Vanadiferous Minerals in Western Colorado. 135 



and mechanical separation impossible. The first specimen 

 received happened to be of a higher grade than any of the 

 subsequent ones, containing about 5 per cent of sand grains 

 and showing only very faint delicate reddish tracings indica- 

 tive of some foreign iron mineral. In mass it was of a beauti- 

 ful canary-yellow color and easily broken down by pressure. 

 Other specimens were more coherent, the degree depending 

 altogether on the extent to which the sandstone had been 

 impregnated and altered, and they sometimes showed more of 

 the peculiar reddish admixture. 



A fact only suspected in making the first analysis was con- 

 firmed by subsequent work on lower grade ores, namely, that 

 the vanadium existed in two conditions, in entirely distinct 

 minerals ; the greater part by far as pentavalent vanadium in 

 the easily soluble carnotite, and a smaller, much less soluble 

 portion, almost vanishing in the purest ores, in the trivalent 

 state as a constituent of a silicate free from uranium. This 

 observation explained the statement of Messrs. Poulot and 

 Voilleque that they had found the low grade ores to be rela- 

 tively richer in vanadium as compared with uranium than the 

 high grade ores. 



While the carnotite dissolves at once in cold dilute nitric 

 acid, unfortunately the vanadiferous silicate is not quite insolu- 

 ble, hence arose an important difficulty in the way of arriving 

 at the true composition of the carnotite. It is true that in one 

 case the silicate has been analyzed (p. 143), but it would be 

 unsafe to correct the carnotite analysis on that basis. More- 

 over, the analyses were not all made on the same plan ; some 

 are less complete than others ; they cannot in some respects be 

 rigidly compared with each other. 



As to the carrying out of the analysis, various procedures 

 were tried and no one found which gave altogether satisfactory 

 results as to each constituent, though many could be deter- 

 mined with the usual degree of accuracy. The difficulty was 

 mainly due to vanadium and the small amount of phosphoric 

 acid usually present. These two constituents were likely to be 

 found in different precipitates and could not be separated from 

 them at one stroke. Their complete removal from other bodies 

 was at times impossible and the weight of the latter had then 

 to be corrected for these residual amounts. 



Two entirely different lines of attack were open. One, that 

 of Fi'iedel and Cumenge, described in their paper on carnotite, 

 had already been used with apparent success. It depends on 

 rendering the vanadium iusoluble in water by evaporating the 

 nitric acid solution to dryness. Water extracts the alkalies and 

 uranium without dissolving the vanadium, iron, or aluminum. 

 Repetition of this process yielded Friedel and Cumenge satis- 



