81 



On decomposition with hot water a small quantity of 

 chlorine is invariably retained by the tungstic acid formed, 

 even after repeated distillation v/ith water. Hence it was 

 necessary in the analysis to reduce the oxide to metal and 

 to collect the hydrochloric acid formed. This was effected 

 by covering the weighed chloride in a porcelain boat with 

 water and bringing it into a bent combustion tube, one end 

 of which was connected with a hydrogen evolution apparatus, 

 and the other with a flask of water in which the acid was 

 collected. On gently heating the fore part of the tube (the 

 greatest care being taken to prevent spirting) the chloride 

 is converted into the yellow oxide, after which it was more 

 strongly heated and the reduced metallic tungsten weighed 

 whilst the chlorine was estimated with silver. 



Six analyses of different material, prepared on different 

 occasions and according to different methods, yielded the 



following results : — 



Calculated. Found. 



Tungsten W 184 46-35 46-49 



Chlorine Cle 213 53-65 53-32 



397 100-00 99-81 



The exact determination of the melting point of the 

 hexachloride is attended with some difiiculty, as the liqui- 

 faction takes place gradually and the smallest traces of 

 impurity depress the melting point down to about 180° C, 

 that given by the older observers. A mean of several 

 experiments gave the number 275° C (corrected) as the 

 melting point and 270° as the point of solidification. The 

 constant boiling point of the hexachloride was found to be 

 346-7° (corr.) under 759-5 mm. of mercury. The vapour 

 density of the hexachloride was determined (1) in sulphur 

 vapour at 440°, and (2) in mercury vapour at 350°. As the 

 hexachloride always leaves on distillation a small quantity 

 of solid residue, the substance was distilled (either in a 

 current of carbonic acid or of chlorine) into the heated bulb 



