DETERMINATION OF ATOMIC WEIGHTS 515 



to the value A = 757 x io~ s , which is a close approximation to 

 the actual value. 



It appears, therefore, that Berthelot's method of calculating 

 leads to results for A' in excess of the true values and con- 

 sequently to molecular weights that are under-estimated. The 

 results obtained by the application of equations (10) to the 

 available experimental data are given in the following table : 



Table VI 



All the values given above require to be multiplied by io~ s . 

 It should be mentioned also that Rayleigh's and Leduc and 

 Sacerdote's results were obtained at room temperatures and 

 corrected to o° C. by theoretical formulae, the necessary 

 corrections being large. Also, it should be remarked that 

 Berthelot has merely stated his results without giving any 

 details. 



Berthelot (13) also states values of A'-l 5 for the gases and 

 deduces from his results the values of e in equation (7). From 

 his figures, the following results have been calculated by 

 equation (8) : 



CO, n 2 o so 2 



A^ x io 5 . . 669 743 2363 



These values naturally agree with those deduced above from 

 equation (10), since equations (10) and (8) rest on the same 

 theoretical basis. 



Jacquerod and Scheuer (15) really carried out their measure- 

 ments between the pressures 800 mm. and 400 mm. and deduced 

 values for Ao in a different manner. The values of pbVb/p a v a , 

 when b = 400 mm, and a = 200 mm, were also determined and 



