BULLETIN OF THE 
No. 143 
Contribution from the Bureau of Soils, Milton Whitney, Chief 
November 13, 1914. 
PROFESSIONAL PAPER. 
THE PRODUCTION AND FERTILIZER VALUE OF CIT- 
RIC-SOLUBLE PHOSPHORIC ACID AND POTASH. 
By Wm. H. Waggaman, 
Scientist in Investigation of Fertilizer Resources. 
INTRODUCTION. 
The extraction of potash from silicate rocks or the rendering of 
this alkali soluble in water has been and probably will continue to be 
for a long time the object of numerous investigations. 
Ross 1 has investigated many of these processes and discussed 
several in some detail. For convenience he divides them into three 
classes, as follows: (1) Processes which yield potash as the only 
product of value; (2) processes which yield potash and some other 
salable material as a by-product; (3) processes in which two or more 
operations are combined in one, yielding a fertilizer containing two 
or more of the constituents, potash, phosphoric acid, and nitrogen. 
He describes two methods for obtaining potash from feldspar by 
treating mixtures of that mineral and lime, collecting the potash 
thus liberated, and using the residue for the manufacture of cement. 
The potash obtained by these processes, however, is in the form of 
oxide or hydroxide, and is therefore more valuable for other purposes 
than for the manufacture of fertilizers. Ross also tried heating 
together feldspar and lime with the addition of phosphate rock, but 
found that the latter substance did not enter into the reaction, there 
being no increase in the quantity of potash thus obtained over that 
produced by the ignition of feldspar and lime alone. 
The production in a single operation of available phosphoric acid 
and potash from insoluble minerals, however, presents possibilities 
which are particularly attractive, and several processes have been 
devised to accomplish this end. It is the purpose of this paper first 
to discuss these existing methods and then to describe a process 
1 Jour, of Ind. and Eng. Chem., 5, No. 9, pp. 725-729 (1913). 
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