I? 



vations have been made on the retentive and solvent powers of 

 some organic soils, but in most cases the work was designed for 

 the investigation of other problems. 



Fleischer and Kissling 1 , in a study of the action of moorland 

 soils on insoluble phosphates, found that the effect was to render 

 a portion of the phosphate soluble in water, amounting in one 

 case to 5.5 per cent of the total. At the same time a portion was 

 reduced to the di-calcium salt, and in one compost as much as 17 

 per cent of the total was brought into this form. When the ratio 

 of soil to phosphate was widened, there was an increase in soluble 

 salt. This increase varied directly with the time of contact. 

 There appeared to be a limit beyond which the soluble salt became 

 reduced. 



In 1892 Berthelot and Andre 2 made some experiments on the 

 absorption of phosphoric acid by artificial humic anhydride pre- 

 pared from sugar. Solutions of phosphates of sodium and am- 

 monium were mixed with the acid anhydride and allowed to 

 stand in the cold for twenty-four hours. The absorption from 

 these salts were very small. In most cases practically no phos- 

 phoric acid was retained. 



The action of humic acid in the soils on the solubility of 

 various natural phosphates was taken up by Minssen and Tacke 3 . 

 Many of the insoluble phosphates were acted on in the presence 

 of the free humic acid of the soil. When lime was added the 

 acid was neutralized and the solvent power thereby largely 

 destroyed. The quantity of phosphoric acid dissolved increased 

 with an increase in the quantity of free humic acid present. The 

 numerical agreement, however, was affected by the reabsorption 

 of the phosphoric acid made soluble. 



Snyder 4 prepared humus by mixing soil with such sub- 

 stances as clover, flour, straw, saw dust, and sugar, and allowing 

 to ferment for a year. At the end of that time the humus pro- 

 duced contained more phosphoric acid than was originally present 

 in the humus- forming material, indicating that some of the phos- 

 phoric acid of the soil had united with the humus. By ' 'humus' r 



1 Bied. Centr., 1883, 155. 



2 Ann. Chim. Phys., 27, 196. 



3 L,andw. Jahrb., 1898, IV, 392. 



4 Minn. Agr. Expt. Sta. Bull., No. 53. 



