ABSOKPTION OF SALTS BY SOILS. 



137 



OBSERVATIONS OF VOELCKER. 



Voelcker studied the absorption of soluble phosphates of five 

 soils, using the super-phosphate, containing 37.20 per cent, of 

 bone-earth, rendered soluble by acids; and the results obtained 

 "by him are brought together in the next table, where the ratio 

 of water to soil, time of contact of the soil with the solution, 

 the amounts of phosphoric acid absorbed, and left in the solu- 

 tion are given. 



In the last' two columns of the table there are also given the 

 amounts of soluble phosphate the soil would contain if charged 

 with 20 per cent, and 10 per cent, of the solutions after absorp- 

 tion had taken place, the amounts being expressed in parts per 

 million of the dry soil. 



Amounts of soluble phosphates absorbed by five soils. 



It is seen from this table that, between the five soils treated, 

 there is a clear and well marked difference in their powers of 

 holding back the phosphoric acid, the calcareous soil exceeding 

 all of the others in this rspect, both in absolute amount ab- 

 sorbed and in the rate of absorption. 



These differences s are 



*Journal Royal Agricultural Society, Volume XXIV, pp. 37-64. 



