1916] Sharp: Soluble Salts and Soil Colloids 313 



TABLE VI 



The Effect of Eemoving Humus from the Soil in its Eelation to the 

 Diffusion Appearing in the Soil After Salt and 

 Water Treatments 



No. Soil 



1 25 grs. (Davis soil) 



2 25 grs. (Davis soil) 



4 25 grs. (Davis soil) 



5 25 grs. (Davis soil) 



6 25 grs. (Davis soil) 



7 25 grs. (Davis soil) 



* The symbols used herein designate the soil treatments on the filter paper 

 with the various substances; as indicated, HjO applications were generally made 

 between applications of the other materials. Solutions approximating normal 

 strength were generally employed. 



pension above the deposited material was drawn oif. An aliquot 

 of this suspension was evaporated to dryness, gently ignited, and 

 weighed to obtain the data of column 4, in Table VI. 



The weight of the suspended matter secured from suspen.sions 

 of Davis soil which had been subjected to the various treatments 

 gives an index of the extent of the physical effects of such treat- 

 ments. The treatment with IICl, followed by Avashing until the 

 filtrate was practically free from chlorides, seemed to reduce the 

 quantity of material capable of being held in suspension, yet the 

 soil had no doubt lost a considerable quantity of its original 

 calcium and magnesium content. This fact certainly indicates 

 that the loss of calcium and magnesium from the soil bears but 

 little relation to the diffusion of the soils as a general proposition. 



The soil treatment in the case of No. 4. which simulates the 

 procedure generally employed in humus determinations, with 

 the exception that water is used as a final application, gives a 

 suspension slightly richer in solids than the soil treated with 

 water alone. If, in addition to the treatment just mentioned, 

 NaCl is then added to the humus free soil,^"' the suspension be- 

 comes a very turbid liquid rich in solids in a highly diffused state. 



19 The term humus here signifies that portion of the soil's organic 

 matter removed by the treatment in vogue for that purpose. 



