Chlorides.— Tungsten forms four chlorides,—WC1 2 , WC1 4 , WC1 5 , WCl 6 . The highest, WCl 6 , is obtained by heating the pure powdery metal in a current of absolutely pure chlorine. In the presence of moisture or air oxy-chlorides are produced. It sublimes off as a dark red liquid, freezing into crystals. These fuse at 275° C. and re-solidify at 270°; the liquid boils at 346° ∙7. The sp. gr. of the vapour is in accordance with the formula at 350°; at higher temperatures it dissociates into WCl 5 and free Cl 2 (Roscoe). When the vapour of WC1 6 is passed over heated trioxide, the two bodies unite, WO 3 with 2WC1 6 into 3WOC1 4 , forming magnificent red needles, which fuse at 210°∙4 and boil at 227°∙5 C. (Wohler). Both compounds, WCl 6 and WOC1 4 , are decomposed by water, the oxy-chloride more readily, with formation of hydrochloric acid and trioxide. For other chlorides and oxy-chlorides, see the ordinary hand-books of chemistry.

Oxides, WO 2 and WO 3 , and Compounds of These with Each Other. —The trioxide, popularly known as tungstic acid, is the more important. Impure trioxide is producible by treating scheelite (WO 3 CaO) with hot hydrochloric acid. Wolframite is not so readily decomposed; but when fused with twice its weight of chloride of calcium it passes into lime salt, obtainable as an insoluble residue by lixiviation of the fuse with water. The oxide obtained forms a yellow powder insoluble in water and in hydrochloric acid. To purify it, it is washed, dissolved in aqueous ammonia, and the filtered solution evaporated, when an acid tungstate of ammonia separates out in scales of great purity. These, when heated in air, leave behind them a pseudo-morphose of pure yellow oxide. Trioxide of tungsten combines with basic oxides into tungstates; but the proportion in which it unites with a given base is subject to great variation: for instance, the quantity Na 2 0 of soda unites into so many definite tungstates with 1, 1½, 2, 2⅓, 2⅖, 2½, 4 times WO 3 and in each case more or less of water. To each of these soda salts corresponds theoretically a certain tungstic acid,—to the salt Na 2 OW 2 0 6 , for instance, the acid H 2 OW 2 O 6 or H 2 W 2 O 7 . But few of these hydrates actually exist, and they are not individual acids in the sense in which the three phosphoric acids are, except perhaps that remarkable substance known as metatungstic acid, H 2 W 4 O 13 + 7H 2 O. This acid forms crystals of the stated composition; it dissolves in water and the solution unites with bases into meta-tungstates. Most meta-tungstates are soluble in water; of the tungstates proper only the alkali salts are so soluble. The soda tungstate, 5Na 2 O.12WO 3 + x H 2 O, known as para-tungstate of soda, is made industrially by fusing wolframite with carbonate of soda and lixiviating the fuse with water. The insoluble oxides of iron and manganese are filtered off; the filtrate, while still hot, is nearly neutralized with hydrochloric acid and allowed to crystallize. It forms large crystals containing twenty-one, twenty-five, or twentyeight times H 2 O according to the temperature at which they are formed. The salt has been recommended as a mordant in dyeing and calico-printing, but has not taken root in these industries. Oppenheim and Versmann recommended it before 1862 as the best means for rendering textile fabrics uninflammable. If a solution of the para-tungstate is boiled with hydrated tungstic acid (as obtained by precipitating any ordinary alkaline tungstate solution with hydrochloric acid in the heat), or is simply mixed with excess of acetic acid, the meta-tungstate is formed; in the latter case it separates out as a heavy oil. Meta-tungstate of soda forms octahedral crystals of the composition Na 2 O. 4WO 3 + 10H 2 O. If concentrated warm solutions of this salt and the equivalent quantity of chloride of barium are mixed and allowed to cool after addition of a little hydrochloric acid, meta-tungstate of barium crystallizes out as BaO. 4WO 3 + 9H 2 O, in large quadratic pyramids which are very easily soluble in water. From this salt the free acid is easily produced by addition of the exact quantity of sulphuric acid required to precipitate the baryta, and from it any other metatungstate is easily produced. Meta-tungstic acid solution is a sensitive and characteristic precipitant for almost all alkaloids (strychnine, quinine, &c.). The alkaloid, whatever its name, goes down as a flocculent insoluble meta-tungstate. Tungstic acid combines with phosphoric acid and with silicic acids into highly complex phospho-tungstic acids and silico-tungstic acids. Of the formel· there is quite a series, each consisting of one P 2 O 5 united with respectively fourteen, sixteen, eighteen, twenty, twenty-two, twenty-four times WO 3 and six H 2 O of basic water. Of silico-tungstic acids three are known, namely, one 4H 2 O . SiO 2 .10WO 3 + 3Aq and two SiO 2 . 12WO 3 x H 2 O. All these complex acids (both kinds) are easily soluble in water. The phospho-acids are delicate precipitants for all alkaloids.

