Licence: Public Domain Mark
Credit: Qualitative chemical analysis / by C. Remigius Fresenius. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![, JJ3 ] OXIDES or VANADIUM. IST a stream of hy^rossn -t sublime. a„^^^ salt is p?ecipitaW^^ oiiduaWe subcHoude Iff ^ I ''^ colourless volatile mass, whieh melts at hyK^Lri^^^^^^^^ co^taing.g acetate -r^on^. ^^^re^ acetic acid a white precipitate of ga hum V.l W s^phSe^^^^^^^^^ of ammonium throws down a white precipitate of pl^^^. ,^3^'^^^^ ?uble in excess of the precipitant; the Presence of tartaric acid preven^^^^^ precipitation. Acetate of ammonia precipitates ^^^i^^^^f/f^^.h from a boiUng solution acidified with acetic acid, but not it ^^^^ ?fThe acetate'is added. Terrocyanide P°;-Xre ™ce oflron bluish precipitate, the colour of which is probably due to the Fesence o± iron it is less soluble in hydrochloric acid than in water. This is a delicate reaction Gallium compounds exhibit a spectrum having two violet lines betw eS G and H. which%an, however only be ^l^-ly/.^^.f ^^^^^^^^ spark is employed. On heating a galhum compound m the Bunsen tiame, only one of these lines is visible, and that but indistinctly. e. Oxides of Vanadium. Yanadium occurs in the form of vanadates, and occasionally in srnall qnantities in iron and copper ores, and m the slags obtamed ±rom ttem There are four oxides of vanadium, the protoxide, YO^ tVO], the sesqui oxide YO,[VA], the dioxide, YO4 [VO,], and yanadic acid, YO5 [V,OJ. The Protoxide is gray, possesses metallic lustre, is insoluble m water but soluble in dilute adds, with evolution of hydrogen, formmg blue solutions which bleach organic colouring matters.by reducing them. The sesquioxide is black, insoluble, not reduced by ignition in hydrogen; when exposed to the air, it is gradually converted into the dioxide: acid solutions containing the sesquioxfde are g^een. The dioxide is dark blue, acid solutions in which it is present are pure blue. All the lower o)ade_s pass into vanadic acid when heated with nitric acid or aqua regia,or by fusion with nitrate of potassa or on igniting them in oxygen or air. Yanadic acid is non-volatile and fusible sohdifying to a crystalline mass, dark red to orange-red in colour. When heated to redness in a current of hydrogen, it is converted into the sesqui- oxide. Yanadic acid is sparingly soluble in water, but reddens litmus- paper strongly. It combines with acids and with bases. a Acid solutions.—The stronger acids dissolve vanadic acid to red or yellow solutions, which gradually become green on exposure to the air (by the reducing action of dust). The sulphuric acid solution when much diluted, treated with zinc and warmed gently, first passes through green to blue (reduction to dioxide), then through greenish blue to green (reduction to sesquioxide), and finally from violet to lavender (reduction to protoxide); on adding ammonia to this solution, a brown precipitate of the hydrate ot the protoxide forms, which readily absorbs oxygen. Sulphurous acid, sul- phuretted hydrogen (with separation of sulphur), boiling hydrochloric acid oxalic acid, &c., also reduce the solutions, but only to the dioxide; hence the colour produced is only blue. Alkalies produce a brown pre-](https://iiif.wellcomecollection.org/image/b21966953_0161.jp2/full/800%2C/0/default.jpg)
