122 CHEMICAL DISCOVERY AND INVENTION 



to combine with nitrogen, and so withdraws a portion of it from 

 the nitric oxide, leaving more oxygen for the remainder. 



It also attacks acetylene and other gases containing carbon, 

 and the result is the production of cyanogen compounds, the 

 presence of which can be demonstrated by shaking up the gas 

 with caustic potash and adding an iron salt in the usual way 

 when Prussian blue is produced. 



Glowing nitrogen also exhibits remarkable phenomena when 

 in the presence of iodine. Its normal yellow glow is replaced by 

 a magnificent light blue flame at the place where it mingles with 

 the iodine vapour. At this point a slight rise of temperature is 

 observed. Active nitrogen also attacks mercury, forming with it 

 a compound which explodes when moderately heated. 



It appears to be certain that the phosphorescent nitrogen 

 does not owe its activity to a state of condensation corresponding 

 with that of ozone, the molecule of which consists of three atoms 

 3 , the instability of the molecule being due chiefly to the 

 tendency to the production of the more stable ordinary molecule 

 which contains only two atoms, 2 . Active nitrogen appears 

 rather to consist of separate atoms of the element produced by 

 the dissociation of the ordinary molecules composed of two 

 atoms, N 2 . The glowing gas does not appear to owe its peculi- 

 arities to the presence of electrified particles, as it is unaffected by 

 passing through an electric field. 



CHAPTER VI 



THE ELEMENTS OF THE CHEMIST 



IT is one of the characteristic features of modern physical 

 science, which is not, like the ancient, content with observation 

 of natural phenomena, but depends for progress on the results 

 of experiment, to be perpetually in a state of flux. Its advance 

 is analogous to the ascent of a mountain ; the higher the 

 traveller rises the broader is the prospect which becomes visible. 

 He may now and then reach a plateau which tempts him to rest 

 and look backward content for the time with the view, at the 

 same time he knows full well that this resting-place is not the 

 summit and that what he now sees will appear insignificant 

 when a higher altitude is reached. Something of the same kind 

 happens in the evolution of physical science. A theory is formed 



