86 



vapour to be 148 (H=l), whereas the calculated density is 

 171. On repeating this determination the numbers (1) 171*3 

 and (2) 171*7 were obtained; whilst experiments made in 

 mercury vapour gave (1) 175-8, (2) 170-8, proving that the 

 vapour density of the monoxychloride is normal, and that 

 the molecule of this substance contains 184 parts of metal. 



The Dioxy chloride WO2CI2 is best prepared by passing 

 chlorine over the brown dioxide. Analysis gave 



Calculated. Found. 



Tungsten W- 64-32 64-11 



Chlorine Cl^- 24-31 24-74 



Oxygen 0^- 11*37 



100-00 



The vapour density of the dioxychloride cannot be deter- 

 mined at 440°, as at that temperature the contents of the 

 bulb remains liquid. 



Bromides of Tungsten. 



Bromine vapour acts rapidly on hot metallic tungsten, 

 forming dark bromine-like vapours which condense to a 

 crystalline sublimate. Especial precautions require to be 

 employed as regards exclusion of oxygen and moisture, as 

 the oxy bromide formed when these substances are present 

 posseeses very nearly the same colour as the bromide, and 

 cannot be easily separated from the latter. 



Tungsten Pentahromide WBr^. 



By the action of excess of bromine on tungsten a penta- 

 and not a hexa-bromide is obtained. Prepared in this way 

 the pentabromide forms dark shining crystals, having a 

 metallic lustre not unlike that of iodine. These crystals 

 melt at 276' and solidify at 273°, the liquid boiling at 333' 

 (corr.) The pentabromide is at once decomposed by excess 

 of water into the blue oxide of tungsten and hydrobromic 

 acid, and immediately undergoes the same decomposition on 

 exposure to moist air. On distillation, a small quantity of 

 of a lower non-volatile bromide remains behind, and this 

 explains the slightly too high percentage of metal found in 

 the analysis. 



