SUMMARY. 69 



SUMMARY. 



The investigation consisted of a very careful quantitative study 

 of three ratios namely , AgClrNaCl, Ag : NaCl, and Ag : AgCl. 

 The effort was made to test every operation involved in the execution 

 of the experiments. In the course of the work, the following points 

 were developed : 



1. Sodic chloride, obtained from many sources and purified in 

 many ways, always gave the same equivalent weight. 



2. Fusion in vacuum of salt already fused in air caused no change 

 in this equivalent weight. 



3. Argentic chloride precipitated from aqueous solutions always 

 occludes traces of other substances present, and those traces can not 

 always be eliminated. Very dilute solutions must hence be used in 

 precipitation. 



4. The conditions governing the occlusion and release of these 

 impurities were minutely studied, and it was shown that Stas's method 

 of dropping solid salt into a silver solution causes occlusion of salt. 

 Many considerations important in all precise chemical work are dis- 

 cussed. 



5. A careful study of the solubility of argentic chloride was made, 

 and the precautions necessary in using the nephelometer in the estima- 

 tion of traces of chloride and silver were ascertained. 



6. Fused argentic chloride probably contains traces of dissolved 

 air, but not enough to affect essentially its weight, since subsequent 

 fusion in vacuum caused no appreciable loss of weight. 



7. The most difficult question in the purification of silver was 

 found to be the elimination of the inclosed mother liquor without 

 introducing other impurities. Fusion on pure lime, first in pure 

 hydrogen and then in a vacuum, is the safest method. Stas's silver 

 must have contained at least as much oxygen as Dumas claimed. 



8. In ten experiments, 44.5274 grams of sodic chloride yielded 

 109.1897 grams of argentic chloride. 



9. In twelve other experiments, entirely distinct from these, 

 49.5007 grams of sodic chloride were found to be equivalent to 91 .3543 

 grams of the purest silver. 



10. In ten other experiments, again entirely distinct from the 

 preceding, 82.6689 grams of the purest silver yielded 109.8395 grams 

 of argentic chloride. Two very different methods of synthesis were 

 used in this series, and the silver came from various sources, these 

 variations being without effect on the result. 



