18 PROCEEDINGS OF THE AMERICAN ACADEMY 



we have assigned. At the time the first two determinations were 

 made, these facts were not known, and no allowance was made for the 

 loss of chloride of antimony which must have been incurred. This 

 loss fully accounts for the difference between the value we obtained, 

 120.6, and 120.3, that of Schneider. 



It was at this stage of the investigation that we presented a pre- 

 liminary notice of our results to the American Academy of Arts and 

 Sciences, at the meeting of June 10, 1873. After this, the work 

 was interrupted for more than two years, and was not resumed until 

 the autumn of 1875. Meanwhile, we had perfected the process of 

 reverse filtering above referred to, and devised a more certain, although 

 indirect method of bringing into solution, in its lower condition of 

 quantivalence, a known weight of antimony. This last consisted, 

 firstly, in dissolving a weighed portion of antimony in hydrochloric 

 acid with the least possible addition of nitric acid; secondly, in reduc- 

 ing the solution thus obtained, by boiling it over bullets of pure 

 antimony, determining from the loss of weight of the bullets the 

 amount of metal dissolved. Evidently, the mass originally taken, plus 

 the amount dissolved from the bullets, gave the weight of antimony 

 used in each determination. Several important facts were observed 

 in connection with each of these steps. 



1st. It is usually stated that antimony is only very slightly acted on 

 by pure hydrochloric acid, even when concentrated and boiling, but 

 that it readily dissolves on the addition of only a very small amount of 

 nitric acid.* We found that, when wholly protected from the air or 

 oxidizing agents, pure antimony not only does not decompose pure 

 hydrochloric acid, but also that in contact with the air the smallest 

 amount of nitric acid will determine the solution of an indefinite 

 amount of the metal. Assuming that the product of the reduction of 

 the nitric acid is wholly NO, and therefore that the smallest amount 

 theoretically required for the reaction would be represented by the 

 expression, — 



Sb + (3HC1 + HNO3 + Aq) = (SbClg -f 2 H^O + Aq) + NO, 



then 40 parts of antimony would require, in addition to an abundant 

 supply of hydrochloric acid, 21 parts of HNO3 ^'^^ '^^^ complete solu- 

 tion. The pure nitric acid which we used had a specific gravity of 

 1.355, and contained therefore about 54% of HNO3. The same acid 

 diluted with nine times its volume of water, to form what we will call 



* Author's Chemical Philosophy, p. 265. 



