Chemistry and Physics. 453 



with it. It is believed that the discharge converts ordinary 

 nitrogen into an allotropic form, probably monatomic nitrogen, 

 which reverts rapidty to ordinary nitrogen. The glow is regarded 

 as the result of this reversion. The glowing nitrogen has some 

 remarkable chemical properties. When it is passed through a 

 tube containing a pellet of yellow phosphorus, a violet-reaction 

 occurs, the glow is destroyed, red phosphorus is produced, and 

 nitrogen is absorbed. In contact with iodine vapor at the 

 ordinary temperature a magnificent light blue flame is produced. 

 A reaction also occurs when sulphur or arsenic is gentty heated 

 in the glowing gas. Selenium, carbon, antimony, and hydrogen 

 are without effect. When oxygen is admitted, the glow is quickly 

 destroyed, but no combination takes place. If there is any trace 

 of oxygen in the nitrogen that is used in the discharge tube, no 

 afterglow takes place. With metallic sodium a little above its 

 melting point in contact with the glowing nitrogen, the complete 

 sodium spectrum is developed and nitrogen is absorbed. When 

 the metal is heated to 250° C, the yellow line D becomes almost 

 invisible and the green line E shows up strongly. There is also 

 a reaction with mercury vapor, forming an explosive compound 

 and developing the mercury spectrum. The reaction with nitric 

 oxide is of particular interest. When this gas is mixed with the 

 glowing nitrogen, a brilliant flame is produced and nitrogen 

 peroxide is formed. This reaction is represented thus : 



2NO + 1ST = N0 2 + N 9 . 



Advantage is taken of this reaction to determine the percentage 

 of active nitrogen in the glowing gas. An excess of nitrous 

 oxide is added to it, and the mixture is led into a U-tube cooled 

 by liquid air where the nitric oxide combines with more of the 

 nitrous oxide, forming N 2 3 , which condenses as a blue liquid. 

 From the weight of the trioxide the percentage of active nitro- 

 gen is calculated. The maximum amount found was 2*46 per 

 cent. Active nitrogen reacts with acetylene, forming cyanogen, 

 and with a large number of organic compounds containing 

 halogens, forming in every case cyanogen and liberating the 

 halogen. Certain substances, notably copper oxide and manga- 

 nese dioxide, destroy the glow very quickly without undergoing 

 any apparent change. 



The effects of temperature are very remarkable. When the 

 glowing nitrogen is led slowly through a tube cooled with liquid 

 air, the glow is greatly increased in brilliancy and dies out before 

 the coldest part of the tube is reached. When the gas is led 

 through a tube moderately heated in one part, the glow is locally 

 extinguished, but reappears beyond the heated part. If the glow 

 is due, as assumed, to the reaction of monatomic nitrogen and the 

 formation of the usual diatomic gas, there is here a negative 

 temperature coefficient in connection with its velocity, and this is 

 unique among known chemical reactions ; but as no other reac- 

 tion between monatomic elements has been studied, it is inferred 



