88 PROF. H. E. ROSCOE ON CERTAIN 



tion, which is rather more stable than the green solution 

 of the pentachloride in water, but which in course of time 

 deposits insoluble oxide. On evaporating the solution in 

 vacuo traces of a crystalline body were obtained. The tetra- 

 chloride is non-volatile and infusible under ordinary pres- 

 sure ; but it is decomposed on heating into pentachloride, 

 which distils off, and a lower dichloride, which remains 

 behind. On heating in hydrogen at a temperature above 

 the melting-pom t of zinc the tetrachloride is reduced to 

 metallic tungsten, some of which is deposited as a black 

 tinder-like powder, undergoing spontaneous ignition on 

 exposure to the air. 



Analyses of Tungsten Tetrachloride, WC1 4 . 



I. II. III. IV. 



Weight of chloride taken ... i-oioo 0*6402 0-4830 10804 grms. 

 „ tungsten obtained 0-5715 0*2780 



,, tungsten trioxide 0*4632 0-7845 



„ silver chloride ... 0*8344 1*8239 



Percentage of tungsten 56*58 57*38 57*55 57*58 



,, chlorine 4273 41*76 



Calculated. Mean found. 



Tungsten, W = 184 56*45 57*22 



Chlorine, Cl 4 = i42 43*55 42*24 



326 100*00 99*46 



The want of exact agreement with the calculated num- 

 bers probably arises from the facts ( 1) that, in the first 

 reduction of WC1 6 , some metal or the lowest chloride is 

 formed which is not entirely reconverted into WC1 5 , and 

 (2) that if the temperature used for the reduction of the 

 pentachloride be a little too high, some dichloride is 

 formed. 



4. Tungsten Dichloride, WC1 2 -**---■ 25 5. — This body is ob- 

 tained in light grey crusts by reducing the hexachloride at 

 high temperatures in hydrogen. It can be best prepared 



