The Relation to Nitrogen 245 



rotation with legumes are supplementary means of nitro- 

 gen restoration. Finally, electric fixation is a source of 

 supply. 



138. Electric fixation of nitrogen. In recent years 

 several methods have been devised for the oxidation of 

 atmospheric nitrogen. These methods involve the use of 

 cheap power, since high-power electric currents are neces- 

 sary. Those which are now important in the production 

 of materials commercially valuable as fertilizers require 

 also a cheap source of lime. The two methods referred 

 to are known respectively as the Birkeland-Eyde process 

 and the calcium carbide process. By the former a basic 

 lime nitrate is produced, and by the latter a lime-nitrogen 

 consisting of calcium cyanamid and calcium cyanide. The 

 first mentioned product, which is much employed in north- 

 ern Germany, is a direct fertilizer, whereas the latter must 

 first undergo decomposition in the soil. The cyanamid 

 is more easily handled, the basic nitrate being strongly 

 hydroscopic. 



LABORATORY WORK 



Ammonification. 1 The decomposition of protein with for- 

 mation of ammonia may be demonstrated by the action of certain 

 bacteria upon egg albumen. Prepare a solution containing about 

 2 grams of egg albumen in 50 cc. of water, and to prevent coagu- 

 lation add 50 cc. of .05 ferrous sulfate. Pour about 10 cc. of 

 the solution into each of several test-tubes, sterilize for 1 hour 

 at 100 C., cool, and inoculate some of these with a pure culture 

 of Bacillus mycoides, or some other organism reported to possess 



1 For more experiments upon ammonification, nitrification, and 

 related phenomena the student should consult especially Percival's 

 "Agricultural Bacteriology," 1910. 



