AND A NEW NIOBIUM CHLORIDE. 191 



When the vapour of niobium oxychloride is passed over 

 red-hot charcoal in an atmosphere of carbon dioxide, no 

 change occurs ; and the pentachloride is obtained when the 

 carbon dioxide is replaced by chlorine. 



A remarkable reaction occurs when niobium trichloride 

 is heated in a current of carbon dioxide ; this gas is de- 

 composedj a white sublimate, consisting of oxychloride, is 

 obtained, and the corresponding quantity of carbon mon- 

 oxide is formed. 



That this is the case was ascertained by analyzing the 

 oxychloride and by collecting the gas over caustic potash 

 and measuring the volume of insoluble gas which came 

 over. This gas was shown to burn with a blue flame ; and 

 the quantity was found in two experiments to correspond 

 closely with the theoretical amount. The following is the 

 composition of the oxychloride thus prepared : — 



Found. 



Niobium 43-48 



Clilorine 47"o3 



Oxygen 9.49 



lOO'OO 



A decomposition of carbon dioxide by a metallic chloride 

 has hitherto not been observed. Phosphorus trichloride 

 absorbs free oxygen on distillation in the air, with formation 

 of oxychloride ; but it does not decompose carbon dioxide. 



