TUNGSTEN COMPOUNDS. 83 



Giving a mean of i68'8 as the density for 440 C. ; whilst 

 the calculated density is 198*5. This closely corresponds 

 to Debray's experimental number of 170. 



Determination of Vapour-density of WC1 6 in Mercury- 

 vapour at 350 . 



As there is only a difference of 3 between the boiling- 

 points of the hexachloride and of mercury, a condensation 

 of the substance in the neck of the bulb may possibly 

 have occurred, although there was no indication of this 

 having happened. In a third experiment the number 

 199 was obtained; but in this case a distinct residue was 

 noticed, the chloride not having been redistilled in the 

 usual way from the small bulb, and this determination 

 is therefore omitted. 



I. II. 



Weight of bulb and air 23-9960 13-6360 gnus. 



Barometer 758-5 756 



Temperature 20 20 



Weight of bulb and vapour, 1 



T 25' 2 °4° 14-1525 grms. 



at 350 C J 



Barometer ' 7585 -56 



Capacity of bulb * x 93' 2 82-7 



Hence vapour-density (H—i) 190-7 191-2 



Giving a mean vapour-density of 190*9 at 350 , instead of 

 198*5 as calculated from the formula. 



The fact of the alteration of the vapour-density from 

 190 at 350 , or only 3 above the boiling-point, to 167 

 at 440 , shows pretty clearly that the anomalous vapour- 

 density is to be ascribed rather to dissociation than ex- 

 plained by Persoz 5 s suggestion of an error existing in the 

 atomic weight of the metal, according to which the 

 atomic weight is five-sixths of 184, and the chloride is 

 supposed to be TuCl 5 , requiring a vapour-density of 165*4. 



* Expansion of gla-ss not allowed for. 



