CLASSIFICATION OF METHODS 321 



Niagara Falls for the production of nitric acid from the air 

 has been abandoned. The success of the experiments in Norway 

 is promising, but attention is called to the fact that the process 

 in Norway utilizes the moving arc method instead of the old 

 spark method, and is dependent essentially on the exceedingly 

 low prices of electric power in that country. 



The second method of utilizing the atmospheric nitrogen, 

 which is now under investigation, is that which starts with cal- 

 cium carbid, the product of the electric furnace, and treats 

 this compound later with nitrogen in such a way as to produce 

 the calcium cyanamid. A company has been formed in the 

 United States to operate a factory upon the above principle, and 

 it is proposed to erect a plant of 20,000 metric tons annual 

 capacity on the Tennessee River in Northern Alabama. In this 

 locality there is abundant and cheap water power, as well as 

 coal and coke. Labor is also abundant and reasonably cheap. 

 The Tennessee River also furnishes water transportation of the 

 cheapest character. It is near some of the great phosphate 

 deposits, so that in the manufacture of the complete fertilizers 

 a large part of the material would be derived from the same 

 localities. 



METHODS OF ANALYSIS 



280. Classification of Methods. In case a microscopic exam- 

 ination of the sample is required it should precede the chemical 

 operations. In general, there are three direct methods of deter- 

 mining the nitrogen content of fertilizers. First the nitrogen 

 may be secured in a gaseous form and the volume thereof, under 

 standard conditions, measured and the weight of nitrogen com- 

 puted. This process is commonly known as the absolute method. 

 Practically it has passed out of use in fertilizer work, or is prac- 

 ticed only as a check against new and untried methods, or on 

 certain nitrogenous compounds which do not readily yield all 

 their nitrogen by the other methods. The process, first perfected 

 by Dumas, whose name it bears, consists in the combustion of 

 the nitrogenous body in an environment of copper oxid, by which 

 the nitrogen, by reason of its inertness, is left in a gaseous state 

 ii 



