THE SOLUBILITY OF ARGENTIC CHLORIDE. 25 



The resulting nitrate, made alkaline with ammonia, was electro- 

 lyzed to remove a suspected trace of iron and filtered through a layer 

 of calcic carbonate upon a Gooch crucible. It was found that 

 amnionic carbonate, of variable composition, could be conveniently 

 distilled with steam from its solution. With such a distillate, pre- 

 pared wholly in platinum, calcic carbonate was again precipitated 

 and well washed. A small portion of this was converted into nitrate. 



Ignition of the calcic carbonate to oxide was carried out in por- 

 celain, since platinum is slightly volatile at high temperatures, and 

 might have contaminated the lime. A dry mixture of calcic oxide, 

 with about a fifth its weight of powdered anhydrous nitrate, was 

 packed into specially made large unglazed boats of Berlin porcelain. 

 The molded mixture when heated to redness sintered firmly together 

 and made a chemically pure receptacle, large enough to contain about 

 50 grams of silver at a time. In order to prevent adhesion of the 

 boat to the glaze of the porcelain tube, the boat should not fit the 

 tube very closely, and it is well to cover the glaze under the boat with 

 a layer of pure powdered lime. 



UTENSILS. 



Of course all the containing pieces of apparatus dishes, funnels, 

 crucibles, retorts, condensers, and so forth were of platinum wherever 

 silica was to be feared and platinum was not itself harmful. In this 

 latter case, according to circumstances, either silver vessels or vessels 

 of the best insoluble glass (Jena, or " nonsol ") or porcelain, or in some 

 cases fused quartz, were used. In this way the greatest possible purity 

 of the preparations was assured. 



THE SOLUBILITY OF ARGENTIC CHLORIDE. 



Mulder pointed out in 1857* that the solubility of argentic chlo- 

 ride is sufficient to affect all quantitative results into which the pre- 

 cipitation of this substance enters. Stas overlooked this solubility in 

 his early determinations, and hence in 1876 repeated some of them.f 

 Other more recent experimenters J have in general confirmed Stas's 

 later conclusions about this solubility, so that it is not important here 

 to give a lengthy statement of our further confirmatory results. 



There can be no doubt that freshly precipitated argentic chloride 

 is soluble in cold water to the extent of several milligrams per liter, and 



*Mulder, Die Silber-Probirmethode. Leipzig, 1859. 

 tStas, Ouvres, 1, 751. 



jFor references see Bofctger, Zeitsoh. phys. Chem., 46, 189 (1903); Rich- 

 ards, Proc. Am. Acad., 29, 69 (1893). 



