Page:Encyclopædia Britannica, Ninth Edition, v. 24.djvu/68

54 Lake Van, which is too brackish to be drinkable for man or beast, is inhabited by a species of blay or bleak, which abound especially about the mouths of the influents, and come to the surface when the spring floods spread over the heavier saline layers. This lake is a completely laud-locked basin, or at least has no visible outlet. But the natives speak of underground channels through which it communicates south-westwards with the head-waters of the Tigris, attributing to the occasional obstruction of these channels the great oscillations of level that have undoubtedly occurred in past and recent times. In the 17th century and again about 1840 the water rose from 10 to 12 feet, and is even now (1888) rising. Lake Erchek perhaps marks its extreme eastern limit in former times. Lake Van is also indirectly connected with the Euphrates through the little Lake of Nazik, which lies west of the Sipan-Dagh, on the water-parting between the lacustrian and fluvial basins, and which by a rare phenomenon sends emissaries to both. The narrow part of Lake Van, which runs for nearly 40 miles towards the north-east, and gives the lake somewhat the appearance of a frying-pan, is very shallow, and was once, according to tradition, a fertile plain. The lake is not regularly navigated. Scattered along the south-east shore are a few picturesque islets, one of which, Aktamar, is the seat of an Armenian patriarch.

VANADIUM, a rare element discovered in 1830 by Sefström, when analysing a kind of iron obtained from the ores of Taberg in Sweden. Berzelius, in the course of an extensive investigation on vanadium, came to the conclusion that it is analogous to chromium, forming like it an acid trioxide, VanO3, in which “Van” signifies 134.4 parts of a radical analogous to the Cr = 52 parts of chromium in chromic acid, CrO3. He succeeded in isolating this radical, and, as it exhibited semi-metallic properties, he had no doubt that it was the element vanadium itself. His results were universally adopted as correct until Roscoe (in 1867) found that Berzelius’s vanadium is an oxide containing O2 = 32 parts of oxygen per Van, whence it followed that the presumed trioxide, VanO3, is really a pentoxide, V2O5, where V2 = 2 x 51.2 = 2 atoms of the real element. Our present knowledge of vanadium is based chiefly upon his investigations. Of vanadium minerals, which are all very rare, we name two only,—mottramite, (Pb,Cu)3(VO4)2 + 2(Pb,Cu)(OH)2, and vanadinite, 3Pb3(VO4)2 + PbCl2. This last is amorphous with apatite, which previous to Roscoe’s discovery was difficult to explain. See, vol. v. p. 539.

