202 BLAIR— URANIUM AND VANADIUM [April 17, 



accuracy it leaves much to be desired in the wa)' of simplicity and 

 ease of manipulation. 



The method given by Carnot^ for the determination of vanadium 

 by adding uranyl nitrate and precipitating the ammonium uranyl 

 vanadate in a solution slightly acid with acetic acid lends itself 

 admirably to the reverse determination, and in the presence of an 

 excess of vanadic acid the uranium may be accurately and easily 

 determined. 



Ammonium uranyl vanadate is a canary yellow flocculent pre- 

 cipitate resembling sulphide of arsenic. It settles rapidly and is 

 quite insoluble in a solution faintly acid with acetic acid. It must 

 be washed with a hot solution containing about 5 c.c. of slightly acid 

 ammonium acetate to 100 c.c. of water, as it is slightly decomposed 

 by pure water, passes through the filter and is reprecipitated in the 

 filtrate. Upon ignition the VoO-, 2U03(NHJoO + H2O loses am- 

 monia and water and becomes V„0-, 2UO3. It burns readily, but 

 should not be heated above a low red, as it fuses and becomes very 

 insoluble. Even when not fused it dissolves with difficulty in a large 

 excess of dilute nitric acid. Fusing the salt does not appear to 

 change its composition or the degree of oxidation of the uranium as 

 the weight remains constant. When fused, a little hydrofluoric acid 

 added to the dilute nitric acid causes it to dissolve more readily. 



Determination of Uranium. 



Boil two grammes of the finely ground ore with 25 c.c. of strong 

 nitric acid and 25 c.c. water for half an hour, dilute and filter. Re- 

 ject the insoluble portion. Neutralize the filtrate with ammonia 

 and after a precipitate has formed add a strong solution of ammo- 

 nium carbonate in excess. A large excess of ammonium carbonate 

 is to be avoided as it dissolves appreciable amounts of both alumina 

 and oxide of iron. This precipitates the alumina, oxide of iron, etc., 

 while the uranium and vanadium are dissolved. The volume of the 

 solution should be about 250 c.c. The solution should be warm but 

 not hot, 40°-50° C. is a good temperature. Stir constantly for 

 fifteen or twenty minutes and allow the precipitate to settle. Decant 

 as much as possible of the clear liquid on the filter, and finally pour 



^ " Traite d'Analyse des Substances Minerales," Vol. II, p. 791. 



