SILVER, POTASSIUM, ETC. 41 



Tlie ratio between silver and pota.ssium 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. Ma- 

 rignac,* reducing all weighings to vacuum, obtained these results. In 

 the third column I give the weight of KCl j)ro})ortional to 100 parts 

 of Ag: 



4.723S grm. Ag = 3.2626 KCl. 69.067 



22.725 " 15.001 " 69.050 



21.759 " 15.028 " 69.066 



21.909 " 15. 131 " 69.063 



22.032 " 15.216 " 69.063 



25.122 " 17-350 " 69.063 



Mean, 69.062, ±0017 



The work of Stas falls into several series, widely separated in point of 

 time. His earlier experiments f upon this ratio may be divided into 

 two sets, as follows: In the first set 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 i)uri- 

 fied with the utmost care. From 10. S to 32.4 grammes of silver were 

 taken in each experiment, and the weighings were reduced to vacuum. 

 The method of operation was, in brief, as follows : A definite weight of 

 potas.sium chloride was taken, and the exact quantity of silver necessary, 

 according to Prout'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 remaining in the liquid was determined by 

 titration w^ith a normal solution of potassium chloride. One hundred 

 parts of silver required the following of KCl : 



First Series. 

 69.105 

 69.104 

 69. 103 

 69.104 

 69.102 



Mean, 69.1036, it .0003 



Second Series. 

 69.105 

 69.099 

 69.107 

 69.103 

 69.103 

 69.105 

 69. 104 



* See Berzelius' Lehrbuch, 5th Ed.. Vol. 3, pp. 119^-3. 

 t Aronstein's translation, pp. 250-257. 



