CHEMICAL CHANGES 237 



Soil Absorptive power 1 



Norfolk sand 4.0 



Tarboro sand 9.8 



Norfolk fine sandy loam 10.7 



Durham sandy loam 17.5 



Porters red clay 17.8 



Cecil clay 18. 7 



Porters black loam 27.5 



The black loam in question appeared to be rich in organic mat- 

 ter. With 100 grams soil to 100 cc. solution containing 0.4283 

 gram potash or 0.3032 gram phosphoric acid, respectively, Bieder- 

 mann observed a variation in absorptive power from 6.0 to 58.7 

 per cent, for potash, and 3.1 to 82.2 for phosphoric acid in 22 soils. 



(3) The Concentration of the Solution. If the ratio of soil to 

 solution is kept constant, the stronger the solution of salt used, 

 the greater the total amount absorbed, but at the same time the 

 percentage is less. That is, the amount absorbed does not increase 

 to the same extent as the concentration of the solution. The fol- 

 lowing table illustrates this point : 



ABSORPTION 2 OF POTASH FROM POTASSIUM SULPHATE. 



(4) Effect of Temperature. Increase of temperature some- 

 times increases absorption of potash but it always increases that 

 of phosphoric acid, according to Biedermann. In the experiment 

 50 grams soil was used and 100 cc. solution containing 0.3032 gram 



P.O.- 



1 Withers and Fraps, North Carolina Report, 1902-3. 



2 Bretschneider, Jahresber, f. Agr. Chem., 1865, p. 19. 



