660 



Professor The Hon. R. J. Strutt 



[Feb. 28, 



enough, is far less conspicuous. Benzene, for instance, almost 

 quenches the nitrogen glow, and little can be seen of the cyanogen 

 spectrum either. In most cases it appears that hydrocyanic acid is 

 formed, but the orange cyanogen glow, only obtained in compounds 

 containing much chlorine, is probably due to the formation of 

 chloride of cyanogen in addition. This, when absorbed in potash, 

 forms a cyanate, which has been detected chemically. 



In the case just considered, the spectrum observed, when active 

 nitrogen is mixed with another substance, is that of the product of 



GAS 

 EXIT 



U 



Fig. 4. 



GAS 



STREAM 

 ENTRANCE 



LIQUID AIR 



the action. In some cases, however, the spectrum developed is that 

 of the substance originally introduced. I admit some of the vapour 

 of perchloride of tin : you see the brilliant blue glow. I introduce a 

 drop of the liquid chloride on a wire loop into the flame of a Bunsen 

 burner, and you see the same blue colour, though less advantageously. 

 The brilliance of the luminous effect does not seem to give any 

 trustworthy indication as to whether much chemical action is going 

 on. If, for instance, we admit bisulphide of carbon vapour to the 



