ABSORPTION OF SALTS BY SOILS. 149 



Both potash and magnesia were absorbed and the potash in 

 largest amounts, as was to be expected ; but, after 24 hours, the 

 surface foot gave back to the solution again large amounts of 

 both bases. 



While the indicated absorption of chlorine is small, compared 

 with other things, we believe it is too large to be set aside as due 

 to errors of method and irregularities in manipulation. 



ABSORPTION OF SALTS BY WASHED SAND. 



A quantity of a rather coarse, white sand, composed chiefly of 

 quartz grains, was subjected to thorough washing under the 

 hydrant during 12 hours, after which it was dried at 110 C, 

 and then three times washed in distilled water with drying be- 

 tween each washing, after draining away all the water which 

 would readily pass off. Samples of this sand were treated in 

 the same manner as the Hagerstown Loam had been treated and 

 with the same solutions, using five times the weight of the sand 

 in each trial. The digestion was done in duplicate, two samples 

 remaining in contact with the solution 24 hours and the other 

 two during 72 hours. 



In order that the conditions under which the sand was placed 

 might be as nearly identical with those of the soil as .possible, 4 

 grains of the carbon black used in rendering solutions colorless 

 were also added to the sand. At the same time two blanks with 

 the carbon black alone in the same solution were run, but in 

 neither of these was there any indication of absorption. 



The results secured from the sand appear in the next table. 



