620 



Journal of Agricultural Research 



Vol. XX, No. 8 



It is of interest to note that in the first series of experiments the potas- 

 sium absorbed from the oxidized solute was equal to that absorbed from a 

 potassium-chlorid solution containing 5 parts per million of potassium 

 oxid. In the second series, the plants grown in the potassium-chlorid 

 solution showed relatively a marked increase in their potassium content. 



INCREASED AVAILABILITY OF POTASH IN OXIDIZED ORTHOCLASE 

 SOLUTIONS NOT DUE TO ACTION OF ACIDS ON SUSPENDED 

 COLLOIDS 



The orthoclase solutions used in the preceding experiments contained 

 some suspended colloidal material. It is therefore possible that the 

 observed increase in the availbility of the potassium may have resulted 

 from the direct action of the acids on the suspended colloids. To deter- 

 mine this point, a saturated solution of orthoclase was prepared and 

 filtered through a Pasteur-Chamberland tube. A part of this filtrate was 

 then treated with acids and evaporated to dryness, as described above, 

 and subsequently diluted to its original volume and used as a culture 

 solution. A portion of the original orthoclase solution which had not 

 received the acid treatment was used as a control. The results of two 

 experiments, made at different times, are given in Table V. 



Table V. — Effect of freeing culture solutions from colloids 



The analyses of the plants show as before a marked gain in the potas- 

 sium content of the plants grown in the acid-treated solutions. The 

 colloids can not in this case be considered the source of the potash made 

 available by the acid treatment, since the colloidal material was removed 

 from the solution before the acids were added. We are consequently led 

 to conclude that the orthoclase solutions contain potassium in true solu- 

 tion (as distinguished from colloidal suspension) and that the potassium 

 is chemically combined in such a manner that it is not available to plants. 



DISCUSSION 



The failure of wheat seedlings to absorb the potassium found by 

 analysis in orthoclase solutions suggests that the potassium is combined 

 with other elements in a slightly soluble molecular complex. This is 

 supported by the fact that the potassium may be made available by 

 treatment with strong acids, which would result from the breaking 



