2 MCDOUCALL AND HOWLES, Nitric Acid from Air. 



This pioneer work, however, opened out a new field, 

 and we find several chemists cndeavourintj to prepare 

 nitric acid by the aid of the electric spark. Amon^ these 

 may be mentioned Newton (1859), whose apparatus con- 

 sisted of a number of platinum wire terminals, between 

 which electric sparks passed, the terminals being contained 

 in a large chamber, the floor of which was covered with 

 water for the absorption of the oxides of nitrogen, with 

 the subsec[uent i)roduction of nitric acid. Arrangements 

 were also made for sup[)lying air, and for drawing off the 

 nitric acid produced. 



Prim (1882) makes use of the combined effect of the 

 spark and the silent discharge. The quantity of nitric 

 acid produced by these processes was almost indefinitely 

 small. It was only with the invention of the modern 

 dynamo, by means of which electrical energy can be 

 produced in any desired quantity, that the idea of preparing 

 nitric acid by its aid could be entertained. 



In 1892, Sir William Crookes exhibited an electric 

 flame produced by a high-tension alternating-current 

 discharge between platinum terminals, and depending for 

 its maintenance upon the combustion of atmospheric 

 nitrogen and oxygen. A flame of this nature was utilised 

 by Lord Rayleigh and Professor Ramsay, for the isolation 

 of argon from the atmosphere {Phil. Trans, vol. 186, 

 pp. 187 — 241) and also in a later research by Lord 

 Rayleigh {C/icin. Soc. Journ. 1897) on " The Oxidation of 

 Nitrogen Gas." 



The electrical arrangements are described in detail in 

 this paper. To generate the high-tension current, a trans- 

 former, insulated in oil, was used. It was found to be 

 necessary to use nearl>' 8,000 volts on the open secondary 

 circuit to maintain a steady flame. When the discharge 

 passed, the voltage fell to 2,000 or less. 



