232 0. S. Ptdman — Determination of Uranium and 



the action of the redactor, and reoxidized on exposure to the 

 air seems to be justitied. 



The details of the procedure were as follows : The uranium 

 sulphate solution, obtained from the standard solution of ura- 

 nium nitrate bj evaporating with 10^"^^ of strong sulphuric 

 acid, as previously described, ranging in volume from 100 to 

 150^""^, and containing a proportion of free sulphuric acid vary- 

 ing between the limits of 1 to 7 and 1 to 5, was heated nearly 

 to the boiling point, and, preceded by a few cubic centimeters 

 of the same strength of acid, was passed slowly through the 

 reductor, using gentle suction. The flask which had contained 

 the solution was washed thoroughly with sulphuric acid of the 

 same strength as was in the solution. This was added to the 

 reductor after the uranium and was followed by 250"''^ of hot 

 water. The contents of the receiving flask were poured into 

 a porcelain dish, diluted with about 200^^""^ of hot water, and 



titrated with a — potassium permanganate solution to a faint 



pink end-reaction. 



In most of the determinations the proportion of the free 

 sulphuric acid in the solution was kept nearly at 1 to 6, since 

 this was found to be the most satisfactory, although the deter- 

 minations in which the ratio was between the limits of 1 to 5 

 and 1 to 7 gave accurate results. When the ratio was at 1 to 5 

 or greater, however, the acid attacked the zinc so rapidly that 

 there was too great an evolution of hydrogen for convenience, 

 so much so that if for any reason the operation had to be inter- 

 rupted the rapidity of the evolution caused the solution to rise 

 in the tube and to be in danger of flowing over the top of the 

 reductor. The ratio of 1 to T required more time than that of 

 1 to 6. With acid in the ratio of 1 to 6, it was found that 

 amounts of uranium sulphate equivalent to 0.2 gram of uranic 

 oxide were not reduced completely in eight to ten minutes, so 

 that for this amount about fifteen minutes or more should be 

 taken for passing the uranium solution and water through the 

 reductor. For 0.3 gram of uranic oxide it was found that eighteen 

 to twenty minutes were not sufficient for complete reduction, 

 so that half an hour or more was allowed for reducing and 

 washing with this amount. With the stronger acid, in the 

 ratio of 1 to 5, it was found that the uranium could be reduced 

 in about two-thirds of the time required by the acid in the 

 ratio of 1 to 6, but the use of the weaker acid- was preferred 

 on account of the rapid evolution of hydrogen and the conse- 

 quent danger of loss connected with using the stronger acid, 

 as above mentioned. 



In using the reductor for estimating the molybdic acid in 



