1161 



20 atmospheres we used the closed hydrogen-inanonieter M 60'). 



We are much indebted to Mr. J. M. Burgers for the care bestowed 

 on the regulation of the temperatures. 



The data in the table which contains tiie results of these measurements 

 (I — VI) have been reduced to the absolute scale according to the 

 corrections for the helium-thermometer, as deduced from the Leiden 

 determinations of the compressibility of helium "). The table also 

 contains the values given by Kam?:rlingh Onnes and Crommelin ^) 

 and those which are due to Kamerlingh Onnes, Crommeun and Cath. ^) 

 Our measurements form the immediate continuation of the latter research. 



The observations may be represented by a formula with three 



constants of the form 



Tlogp = A-^BT-{- CT\ 



where A = — 65.061 



B= 2.8191 



C= 0.01118, 

 for which we are indebted to Professor J, E. Verschaffelt ^). 



The agreement with the observations may be judged from the 

 b^^^ and 6''i column ^). 



At some of the temperatures readings were taken with larger and 

 smaller quantities of liquid in order to test the influence on the 

 vapour-pressure of possible impurities of the neon used. It appears 

 from these measurements that the purity of the neon was not as 

 high as we should have wished, although it had repeatedly been 



1) Leiden Gomm. N». 97a (§ 3). These Proceedings IX, p. 754. 



3^ Leiden Comm. W. 102Ö. These Proceedings X, p. 58i). 



8) Leiden Comm. N». 147d. These Proceedings XVIII (1) p. 515. 



*) Leiden Gomm. N''. 151/?. These Proceedings XIX (2) p. 1058. 



») According to this formula the critical pressure (at 7^=44.74 K.» would be 

 PA = 27.11 int. afm., as against 26.86 found in Gomm. N". 15 Id. 



6) The formula was chosen so as to give a good correspondence with the 

 observations beyond 29^.40. At the lower temperatures the coirespondeuce is not 

 so satisfactory. 



