384 PROCEEDINGS OF THE AMERICAN ACADEMY. 



adding to the bromide solution, thus reducing to a minimum the possi- 

 bility of too vigorous oxidation, with consequent liberation of bromine. 



After the oxidation, bromine was precipitated by pure silver nitrate in 

 the usual manner. This precipitation was conducted in an Erlenmeyer 

 flask fitted with a ground glass stopper. The silver bromide was col- 

 lected on a Gooch crucible, and dried in an electrically heated drying 

 oven. Of course the asbestos shreds carried away in washing the silver 

 bromide were collected by passing the filtrate and wash water through a 

 fine filter, and their weight was added to that of the silver bromide. 

 The bromine determination was carried on in orange colored light. 



It was found in the work upon cobalt and nickel that the porcelain 

 tube is attacked by bromine vapor at the high temperature employed 

 during the sublimation, with the result that sodium bromide was always 

 present in the sublimate. In these investigations this impurity was de- 

 termined by the reduction of the bromide to the spongy metallic state by 

 means of hydrogen, and extraction by water.* A somewhat similar 

 method was tried with uranium. Since hydrogen reduces uranous bro- 

 mide only to the tri-bromide, the bromide was ignited in a current of air 

 and the resulting oxide leached with water. It was found to be impos- 

 sible to oxidize the bromide completely. A little uranous bromide 

 invariably remained and was washed out with the alkali. Both dry and 

 moist air was tried, also ignition in steam, but in every case uranium was 

 washed out in considerable quantity. 



Precipitation of the uranium by hydrogen dioxide was next tried, but 

 it was found impossible to precipitate the uranium completely. The 

 rather unsatisfactory method of determining the sodium in the filtrate 

 from the bromine precipitation, or in a new sample of uranous bromide 

 as nearly similar as possible, after removing the uranium with ammo- 

 nium sulphide, appeared to be the only available method. The filtrate 

 and wash waters from the bromine precipitation were evaporated in 

 platinum to small bulk, and the uranium and excess of silver precipitated 

 by pure colorless ammonium sulphide. This reagent precipitates uranium 

 completely. The filtrate was then evaporated to dryness, the ammonium 

 salts expelled by ignition, and the residual sodic nitrate converted to the 

 sulphate and weighed as such. Of course these operations were all con- 

 ducted in platinum vessels. This method of work is not wholly satisfac- 

 tory, on account of the complexity of operations involved, but it seems to 

 be the only practical method. 



* These Proceedings, 34, 329, 359 (1899). 



