TUN

TUN

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manganefe, but nothing elfe. The refidueconfifted of undecompofed wolfram, mixedwith a yellow powder, which lull was entirelytaken up by liquid ammonia. On the otherhand, when ftrong and very pure muriatic acidwas employed, the liquor acquired a brownifhgreen colour, no oxy-mumtic acid gas wasgiven out, and the iblution, befides iron andmanganefe, contained oxyd of tungften, whichwas„ thrown down by the addition of diftilledwater, in the form of a pale yellowifh greenpowder; this powder was not refoluble in mu-riatic acid ; it became white on the addition ofammonia, but was very fparingly foluble. Itsgreenifh tinge was changed to bright yellow bynitric acid, nitrous gas being dilengaged. Thedecompofed refidue of the ore not taken up bymuriatic acid, was of a dirty green colour, buton the addition of ammonia became of a deepblue, which blue powder was infoluble in am-monia. We cannot therefore but conclude thatthe acid employed by Vauqueiin was mixedwith nitric acid; and that the tungften exiftsin wolfram in the ftate of blue fub-oxyd.

§. 3. ReduBion of ores.

Metallic tungften not being applied to anyufe, the only attempts to reduce it have beenmade on fmail quantities in the laboratory.The Elhuyars were the firft who obtained it inthe reguline ftate.® For this purpofe they put100 grains of the yellow oxyd into a cruciblelined with charcoal, and gave it a ftrong heatfor an hour and a half. The crucible was brokenwhen cold, and was found to contain a friablecongeries of metallic globules, of the colourand luftre of fteel, and weighing 60 grs. Vau-queiin f afterwards repeated the experiment, byfirft mixing the yellow oxyd with oil, and thenexpofmg it in a lined crucible for two hours tothe violent heat of a forge furnace : he obtaineda darkifh grey mafs, coniifting of a number offmail globules. In another experiment, wherethe oxyd and oil was mixed with boracic acid,he obtained a porous mafs of a greyilh whitecolour, with the cavities lined with minute,brilliant, metallic cryftals. A third method hasbeen pra£tifed with fuccefs by the writer of thisarticle, affifted by Mr. Allen. 240 grs. oftunftat of ammonia, in acicular cryftals, wereput into a crucible lined with charcoal, and ex-pofed for "two hours to a powerful wind furnace;there was thus produced a Uightiy coheringmafs, weighing 161 grs. of roundilh grains,

• Chemical analytic of Wolfram, &c, p.58.

about the fize of a pin’s head, with a very bril-liant metallic luftre.

§■ 4v Phfcal and Chemical properties.

The colour of tungften is a light fteel-grey,with a brilliant metallic luftre : it is in the formof minute grains, flight]y agglutinated; it isvery hard, yielding with difficulty to the file.Its fp. gr. according to the Elhuyars, is = 17.6,according to an experiment of my own is= 17.33. It does not at all affetft the magneticneedle : when expofed to a ftream of oxygengas on charcoal it burns with a yellow flamewithout melting, and is entirely volatilized inthe form of a thick vapour, which when col-le£ted is the yellow oxyd of this metal.

Neither the muriatic norfulphuric acids haveany perceptible a£tion on this metal, even at aboiling heat; but when mixed with a littlenitric acid, a difengagement of nitrous gasenfues, and the metal is partly difl'olved, andpartly diffufed through the liquor in the ftate ofyellow oxyd. This folution undergoes nochange on dilution with water ; by the additionof a few drops of pruffiat of potafli, its colourbecomes a deep fomewbat iridefeent green, butno precipitation takes place ; by cauftic potafhit is changed to a brown olive, and the greencolour is again reftored by the addition of a fewdrops of nitric acid.

By a red heat, with accefs of air, tungften isreadily converted into a lemon yellow oxyd.100 parts of the metal afford, according to theElhuyars, 124 of oxyd.

The above are all the faffs hitherto publifhedconcerning metallic tungften, thofe. which fol-low being the refults of experiments made onthe oxyd of this metal, as extracted from itsores, without having been fubfequently reducedto the reguline ftate.

There are two oxyds of tungften, the yellowor per-oxyd, and the blue or fub-oxyd. Theformer may be prepared in various ways ; firft:,as already mentioned, by calcination of themetal; fecondly, by fufing two parts of wol-fram with three of nitre, and digefting thefalirte mafs thus produced in hot water; theliquor contains the oxyd of tungften combinedwith potafh, and holding in folution a littleoxyd of manganefe : by expofure to the air fora day or two, the latter oxyd is precipitated ;the clear liquor being then evaporated to drynefsis to be digefted with three or four fucceffiveportions of nitric acid, by which the alkali will

1 Journ. ties Mines, No 19, p. *4,