1001 



the calorimeter-vessel l)eiiig inore or less, owing- to the difference 

 in the teniperatnre which the supply- wires assume dnring ihe heating. 

 These ditrerences in the resistance of the heating-wire did not amounl 

 to more than 0.9 '/« i'l those cases where the resistance could be 

 derived f'ron) the tension and current duiing the liealing. They fall 

 within the limits of accuracy which could be reached in these 

 measurements ^). 



§ 2. Specific heat of liquid hydrogen. The correction to be applied 

 for the evaporation of hydrogen during the calori metric experiment 

 is somewhat larger than in the case of nitrogen (Comm. N". 149a § 5): 

 the largest value was 4.5 "/o of the heat supplied. 



The results ai-e combined in table 1 and represented in tig. 2. 



In this figure we have also included the results of Eucken's 

 measurements ") (indicated by AA) concerning the specific heat of 

 liquid hydrogen between 17.3° and 21.2'' K. Our results, which, 

 however, reach down to lower temperatures, agi-ee at these higher 

 temperatures with those of Eucken within the limits of accuracy of 

 the measurements. 



It is represented in Fig. 1. Au is llie spirally wound 

 wire of the purest gold to be obtained ; diameter 0.05 mm., 

 resistance at room-temperature 1,2 52- The spiral is 

 suspended between two insulated supply-wires of gold 

 (1 m.m.) which protrude through glass tubes through 

 the lid of the copper chamber Ka. The glass tube g 

 serves for filling the chamber with gas (Ho or He). A 

 constantin wire with platinum supply-wires was wound 

 round the chamber in exactly the same manner as 

 described in Comm. N*\ 143 § 2, to which we here refer. 

 Special tests showed that at the temperature of liquid 

 hydrogen the resistance of a spiral of the same gold 

 wire, suspended in a space filled with gaseous hydrogen, 

 could be measured with a current of 35 milli-ampères, 

 without the Joule-heat raising the temperature of the 

 wire by more than 0.01 of a degree above that of the 

 bath. 



The resistance of the gold wire which after winding 

 is liealed to 300° G. does not attain constant values, 



until it has been cooled in liquid air several (say 5 or more) times and brought 



back to room-temperature. 



') Our thanks are again due to Mr. J. M. Burgers for his assistance in the 



temperature-measurements. 



2) A. Eucken, Verb. d. physik. Ges. 191(3, p. 4. 



Fig. 1. 



