44 ATOMIC WEIGHTS OF SODIUM AND CHLORINE. 



The ratio of sodic and argentic chlorides. 

 FINAL SERIES. 



If the atomic weight of silver is taken as 107.930 and that of 

 chlorine as 35.455, the atomic weight of sodium, calculated from the 

 above average, will be 23.017, a result 0.14 per cent lower than Stas's. 



In spite of every effort to detect some error tending to diminish 

 the atomic weight of sodium and thus to cast doubt on this low value, 

 and in spite of increasing precautions and increasing skill in the details 

 of the experimentation, the last results are no higher than the very 

 first one. Hence further prosecution of this method seemed to be of 

 no avail. The reason for the difference between this value 23.017 for 

 the atomic weight of sodium and Stas's 23.048 is best discussed after 

 the results of the comparison of sodic chloride with metallic silver 

 have been detailed. 



THE RATIO OF SODIC CHLORIDE TO SILVER. 



Since the time of Gay-L,ussac, the method of titration has been a 

 favorite way of determining ratios between silver and soluble halogen 

 salts. If the end-point were definite, this method would be capable 

 of extreme accuracy. It involves no transference, collection, or 

 weighing of a precipitate ; consequently the introduction of silica or 

 alkali from a glass-stoppered flask, occlusion of sodic nitrate, loss of 

 asbestos, and other sources of error, are altogether avoided. After 

 weighing the factors in the proper proportions, dissolving and pre-' 

 cipitating, one has only to withdraw a portion of the mother liquor 

 and determine whether or not the true end-point of the reaction has 



