hillebrand.] CARNOTITE AND ASSOCIATED MINERALS. 23 
dissolving the vanadium, iron, or aluminum. Repetition of this proc 
ess yielded Friedel and Cumenge satisfactory results. They recom- 
mended washing with water containing ammonium nitrate. 
The other method involved the quantitative removal of vanadium by 
dry hydrochloric acid gas in the manner already described (pp. 18-19). 
Smith and Hibbs had shown that this method is perfect for alkaline 
pyrovanadates and it was hoped that it might succeed even with such 
complex mixtures as those under consideration. The distillations were 
made on the crude ore and also on the nitric acid solution after filtra- 
tion from the insoluble matter and evaporation to thorough dryness. 
The action is immediate in the cold, copious red-brown vapors coming 
off and condensing in part as a dark red liquid in the tube. But 
repeated distillations and the application of heat were required to 
effect complete removal of the vanadium accompanied by the arsenic 
and molybdenum. After each distillation the contents of the boat had 
to be evaporated with nitric acid. The blue and green colorations 
apparent on adding this acid showed that the hydrochloric acid gas 
had reduced a good deal of the vanadium to a lower state of valence, 
and in this condition it was incapable of forming the volatile body. 
A somewhat more satisfactory separation sometimes resulted when 
this distillation method was combined with that of Friedel and Cumenge 
by subjecting both the evaporated uranium nitrate solution and the 
residue insoluble in water to the action of hydrochloric acid gas. 
The distillates obtained by either way were evaporated with sulphuric 
acid, the arsenic and molybdenum were separated by hydrogen sul- 
phide, and the vanadium was then titrated by permanganate at a tem- 
perature near boiling and again after reduction by sulphur dioxide 
gas. In one or two cases when the temperature of distillation had 
been high and it was feared some iron had passed over, the distillates 
were evaporated in porcelain with nitric acid, transferred to a platinum 
crucible, evaporated therein with sulphuric acid, and fused with sodium 
carbonate. The aqueous extract was then treated as above for arsenic, 
molybdenum, and vanadium. 
The mode of separation practiced by Friedel and Cumenge, while 
perhaps adequate for technical purposes in ores free from phosphorus,'' 
ioes not in my hands give perfect satisfaction even then. It is impos- 
sible to prevent a little of the vanadium, also of the iron and alumi- 
lum, from going with the uranium, and on the other hand a little 
aranium may stay with the vanadium. Again when the vanadic acid 
«With even only half a per cent of P 2 5 many times that amount of U0 3 is rendered insoluble in 
water after evaporation to dryness with nitric acid. The compound formed is of a lemon-yellow color, 
Lvhich is masked by the separated vanadic acid until tliis lias been removed by ammonia. This 
insoluble body was treated as follows in order to arrive al (lie P 2 6 and U0 3 il contained. After 
Iblution in nitrite acid the phosphorus was precipitated by ammonium molybdate, and from tbe 
■nitrate the uranium by three precipitations by ammonia. 
