jan is, 1921 Concentration of Potassium in Orthoclase Solutions 619 



SOLUBLE POTASSIUM IN ORTHOCLASE SOLUTIONS IS MADE AVAIL- 

 ABLE BY OXIDATION WITH ACIDS 



To determine whether the soluble potassium in orthoclase could be 

 available by oxidation with acids, the following experiment was car- 

 ried out. 



Finely ground orthoclase was added to about 100 liters of water, and 

 this mixture was shaken at intervals until equilibrium was established 

 and the maximum solubility of the potassium in the feldspar had been 

 obtained. 



One-half of this solution was filtered through a padded folded paper 

 filter, and the clear solution, together with a few cubic centimeters of a 

 mixture of hydrochloric and nitric acids, was then evaporated to dryness 

 in Jena beakers. The excess of acids was driven off, and the solution 

 was brought back to volume with purified distilled water. A little cal- 

 cium carbonate (CaC0 3 ) was then added to insure alkalinity. Wheat 

 seedlings were grown in such cultures for 14 days, the solutions being 

 changed daily. The results are given in Table IV, series a. 



Table IV. — Effect of oxidation of soluble potassium in orthoclase on its availability 



Culture 

 No. 



ia 

 2a 

 3a 



4 a 

 ib 

 2b 

 3b 



4b 



Culture solution. 



Control 



Orthoclase (solid phase present) 

 Orthoclase solution filtered and 



evaporated with acids 



KC1 



Control 



Orthoclase (solid phase present) 

 Orthoclase solution filtered and 



evaporated with acids 



KC1 



K 2 in- 

 crease over 

 control. 



+ 7 



+ 121 

 +90 



o 

 + 11 



+ 76 



The wheat seedlings grown in orthoclase solutions in which the potas- 

 sium compounds had been oxidized showed a total potash content at 

 the end of the experiment about twice that of the plants grown in dis- 

 tilled water. On the other hand, the plants grown in the untreated 

 orthoclase solution showed as before no gain in potash over the control. 



A repetition of the experiment, Table IV, series 6, again showed a 

 marked increase in the potash content of the plants grown in the solu- 

 tions prepared from the oxidized solute. The orthoclase solution used 

 in this series of experiments had stood in contact with the powdered 

 mineral for about 2 months, being shaken at frequent intervals. The 

 experiment extended over 19 days, the culture solutions being changed 

 daily. 



17776°— 21 3 



