452 Hillebrand, Turner and Clarke — Roscoelite. 



exist in a lower state of oxidation than V 2 B . The second 

 gave all iron as FeO and all vanadium as Y 2 4 . 'Deduct from 

 both the figure for FeO and the remainder gives that for 

 vanadium. In this way two very concordant results were 

 obtained for total vanadium as Y 2 4 which were supplemented 

 by tests on portions used for other constituents, but only one 

 was obtained for the vanadium as it exists in the mineral, a 

 second being vitiated by evident oxidation during decomposi- 

 tion in the tube. As a check, however, a fresh sample of 

 unpurified mineral was similarly treated and it was found that 

 fully nine-tenths of the vanadium existed as Y 2 3 , a result 

 confirming the single test on the purified material which 

 showed 93*5 per cent as Y 2 3 . It is not impossible that slight 

 oxidation had taken place even in these cases, and I feel justi- 

 fied in assuming with Genth that the vanadium should be con- 

 sidered wholly as V 2 3 . 



In the other portions analyzed the vanadium was likewise 

 titrated in Y 2 4 condition, but only after separation from iron, 

 titanium and aluminum by fusion with Na 2 C0 3 , extraction 

 with water and separation of dissolved alumina by ammonium 

 carbonate. A second fusion of the residue and of the precipi- 

 tated alumina was necessary in order to extract all the vana- 

 dium. These numerous manipulations render the figures for 

 A1 2 3 perhaps the least trustworthy of all, but the average 

 given is probably not far from correct. 



The iron is assumed to be present as FeO ; and the titanium 

 to belong to a foreign mineral, since a test on unpurified mate- 

 rial gave much more, namely, 1*50 per cent Ti0 2 , without 

 accompanying increase in FeO, which latter observation seems 

 to exclude ilmenite as the source of the titanium. 



Both the iron and magnesium are supposed to belong to the 

 roscoelite, since they were found by Genth in nearly the same 

 amounts and no recognizable iron or magnesium minerals were 

 noticed in the purified powder. 



For comparison, the mean of Roscoe's analyses and that one 

 of Genth's considered by himself to be his best are also given 

 in the table on the following page. 



Yery marked differences are apparent in the three analyses 

 by different chemists. If titanium was present in the mate- 

 rial analyzed by Genth and Eoscoe, as is very probable, their 

 high results for alumina are in great part at least accounted for. 

 It is inconceivable how Genth obtained his value for water by 

 ignition, since the mineral oxidizes when heated in air. In 

 fact the oxidation in one of my own analyses, after allowing 

 for loss of water as ascertained by direct weight, was almost 

 what theory requires for the oxidation of Y 2 3 to Y 2 5 and of 

 FeO to Fe 2 3 , or 5'14 per cent instead of 5*27 per cent. It 



