1906.] Prof. Thompson on Electric Production of Nitrates. 22b 



AVEEKLY EVENING MEETING, 



Friday, February 2, l'.)()6. 



His Grace the Duke of Northumberland, K.G. D.C.L. F.R.S., 

 President, in the Chair. 



Professor Silvanus P. Thompson, D.Sc. F.R.S. M.R.L, Principal 

 and Professor of Physics in the City and Guilds Technical College. 



The Electric Production of Nitrates from the Atmos^jhere. 



As the demand of the white races for wheat as a food-stuff increases, 

 the acreage devoted to wheat growing increases, but at a less rapid 

 rate ; and being limited by climatic conditions will, in a few years, 

 perhaps less than thirty, be entirely taken up. Then, as Sir William 

 Crookes pointed out in his Presidential Address in 1898, there will 

 be a wheat famine, unless the world's yield per acre (at present about 

 12*7 bushels per acre on the average) can be raised by use of fertilizers. 

 Of such fertilizers the chief is nitrate of soda, exported from the nitre 

 beds in Chili. The demand for this has risen from 1,000,000 tons 

 in 1892 to 1,548,120 tons in 1905 ; and the supply will at the present 

 rate be exhausted in less than fifty years. Then the only chance of 

 averting starvation lies, as Crookes pointed out, through the labo- 

 ratory. 



In 1781, Cavendish had observed that nitrogen, which exists in 

 illimitable quantities in the air, can be caused to enter into combina- 

 tion with oxygen, and later he showed that nitrous fumes could be 

 produced by passing electric sparks through air. Although this 

 laboratory experiment had undoubtedly pointed the way, though the 

 chemistry of the arc flame had been investigated in 1880 by Dewar, 

 and though Crookes and Lord Rayleigh had both employed electric 

 discharges to cause nitrogen and oxygen to enter into combination, 

 no commercial process had been found practical for the synthesis of 

 nitrates from the air, until recently. 



After referring, in passing, to the tentative processes of Bradley 

 and Lovejoy, of Kowalski, of Naville, and to the cyanamide and 

 cyanide processes, attention was directed to the process of Birkeland 

 and Eyde, of Christiania, for the fixation of atmospheric nitrogen, 

 and their synthetic production of nitrates, by use of a special electric 

 furnace. In this furnace an alternating electric arc was produced at 

 between 8000 and 4000 volts, but under special conditions which 

 resulted from the researches of Professor Birkeland ; the arc being 

 formed between the poles of a large electro-magnet, which forced it 

 to take the form of a roaring disc of flame. Such a disc of flame was 

 shown in the lecture room by a model apparatus sent from Christiania. 

 Vol. XVIII. (No. lOoj Q 



