SODIUM. ASTON. 147 



The standard atomic ratio of this process accordingly is 

 117 : 202=0.57 921. 



Actually performing the operation five times (Nos. 22 to 

 to 26), Ramsay and Aston found their mean analytical ratio 

 "9 high," that is 0.57 930. 



If this " 9 high " be ascribed as exclusively due to 



Bo, its atomic weight must be O.oi low, or 10.99; 

 Na, " " " " " 0.02 high, or 23.02; 



Cl, " " " " " o.oi high, or 35.51; 



O, " " " " " 0.005 low > or l S-995- 



In actual practice, we must arrange it so, that all but one 

 atomic weight involved are determined beforehand ; thus that 

 last one will be determined'by the chemical reaction used. 



To the student of higher mathematics, we need not say 

 that this process is merely the use of partial differentials, 

 considering only one of the atomic weights subject to vari- 

 ation, at a time. 



I have also referred this subject properly to the general 

 theory of the variation of constants, so important in 

 astronomy. See True Atomic Weights, 1894, p. 158. 



We have purposely taken the entire amount of " 9 high " 

 given by Ramsay and Aston, without change or reduction of 

 any kind. 



But we do know that this value is itself too high, as 

 indicated by the authors themselves, and as proved by the 

 minute action on the glass. 



Probably half this excess is all that should be taken into 

 account. Thus all departures would be reduced to half the 

 values above given. 



II. THE ATOMIC WEIGHT OF SODIUM. ASTON. 



We have just seen that, if the " high " of the process be 

 ascribed to the sodium exclusively, the atomic weight 

 thereof can only depart at most 0.02 from the standard 23 

 and be "high" too; i. e. 23.02. 



But we know, that the action on the glass accounts for 

 part of this high, so that probably 23.01 would really be the 

 limit, if the determination could have been made in abso- 

 lutely resistant glass. 



