310 AGRICULTURAL ANALYSIS 



271. Utilization of Atmospheric Nitrogen. In the first vol- 

 ume of this work attention has been called to the fixation and 

 utilization of atmospheric nitrogen by the action of bacteria, 

 -especially those living in symbiosis with leguminous plants. 77 Ber- 

 thelot in the first volume of his Vegetable and Agricultural Chem- 

 istry, has set out at great length the various methods in which 

 atmospheric nitrogen may be rendered available for agricultural 

 purposes. 78 It will prove convenient for the analyst and student 

 to have a summary of the different methods described in which 

 atmospheric nitrogen may be rendered useful for plant food. 



The methods as set forth by Berthelot are as follows: 



(1) Fixation of atmospheric nitrogen by means of microbes 

 in the earth and upon vegetables. 



(2) The continued fixation of free nitrogen by the organic 

 compounds under the influence of atmospheric electricity of feeble 

 tension. 



(3) The fixation of nitrogen under the influence of slow oxi- 

 dation. 



There are many subdivisions made under these various heads 

 but those represent in general the principal methods which Ber- 

 thelot has studied. All these methods, it is noticed, are purely 

 natural, that is, those which are going on constantly in nature, 

 Berthelot not having taken up the study of the artificial production 

 of nitrogen under strong electric influences in the first volume 

 of his work. 



272. Historical Development of the Fixation of Atmospheric 

 Nitrogen by Means of Electricity. The principal steps in the de- 

 velopment of the investigation looking to the fixation of atmos- 

 pheric nitrogen have been traced by Erlwein. 79 Attention is 

 called to the researches of Crookes, Lord Rayleigh, Bradley, 

 Lovejoy, Birkeland, Kowalsky, and Pauling in the research 

 work and practical application of the principles discovered. Spe- 

 cial attention is given to the work done by Siemens 

 and Halske. These investigators studied the problem of 

 the production of nitric acid by electrical discharges between 



77 Wiley, Principles and Practice of Agricultural Analysis, and Edition, 

 1906. 1 : 521. 



78 Chimie ve'ge'tale et agricole, 1899, 1. 



79 Elektrotechnische Zeitschrift, 1907, 14 : 41, 62. Electrochemical 

 and Metallurgical Industry, 1907, 5 : 77. 



