PRESENT PROBLEMS 689 



plished much toward this end when he showed that feldspar could 

 be made to yield the greater part of its potash when it was heated 

 with lime and common salt. Clark has found that when the min- 

 eral leucite, with its 21 per cent potassium oxide is heated with 

 ammonium chloride, the potassium is converted into chloride and 

 is easily separated from the melt. If this reaction could be ex- 

 tended to orthoclase and the ammonia recovered by treatment with 

 lime, the enormous quantity of potash contained in this mineral 

 would be at our service. 



It is, however, to the supply of available nitrogen that the great- 

 est importance attaches. The sodium nitrate producing countries 

 of South America exported last year 1,300,000 tons, a large per- 

 centage of which came to America. Egypt and the Southwestern 

 United States have nitrate deposits, but of their extent and value 

 little is as yet known. Of the other form of available nitrogen, 

 ammonia, our main supply is at present from the destructive dis- 

 tillation of coal. Although the introduction of by-product coke- 

 ovens has increased this supply, our domestic production is now 

 not over 40,000 tons a year. 



In the atmosphere, however, we have a never-failing source of 

 nitrogen which needs only to be converted into other forms to be 

 of the greatest value. It is interesting to note that even as long 

 ago as 1840 this same problem was the subject of considerable 

 experimentation and the basis of several technical processes. In 

 this year there was erected in France a plant for the manufacture 

 of potassium ferro-cyanide, which depended on the atmosphere for 

 the supply of nitrogen, and which at one time turned out almost 

 a ton of product per day. From this time until the present, the 

 utilization of this inexpensive and inexhaustible supply of raw 

 material has been an attractive field, and has held the attention 

 of many investigators. It had long been known that w r hile carbon 

 and nitrogen alone could not be made to unite, the union was effected 

 when these elements were brought together in the presence of a 

 strong alkali. The technical difficulties in the way of successfully 

 applying this reaction seem to have been the rapid destruction of 

 the retorts and the loss of alkali through volatilization. With the 

 advent of cheap electricity and the consequent development of the 

 electric furnace, this idea was made the basis of further work. The 

 destruction of the retorts was largely overcome by generating the 

 heat within the apparatus rather than without. When a non-vola- 

 tile alkali was used to eliminate the loss from this source and a 

 higher temperature maintained, it was found that a carbide was 

 formed as an intermediate product and that nitrogen readily re- 

 acted with the carbon thus held in combination. 



Among the investigators who have thus far taken advantage 



