 252.76°C.=') 

 Extrapolation by (1) would give 5.41 cm. for the pressure corre- 

 sponding to the triple-point temperature found in § 3 (with extra- 

 polation of the calibration curve of Ptj). The double extrapolation 

 makes this value somewhat uncertain ; it can in the mean time be 

 regarded as a confirmation of the value found by Kamerijngh Onnes 

 and Braak '). 



§ 5. The heat of vaporization of hydrogen at a pressure of 

 75,15 cm. calculated according to Clapeyron-Clausius from (1), if 

 for calculating i\^„p the value Ba{i\) is taken from Kamerlingh Onnes 

 and W. J. DE Haas, Comm. N". 127c, with vu^^ after Kamerlingh 

 Onnes and Crommelin, Comm. N". 137a, becomes: 



A = 105 5 cal,.. 



enable a comparison with the data given by Travers and Jaquerod. 



*) Temperatures measured with a hydrogen thermometer, corrected by us to 

 the Kelvin scale with corrections derived from the numbers given in § 2. [Added 

 in the translation]. 



1) Gf. H. Kamerlingh Onnes and VV. H. Keesom. Math. Enz. V 10, Leiden 

 Comm. Suppl. N'\ 23, § 83^. 



2) Gf. 442 p. note 2. 



•^) This number coincides with that derived from the meaaurements of Travers 

 and Jaquerod, cf. note 1. [Ad' led in the translation]. 



*) H. Kamerlingh Onnes and G. Braak. Gomm. N". 95e (Oct. 1906). 

 According to (1) to the pressure 5,38 cm. found there a temperature of 13°.94 K. 

 corresponds. 



