Per se, it fuses when held in the forceps, and presents, on refrigeration, its yellow tinge.

Vanadium, per se, on the platinum wire, in the oxidating flame, is converted into vanadic acid, which, with borax, gives, while hot, a dark yellow, and on cooling, a pale yellow glass. In the reducing flame, the glass is greenish or brownish, while hot, but, on cooling, chrome-green,-it is not colored blue by the addition of tin.

Vanadic acid, with microcosmic salt, dissolves readily, producing a reddish-yellow glass, which is, on cooling, pale yellow. It acquires a fine transparent green hue in the reducing flame, but the dark yellow color is recalled in the oxidation.

With soda it easily dissolves, and is absorbed by the charcoal. On platinum foil, it fuses to a deep yellowish-red fluid, which becomes crystalline on refrigeration.

Vanadic acid is distinguished from oxide of chromium by producing a yellow glass on platinum wire in the oxidating flame, which is never the case with the latter.

The following is SEFTSTROM's method for obtaining the vanadic acid from slags or the minerals:-Fuse with an equal part of saltpetre, and two parts carbonate of soda,-when the temperature is very high, vanadiate of soda is formed,-affuse the resulting mass with boiling water, and neutralize the liquid with nitric acid, then add chloride of barium, or acetate of lead, by which a precipitate of vanadiate of baryta, or lead, is obtained; treat with sulphuric acid, and then separate the red liquid from the sulphate, digest it with alcohol, whereby, under formation of ether, the vanadic acid is resolved into the binoxide of vanadium, and the solution is blue; evaporate to dryness, and then heat the residue to strong redness to expel the sulphuric acid-impure vanadic acid remains; smelt it with nitrate of potassa until a portion of the cold sample loses its reddish appearance. Dissolve, filter, and immerse in the liquid a large piece of chloride of ammonium ; a white precipitate of vanadiate of ammonia will appear, which is insoluble in a saturated solution of the precipitant; filter and edulcorate, first with a solution of chloride of ammonium, and then with spirits of wine, of specific gravity 0-860; dissolve in boiling water, containing a few

drops of free ammonia, and, upon cooling, pure vanadiate of ammonia is obtained, the salt from which all the other compounds of vanadium are formed.

From the solution of the vanadiate of lead in nitric acid, the lead and arsenic can be separated by sulphide of hydrogen; the resulting blue solution of binoxide of vanadium, on evaporation to dryness, yields vanadic acid, with which pure vanadiate of ammonia may be formed, by following the foregoing method.

§ 21. TANTALUM-Ta-NIOBIUM—NÚ—PELOPIUM-Pp— Presence in the Mineral Kingdom.

These three metals are only found as acids in combination with bases in the following minerals :—

Tantalite, Columbite, Pyrochlore, Yttro-Tantalite, Fergusonite, Samarskite, Aeschynite, Euxenite, Polykras, Wöhlerite, Eukolite, and in many Tin-Stones.

Examination for Tantalum, Niobium, and Pelopium.

Tantalic, Niobic, and Pelopic acids, when they constitute the chief ingredients of minerals, and when sufficient quantities of such are dissolved in borax, may frequently be recognised by giving an opaque or enamel-like glass by exposure to an irregular flame, particularly after treatment in the reducing.

Since Rose has discovered niobium and pelopium in the Columbite of Bodenmais, the acids of which have several properties in common with tantalic acid, it is necessary, in the examination of those minerals which contain these acids, to seek a method for their complete separation. The surest way to effect this object with their very complex combinations, is to fuse a considerable quantity of the mineral, as finely pulverized as possible, with bisulphate of potassa, and the fused mass, after having been powdered, is dissolved in water. If the mineral contains tantalic acid, or niobic and pelopic acids, and also, perhaps, tungstic acid, these are separated by treatment with water, while any titanic acid present, as well as the bases, is dissolved.

The residue can either be fused with carbonate of potassa, or, when it is free from titanic acid and zirconia, treated at once with sulphide of ammonium, to separate the tungstic acid and oxide of tin. After filtration and a thorough edulcoration, what remains is immediately treated on the filter with dilute hydrochloric acid to get rid of traces of iron, and now the operator ascertains whether he has to deal with tantalic, or niobic and pelopic acids.

For this purpose there are two ways: the first is, to examine the residuum, well washed, with microcosmic salt on platinum wire, as well as with cobalt solution on charcoal, to ascertain whether the microcosmic salt is tinged in the reducing flame, and what color the acid in question assumes by this treatment. The acid which, for example, separates from the Columbite from Bodenmais, or from the Pyrochlore from Miask, and which consists of niobic and pelopic acids, affords in the reducing flame a brown bead passing into violet, by which it is easily distinguished from tantalic acid, which occasions almost no coloration.

