36 



bacteria in conserving and increasing the supply of combined 

 nitrogen there will always be a demand, in intensive culture 

 especially, for an immediately available supply of nitrates or 

 other forms of fixed nitrogen. The great Chilean deposits, which 

 furnished more than one and a half million tons in 1 905, will, at 

 the present rate of use, according to careful estimates, be ex- 

 hausted in less than fifty years. It has long been known, how- 

 ever, that atmospheric nitrogen can be oxidized under the in- 

 fluence of electricity, producing nitric oxid fumes, which are then 

 combined with water, to form nitric acid, or with quicklime, 

 forming calcium nitrate. Other bases may also be used. Various 

 attempts have been made from time to time to develop a process 

 by which nitrogen can be combined commercially. The most 

 promising results have thus far been secured with Franck's pro- 

 cess of making calcium cyanamid and with the Birkland and 

 Eyde process of producing nitra. The former process consists 

 in combining nitrogen with the carbides of alkalis, producing 

 cyanids, or, in the case of calcium, producing calcium cyanamid 

 (CaCN2), containing 35 percent of nitrogen more than twice the 

 amount present in Chile saltpeter. The calcium cyanamid, when 

 properly used, has proved to be an excellent nitrogeneous fertili- 

 zer for many crops, and quite equal to ammonia compounds, into 

 which it can be readily converted. The ammonia thus produced, 

 can be further oxidized by conducting it over highly heated 

 metallic oxids, thus producing nitric acids. 



The Birkland and Eyde process, however, appears to be the 

 most promising as a means of producing nitrates. A special 

 electric furnace is used, in which an alternating electric arc 

 between 3,000 and 4,000 volts is produced in connection with 

 a large electro magnet, which forces it to take the form of a 

 roaring disk of flame. Air is forced through this furnace at the 

 rate of about 3,000 cubic feet per minute, the nitrogen being oxidi- 

 zed in the furnace to nitric oxid. These fumes are then collected, 

 and after further oxidization are absorbed in water towers, 

 forming nitric acid, or by powdered quicklime, forming calcium 

 nitrate. Of course the nitric acid can be combined with almost 

 any desirable base, such as soda or potash. With cheap water 

 power nitrates can be produced by this process to compete in 

 cost with nitrate of soda.* 



These direct processes of securing nitrogen will be rapidly 

 improved, and what has been accomplished already in this 

 direction should remove the last vestige of doubt that we shall 

 be able to secure at a reasonable cost all of the immediately 

 available nitrogen we may need, in addition to the great supply 

 that may be secured through bacterial action. 



* See "Nature", vol. 75, p, 355; also, Exp. Sta. Record, vol. XVII, pp. 746-750. 

 For a full illustrated account see Engineering News, vol. 57, No. 6. pp. 150, 151. 



