Trioxide of Tungsten. (WO3.) Syn. Tungstic anhydride. This may be obtained by decomposing wolfram with aqua regia, and evaporating to dryness. The resulting tungstic acid is dissolved in ammonia, and the ammonic tungstate purified by crystallisation. When this ammonic tungstate is heated in the air, it loses ammonia and water, pure tungstic trioxide being left behind.
Tungstic Acid. (H2WO4.) This compound may be procured by adding an excess of hydrochloric acid to a boiling solution of the trioxide in any of the alkalies. It occurs as a yellow powder.
Tungstic Chloride. (WCl6.) This may be obtained by heating tungsten in chlorine, when it sublimes in bronze-coloured needles, which are decomposed by water. When gently heated in hydrogen, this chloride becomes converted into tetrachloride (WCl4).
Bisulphide of Tungsten. (WS2.) By heating a mixture of bitungstate of potash with sulphur, and washing the product with hot water, a black crystalline substance, having the above composition, may be obtained, resembling plumbago in appearance.
Of the salts of tungsten, tungstate of baryta has been used as a substitute for white lead in painting; but the most important of these is the tungstate of soda, described below. See also Tungstic glue.
TUNGSTATE OF SODIUM. Na2WO4. This salt is used for rendering linen, cotton, and other fabrics uninflammable; also as a substitute for stannate of sodium as a mordant in dyeing. It may be prepared by adding 9 parts of finely-powdered tungsten to 8 parts of fused carbonate of sodium, and continuing the heat for some time; on boiling the cooled and pulverised mass with water, evaporating the filtrate to dryness, and treating the residue with luke-warm water, the salt dissolves out. Muslin steeped in a 20% solution of this salt is perfectly uninflammable when dry, and the saline film left upon its surface is so smooth that the muslin may be ironed without difficulty.
TUNGSTIC GLUE. Tungstic glue has been suggested as a substitute for hard india rubber, as it can be used for all the purposes to which this latter is applied. It is thus prepared:—Mix together a thick solution of glue with tungstate of soda and hydrochloric acid. A compound of tungstic acid and glue is precipitated, which, at a temperature of 86° to 104° F., is sufficiently elastic to be drawn out into very thin sheets.
TUNNY FISH, a la Parisienne. As a rule tunny fish is very indigestible, and may be described as “neither fish, flesh, fowl, nor good red herring;” nevertheless, some of our readers may come across this fish, and will be
glad to hear of a way in which to make it palatable and digestible. Take three or four pounds of fresh tunny fish, lard it with bacon as you would veal; cook it gently in its own gravy for three hours, with salt, pepper, sweet herbs, little onions, and a small quantity of water. When well cooked, tunny fish makes a nice dish cold for breakfast.
TUR′BOT. The Rhombus maximus (Cuvier), said to be the best, and excepting the halibut, the largest of our flat fishes. Dutch turbots are the most esteemed.