DETERMINATION OF ATOMIC WEIGHTS 511 



The various results that have been obtained for the difficultly 

 liquefiable gases are contained in the accompanying table : 



Table II 



These values refer to the compressibilities at o° C. ; it is 

 necessary to point out that Rayleigh's measurements and also 

 those of Leduc and Sacerdote were carried out at room tem- 

 peratures and hence their values had to be reduced to those 

 at o° C. from theoretical considerations ; also that Berthelot has 

 merely stated his results without giving any details whatever. 



In the calculations which follow, the following values will be 

 adopted 



To these may be added Gray and Burt's value for hydrogen 

 chloride deduced by graphically extrapolating the compressibility 

 curve from p = 180 mm. to p = o : 



A; at o° C. for HC1 = 743 x lo~' 



The data for other gases are not very trustworthy and will 

 be considered later (p. 512). 



Molecular Weights. — The foregoing data may now be used 

 in calculating molecular weights, for which purpose the equation 

 (P- 507) 



m = l % 1 a; 



M' V ' \(- A'o 

 is utilised. It is only necessary to substitute the numerical 

 values of L and A lor a gas and the values of M', L' and A'o for 

 oxygen (viz. 32, 1-4290 and 96 x io~ 5 ), to deduce the value of M. 

 Values of L/L' are given in Table I. 

 33 



