TUNGSTEN COMPOUNDS. 85 



grm. of WC1 5 * so that the residual chloride contained 3*3 

 per cent, of pentachloride. In a second experiment about 

 6 grms. of the hexachloride were distilled upwards in a 

 current of carbonic acid for eighteen hours; 3*9763 grms. 

 of this residue were oxidized with water, sulphuric acid, 

 and permanganate, when 17 cub. centim. of the standard 

 solution were needed. This corresponds to 0*0217 grm. 

 oxygen, or to 0*9806 grm. of WC1 5 oxidized, or the residue 

 contained 24*6 per cent, of the pentachloride. The penta- 

 chloride treated in a similar way yields no free chlorine, 

 and therefore does not undergo a similar decomposition at 

 high temperatures. 



2. Tungsten Pentachloride, WC1 5 = 361*5.^ — On distilling 

 the hexachloride in a current of hydrogen, a reduction 

 always takes place. If the temperature is kept but little 

 above the boiling-point of the hexachloride the dark red 

 colour of the vapour is seen to vanish, and a light greenish- 

 yellow coloured vapour makes its appearance, which soon 

 condenses either to black drops or long shining black 

 needles. After two or three distillations in hydrogen, a 

 pure volatile product is obtained. It is, however, more 

 convenient to reduce at a higher temperature ; and in this 

 case the loss of chlorine goes further than one atom, and 

 the distillation is repeated in hydrogen until a solid 

 residue of a lower non-volatile chloride remains, showing 

 that all the hexachloride has been decomposed. The 

 mixture of chlorides thus obtained is then redistilled in 

 a current of dry carbonic acid, when pure pentachloride 

 comes over. 



Tungsten pentachloride crystallizes in long, black, 

 shining crystals ; if condensed in fine powder its colour is 

 dark green, and the crystals also yield a green powder like 

 potassium manganate when finely divided. The penta- 

 chloride is exceedingly hygroscopic, the solid becoming 

 instantly covered with a dark golden- green film on exposure 



