1916] Sharj) : Soluble Salts and Soil Colloids 321 



0.015 N NaOH has a flocculating effect on the colloidal matter 

 of a sandy loam soil, while more dilute solutions of NaOTI stabil- 

 ized the difPusible colloidal matter. He further asserts that alkali 

 carbonates act much in the same manner. Despite the preceding 

 evidence, Rohland-" still contends that the flocculation of clay 

 soils by lime is due to the OH-ion. 



"While working along similar lines, the author has noted that 

 a suspension of the Davis clay loam settles out more rapidly in 

 a 0.05 N solution of NaOII than in distilled water, but that solu- 

 tions of greater dilution were stabilizing in their effects. On the 

 other hand, no solution of NaoCOj^*' proved effective as a stabiliz- 

 ing agent as compared with distilled water, while solutions of 

 NasCOy stronger than 0.022 N had a decided flocculating effect. 

 This difference in the behavior of NaOH and Na.COg has not come 

 to the writer's attention before in the literature of the subject, 

 and fails to support the widespread teaching that NaoCOg and 

 salts which hydrolize similarly deflocculate the soil colloids 

 through the agency of the OH-ion. But the most striking fea- 

 ture of the action of NaOH on the soil suspension was the marked 

 resemblance of the soils suspended in that medium to the 

 NaCl -f- H„0 soil suspended in distilled water. The yield of 

 suspended matter from these two suspensions proved to be of 

 about the same magnitude, as shown in Table II. A cursory con- 

 sideration of this fact obviously supports the contention that the 

 OH-ion content, or the alkalinity of the suspending solution, may 

 be responsible for the diffusion of the soil colloids in the cases 

 under consideration. However, an interesting point to the con- 

 trary lies in the fact that suspensions of the Davis soil in very 

 dilute solutions of NaOH can not be distinguished from sus- 

 pensions of the same soil in distilled water. That is to say, NaOH 

 solutions of a concentration of N/1500 to N/2000 exercised no 

 recognizable effect on the soil colloids. The concentrations here 

 referred to approach the same order of alkalinity as that found 

 in the solution bathing the particles of the highly diffused 

 NaCl -|- H.O soil. Evidently some other factor than the OH-ion 



29 Land w. Jahrb., vol. 44, no. 3, p. 437, 1913; and Landw. Vers. Stat., 

 vol. 85, nos. 1-2, p. 123, 1914. 



30 Baker's analyzed NaoCOg was used in these experiments except where 

 otherwise noted. 



