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. 



