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THE NATIONAL GEOGRAPHIC MAGAZINE 



covering an immense area, are also rich 

 in potash. In Utah and in the Goldfield 

 district of Nevada important occur- 

 rences of alunite are reported, contain- 

 ing a possible important commercial 

 source of potash. 



The supply of potash is, therefore, 

 limitless. The trouble has been that in- 

 asmuch as the potash in these rocks is 

 not soluble, as are the potash salts, it is 

 not readily available as plant food. But 

 it is not conceivable that it will long re- 

 main an unsolved problem to the chemist 

 to extract potash from rocks on a com- 

 mercial basis. Indeed it has been done 

 in the laboratory again and again, and 

 very recently several patents have been 

 granted for processes devised for large- 

 scale operations. One method only may 

 be mentioned as showing that success is 

 practically assured in unlocking the pot- 

 ash treasure vault and thus challenging 

 German supremacy. Dr. Allerton S. 

 Cushman, late of the Department of 

 Agriculture, has perfected a process for 

 treating ground feldspar with lime and 

 other reacting substances and furnacing 

 the mixture. He has already succeeded 

 in thus rendering soluble 60 per cent of 

 the potash contained in the feldspar, 

 and expects to release the entire potash 

 content when the process is put into 

 commercial operation, using large rotary 

 kilns, such as are employed in Portland 

 cement manufacture. Working with 10 

 per cent potash feldspar, he will thus ob- 

 tain a marketable product from three to 

 four times as rich in potash as the ordi- 

 nary "complete fertilizer" used by the 

 farmer. 



Methods of releasing the potash by 

 electrical methods and others for recov- 

 ering it as a by-product in the manu- 

 facture of cement and in various other 

 ways are being worked out. In the 

 grinding and converting of. rock into ce- 

 ment, immense quantities of the potash 

 of our hillsides are now wasted which 

 might perhaps be saved. If science has 

 already solved the intricate problem of 

 converting the free nitrogen in the at- 

 mosphere into nitrate salts for fertilizer, 

 the counterpart of Chilean nitrate of 

 soda, it is not to be doubted that under 



the spur of necessity American chemists 

 will get the potash out of rocks which 

 are to be found at every hand. More- 

 over, there are vast fortunes in it for 

 the men who develop practicable proc- 

 esses. 



Doctor Cushman carried on, under the 

 Department of Agriculture, a series of 

 experiments, which indicate that the 

 simple process of pulverizing feldspar 

 makes it largely available as a plant 

 food. He matured tobacco plants, which 

 require large quantities of potash, using 

 the ground feldspar as the sole potash 

 fertilizer. If there were no better pot- 

 ash supply possible, ground feldspar or 

 granite would undoubtedly be in general 

 use as a fertilizer. It is probable that 

 further experiments along these lines 

 under various conditions will show a 

 still greater and possible practical value 

 for ground raw feldspar as a fertilizer. 



Lime and water will have a dissolving 

 effect on the potash in the fine particles 

 of the rock, and it may be shown that if 

 instead of spreading lime alone, as is 

 common farm practice, considerable 

 ground feldspar is added, the potash 

 may be released year by year, just about 

 as the plant needs it. In a similar way 

 ground rock phosphate is now used to a 

 considerable extent, although for years 

 the statement was accepted that the 

 phosphorus in rock phosphate was abso- 

 lutely unavailable as a plant food unless 

 the rock was treated with sulphuric acid. 

 But it has been shown by several of the 

 agricultural experiment stations that 

 when applied to certain kinds of soils, 

 heavy in humus, or when used in connec- 

 tion with barnyard manure, raw ground 

 phosphate has a very great fertilizing 

 value. With more extensive experi- 

 ments similar good results may be ex- 

 pected in the use of potash-rich rocks. 



In the agricultural appropriation law 

 Congress also appropriated $12,500 to 

 enable the Bureau of Soils to carry on 

 potash investigations, and with the work 

 vigorously pushed some definite results 

 will in all probability be attained. This 

 Bureau has a magnificent opportunity to 

 determine and perfect a practicable 

 method of extracting potash from rocks, 



