18 THE ATOMIC WEIGHTS. 



The ratio between silver and potassium chloride, or, in 

 other words, the weight of silver in nitric acid solution 

 which can be precipitated by a known weight of KCl, has 

 been fixed by Marignac and by Stas. Mai;ignac,* reducing 

 all weighings to vacuum, obtained these results. In the 

 third column I give the weight of KCl proportional to 100 

 parts of Ag. 



4.7238 grm. Ag = 3.2626 KCl. 69.067 



.0017 



Stas' experiments upon this ratio may be divided into two 

 series.f In the first series the silver was slightly impure, 

 but the impurity was of known quantity, and corrections 

 could therefore be applied. In the second series pure silver 

 was employed. The potassium chloride was from several 

 different sources, and in every case was purified with the 

 utmost care. From 10.8 to 32.4 grammes of silver Avere 

 taken in each experiment, and the weighings were reduced 

 to vacuum. The method of operation was, in brief, as fol- 

 lows: A definite weight of potassium chloride was taken, 

 and the exact quantity of silver necessary, according to 

 Front's hypothesis, to balance it was also weighed out. The 

 metal, with suitable precautions, was dissolved in nitric 

 acid, and the solution mixed with that of the chloride. 

 After double decomposition the trifling excess of silver re- 

 maining in the liquid was determined by titration with a 

 normal solution of potassium chloride. One hundred parts 

 of silver required the following of KCl : 



* See Berzelius' Lehrbuch, 5th edition, Vol. 3, pp. 1192, 1193. 

 f Aronstein's Translation, pp. 250-257. 



