THE QUANTITATIVE SYNTHESIS OF ARGENTIC NITRATE, AND THE 

 ATOMIC WEIGHTS OF NITROGEN AND SILVER, 



INTRODUCTION. 



The composition of argentic nitrate is one of the questionable premises 

 in the lively argument which has recently taken place concerning the 

 atomic weights of nitrogen and silver. 1 Although Stas's syntheses of this 

 salt were carried out on a large scale, and far more carefully than those of 

 anyone before him, several points concerning the details of the work were 

 not investigated with the care which modern physicochemical knowledge 

 demands. Accordingly, a repetition of this work of Stas's seemed to be 

 worth the trouble involved ; and the following pages contain a brief 

 account of nine months' thought and labor upon it. 



The method appears at first sight to be extremely simple, consisting 

 merely in the weighing of pure silver, the dissolving of this silver in nitric 

 acid, and the weighing of the resulting nitrate. The preparation of pure 

 silver having been already solved, the great difficulty consisted in the 

 procuring of satisfactory evidence that the nitrate was free from impurity, 

 and in making sure that none of the silver was lost during the process. 

 The main emphasis of the subsequent discussion will therefore be laid on 

 these points, the other details being often indicated with but few words, 

 because they so closely resemble the details of previous investigations 

 carried out in the Chemical Laboratory of Harvard College. 



The research naturally divided itself into four sections, namely, first, 

 the preparation of pure materials ; second, the quantitative synthesis ; 

 third, the determination of the purity of the product ; and fourth, the final 

 result and its relations to the table of atomic weights. These will be con- 

 sidered in order. 



PREPARATION OF PURE MATERIALS. 



All the substances used in the research were purified with very great 

 care. Nitric acid and silver were the two most important. 



Nitric acid was supplied by two firms. Each sample was warranted 

 by the manufacturers to be of a very high grade of purity. Each was 

 redistilled twice just before adding to the silver, using only the middle 



especially Guye, Nouvelle Rech. s. I. Poids Atom, de 1'azote, Soc. Ch., Paris, 

 1905. The reader is referred for a convenient resume to the Report of the Interna- 

 tional Committee on Atomic Weights, Journ. Am. Chem. Soc., 28, 1 (1906), and 

 many other places; also to Clarke, Journ. Am. Chem. Soc., 28, 293 (1906); Gray, 

 Trans. Chem. Soc. (London), 89, 1173, (1906). 



47 



