468 



Table III contains tlie results of a comparison of our observations 

 with Schalkwijk's formula: 



4. Discussion. As will be seen from Table III, the deviations 

 from Schalkwijk's foi'mula follow a very distinct syslematic course; 

 near 60 atmospheres they are still small, but at higher pressures 

 they become much larger and largel}' exceed the limits of our accuracj. 



In deducing a new formula we have assumed for Aa'^. ') at 0° C. 

 the value given by Kamf,rlingh Onnes and Braak Aaq = 0.99942, 

 which gives at 20^ y^^i.^o = J .07261 and calculated Ba and 

 Ca by the method of least squares from all the observations from 

 4 to 100 atmospheres, viz. those of Schalkwijk and those of this 

 paper ; the formula thus represents the isothermal of hydrogen of 

 20° from 4 to 100 atmospheres. 



Table IV gives the deviations from this formula of Schalkwijk's 

 observations, those of the preceding and those of the present com- 

 munication. 



The observations of the preceding communication have not been 

 used in the calculation of the constants of the formula. They are 

 however given in the Table. It has to be mentioned, that in the 

 preceding commumcation the normal volume was calculated by 

 means of Schalkwijk's formula, whereas now it seemed preferable 

 to determine it with our own more tinal one. The figures are 



1) For tlie notation used for the virial-coefficients eomp. Comm 71. 



