CONCLUSION 525 



potash the question of the extraction of this element from ground 

 feldspar becomes a matter of importance. 



The extraction of potash from rock has not as yet been ac- 

 complished on a commercial basis, but it has been done in the 

 laboratory, and the method has been published in a recent bul- 

 letin. 16 The full details of the investigation are too technical 

 for insertion here, but if the processes described could be car- 

 ried on at a cost low enough, the potash in ground rock could be 

 rendered sufficiently soluble for all practical purposes. Brief- 

 ly, the method consists in sliming the ground feldspar with 

 water to which a small quantity of hydrofluoric acid has been 

 added. This slime is placed inside a suitable wooden vessel 

 and a current of electricity is passed through it. The alkali set 

 free by the action of the acid is carried away by the electric 

 current, while the acid appears to be used over and over again. 

 Finally, by combining the acid and alkaline products, a material 

 is obtained in which the potash which has been set free is solu- 

 ble and available. 



A number of methods for extracting potash from feldspathic 

 rocks by means of fusions with various substances have 

 been devised and even patented. In all of these methods, 

 however, large quantities of by-products are formed which, 

 though made from more or less costly material, are generally of 

 no value. From laboratory investigations it would seem that the 

 use of potash compounds to attack the feldspar would in some 

 measure overcome this difficulty, since the potash used is just as 

 valuable after the process is completed as it was before. An- 

 other method, which shows some promise of success consists in 

 mixing the feldspar with lime and treating the mixture with 

 live steam under pressure. By this means the potash is made 

 easily acid soluble. It is hoped that further investigation will re- 

 sult in some method based on these principles for making the 

 vast quantities of potash contained in feldspathic rocks com- 

 pletely available." 



445. Conclusion. "A careful reading of the foregoing pages 

 will show that no claim has been made that ground feldspar is 

 an efficient substitute, under all circumstances, for potash salts. 

 16 Bui. 28, U. S. Dept. of Agriculture, Office of Public Roads. 



