22 PEOCEEDINGS OP THE AMERICAN ACADEMY 



solution of a ferrous salt. A solution reduced as we have described, 

 which has at first no action on the iodized starch paste, will strike the 

 blue color after it has been exposed to the air for only a few minutes. 

 This property of an acid solution of antimonious chloride is mentioned 

 by Dexter, in the paper already referred to, but we were wholly sur- 

 prised by the energy of the action. By means of it, antimony can be 

 dissolved in hydrochloric acid without the aid of nitric acid, or of any 

 other oxidizing agent save the air, if only a certain amount of antimoni- 

 ous chloride has once been formed. When, after exposure to the air, 

 the solution is boiled over pulverized antimony, the solution is reduced, 

 and a further portion of the metal enters into solution. After a second 

 exposure, the same process can be repeated, and so on indefinitely. The 

 process is very slow and tedious, but, in one experiment, we succeeded 

 in bringing into solution in this Avay several grammes of antimony. 



The method of precipitating the antimony after the solution was thus 

 prepared has already been described (page 14). It is important, how- 

 ever, to add a few additional facts, which we observed in regard to the 

 two impurities which the precipitated sulphide of antimony occludes ; 

 namely, tartaric acid and oxichloride of antimony. In the first place, 

 we found that the relative amounts of these occlusions might be varied 

 indefinitely by changing the relative proportions of tartaric and hydro- 

 chloric acids in the solution in which the precipitate was formed. As 

 is well known, the antimony cannot be kept in solution without a certain 

 excess of one or of both of these reagents. In proportion as the amount 

 of one is diminished, that of the other must be increased ; and we made 

 a series of experiments to determine what were the minimum quantities 

 required under different conditions. We made determinations in which 

 the antimony was held in solution by hydrochloric acid only ; and we 

 found that, in that case, as much as one part of strong acid was required 

 to five parts of water. We thus, of course, wholly avoided the occlusion 

 of tartaric acid ; but the amount of oxichloride carried down was so great 

 that the results were worthless. On the other hand, in some more re- 

 cent analyses, in which we began with pure chloride of antimonj'-, we 

 used only tartaric acid, and, in this case, although the carbonaceous 

 residue was at times large, there was no loss by sublimation. Of the 

 two occlusions, the tartaric acid is by far the least objectionable. This, 

 as we have seen,* is wholly charred when the red sulphide of antimony 

 is converted into the gray modifications, and the carbonaceous residue 

 can be exactly estimated. In the case of the oxichloride of antimony, 



* Page 15. 



