4 THE PHYSICAL ACTION OF LIME ON CLAY SOILS 



Penetrability. 



16. Penetration Method (Laboratory). 



17. Dynamometer Method (Field). 

 Oxidation. 



18. The Oxidation Method. 



1. The Suspension Method has been used more extensively than any 

 other. It consists essentially in making a suspension of the material in 

 the particular solution to be tested, and observing the time required for 

 precipitation. For a number of decades the suspension method was the 

 only means by which the effect of ions on the stability of colloidal ma- 

 terial could be determined. In the hands of Schulze, Bams, Picton and 

 Limler, Bodlander, and Hardy, it was of immense assistance in the form 

 ulation of the fundamentals of colloid chemistry. The specific action of 

 various salts, and the valence and mass relations, have been popular sub- 

 jects for study. The most recent work with clay suspensions has been 

 performed by Masoni, and by \VolkotT. 



Valuable as the suspension procedure has been in the preliminary 

 studies, the question nevertheless arises whether it should be considered 

 a legitimate method for correctly estimating the physical effects of salts 

 on soils. The writer is of the opinion that the precipitation of a sol by 

 an electrolyte is of little value in gauging the action of the same salt 

 applied to a soil under natural conditions. In a suspension the forces 

 inhibiting the neutralization of charges are very small, while in a heavy 

 soil the internal friction prevents the formation of the large floccules 

 characteristic of the suspension. Probably in many heavy clays the posi- 

 tively changed colloidal iron remains indefinitely in approximate con- 

 tiguity to the negative silicia without neutralization taking place. 



A somewhat similar view regarding the inapplicability of the suspen- 

 sion method is held by Free. He thinks that in the soil, the tension at 

 the liquid-vapor surface may be the determining factor in precipitation. 



2. Fraps has studied the ammonia soluble inorganic soil colloids. He 

 does not propose his method as a means by which the entire colloidal 

 content of the soil may be measured. 



3. The Van Bemmelen Method for the estimation of soil colloids con- 

 sists in the determination of the material made soluble on prolonged 

 digestion with hydrochloric and sulfuric acids. In the hands of Blanck 

 and Dobrescu, and Vander Leeden and Schneider, the Van Bemmelen 

 procedure has not yielded significant results. A serious criticism of the 

 method lies in the fact that crystalloidal as well as colloidal matter may 

 be rendered soluble. 



4. The Endosmometer Method has been used by Konig, Hasenbaumer 

 and Hassler for the determination of the absorbed ions in the soil. The 



