318 University of California Publications in Agricultural Sciences [Vol. 1 



measiireably increase the colloidal content of the soil, nor does 

 it materially affect its physical condition. 



At least one interpretation of these facts seems plansible, 

 namely, that the nentral salts or their ions function as the creative 

 agent whereby diffusible colloidal matter is formed, while the 

 washing with water serves in the entirely separate capacity of 

 removing from the sphere of activity any flocculating agents in 

 the shape of soluble salts which may have been present. 



Certain modifications of the hypothesis just presented must be 

 considered in order to account for the action on soils of the salts 

 which give an alkaline reaction. First of all, the chemical pro- 

 ducts that can possibly be formed when the latter class of salts 

 is allowed to act upon soils are on the whole comparatively in- 

 soluble and hence possess relatively small flocculating powers. 

 Owing to this fact the washing process, which seems to be essen- 

 tial for the appearance of the diffusion in soils treated with 

 neutral salts, is. not such an important factor in case of soils 

 treated with salts giving rise to an alkaline reaction. 



Instead of attributing the detlocculation of soils which have 

 received NaOH or alkaline carbonates, wholly to the OH-ion 

 content of the solution or to the alkaline reaction so produced, 

 our present theory, supported by the facts already presented, 

 proposes to account for the diffusion of the soils so treated by the 

 formation of colloidal sodium alumino-silicate complexes under 

 conditions which permit of an immediate defiocculation. Therein 

 lies the difference in the behavior of neutral salts on soils, as 

 compared with that of salts of an alkaline reaction. In all prob- 

 ability somewhat similar compounds are formed in the two cases, 

 but in the first case, with the exception of certain circumstances, 

 the conditions are such as to prevent defiocculation, while in the 

 second case defiocculation is at least permitted and perhaps 

 accentuated. 



A Possible Relation Between the Composition of the Soil 



Solution and the Diffusion Phenomena in Certain 



Salt- Treated, Water- Washed Soils 



The first two hypotheses formulated to explain the diffused 

 condition of the salt-treated soils dealt largely with the soil itself 

 and with the absorption of sodium by the soil. A third hypothesis 



