348 



^ 4. In the determinations with neon an apparatus was used the 

 dimensions of which are contained in table 2. 



In order to be able (o use the apparatus at the temperatures of 

 liquid air it is necessary to comj)are its resistance with the resistance 

 of a platinum thermometer, whose resistance is known. If this 

 thermometer is calibrated, so that from its resistance the absolute 

 temperature on the Kelvin-scale can be deduced, it becomes possible 

 from the resistance of the coiuliiction-apparatus to determine the 

 corresponding absolute temperatui'e. P^or this purpose I have chosen 

 the platinum thermometer /^/',, the standard thermometer of the 

 cryogenic laboratory at Leiden. For this thermometer there is a 

 table ^) which gives the relation between IT, or properly speaking 



W 



— , ami the absolute temperature. 



ir ; ' 



I have carried out the comparison in the following manner: in 

 a closed crjostat, provided with a stirring arrangement and filled 

 with pure liquid oxygen, the double conduction-apparatus and an 

 oxjgen-thermometer according to Stock ^) are mounted side by side. 

 When the condition had become stationary, the resistance of the 

 apparatus tu' = W — w was measured and simultaneously the vapour- 

 pressure of the oxygen-thermometer was read. The following 

 corresponding values were obtained in this vvay. 



Vapour-pressure of oxygen /> = 742.35 mm and ?(;'=: 0.75828 52. 



From p according to Kamerlingh Onnes and Braak') the absolute 

 temperature T of the oxygen-bath is calculated by means of the 

 following relation which holds from 83 and 91° K: 



1) G. Holst. Leiden Oomm. N". U8a. 



«) A. Stock and C. Nielsen. Ber. d. D. Ghem. Ges. 39 (11), 1906, p. 2066. 

 3) H. Kamerlingh Onnes and C. Braak. Leiden Comm. N^. 107a, comp. 

 Holst loc. cit. 



