322 University of California Publications in Agricultural Sciences [A^ol. 1 



content of the solution is either responsible for the diffused con- 

 dition of the soil colloids, or at least is of material assistance in 

 producing this effect. 



Moreover, it has been demonstrated that the washing out of 

 the excess NaOH does not materially benefit the injured physical 

 condition of the soil, although the alkalinity of the soil solution 

 was thereby reduced to a concentration comparable with that of 

 the dilute solutions to which reference has just been made. 

 Actual determinations of the alkalinity of the final portions of 

 the percolate from soils to which XaOH has been added show 

 only such alkalinity as the percolate from the normal soil. If 

 we accept the ^aew brought forth by Cameron, '^^ which seems 

 justifiable, then the percolates from these soils approach, as a 

 limit, the chemical composition of the soil solution and hence 

 we may conclude that the alkalinity of the soil solution is of the 

 same order of magnitude as that of the percolate. The fact that 

 washing the NaOH from the soil is not accompanied by an im- 

 provement in the physical condition of the soil may be fairly 

 interpreted as substantially affirming the view that the OH-ion 

 is of little moment in the diffusion of the NaCl -|- II-.O soil, and 

 pos.sibly has but little connection with the deflocculation of soils 

 to which NaOH has been added. Furthermore, the facts just 

 discu.ssed, taken in conjunction with those considered under the 

 heading of sodium absorption, lend an appearance of reality to 

 the assumption that the sodium, even in the case of direct addi- 

 tion of NaOH to soils, is the principal agent in creating the 

 diffused condition in soils so treated. 



Moreover, the writer has found that NaHCOg, Na._,CO,. and 

 NaOH have distinctive effects on the soil colloids. In higher 

 concentrations all three salts prove to be fiocculants ; in very weak 

 concentrations, as of the order of N/2000 or less, they seem to 

 resemble distilled water in their behavior toward the soil col- 

 loids. In medium concentrations, that is, those less than 0.05 

 N, NaOH is a deflocculating agent, NagCOg acts much like dis- 

 tilled water, while NaHCO, seems to be a pronounced flocculant. 

 At lea.st the NaOH and NaoCOg yield a certain amount of 

 OH-ions, and in the wide range of concentrations employed some 



31 Eighth Intern. Cong. Appl. Chem., vol. 15-16, p. 49, 1912. 



