692 



TUNE TUNGSTEN. 



wood, interspersed with rich meadows, and enclos- 

 ing a large common, in which are walks, rides, hand- 

 some rows of trees, and various other objects. 

 Here are excellent accommodations for visitants, 

 also assembly rooms, a theatre, libraries, chapel, 

 market place, &c. The waters are chalybeate (see 

 Mineral Waters"), extremely clear and pellucid at 

 the fountain head, and the taste is strongly impreg- 

 nated with iron. They are of great use in remov- 

 ing complaints arising from sedentary habits, weak 

 digestion, and nervous and chronic disorders. The 

 discovery of their virtue is ascribed to Dudley, lord 

 North, a courtier in the reign of James I., \vlio was 

 restored to health by drinking them. A variety of 

 toys in wood of various kinds is manufactured here, 

 and known by the name of Tunbridge ware. The 

 high rocks, one mile and a half from the wells, are 

 much celebrated. In some parts they are sevcin_\- 

 five feet high, and form a very striking and romantic 

 picture. Population of market-town and parish of 

 Tunbridgein 1841. 12,53<. 



TUNE. See Tone and Melody. 



TUNGSTEN ; one of the metals, so named from 

 the Swedish word twig, heavy, in allusion to the 

 great specific gravity of the mineral in which it was 

 first detected as an ingredient. The ores of this 

 metal are three, viz. wolfram, tungsten, and yellow 

 oxide of tungsten. 1. Wolfram occurs in short, 

 highly modified prisms, whose primary form is a 

 right oblique-angled prism, the larger angle of the 

 lateral planes being 117 22'. The secondary forms 

 are produced through the replacement of the lateral 

 edges and of the longer terminal edges. Cleavage 

 parallel to the primary form, perfect ; surface of 

 the crystals streaked parallel to the axis ; lustre 

 metallic adamantine, or imperfect metallic ; colour 

 dark grayish, or brownish-black ; streak dark red- 

 dish-brown ; opaque ; not very brittle ; hardness 

 between apatite and feldspar; specific gravity 7'15. 

 Besides occurring in single crystals, it occasionally 

 presents itself under the form of twin-crystals, anc 

 massive. The massive varieties are irregularly la- 

 mellar, sometimes columnar. It is also found in 

 pseudomorphs, in the shape of tungsten. It con- 

 sists of 



Tungstic acid, 

 Protoxide manganese 

 Protoxide iron, . 

 Silex, . 



78-77 

 6-22 



18-32 

 1-25 



It decrepitates before the blow-pipe, but may be 

 melted, in a sufficiently elevated temperature, into a 

 globule, having its surface covered with crystal 

 possessing a metallic lustre. It is easily soluble in 

 borax. Wolfram occurs very frequently along with 

 tin ore, in veins and in beds. It is met with also 

 in veins along with galena. Its localities are the 

 Saxon and Bohemian tin mines, as at Schlackenwald 

 Zinnwald, Ehrenfriedersdorf and Geyer ; also man) 

 places in Cornwall. It is also found in France an 

 Siberia. 2. Tungsten is found in crystals of an 

 octahedral figure, and depending upon a primar 

 form, which is an acute octahedron, the uppe 

 pyramid inclining to the lower one under an angl 

 of 128 40', parallel with whose faces it cleaves 

 and also with the faces of an octahedron less acute 

 The surfaces of the crystals are commonly drusy 

 lustre vitreous, inclining to adamantine ; colon 

 generally white, often indinirig to and passing hit 

 yellowish-gray, yellowish and reddish-brown ; strea 

 white ; semitransparent to translucent ; brittle 

 hardness a little above that of fluor; specific gravit 

 6-07. Besides the crystals, tungsten is found mas- 



ve. It consists of lime 19-40 and tungstic acid 

 JO-42. Alone upon charcoal, it is infusible before 

 ic blow-pipe, except that the thinnest edges are 

 inverted, in a very strong heat, into a semitrans- 

 arent vitrified mass. It gives a white glas-s with 

 orax. It is found in similar repositories with wul- 

 am. The principal localities of tungsten are 

 chlackenwald and Zinnwald in Bohemia, Kluvn- 

 iedersdorf in Saxony, and Cornwall, England. 

 plendid specimens have lately been found at ' 

 uck in Cumberland. 3. Yellow oxide of tun^ 



found in the state of an orange-yellow powder 

 nvesting tungsten, from v.hose decomposition it 

 ppears to result. It is readily soluble in warm 

 quid ammonia, and is precipitated white by acids ; 

 lie precipitate, by standing, reacquiring the yellow 

 olour. It has only been met with at Munroe, 

 onnecticut. The easiest method of obtaining 

 ungsten in the metallic state is the following : Fuse 

 ogether a mixture of wolfram and carbonate of 

 otash in a crucible. Then digest the fused i 

 [i water, which will dissolve the tungstate of potash 

 ormed. To this solution add a quantity of solu- 

 ion of sal-ammoniac in water, and evaporate the 

 >vhole to dryness. Put the dry saline residue into 

 a Hessian crucible, and heat till the sal-ammoniac 

 s entirely dissipated. The residual matter being 

 low dissolved in hot water, a heavy black powder 

 eparates, which is oxide of tungsten. Let it be 

 wiled in a weak solution of potash, and, finally, in 

 >ure water. When this powder is heated in an 

 open crucible, it takes fire, and is converted into 

 ;ungstic acid. The affinity of tungsten for oxygen 

 not being very strong, it is easily reduced to the 

 metallic state by passing a current of dry hydrogen 

 gas over tungstic acid, heated to redness in a glass 

 ;ube. Thus purified, tungsten (Scheelium of the 

 Germans) is of a grayish- white colour, or rather the 

 ;olour of steel, and is possessed of considerable 

 brilliancy. It is one of the hardest of the metals, 

 t being almost impossible to make an impression 

 upon it by the file. It seems also to be brittle. 

 Its specific gravity is 17*6. It is therefore the 

 heaviest of the metals after gold, platinum and iri- 

 dium. It requires for fusion a very high tempera- 

 ture. It is not attracted by the magnet. When 

 heated in an open vessel, it gradually absorbs oxy- 

 gen, and is converted into an oxide. Tungsten 

 seems capable of combining with oxygen in two dif- 

 ferent proportions, and of forming the brown or 

 black oxide, and the yellow, or tungstic acid. The 

 first of these is obtained by putting a quantity of 

 tungstic acid in a glass tube, heating it to a very 

 low red heat, and passing through it, while in that 

 state, a current of hydrogen gas. Water is formed, 

 and the acid is deprived of a portion of its oxygen. 

 The oxide has a flea-brown colour, and, when heated 

 in the open air, takes fire, and burns like tinder, 

 and is converted into tungstic acid. This oxide 

 has the power of uniting with soda, and would ap- 

 pear to play the part of an acid. The tungstic acid, 

 obtained as described above, has a pale lemon-yel- 

 low colour. When strongly heated, it becomes 

 green, as it does also when exposed to the rays of 

 the sun. Its specific gravity is 5-6. It is tasteless, 

 insoluble in water, but is very soluble in the caustic 

 alkalies. It has the property of combining with 

 other acids. When precipitated from tungstate of 

 ammonia by an acid, the precipitate is always a 

 compound of tungstic acid and of the acid employed 

 to throw it down. Tungsten forms three compounds 

 with chlorine, all of which are chlorides. It com- 



