TUNGSTEN COMPOUNDS. 95 



I. II. III. IV. 



Percentage of tungsten 3672 36*87 36*50 



„ bromine 60*25 61*83 



Calculated. Found. 



Tungsten, W =184 35*38 36*69 



Bromine, Br 4 = 32o 6154 6104 



Oxygen, O = 16 308 



520 ioo*oo 



2. Tungsten Dioxy bromide, WBr z 2 . — This compound 

 is formed on passing bromine- vapour over red-hot tungsten 

 dioxide, or (together with the monoxybromide) by passing 

 the vapour of the pentabromide over tungsten trioxide. 

 The light, reddish-brown coloured vapours of dioxybro- 

 mide easily condense to dark, reddish-brown coloured, well- 

 formed crystals and crystalline crusts, which, on cooling, 

 form light red, transparent crystals, yielding a yellow 

 powder. The crystals do not melt, but volatilize at a 

 temperature near to a red heat. On resublimation, a par- 

 tial decomposition occurs, a small quantity of tungstic 

 oxide remaining, and a sublimate of the two oxybromides 

 being formed, from which the more volatile monoxybro- 

 mide can be expelled by a gentle heat. The dioxybromide 

 is not acted upon by water. In the following analyses, 

 the metal was estimated by dissolving the substance in 

 ammonia, evaporating and igniting with access of air ; the 

 bromine was determined (collecting the hydrobromic acid 

 formed) by passing hydrogen over the heated substance in 

 a boat ; a partial volatilization occurs, but the volatile por- 

 tion is completely decomposed in the red-hot part of the 



tube. 



I. II. III. IV. 



Weight of substance taken ri 55° 0*9910 1*0077 0*7692 



„ tungsten oxide obtained 0*6265 0*4760 



„ silver bromide 1*1080 0*9889 



,, silver 0*0131 



Percentage of tungsten 49' 2 7 49"°7 



,, bromine 4 I% 65 4246 