The second way depends upon some investigations made by ROSE. As, according to this chemist, tantalic acid is precipitated of a light yellow, pelopic acid of an orange-yellow, and niobic acid of a dark orange-red color from the solution of tantalate, niobate, and pelopiate of potassa in water, when it is acidulated with hydrochloric acid and then mixed with tincture of galls, the examination may be conducted in the following manner :-The residual acid in question is mixed carefully with five times its volume of carbonate of potassa in an agate mortar, and the mixture is converted, with a few drops of water, into a pasty mass, which is fused in small portions in the loop of a strong platinum wire to a clear bead, and every time the loop is full, the still hot bead is cast into a small porcelain dish. The fused beads are pulverized, the powder first treated in a porcelain dish with a little cold water, to dissolve the carbonate of potassa added in excess, and also niobate of potassa, if present, which appears to be more easily soluble in cold water than tantalate and pelopiate of potassa, and after the whole has been well stirred with a glass rod, the insoluble salts are allowed to deposit. If the supernatant

liquor appears clear, it is removed by means of a small pipette into another porcelain dish, and the salt remaining dissolved in boiling water. Both solutions are then acidified with hydrochloric acid, and the observation is made whether a strong turbidity or only an opalescence thereby ensues, as in the former case niobic and pelopic acids, and in the latter tantalic acid are to be suspected. A few drops of tincture of galls are then added to each, and while stirring, the color of the precipitate must be minutely noticed. Niobic acid, from the Bavarian Columbite, which contains pelopic acid, fused in the manner prescribed, with carbonate of potassa, and the resulting mass pulverized and treated with cold water, gives a solution in which, after it has been cleared and separated from the residue, hydrochloric acid produces a strong turbidity, and the tincture of galls, subsequently added, a dark orange-red precipitate. When the residual salt is dissolved in boiling water, and acidified with hydrochloric acid, a turbidity results, but tincture of galls produces only an orange-red precipitate indicative of pelopic acid.

When compounds have to be examined, which are free from tungstic, molybdic and silicic acids, for tantalic, niobic, and pelopic acids, the substance to be tested, already in a powdered condition, can be fused at once with carbonate of potassa in small portions in the loop of a platinum wire. The presence of titanic acid does not interfere, because the titanate of potassa formed, only slightly passes into solution by the after treatment of the fused mass with water. Four parts of carbonate of potassa are mixed with the substance to be tested, and when the basic constituents are in a low degree of oxidation, one part of nitrate of potassa is added. After pulverization, the fused mass is first treated with cold, and then with boiling water as already described, and after the solutions have cleared, they are drawn off with a small siphon or pipette from the residue of basic constituents, which is, at last, mixed with insoluble titanate of potassa if titanic acid were present. Each solution is now acidified with hydrochloric acid by itself in a porcelain dish, and a few drops of tincture of galls added. As before stated, a light yellow precipitate indicates tantalic acid, an orange-yellow pelopic acid, and a

dark orange-red niobic acid. When manganese is present, the fusion with carbonate of potassa converts it into manganate of potassa, which dissolves in cold water with a green color; but as this salt, by the addition of hydrochloric acid is first converted into permanganate of potassa, and subsequently into chloride of manganesium, with which tincture of galls produces no precipitate, it is not prejudicial to the operation.

If a compound of tantalic, niobic, and pelopic acids contains silicious matter, the examination for these acids will answer without any alteration for minerals, which can be decomposed by hydrochloric acid, as Wöhlerite and Eukolite: but if not decomposible by that acid, it must be fused with soda and borax, the mass heated to dryness with hydrochloric acid, and afterwards treated with water. The acids remaining undissolved, are then washed on a filter with acidulated water, and after being dried and fused with five times their volume of carbonate of potassa in small portions on a platinum wire, the fused beads are pulverized and treated as above directed. The presence of silicic acid does not throughout prevent the reaction on the acids under consideration.

Both pelopic and niobic acids were formerly prepared by means of water from their chlorides, as other methods were not so advantageous.

But the separation of both was incomplete, and even when it was repeated in such a way that the chlorides obtained were decomposed into their corresponding acids by means of water, and these again converted into chlorides by treatment with charcoal and chlorine, the acids could not be obtained even moderately pure, and though the operation was repeated twenty or thirty times, the result was still unsuccessful.

After several laborious but vain researches, ROSE succeeded in converting, under very peculiar conditions, a small quantity of niobic acid, which had been separated from pure niobate of soda, into a chloride. It was mixed with an extremely large quantity of charcoal, exposed to a strong current of chlorine, and subjected from the beginning to a very gentle temperature. This experiment led to the most surprising results. The pure niobic acid