NITROGEN FIXATION LOF 217 



The raw material, consisting of anthracite, sodium carbonate, and 

 iron sponge, is formed into small balls, in which shape they are fed 

 into the furnaces. These are of the shaft type, the material resting 

 on grates which are intermittently turned in order to facilitate dis- 

 charging and to avoid baking. The furnaces are further of the elec- 

 trode type, operating on the resistance principle, the balls themselves 

 conducting the electric current from one electrode to the other and 

 becoming in this way heated to the temperature required for the re- 

 action, which is around 1,700° F. The nitrogen, under pressure, is 

 admitted directly at the bottom of the furnace, and the gases are 

 given off at the top. They contain principally hydrogen and carbon 

 oxide, which are afterwards used as fuel gas for the nitrogen ovens 

 and for drying purposes, etc. The bottom of the furnace is connected 

 to an air-tight conveying system for transporting the cyanide to 

 the ammonium-sulphate building. 



A large surplus quantity of nitrogen is needed for the fixation, 

 and a method has been worked out for its production at a very low 

 cost. The process is chemical, the oxygen of the air being bound by 

 an alkali iron to Fe 2 3 , setting the nitrogen free. This ferric oxide 

 is then reduced by the above-mentioned waste gas from the furnaces 

 and the iron used over again. In practice, air is not used in the 

 manufacture of the nitrogen, but the waste gases from the sulphuric 

 acid factory, as these gases contain only a few per cent of oxygen, 

 thus materially reducing the energy required for binding the oxygen. 



The cyanide from the furnaces is, as mentioned, conveyed to the 

 ammonia department where ammonium sulphate is produced in the 

 same manner as for cyanamid, with the exception that the sludge left 

 in the autoclaves after proper treatment is used again as raw ma- 

 terial for the furnace charge. 



The power consumption with this process is claimed to be about 

 iy 2 horsepower years per ton nitrogen fixed as cyanide. 



Sodium cyanide is also made by fusing cyanamid with ordinary 

 salt in an electric furnace. This product is extensively used for 

 case-hardening of steel, for the separation of gold from its ore, and 

 for the manufacture of hydrocyanic acid for fumigation of fruit 

 trees. Large quantities of such cyanide is manufactured by the 

 American Cyanamid Co. at their Niagara Falls plant. 



THE NITRIDE PROCESS 



The fundamental principle underlying this process is the combina- 

 tion of nitrogen with metals, such as aluminum, titanium, lithium, 

 etc., to form nitrides from which ammonia can readily be obtained 

 by decomposition. 



