THE SYNTHESIS OF ARGENTIC CHLORIDE. 59 



30,000,000 of water, which is about the order of the possible solubility 

 of undissociated argentic chloride, and hence may have represented 

 that quantity. The determination was made by evaporating the hydro- 

 chloric acid solutions, rinsing out the dish with ammonia and testing 

 the resulting solution nephelometrically by comparison with similarly 

 prepared known solutions of silver chloride, as has been said. 



The third correction was for an occasional loss of chlorine by the 

 argentic chloride on fusion, owing either to the presence of argentic 

 nitrate or to traces of dust. The darkening thus caused represents a 

 real although often trivial deficiency of weight, but, fortunately, this is 

 easily restored by fusion in a mixture of pure chlorine and hydro- 

 chloric gas. Of course this process must not be adopted when argen- 

 tic nitrate is occluded during the analysis of a metallic chloride, for it 

 would then lead to a large excess of argentic chloride ; but it is perfectly 

 safe in the present case. The only suspicion which attaches to it is 

 the possibility that an excess of one of these gases might be dissolved. 

 This is undoubtedly a real danger, unless the fused salt is exposed to 

 the air and agitated in contact with it while fused. If this is done, 

 we have assured ourselves by repeated experiments that no essential 

 excess of chlorine remains dissolved.* Two facts pointed to this con- 

 clusion first, that those samples of argentic chloride, which after the 

 preliminary fusion merely in air were perfectly colorless, transparent, 

 and pearly, gained no essential weight on fusion in chlorine (Expts. 

 80, R. 2 and R. 3, final series, p. 65) ; and secondly, that argentic 

 chloride fused in chlorine, properly freed from it, and subsequently 

 again and again fused in pure air lost no essential weight. 



We always secured elimination of the possible trace of dissolved 

 chlorine by continuing to fuse in air with occasional removal of the 

 cover, and by carefully rolling the inclined crucible around, while 

 held with forceps, during the solidification of the fused mass. Spread- 

 ing the solid in this way makes it easier to fuse the salt once more 

 without breaking the very fragile quartz crucibles. 



The attacking of glass by chlorine in contact with silver chloride 

 and a consequent loss of weight gave Stas considerable difficulty. 

 Baxter has found that even porcelain is attacked in displacing iodine 

 with chlorine in the silver salts. We did not greatly fear a loss of 

 weight of the porcelain crucibles, since our chlorine was dilute, and 

 was applied only for a few minutes ; nevertheless we adopted the 

 use of quartz as an added precaution in the later experiments. No 

 difference in results could be detected by its use. 



*Dr. Baxter has come to the same conclusion. Proc. Am. Acad., 40, 432 

 (1904). And so also have Kothner and Aeuer, Lieb. Ann., 337, 127 (1904). 



