264) F. Wohler o?j Tungsten. 



tungsten,— it might rather be presumed that this is the tungsten 

 in its metallic state, especially when I observe, that this black 

 body acquires a white metallic brilliancy, although a very 

 deep one, when burnished. But the degree of increase of 

 weight it acquires in combustion proves that it is oxide of tung- 

 sten, and not the metal itself. Heated in the air it burns long 

 before it reddens; and according to many experiments, 100 parts 

 always combine with 8 parts of oxygen [i, e. with the same 

 quantity as the brown oxide) while passing into the acid state; 

 whilst 100 parts of metallic tungsten require nearly 25 parts 

 of oxygen in order to be converted into tungstic acid. It 

 seems to me remarkable that the same combination should 

 exhibit itself under such different foi-ms. It is probable that 

 the different state of the aggregation of its molecules is the 

 cause of this phaenomenon, as is also observed in native oxide 

 of iron, cinnabar, &c. 



In preparing the brown oxide of tungsten by heating the 

 acid in a current of hydrogen gas, another phaenomenon is 

 presented, which I cannot well explain. It is a fact that it is 

 difficult to prepare pure tungstic acid when it once contains a 

 fixed alkali. On using such an acid containing a little potash 

 or soda, to prepare the brown oxide by the hydrogen, this 

 oxide is never obtained, but always metallic tungsten, — a me- 

 thod by which this metal may also be easily procured. It is 

 washed with pure potash, in order to dissolve the difficultly 

 soluble tungstate with which it is mixed : it is then a metallic 

 powder, rather white, very heavy, which, heated in the air, ig- 

 nites, and of which 100 parts increase by nearly 25 parts. 



Combination of the Oxide of Ttmgsten -with Soda. 



On melting and igniting the neutral tungstate of soda in hy- 

 drogen gas, no action of the latter substance on the former is 

 observed ; but if the same experiment be made with super- 

 tungstate of soda, the surface of the mass soon assumes the 

 colour and metallic brilliancy of copper, which is gradually 

 communicated to the whole mass. On cooling, the colour be- 

 comes a gold-yellow; and if the mass be then treated with 

 water, the neutral tungstate of soda is dissolved, and a heavy 

 crystalline powder, of the colour and almost the metallic lustre 

 of gold, is left. The best method of making the experiment 

 is by using a glass tube which has a bulb in the middle, or 

 by making the salt almost red-hot in a current of dry hydrogen 

 gas. The mass is then boiled with water. The remaining 

 powder is first digested in concentrated muriatic acid, in order 

 to decompose the insoluble tungstate attached to it: it is then 

 boiled with a solution of pure potash ; and at last washed in 



water. 



