66 Scientific Intelligence. 



If, on the other hand, the gas is led through a tube immersed in 

 liquid air, it glows out with increased brilliancy where it 

 approaches the liquid air. The luminosity is completely and 



finally extinguished when, or before, the Fully cooled portion of 

 the tube is reached. The kind of atomic or molecular change 

 which might be expected to behave in this way is an association, 

 e. g, of dissociated nitrogen atoms into molecular nitrogen. 



The glowing nitrogen has remarkable chemical properties. 

 When it is pumped over a small pellet of phosphorus a violent 

 reaction occurs, red phosphorus is formed, and the yellow glow is 

 quenched. At the same time about one-half of one per cent of the 

 gas is absorbed. This is a measure of the proportion of active 

 nitrogen present in the whole stream and it is of the same order 

 of magnitude as the percentage of oxygen converted in an ozon- 

 izer. When the discharge tube is closed at both ends and the 

 afterglow is allowed to diffuse until it meets the phosphorus 

 vapor the same reaction takes place. The absorption reduces the 

 pressure of the gas so low as to stop the electrical discharge. 

 The reaction is not affected by removing the ions from the gas 

 by means of a suitable electrostatic field. The fact that nitro- 

 gen and phosphorus can combine under these conditions was not 

 known before. 



The glowing nitrogen also exhibits remarkable phenomena 

 -when led over iodine. Its normal yellow glow is replaced by a 

 light blue flame at the place where it mingles with the iodine 

 vapor. A slight rise of temperature is observed in this region. 

 "The flame gives a magnificent spectrum of broad bands." 

 " Details will follow in a later paper." 



Antimony, carbon and selenium had no effect on the glow of 

 the nitrogen. Hydrogen simply diluted the glow, while oxygen 

 extinguished it. Arsenic and sulphur gave reactions which were 

 not very striking. 



Perhaps the most important discovery recorded in the paper is 

 the fact that glowing nitrogen reacts quite vigorously with many 

 metals and metallic compounds, and simultaneously gives rise to 

 the characteristic spectra of the metals involved. 



As Strutt remarks : " It opens up a new field of experiment to 

 be able to produce metallic spectra in a vessel at so low an aver- 

 age temperature, and in the absence of an electric field." 



The line spectra of cadmium, lead, magnesium, mercury, potas- 

 sium, sodium, and zinc were obtained with the pure metals. 

 Thallium was tried in the form of the chloride and gave a mag- 

 nificent green light, in striking contrast to the yellow afterglow 

 which it replaces. As with phosphorus, so also with metallic 

 sodium and mercury, the absorption of nitrogen was demon- 

 strated. It was also shown that none of the phenomena is due 

 to the presence of ions in the glowing nitrogen, but only to the 

 uncharged, "active" nitrogen. The ions were removed, of course, 

 by means of a strong, electric cross-field introduced in the path 

 of the flowing gas between the region of discharge and the place 

 where the various reactions were observed. 



