This uncommon metal occurs as carbonate, phosphate, and tantalate in some rare minerals, but its only commercial source is pitchblende, which contains 40 to 90 per cent. of uranoso-uranic oxide. Several processes are in vogue for extracting uranium from pitch-blende, as follows. (1) The powdered ore is digested with sulphuric acid supplemented by occasional small additions of nitric acid; when the precipitate is converted into a white powder (and partially dissolved), the sulphuric acid in excess is driven off, and the residue is digested in water, affording a deposit of bismuth arsenate and sulphate, lead sulphate, and silica; on passing a current of sulphuretted hydrogen through the warmed filtered solution, the remaining bismuth and lead, with antimony, arsenic, and copper, are precipitated, and the filtrate is then oxidized by nitric acid, and treated with ammonia in and evaporated to crystallization in a platinum receptacle.
Protoxide of iron....
Oxide of manganese..
Consequently, metallic vanadium is present to the extent of 1.08 per cent. For the Creusot works alone, the quantity of vanadium thus concentrated may be estimated at 130,000 lb. yearly. This is, therefore, an abundant source, from which the authors have succeeded in extracting both the meta-vanadiate of ammonia and certain new vanadic products, more specially applicable to the production of aniline blacks. Their principal procedures ore the following:-
(1) Simple Solution Of The Crude Slags
The slags, coarsely broken, are left in excess in contact with hydrochloric acid at the common temperature, until the acid is almost entirely saturated, and the solution marks 64° Tw. It may then be let down to 12° Tw. with water, the silica allowed to settle, and the strength taken. The liquid thus prepared contains vanadium in the hypo-vanadic state, and, notwithstanding the presence of foreign salts, it may be used as it is in printing. The industrial experiment has been made by one of the authors, who, in the course of more than a year's working, has found no inconvenience from its use.
(2) Preparations With A Base Of Hypo-Vanadic Phosphate
The hydrochloric solution of the crude slags, suitably neutralized and mixed with soda acetate, deposits a copious bluish-grey precipitate, which contains the greatest part of the vanadium in the state of hypo-vanadic phosphate mixed with other sparingly soluble phosphates. By repeating the same treatment a second time there is obtained a new precipitate, containing 20 per cent. of metallic vanadium, if the original slag contained at least 1 5 per cent. The common slags, which do not reach this standard, may be enriched by a very simple process. To the muriatic solution is added an excess of slag, in powder, which neutralizes the free acid, and precipitates the metals whose phosphates are least soluble, especially vanadium. The first precipitate, which is light and of a greyish white, is taken up in hydrochloric acid, and treated with soda acetate, as above. These preparations, very soluble in acids, have been. tried with success in several large print-works.
The phosphate precipitates, obtained by the slag itself, or, better, by an acetate, instead of being enriched and sent out, are dried and roasted at a dull red heat. The powder, at first of a light grey, takes an ochre yellow. It is treated with ammoniacal water, which gives an orange-yellow solution of ortho-vana-diate. It is boiled till colourless, filtered, and the ammonia meta-vanadiate is precipitated in the ordinary manner.-(Witz & Osmond, Compt. Rend.)
Metallic vanadium is prepared by reducing the dichloride in perfectly pure hydrogen,-an extremely difficult operation, owing to the necessity for excluding every trace of air and moisture. The metal forms a greyish powder, having a sp. gr. of 5.5 at 59° F. (15° C.); it burns in a flame or when heated in oxygen, and oxidizes slowly in the air; it is insoluble in hydrochloric acid, but slowly dissolves in hot strong sulphuric and in hydrofluoric, and violently oxidizes in nitric acid of all strengths.