TEE CHEMIST IN CONSERVATION 295 



by him — the fixation of atmospheric nitrogen, that is, the conversion of 

 this gas, inert and non-utilizable, into nitrogen compounds which could 

 be assimilated by the plant and from this pass to the animal for the 

 building and repair of its tissues. There was the problem for the chem- 

 ical engineer and the chemical engineer has worked out its solution. 

 The principle employed is to burn the nitrogen of the atmosphere 

 through the agency of the oxygen, by passing the air through a flaming 

 electric discharge. Although this sounds simple, the commercial opera- 

 tion was most complex. The shape and size of the electrodes and their 

 container, the correlation of quantity and intensity of the electric cur- 

 rent, of the temperature and volume of air, all demanded patient care 

 as well as expert knowledge. Not only must oxidation be controllable, 

 but the costs must be studied and reduced until a commercial success 

 was assured. The first companies did not succeed and went into bank- 

 ruptcy, but now, using the power of the mountain streams of Norway 

 and the Tjrrol, the nitrogen of the air yields its freedom and leaves the 

 factory as calcium nitrate and sodium nitrate, which go to be mixed 

 with the other constituents of artificial plant foods, or as nitric acid, 

 which is used in so many technical processes. There are now in opera- 

 tion chemical plants which can place upon the world's markets an- 

 nually 100,000 tons of pure calcium nitrate thus obtained through the 

 use of atmospheric nitrogen. 



While one group of chemists were following this solution of the 

 nitrogen problem others had taken another line, influenced partly by a 

 different motive. This was the development and an outgrowth of the 

 calcium carbide industry. After the French chemist, Moissan's, bril- 

 liant work upon the production of carbides by the electric furnace the 

 field was occupied commercially and in many places where cheap water- 

 power could be obtained — Niagara Falls, Norway, Switzerland and 

 others — calcium carbide was made for acetylene lighting. The annual 

 output is about 200,000 tons. But this is more than is called for in the 

 preparation of acetylene. There must be some way of using the excess, 

 and the services of the chemist were in demand. 



When free nitrogen is led over calcium carbide at the proper tem- 

 perature it is absorbed, forming calcium cyanamide. The latter is 

 decomposable by steam, its nitrogen being evolved as ammonia, a valu- 

 able plant food. There is the same decomposition when the calcium 

 cyansmiide is placed in the ground; the decomposition is then so slow 

 that the ammonia does not escape into the air, but is held in the soil 

 until it is utilized by the plant. 



Thus the chemist has built another bridge over the gulf between 

 free and combined nitrogen, cyanamide, or " nitrolime," acting as the 

 middle pier. Nearly 200,000 tons can be annually furnished by the 

 works now built or under construction. 



