J 004 



meter-zero, change of temperature bj radiation '), in the measurements 

 of F'ebr. — May 1916 possibly owing to the formation of gaseous 

 spaces in the bath of solid hydrogen by the evaporation) and we 

 conclude from the whole of eight cooling-curves, that our experiments 

 do not give an indication of the existence of a point of transfor- 

 mation for solid hydrogen between the triple point solid-liquid- vapour 

 and 10°.6 K. ') 



Taking as a mean for the specific heat of solid hydrogen at 

 7'= 12.55° K. the value 0.64, we find (neglecting the difference 

 C„ — Csat) ii^ Debuk's formula for hydrogen 6 = IM (comp. the 

 curve in fig. 2), To an e\en higher degree than in the case of 

 nitrogen this value is smaller than the one which would follow from 

 Lindemann's formula (Oomm. N". A^la § 5), viz. 6 .-= 212. As for nitrogen 

 (Comni. N". 149»^/ § 4) we conclude that presumably hydrogen in the 

 solid condition is more-atomic in the sense given tiiere. 



§ 4. Heat of fusion of hi/droc/eii. We have made two experiments 

 (May 11 1916 and Sept. II 1917) for the determination of the heat 

 of fusion, by measuring the heat which iiad to be supplied to heat 

 the flask with hydrogen from 0.2° and 0.7° respectively below to 

 0.9° and 1,6° respectively above the triple-point-temperature. These 

 experiments gave for the heat of fusion per gramme of hydrogen : 

 13.3 and 16.4 cal. ,5 respectively, with a mean value of 15 cal., 5. 



1) It was also partly to obviate the radiation referred to here, which is due 

 to the walls at a higher temperature, that the calorimeter-vessel was afterwards 

 surrounded by a copper cylinder (comp. § 1). 



') On the linearly extrapolated temperature-scale of ConstcS (comp. the beginning 

 of this §). 



