362 SCIENCE PROGRESS 



Chemists and engineers have followed Sir Joseph Swan's 

 advice, and have been busy with the problem since the above 

 words were written and published, five years ago. After many 

 experiments, and the failure of an American company with 

 works at Niagara Falls, the difficulties are believed to have 

 been overcome, the successful scientists being Prof. Birkeland, 

 of Christiania University, and S. A. M. Eyde, a Norwegian 

 engineer. 1 



Air contains roughly 21 per cent, by volume of oxygen and 

 79 per cent, by volume of nitrogen. If an electric spark be 

 passed through dry air, a small amount of nitrous oxide gas 

 is formed by oxidation or " burning " of portions of the nitrogen. 

 This experiment was performed in the laboratory by Cavendish 

 over a hundred years ago. The problem that confronted the 

 chemist was — How to enable this combination of the oxygen 

 and the nitrogen to become sufficiently rapid, to render the 

 process a profitable and practicable one for the manufacture of 

 nitrates ? The earlier inventors used an enormous number 

 of small sparking points for obtaining the electric discharge, and 

 found even then that the yield of nitrous gases was too small 

 to render the process of practical utility. The reaction was also 

 found to be a reversible one, and the same electric spark energy 

 which caused the combination of the two elements (oxygen and 

 nitrogen) also brought about the disruption of the union. These 

 and other difficulties caused the failure of the Atmospheric 

 Products Company of Niagara Falls, which had been founded 

 in 1902, with some flourish of trumpets on the part of our 

 American cousins, to supply the world with nitrates by the 

 Bradley and Lovejoy process. The problem was, in fact, more 

 difficult than the American chemists and electricians had realised ; 

 and, as already stated, it has been reserved for two Norwegian 

 scientists to show the way in which it may be solved. Messrs. 

 Birkeland and Eyde, in place of using a large number of small 

 sparking arcs, make use of one large flame arc, produced by 

 alternating current at 3,000 to 4,000 volts pressure, this flame 

 being made to take the form of a disc, 4 to 5 ft. in diameter* 

 by a special method, the details of which were discovered by 



1 Another method of extracting nitrogen from the air, by means of calcium 

 carbide, has been patented by two German chemists, Messrs. Frank and Caro, 

 and is now being developed commercially in Italy. This method will be described 

 in a later article. 



