THE DETERMINATION OF URANIUM AND VANADIUM 



IN THE CARNOTITE ORES OF COLORADO 



AND UTAH. 



By ANDREW A. BLAIR. 

 (Read April 17, 19 13.) 



The determination of uranium in ores has become a matter of 

 importance, due to the discovery of ores containing this element in 

 Colorado and Utah and the constantly increasing demand for them. 

 In these ores the uranium is associated with two to four times as 

 much vanadivmi and varying amounts of silica, alumina, oxide of 

 iron, lime and magnesia. They are practically free from phosphoric 

 acid and sulphides, and contain very small amounts of metals pre- 

 cipitated by hydrogen sulphide in an acid solution. The problem 

 thus is practically the separation of the uranium and vanadium from 

 the alumina and oxide of iron, and their separation from each other. 

 The first part of the problem is readily solved by the use of ammo- 

 nium carbonate, which dissolves the uranium and vanadium and 

 precipitates the oxide of iron and alumina. The separation of ura- 

 nium from vanadium is more difficult, owing to the strong affinity 

 between these elements. The volumetric method seems to ofifer an 

 ideal separation as hydrochloric acid reduces the vanadium to the 

 vanadyl condition without affecting the state of oxidation of the 

 uranium and subsequent evaporation with sulphuric acid and titra- 

 tion with permanganate gives an accurate method for the determina- 

 tion of the vanadium. Subsequent reduction by aluminum reduces 

 the uranium to UO,, but it also reduces the vanadium theoretically 

 to the state of VjOg, but upon the removal of the aluminum the 

 vanadium absorbs oxygen so quickly that the actual state of oxida- 

 tion is uncertain and the titration becomes unreliable. In Low's 

 " Technical Methods of Ore Analysis," page 204, the method relies 

 on the precipitation of the vanadium as lead vanadate in the pres- 

 ence of free acetic acid for its separation from the uranium, and 

 while with great care this may be accomplished with more or less 



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