'9'3.] IN ORES OF COLORADO AND UTAH. 203 



on the precipitate and wash it two or three times with water con- 

 taining two grammes of ammonium carbonate to the lOO c.c. Evap- 

 orate the filtrate. Dissolve the precipitate in a small quantity of hot 

 dilute nitric acid and reprecipitate as before. Filter and add the 

 filtrate to the first one. Evaporate until the ammonium carbonate 

 is expelled and acidulate with a few drops of nitric acid. Evaporate 

 until the volume of the solution is about 200 c.c, transfer to a 

 400-c.c. beaker, and add ammonia until a precipitate appears. Add 

 nitric acid drop by drop until the solution clears, then add 10 to 15 

 c.c. of ammonium acetate, made by adding 30 per cent, acetic acid 

 to strong ammonia until the liquid is acid to litmus paper. This will 

 require a little over three volumes of acetic acid to one volume of 

 ammonia. The precipitate which forms immediately is the ammo- 

 nium uranyl vanadate VoOg, 2UO3, (NH4)20 -|- H.O, mentioned by 

 Carnot. After boiling for a few minutes it settles rapidly, leaving 

 a clear supernatant liquid. Decant the clear liquid on a filter and 

 wash twice by decantation with hot water containing 5 c.c. of the 

 ammonium acetate mentioned above to 100 c.c. of water. Wash the 

 precipitate onto the filter and wash several times with the same 

 solution. Dissolve the precipitate adhering to the beaker in hot 

 dilute nitric acid, pour it on the filter allowing the solution to run 

 into a small beaker. Wash the filter with dilute nitric acid and hot 

 water and evaporate the solution to dryness, without heating above 

 water bath temperature. Dissolve in a little hot dilute nitric acid 

 and add ammonia until a precipitate forms, then ammonium car- 

 bonate to dissolve the uranium and vanadium and precipitate any 

 alumina and silica. Allow to stand until the precipitate settles, filter, 

 wash with ammonium carbonate, acidulate the filtrate with nitric 

 acid, boil ofif the carbonic acid and precipitate by ammonia and am- 

 monium acetate as above. Filter, wash, ignite at a low red heat and 

 weigh as VoO.,, 2UO3, which contains 74.48 per cent of UyOs. 



The success of this method depends on the presence of more than 

 a sufficient amount of vanadic acid to form a precipitate of the com- 

 position mentioned, and this is the case with all the ores I have seen 

 from these localities. It is well, however, to make sure of this and 

 therefore the filtrate from the first precipitation of ammonium 

 uranvl vanadate should be acidulated with nitric acid and a few 



