.'520 University of California Publications in Agricultural Sciences [Vol. 1 



under the conditions of the experiments and lience merits first 

 attention. Probably the most striking evidence of the possibility 

 that the OH-ions in the soil solution may be justly deemed the 

 cause of the diffusion of the soils with which this paper is chiefly 

 concerned, lies in the well-known defloeculating effect of dilute 

 solutions of NaOri on the soil colloids. Thus the poor tilth and 

 cultivating qualitit^s of lands impregnated with black alkali 

 (NaoCO.,) has been rather vaguely attributed to the OH-ions 

 derived from the hydrolysis of the NaoCO,. This expression fails 

 to offer any explanation of the mechanism whereby the OIT-ion 

 induces the observed effects, neither does it allow of any possible 

 effect of the Na-ion on the physical properties of the soil. How- 

 ever, if our interpretations be not too far amiss, there are several 

 reasons, not based on theoretical considerations alone, but sub- 

 stantiated by facts, for suspecting that the OH-ion is of much 

 smaller significance than the accompanying Na or other basic ion 

 in the final eff'ect of the chemical compound on the physical condi- 

 tion of the soil. 



The common conception that substances which yield an alka- 

 line reaction on hydrolysis occasion the deflocculation of the soil 

 colloids is frequently accepted without qualification, even by 

 those working with alkali soils, notwithstanding some facts now 

 extant which deny its validity. Thus, as early as 1874 Durham-" 

 pointed out that clay suspensions cleared more rapidly in strong 

 NagCOg solutions than in distilled water. Whitney and Straw'-' 

 have also .shown that NaOH in dilute solutions tends to stabilize 

 suspensions of colloidal silver, china clay, and lampblack, and 

 that emulsions of turpentine, carvene, and carvol are also acted 

 upon in a similar manner. The behavior of these substances also 

 gave evidence that the maximum .stability occurred at certain 

 concentrations of NaOH, above which flocculation was produced 

 and below which the effect of the NaOH was not so pronounced. 

 The investigations of Hall and Morison already referred to sub- 

 stantiate, in the main, the previous citations on the point under 

 discussion. Quite recently Maschhaupt-^ has found that even 



2(i Chem. News, vol. 30, do. 676, i>. 57, 1874. 



27 Journ. Amer. Chem. Soc, vol. 29, p. 325, 1907. 



28 Landw. Vers. Stat., vol. 83, p. 467, 1914. 



