30 ATOMIC WEIGHTS OF SODIUM AND CHLORINE. 



The solubility of silver chloride in a liquid containing a large 

 excess of one of its ions has been stated to be " practically negligible 

 in most cases" (p. 27). In determining the ratio between silver and 

 silver chloride, however, it seemed advisable to determine even this 

 solubility, which may partly represent the solubility of the undissociated 

 silver chloride, as distinguished from that ionized, and also includes 

 the slight correction for the imperfect retaining power of even the best 

 filters. The fact that a single part of silver chloride may be detected 

 in 30,000,000 parts of water by the nephelometer in the presence of 

 an excess of silver nitrate shows the approximate order of this solu- 

 bility.* 



In five experiments, in which silver chloride was precipitated by 

 an excess of hydrochloric acid, the combined mother liquor and wash 

 waters remaining after filtration were evaporated to dryness. The 

 residue was taken up with a very small quantity of ammonia and 

 then neutralized with nitric acid. After the addition of a slight 

 amount of sodic chloride, the silver chloride was estimated by the 

 nephelometer, by comparison with tubes made up with known amounts 

 of silver in the same way. 



Silver chloride found. 



In 3 liters 0.09 <mg. AgCl. 



In 3 liters 13 



In 3 liters 05 



In 2 liters 05 



In 2 liters 05 



Mean 03 mg. per liter 



This value represents the solubility of argentic chloride in water 

 containing sodic nitrate and an excess of hydrochloric acid, together 

 with those traces of the substance which could not be collected upon a 

 filter. It is not certain that the same value would be obtained if it 

 were possible to determine this infinitesimal solubility in the presence 

 of an excess of argentic nitrate ; but the fact that the limiting value 

 previously found by one of us is about of this order seems to render 

 this probable. Hence, for the sake of completeness, the correction 

 was applied to the results in the latter case as well as in the former, 

 although it was so small as not even to affect the third decimal place 

 of the atomic weight of sodium. 



Further consideration of the solubility of argentic chloride will be 

 given in other appropriate places. 



Richards, Proc. Amer. Acad., 29, 74 (1893). 



