482 



A. P. Mathews 



The density values show a tendency to advance. The mean 

 value of about 0.2330 is very close to that determined by 

 Young of 0.2327. 



The critical density calculated for various other sub- 

 stances from the liquid and vapor densities resulted as follows 

 when compared with the found values : 



The foregoing figures show that the formula used for the 

 calculation of d c , which was derived from two of the formulas 

 used in the calculation of ''a," gives results which agree 

 generally within i percent of the values of the critical density 

 determined by experiment, but in some cases there is a devia- 

 tion of about 3 percent. We may, I think estimate the un- 

 certainty in the value of "a" and hence of M 2 K, as not more 

 than 2-3 percent. 



The formula which I have chosen for the calculation of 

 the value of u a" is that which is based on the assumption that 

 the value of b c is 2V C /S. This formula is : a = ((S 2 S + 2)/- 

 (S -- 2))P C VJ. This equation involves only the critical data 

 and may be applied to the largest number of substances. 



While the calculation of the total valence of the molecules 

 is thus subject to these uncertainties, it is probable that the 

 substances are arranged in their proper order of the amount of 

 residual valence and that the error in the total valence of the 

 molecule is not more than 5 percent at the outside. The re- 

 sults are given in Table III. The values of "a" are taken 

 from column 4 of Table VIII of my paper 1 on the internal 

 pressures of liquids. 



1 Mathews: Loc. cit., p. 622. 



