TUNGSTEN 1039 



TtTXiA JVEETAZi is an alloy of silver; copper, aud ler.d; made at Tula in 



Russia. 



TUKTGSTBW or WOLFRAM. (Tungstens, Fr. ; Wolframiwn, Ger.) SywiAof 

 Ts or W ; arf. tf. 92. Its name is derived from the principal mineral from which it is 

 obtainable Tungsten (Swedish tung, 'heavy,' stcn, 'stone,') or Wolfram. This metal 

 was discovered by the Brothers Do Luyart, about 1784, shortly after the discovery of 

 tungstic acid by Scheele, from whom it has been sometimes called Scheelium. It is never 

 found in the native state, but is produced by a variety of processes. First, and most 

 easily, by mixing the dried and finely- powdered tungstate or bitungstate of soda with 

 finely-divided charcoal, such as lamp-black ; placing the mixture in a crucible lined with 

 charcoal, covering it with charcoal in powder, and then exposing the whole to a steady 

 red heat for two or three hours. On removal of the crucible and cooling it, a porous 

 mass is found, from which the soda is removed by solution in water, and the uncon- 

 sumcd carbon is separated by washing it off, the metal being left as a bright, glistening 

 blackish-grey metallic powder. It may also be obtained by treating tungstic acid in a 

 similar manner, or by exposing the acid at a bright red heat, in an iron or glass tube, 

 to a current of hydrogen gas. Tungsten is one of the heaviest metals known, its 

 specific gravity being 17 '22 to 17'6. It requires such a very high temperature for 

 fusion that it has never yet been obtained in mass, more commonly as a fine powder, 

 but sometimes in small grains. It is not magnetic. It is very hard and brittle. 

 Alone it lias not been rendered available for any useful purpose, but it has lately been 

 employed for the manufacture of certain alloys. Tungsten is comparatively a rare 

 substance, and is remarkable for the very limited extent to which in nature it is found 

 to have been mineralised by combination with other substances. In none of these 

 does it exist as a salifiable base, but as an acid, as in wolfram, Scheelite, yttrotantalite, 

 and the tungstate of lead. 



The most common ore of this metal is wolfram, known also to the Cornish miner 

 as ' cal' or ' callen.' It is most commonly found associated with tin ores, which contain 

 besides the black oxide of tin or cassiterite, the metallic minerals, arsenical iron, 

 copper, lead, and zinc sulplrdes : but its peculiarly characteristic associate is the 

 metal molybdenum, for the most part mineralised as a sulphide. This metal is 

 remarkable in connection with tungsten as producing isomeric compounds, and as 

 having both its equivalent and its specific gravity equal to about one-half that of 

 tungsten, they being, respectively, as follow: equivalents, W 92, Mo 49; sp. gr. 

 W 16-22, Mo 8-615. 



Amongst miners wolfram has the reputation of being an abundant mineral, but 

 it is comparatively rare, schorl, specular and other iron ores, and gossan being often 

 mistaken for it. From its association with tin ores, it has been until lately the 

 source of great loss to the miner, as it was found quite impossible to sepvrate it from 

 the ore in consequence of its specific gravity, 7'1 to 7'4, being so near to that of black 

 tin, 6-3 to 7'0. 



Pryce, in his ' Mineralogia Cornubiensis, 1778,' says : ' After the tin is separated from 

 all other impurities by repeated ablutions, there remains a quantity of this mineral 

 substance (gal), which being of equal gravity cannot be separated from the tin ore by 

 water, therefore it impoverishes the metal and reduces its value down to 8 or 9 parts 

 of metal for twenty of mineral, which without its brood, so called, might fetch twelve 

 for twenty.' This description of tin ores containing wolfram was still applicable until 

 a vory recent period, who a new process was invented by Mr. Robert Oxland, of 

 Plymouth, and by him successfully introduced at the Drake Walls Tin Mine, at Gunnis 

 Lake, on the banks of the Tamar, where it was continued in operation until the mine 

 was closed. At this mine, although the tin ore raised was of excellent quality, it was 

 left associated with so much wolfram that the ore fetched the lowest price of any 

 mine in Cornwall. By Oxland's process, it was brought up to the price of the 

 best black tin. The process is now employed at East Huel Rose, near Cam- 

 borne. 



At the time of the introduction of the process the greater portion of the ore was 

 sold for 42. per ton. The improvement effected by it was so great that the same sort 

 of ore fetched the price of the best black tin. 



The process consists in taking tin ores mixed with wolfram, dressed as completely 

 as possible by the old process, and having ascertained by analysis the quantity of 

 wolfram contained therein, then mixing therewith such a quantity of soda-ash of 

 known value as shall afford an equivalent of soda for combination with the tungstic 

 acid of the wolfram, which is the tungstate of iron and manganese ; the object of the 

 process being by calcination to convert the insoluble tungstate of iron and manganese 

 into the soluble tungstate of soda, leaving the oxides of iron and manganese in a very 

 finely -divided state of low specific gravities, so that they can be easily washed off with 

 water. 



