Hillebrand — Vanadium and Molybdenum in Rocks, 213 



Chemical method employed. 



In conclusion it is proper to outline the method by which 

 the foregoing tests were carried out and to indicate the precau- 

 tions that must be observed in order to insure good results. 



Quite a number of workers have busied themselves with the 

 problem of vanadium estimation in ores and rocks, particu- 

 larly magnetites and other iron ores, and the methods used 

 have been often diverse in parts if not altogether. There is 

 nothing absolutely novel in the following except that chromium 

 and vanadium when together need not be separated, but are 

 determined, the former colorimetrically, the latter volumetrically 

 in the same solution as detailed elsewhere.* 



Five grams of the rock are thoroughly fused over the blast 

 with twenty of sodium carbonate and three of sodium nitrate. 

 After extracting with water and reducing manganese with 

 alcohol it is probably quite unnecessary, if the fusion has been 

 thorough, to remelt the residue as above, though for magne- 

 tites and other ores containing larger amounts of vanadium 

 than any of these rocks, this may be necessary, as Edo Claassen 

 has shown. f The aqueous extract is next nearly neutralized 

 by nitric acid, the amount to be used having been conveniently 

 ascertained by a blank test with exactly twenty grams of sodi- 

 um carbonate, etc., and the solution is evaporated to approxi- 



nearly all rock analyses heretofore made are subject to correction for the vana- 

 dium the rock may have held. This correction is of course to be made in terms 

 of YoO.-, and uot of Y 2 3 . 



All determinatioQS of iron are likewise affected by its presence whether as 

 V 2 3 or V 2 3 . As V0O3 it will make the FeO appear too high in the proportion 

 V 2 3 :4FeO, or 1508:288, an error winch becomes appreciable in some of the 

 basic rocks and amounts to '25 per cent in the biotile 23*. As V~ 9 6 the FeO will 

 not be affected, but in either erudition the Fe 2 3 will need correction and to a 

 different extent, according as the titration of iron is made after reduction by 

 hydrogen sulphide or by hydrogen. If the former is used, as should always be 

 the case in presence of titanium, the vanadium is reduced by it to V 2 4 . which in 

 its action on permanganate is equivalent to two molecules of FeO representing 

 one of Fe 2 3 . or only one-half as great as the influence on the FeO titration of the 

 same vanadium as V 2 3 . An example will make this clear. 

 Found 2 , 50 per cent apparent FeO in a rock 

 containing -13 per cent V 2 3 

 Deduct '25 per cent FeO equivalent in its action on 

 KMn0 4 to -13 V a O a 

 Leaving 2*25 per cent FeO corrected. 

 Found 5-00 per cent apparent total iron as Fe 2 3 in the same rock. 

 Deduct *14 per cent Fe 2 3 corresponding to -13 per cent Y 2 3 

 Leaving 4 - 86 per cent corrected total iron as Fe 2 3 

 Deduct 2 - 50 per cent Fe 2 3 equivalent to 225 per cent FeO 

 Leaving 2 36 per cent Fe 2 3 in the rock. 

 Failure to correct for the vanadium in both cases would have made the figures 

 for FeO and Fe 2 3 respectively 2*50 and 222 instead of 2*25 and 2-36 as shown 

 above. 



* Jour. Am. Chem. Soc, xx, pp. 454 and 461, 1893. 

 f Am. Chem. Jour., viii, 431. 



