84 



Tungsten pentachloride melts completely at 248° C. and 

 solidifies at 242° ; the boiling point is 27o°-6 (coit). The 

 vapour density of this chloride taken in sulphur vapour at 

 440° was found to be (1) 186'4, (2) 186-5, (3) 185-7; the 

 normal calculated density (H = l) being 180-7. 



Hence the molecule of pentachloride contains one atom 

 (W=:]84) of metal. 



3. Tungsten Tetrachloride WCI4. 



The tetrachloride forms the nonvolatile residue produced 

 in the distillation of the hexachloride in hydrogen. In 

 order to obtain it in a pure state the mixture of the two 

 higher chlorides is distilled at a low temperature, (best in a 

 bath of melted sulphur,) and in a current of dry hydrogen 

 or carbonic acid. The tetrachloride is a loose soft crystal- 

 line powder of a greyish brown colour. It is highly 

 hygroscopic, but not so much so as the pentachloride, and 

 it is partially decomposed by cold water into brown oxide 

 and hydrochloric acid, forming also a greenish brown solu- 

 tion, which is rather more stable than the green solutions of 

 the pentachloride in water. The tetrachloride is non- 

 volatile and infusible under ordinary pressure, but it is 

 decomposed on heating into pentachloride, which distills 

 off, and a lower dichloride which remains behind. On 

 heating in hydrogen at a temperature above the melting 

 point of zinc, the tetrachloride is reduced to metallic 

 tungsten, which is sometimes deposited as a black tinder- 

 like mass, undergoing spontaneous ignition on exposure to 

 the air. 



Analyses of four portions gave the following mean 

 numbers : 



Calculated. Found. 



Tungsten W=184 56-45 57-22 



Chlorme Ch-142 43-55 42-24 



326 100-00 99-46 



4, Tungsten Dichloride, WCI2. 



This body is formed in light grey crusts on reducing the 

 hexachloride at high tem.peratures. It can be best prepared 



