VALO′NIA. The cup of a large species of acorn, imported from the Levant. Used in tanning leather.
VANAD′IC ACID. V2O2. Syn. Vanadic anhydride, Teroxide of v.; Acidum vanadicum, L. Prep. (Johnston.) From the native vanadate of lead, by dissolving it in nitric acid, passing sulphuretted hydrogen through the solution, to throw down lead and arsenic, filtering, and evaporating the resulting blue liquid to dryness; the residuum is then dissolved in a solution of ammonia, and a piece of sal ammoniac, considerably larger than can be dissolved, introduced; as the latter dissolves, a pulverulent precipitate of vanadate of ammonium is formed, which must be washed, first in a solution of sal ammoniac, and then in alcohol of ·860; by exposing this salt, in an open platinum crucible, to a heat a little below redness, and keeping it constantly
stirred, until it acquires a dark red colour, pure vanadic acid is obtained.
Prep., &c. Vanadic acid is orange coloured, scarcely soluble in water, and forms, with the alkaline bases, soluble salts called vanadates; and with the other bases sparingly soluble salts. All of these have an orange or yellow colour. “Vanadate of ammonia mixed with solution of galls forms a black fluid, which is the best writing ink hitherto known. The quantity of salt required for this purpose is very small; the writing is perfectly black, and not obliterated by alkalies, acids, chlorine, or other reagents,” (Ure.)
VANA′DIUM. V. A rare metal discovered by Sefstom, in 1830. in some Swedish iron extracted from an iron mine near Jönköping. It has since been found in a Vanadinite lead ore met with in Scotland, Zimpanan in Mexico, and Chili, and in the iron slag of Staffordshire. Of late years a more abundant source of Vanadium has been discovered by Professor Roscoe in the cupriferous stratum of the New Red Sandstone at Alderley Edge in Cheshire. There are four, and possibly five oxides of this element.
Vanadic oxychloride. Syn. Vanadic oxytrichloride. (VOCl3.) Roscoe states there are several oxychlorides of vanadium, which, however, have not been studied. The most interesting of them is the oxytrichloride, which corresponds to the phosphorous oxychloride. This oxytrichloride is a yellow fuming liquid, which is instantly decomposed by water into vanadic and hydrochloric acids. The oxytrichloride may be obtained by heating vanadic anhydride and charcoal (mixed together) in a current of hydrogen, after which it is heated in a current of dry chlorine. An easier method is by passing dry chlorine over the sesquioxide of vanadium.
Vanadic pentoxide. Syn. Vanadic Anhydride (V2O5.). At a red hot heat this oxide fuses, and on cooling, crystallises in rhombic prisms. It is but little soluble in water; the aqueous solution, which is of a yellow tint, is strongly acid, and produces a marked reddening effect on litmus. Vanadic anhydride forms both normal and acid salts. The ammonic vanadiate (Roscoe’s meta vanadiate) is the chief source of the acid. This salt may be obtained by adding pieces of sal ammoniac to a crude solution of potassic vanadiate, the resulting ammonic vanadiate being insoluble in a saturated solution of sal ammoniac, is deposited in small crystalline grains. The vanadic anhydride may be obtained from the ammonic vanadiate by heating an aqueous solution of the salt in the open air, when the ammonia is driven off, and the vanadic anhydride is left behind. The acid ammonic vanadiate, mixed with tincture of galls, makes a very durable writing ink, unacted upon either by alkalies or chlorine. Acids turn such blue without, however, destroying it.
Vanadic triox′ide. (V2O2.), is the Vanadyl of Roscoe, who obtained it in the form of a grey metallic-looking powder, by the transmission of a current of dry hydrogen charged with the vapours of oxychloride of Vanadium, through a tube containing ignited charcoal. It dissolves in dilute acids, with evolution of hydrogen. Solutions of its salts are lavender coloured. Berzelius regarded this oxide as a metal.
Tests. The vanadiates mostly occur of a red or yellow colour. When treated with sulphuretted hydrogen, they yield a solution of a fine blue colour, a reaction that distinguishes them from the chromates, which, under similar treatment, would give a green liquid. When mixed with borax and exposed to the reducing flame of the blowpipe, compounds containing vanadium give a green glass, which turns to yellow in the oxidizing flame. Professor Roscoe, to whose researches we are indebted for all the chemical knowledge we possess respecting vanadium, says:—“All the main facts now established in connection with the chemical department of this element proved it to bear a strong analogy to the elements phosphorus and arsenic; in fact, it occupied a previously vacant place in a well-defined group of triad, or, as some chemists prefer to consider them, pentad elements. There was a property of vanadium in virtue of which it might ultimately obtain considerable importance in the arts, though in the present infancy of the history of the metal it was difficult to foretell this with any certainty. This property was the power of forming a permanent black for dyeing purposes. The black produced by the action of vanadium had the advantage over copper and aniline blacks, viz. that it was permanent, whereas the latter were liable to turn green. This application of an element that was first introduced into notice as a chemical curiosity furnished one more example of the importance of original scientific investigation. However far a newly discovered substance might seem to be removed from purposes of practical utility, we never know at what moment it might be turned to account for the benefit of the human race.”
VANIL′LA. Syn. Vanille, Fr. The dried pods of various species of Vanilla, a genus of the natural order Orchidaceæ. It is chiefly used in the manufacture of chocolate and perfumery. As a medicine it is much employed on the Continent as an aromatic stimulant and neurotic.—Dose, 6 to 12 gr.; in asthenic fevers, hysteria, hypochondriasis, impotency, &c.