20 PROCEEDINGS OF THE AMERICAN ACADEMY 



the boiling point. The effect of this was to arrest the chemical action 

 by driving off the nitric oxide ; and, if the point was rightly chosen, the 

 small residue of antimony, in passing into solution, would reduce 

 almost all of the higher chloride of antimony which had been pre- 

 viously formed, AVe found it better, however, that some of the 

 higher chloride should be left unreduced rather than that the least 

 trace of antimony should remain undissolved. In the last case, it was 

 necessary to add additional nitric acid, which made trouble at the next 

 stage of the process ; and the fact repeatedly observed, that under 

 these circumstances a few milligrammes of antimony will not dissolve 

 in a large excess of hydrochloric acid, even after prolonged boiling, is a 

 sufficient proof of the statement made above, — that pure antimony will 

 not decompose pure hydrochloric acid, unless some oxidizing agent is 

 also present. 



2d. Having thus brought a weighed amount of antimony into solu- 

 tion, so that almost the whole was in the condition of antimonious 

 chloride, we completed the reduction by boiling the acid solution over 

 bullets of pure antimony. These bullets were cast in a bullet-mould, 

 and afterwards turned in a lathe, so as to secure a perfectly clean, 

 smooth, and compact surface. Two or three of them were next 

 weighed together in a platinum tunnel, supported vertically by a light 

 glass stand, on the pan of the balance. From the tunnel they were 

 transferred one by one, without touching with the fingers, to the flask 

 containing the solution of antimony made as just described. The flask 

 was then again connected with the reverse condenser, and the licjuid 

 boiled ; while through a second opening in the cork a slow current of 

 carbonic dioxide was caused to flow through the apparatus. The boiling 

 was continued until the reduction was complete, and the point was 

 indicated by the circumstance that, when it is reached, the solution, at 

 first having a light straw color, becomes perfectly colorless. The origi- 

 nal color is caused by the presence of an exceedingly minute amount of 

 iron, which it is almost impossible to keep out of the solution. Indeed, 

 the very dust of the atmosphere will impart enough for the purpose ; 

 and this color under these conditions is as delicate a test for iron as that 

 caused by potassic sulphocyanide. It served here as a very useful indi- 

 cator, but it was no sign whatever of any appreciable amount of im- 

 purity, either in the metal or the acid. Another indicator which can 

 be used, although not nearly so conveniently, is the well-known solution 

 of potassic iodide in starch paste, the acid solution of chloride of anti- 

 mony giving with this reagent the familiar blue color before, but not 

 after, it has been reduced. 