The binoxide, WO 2 , is obtained when the trioxide is reduced by hydrogen at a dull red heat. This oxide is very prone to pass into trioxide or tungstate. An interesting and beautiful class of compounds of WO 3 , WO 2 , and bases are known as tungsten bronzes. The first of these was discovered by Wohler. Normal tungstate of soda, Na 2 OWO3, is fused, and trioxide added to it as long as it dissolves. The product is then heated in hydrogen as long as water goes away, and the substance thus reduced is exhausted successively with water, hydrochloric acid, caustic potash ley, and again with water. A residue of the composition Na 2 O. W 2 O 6 +WO 2 remains in the shape of magnificent gold-like lustrous cubes, of specific gravity 6∙617, which conduct electricity like a metal. Only hydrofluoric acid dissolves this soda-tungsten bronze. There are a number of other tungsten bronzes, all distinguished by metallic lustre and magnificent purple, red, yellow, or blue colours.

Analysis.— Oxides of tungsten dissolve in fused microcosmic salt, Na 2 OP 2 O 5 ; the bead becomes blue in the reducing flame, in the presence of iron blood-red, and in the oxidizing flame colourless. When heated on charcoal with (not too much) carbonate of soda or cyanide of potassium in the reducing flame, they yield a grey heavy powder of metal, obtainable by elutriation. The process fails in the presence of too much alkali. Insoluble tungstates (e.g., the ordinary tungsten minerals) are disintegrable by fusion with alkaline carbonate; the fuse, when treated with water, yields a solution of alkaline tungstate. This solution, when mixed with excess of hydrochloric acid, gives a white precipitate of hydrated trioxide, which on boiling becomes yellow by partial dehydration. The yellow unignited precipitate is soluble in aqueous ammonia. If tungstate of alkali solutions are mixed with hydrochloric acid and then treated with metallic zinc, they become blue through the formation of a compound of WO 3 and WO 2 or rather the respective chloride; this reaction gains in definiteness through the presence of phosphoric acid.

The Tungus type is essentially Mongolie, being characterized by broad flat features, small nose, wide mouth, thin lips, small black and somewhat oblique eyes, black lank hair, dark olive or bronze complexion, low stature, averaging not more than five feet four inches; they are distinguished from other Mongolic peoples by the square shape of the skull and the slim, wiry, well-proportioned figure. This description applies more especially to the Tunguska tribes, who may be regarded as typical Tunguses, and who, unlike most other Mongols, betray no tendency to obesity. They are classed by the Russians, according to their various pursuits, as Reindeer, Horse, Cattle, Dog, Steppe, and Forest Tunguses. A few have become settled agriculturists; but the great bulk of the race are still essentially forest hunters, using the reindeer both as mounts and as pack animals. Nearly all lead nomad lives, in pursuit of fur-bearing animals, whose skins they supply to Russian and Yakut traders, in exchange for provisions, clothing, and other necessaries of life. The picturesque and even elegant national costume shows in its ornamentation and general style decided Japanese influence, due no doubt to long-continued intercourse with that nation at some period previous to the spread of the race from the Amur valley to Siberia. Many of the Tungus tribes have been baptized, and are, therefore, reckoned as “Greek Christians’’; but Russian orthodoxy has not penetrated far below the surface, and most of them are still at heart Shamanists and nature-worshippers, secretly keeping the teeth and claws of wild animals as idols or amulets, and observing Christian rites only under compulsion. But, whether Christians or pagans, all alike are distinguished above other Asiatics, perhaps above all other peoples, for their truly noble moral qualities. All observers describe them as "cheerful under the most depressing circumstances, persevering, open-hearted, trustworthy, modest yet self-reliant, a fearless race of hunters, boni amidst the gloom of their dense pine-forests, exposed from the cradle to every danger from wild beasts, cold, and hunger. Want and hardships of every kind they endure with surprising fortitude, and nothing can induce them to take service under the Russians or quit their solitary woodlands” (Keane’s Asia, p. 479). Their numbers are steadily decreasing owing to the ravages of small-pox, scarlet fever, and especially famine, their most dreaded enemy. Their domain is also being continually encroached upon by the aggressive Yakuts from the north and east, and from the south by the Slavs, now settled in compact bodies in the province of Irkutsk about the upper course of the Yenisei. It is remarkable that, while the Russians often show a tendency to become assimilated to the Yakuts, the most vigorous and expansive of all the Siberian peoples, the Tunguses everywhere yield before the advance of their more civilized neighbours or become absorbed in the surrounding Slav communities. In the Amur valley the same fate is overtaking the kindred tribes, who are disappearing before the great waves of Chinese migration from the south and Russian encroachments both from the east and west. In 1880 the Oroches were already reduced to about 260, and the Tazi to a little over 200. For the philological relations of the Tunguses, see vol. xviii. p. 779.

T UNICATA