Traces of vanadium are found in certain iron ores and in many other minerals. Roscoe utilized a kind of sandstone from Alderley Edge and Mottram in Cheshire which contains a small admixture of mottramite. Another suitable material is the “Bohnerz” of Steinlade and Haverloh, essentially a hydrated ferric oxide. For the extraction of vanadium from this latter mineral Wöhler recommends the following method. The finely powdered mineral is mixed with one-third of its weight of nitre and the mixture kept at a dull red heat for an hour. The ignited mass is powdered and lixiviated with water, which extracts the potash salts of the oxides V2O5, CrO3, MoO3, As2O5, P2O5, and SiO2. The filtered solution is almost neutralized with nitric acid, but not completely, or else some of the V2O5 would be reduced by the nitrous acid to lower oxides; and the vanadic and most of the other acids named are precipitated as baryta salts by addition of chloride of barium. From the washed precipitate the acids are liberated by boiling dilute sulphuric acid, and the sulphate of baryta is filtered off. The solution is neutralized with ammonia, concentrated by evaporation, and, after cooling, kept in contact with a solid piece of sal-ammoniac more than sufficient to saturate the solution with this salt. Meta-vanadate of ammonia, V2O5(NH4)2O, being characteristically insoluble in sal-ammoniac solution, separates out as a yellowish crystalline precipitate. This is collected, washed with sal-ammoniac solution and after that with alcohol, and purified by re-crystallization or otherwise. The pure salt when heated to dull redness leaves the pentoxide, V2O5 (vanadic acid), as a red liquid, which freezes into a red-brown crystalline mass of sp. gr. 3.35 (J. J. Watts). It dissolves in about 1000 parts of water, forming a yellow solution which reddens litmus. The pentoxide, though capable of uniting with strong acids, e.g., with sulphuric into a salt, V2O2(SO4)3, behaves on the whole as an acid oxide analogous in its combining habits to phosphoric (see, vol. xviii. p. 818, and , vol. v. p. 540). Solutions of vanadates are easily recognized: on addition of mineral acid they assume the yellow colour characteristic of the pentoxide, and if the mixture is then kept in contact with zinc it passes through all shades of (intense) green till it ultimately assumes a lavender colour. The solution then contains a chloride corresponding to the oxide V2O2 (Berzelius’s metal). It absorbs atmospheric oxygen with an extraordinary degree of avidity, assuming, in the absence of free acid, a dark brown colour. An acidified vanadate solution, if shaken with peroxide of hydrogen and ether, furnishes a dark red reduction product, which passes into the ethereal layer. One part of vanadic acid in 40,000 parts of water can thus be rendered distinctly visible (Werther). If a mixture of the pentoxide and charcoal is heated in dry chlorine, it is converted into an oxychloride, VOCl3 (trichloride of Berzelius), which distils over and may be purified by re-distillation over sodium. It is a canary-yellow mobile liquid, freezing below -15° C. and boiling at 126°.7 C., and its sp. gr. at 14° C. is 1.841. Water decomposes it with formation of hydrochloric acid and pentoxide V2O5. If the vapour of this chloride is passed over red-hot charcoal in a current of chlorine, the tetrachloride VCl4 is produced as a dark brown liquid, boiling at about 154° C. A mixture of the vapour of this chloride with hydrogen, when passed through a dull-red-hot tube, yields (more or less of “sesqui-” chloride, V2Cl6, and) the dichloride VCl2, which, if pure, forms apple-green, mica-like, hexagonal plates. From this dichloride Roscoe for the first time prepared the true metal by heating it to redness in hydrogen gas, a simple enough method in theory, but in practice one of the most difficult of operations, because the dichloride is very difficult to prepare and highly hygroscopic, and because the metal is extremely prone to take up oxygen. Even the purest product which Roscoe succeeded in obtaining contained an appreciable admixture of oxide. Vanadium is a light grey powder, which under the microscope appears crystalline and exhibits a silvery lustre, sp. gr.=5.5. Of its chemical properties the most remarkable is that it combines directly with nitrogen gas, N2, into a bronze-coloured nitride, VN. Rare and expensive as vanadium is, it has found a practical application in the production of aniline black. The black is produced from aniline by the action of chloric acid, aided by the presence of some oxygen carrier. Sulphide of copper is usually employed; but, as Lightfoot found, a mere trace of vanadic acid (or vanadate of ammonia) acts more energetically than any other available agent. According to Witz, 1 part of vanadic acid suffices for 67,000 parts of aniline salt.

 VANBRUGH, SIR JOHN (1666–1726), dramatist and architect, was the son of a wealthy sugar-baker in Cheshire and grandson of a Protestant refugee of Ghent. From a passage in one of his letters to Tonson it might be supposed that he was born in the Bastille, though in what year is uncertain, probably in 1666. He was educated in France, but what he learnt there, whether architecture or merely that art of good-fellowship which he found to be the true Aladdin’s lamp of social life, is a question that will be variously answered by those who, like Sir Joshua Reynolds, admire Blenheim and Castle Howard, and those who, like the wits of Vanbrugh’s time, scoff at them. This, however, is certain, that after his return from the Continent to England what he did was, not to pursue architecture, but to work, with a gusto and a success that are humorous and exhilarating, the “Aladdin’s lamp” above mentioned. His first step towards becoming a power in society was, of course, to enter the army. Perhaps, however, had he begun life in any other way his advance would have been just as rapid. For, strong as are social conditions, character is stronger still, and Vanbrugh’s equipment wit, tempered by good humour, a genuine feeling of comradeship, an exceedingly fine presence (according to Noble’s description), and a winsome face (according to Kneller’s portrait)—would, under any circumstances, have been irresistible. One of the points of difference between the dialogue in Vanbrugh’s comedies and the dialogue in the comedies of Congreve is this: we feel that the characters in the Relapse and the Confederacy talk as Vanbrugh must have talked; we feel that the characters in the Old Bachelor and the Way of the World talk, not as Congreve talked, but as Congreve wrote. We feel that, while such dazzling sword-play as Congreve’s would in society have chilled, even as it illumined the air, talk so hearty, good-humoured, frank, and daring as that we get in Vanbrugh’s plays would have made the fortune of any man of fashion, made it as certainly at a Roman supper party in the time of Augustus as at a London drinking-bout in the days of

