1913.] on Active Nitrogen 659 



present is almost instantly nsed np. Incidentally, the experiment 

 illustrates the extremely rapid diffusion of the gaseous residuum in 

 an exhausted vessel, for every particle of the active nitrogen must 

 evidently find its way to the surface of the wire in the fraction of a 

 second. 



We pass now to consider the effect of nitrogen in this condition 

 on other substances. The yellow glow we have studied so far is due 

 to the recombination of nitrogen atoms, and accordingly it shows a 

 nitrogen spectrum, though with very curious modifications. 



If we offer to the monatomic nitrogen other substances, it will 

 often unite chemically with them, which of course cold ordinary 

 nitrogen will not do. I go back to the apparatus used in the first 

 experiment, and admit some acetylene by a stopcock {c, Fig. 1). 

 The jet of active nitrogen now enters an atmosphere of acetylene, 

 and you see that the character of the light is at once changed ; it 

 has become lilac. I turn off the acetylene and substitute chloroform 

 vapour. We now get an orange light. This may appear very 



Pig. 3. 



different, but the difference is unessential. The spectrum is in each 

 case that characteristic of cyanogen and its compounds, only the violet 

 portion of this spectrum is more intense with acetylene, the red 

 portion with chloroform. 



Since we get the cyanogen spectrum without having any cyanogen 

 compound originally present, we may suspect that some such com- 

 pound has been formed. Let us pass from suspicion to proof. 

 Using chloroform vapour from a bulb containing the liquid {see 

 Fig. 1), we pass the gases through a vessel in which a test-tube is 

 inserted. This test-tube contains liquid air, and any condensable 

 constituent is frozen out on to its external surface (Fig. 4). After a 

 few minutes' run, we take out the test-tube and dip it in a solution 

 of potash. I now add a mixture of ferrous and ferric salts and excess 

 of hydrochloric acid. I pour out the liquid on to this white porcelain 

 dish, and you see that abundance of prussian blue has been formed. 

 This proves the presence of some cyanogen compound. 



We can get the same result with pentane, ether, benzene, or 

 almost any other organic vapour. With these the amount of cyanogen 

 formed is much the same, but the cyanogen spectrum, curiously 



