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



as shown in the case of No. 6. Evidently the loss of humus and 

 its organic colloids increases, rather than decreases, the amount 

 of material finally found in suspension, for No. 5, receiving HCl 

 and NaCl treatment, yields a suspension containing less colloidal 

 material than does No. 6. In all probability the increase of 

 colloidal material in No. 6 over No. 5 is in no way connected with 

 the loss of organic matter of No. 6, but is more likely to be due 

 to the conditions and treatments involved in extracting the 

 humus. Furthermore, the organic colloids of soils seem to have 

 but little direct relation to the phenomena which appear when 

 certain salts are washed from soils. 



That the deflocculated condition of the salt-treated soils might 

 be due in some measure to the loss of calcium and magnesium 

 from the soil, in a manner somewhat analogous to that outlined 

 by Foerster.-" appeared as a secondary consideration. The actual 

 loss of calcium and magnesium, however, cannot be considered 

 the sole factor in producing the striking conditions observed. 

 For, if that were the case, the application of acids followed with 

 washing should bring about similar results. On this point War- 

 ington has already noted that normal diffusion of the colloids 

 will reappear in a soil which has once been flocculated by acids 

 when the acids and such salts as they have formed are removed 

 by washing. Our experience with soils treated in the manner 

 just described fails to show any marked increase in colloids, as 

 is the case when the soil is treated with NaCl. The treatment 

 with HCl followed by leaching with water seems to retard to a 

 notable extent the rate of percolation through the Davis soil. 

 However, if any new colloids are formed by this treatment, or if 

 the original colloidal content of the soil is thoroughly diffused 

 thereby, as the case may be, then these effects are entirely oblit- 

 erated by the subsequent drying of the soil, for a suspension of 

 the dry soil so treated yields no additional colloidal matter. This 

 fact tends to confirm the view that the loss of calcium and mag- 

 nesium is not alone responsible for the diffusion of the soils. 



Furthermore, the w^riter has shown clearly by a rather simple 

 procedure that a considerable exchange or a direct addition of 

 bases is essential for the production of the dift'used condition. 



20 Chem. Ind., vol. 28, no. 24, p. 733, 1905. 



