14 PROCEEDINGS OF THE AMERICAN ACADEMY 



excess to tlie powdered antimony, previously moistened with water, and 

 as soon as, on gently heating the beaker, the action began, we kept the 

 mass in constant agitation, so as to prevent the temperature from rising 

 too high at any point. If during this reaction, or during the subsequent 

 evaporation of the excess of acid, the dry nitrate is lieated even to 

 100*^, decomposition ensues, and higher oxides are formed, which are 

 insoluble in tartaric acid. Indeed, this is probably the order of the 

 change even during the violent action of nitric acid on antimony, when 

 antimonic oxide, Sb^O^, is the chief product, autimonious nitrate being 

 in all cases formed first, and subsequently decomposed. Unfortu- 

 nately, we could not always succeed in obtaining a clear solution in this 

 way ; and the loss of pure material occasioned by the unsuccessful trials 

 was so considerable that we soon abandoned the method. Still, it was 

 capable of yielding good results, as the determinations given below 

 will show. 



The rest of the process was as follows : The tartaric acid solution 

 having been brought to the proper degree of dilution, — about 250 cubic 

 centimetres to each gramme of antimony, — the free acid was fii'st 

 carefully neutralized with pure caustic soda. A small amount of 

 hydrochloric acid was next added, and the antimony precipitated with 

 HgS. In these, as well as in all the subsequent determinations, the 

 precipitation was conducted thus : The solution having been made in 

 a large Erlenmeyer flask, and this firmly supported over a gas lamp, a 

 current of washed carbonic dioxide gas was conducted into the li(juid 

 from a suitable generator, the glass tube conducting the gas reaching 

 to the bottom of the flask, so that the gas might bubble up through the 

 whole column of liquid. The atmospheric air having been thus com- 

 pletely expelled, then, through a second glass tube similarly arranged, 

 au excess of a supersaturated solution of H^S was drawn into the vessel 

 from the fountain or siphon described in the paper above referred to. 

 The temperature of the mass was now slowly raised to the boiling 

 point, and the liquid actually boiled for ten or fifteen minutes. The 

 current of carbonic dioxide, continually passing meanwhile, not only 

 excluded the air, but kept the mass in constant agitation and pre- 

 vented '' bumping." 



The precipitate thus forms in a granular condition excellently well 

 adapted to bear without alteration the processes of washing and 

 filtering which follow. It does not adhere to the tubes or sides of 

 the flask, and unless there is some oxidizing agent in the solution 

 it does not contain the least trace of free sulphur. The precipitate 

 was washed with boiling water, and as it settles rapidly and quite 



