308 University of California Publications in Agricultural Sciences [Vol. I 



diflPiision of the colloids, or to a change in the nature of the 

 colloid. However, the fact is patent that more NaCl, or a 

 greater length of time for equal quantities of NaCl, is required 

 to produce effects on the NaCl + IIoO soil commensurate with 

 those on the check HoO soil. Table III shows clearly the relative 

 effectiveness of varying concentrations of NaCl in flocculating 

 the colloidal matter as measured by the time required for clearing 

 the suspension. Thus N/100 NaCl flocculates the colloidal matter 

 of the washed soil in one hour, while 360 hours were required to 

 accomplish the same result with the NaCl + H^O soil. Never- 

 theless, the colloidal matter of the NaCl + IT.,0 soil seems to be 

 more readily flocculated per unit of NaCl than does that of the 

 H.O soil, as is shown in Table IV. Thus the NaCl + U,0 soil, 

 when suspended in distilled water, yields a suspension containing 

 0.8345 grs. of solid matter, while the .same soil suspended in N/250 

 NaCl yields but 0.4570 grs. of solid matter. The deposition of 

 0.3775 grs. of solid matter, in this case, was brought about by 

 0.058 grs. of NaCl, or at the rate of 6.5 mgs. of solid matter to 

 1 mg. of NaCl. Similar calculations for the same suspensions 

 of HoO soil showed that but 0.14 mgs. of suspended matter was 

 flocculated per mg. of NaCl. Although the NaCl is relatively 

 more effective on the suspended matter of the NaCl -4- H^O soil 

 than on that of the control soil, yet, in but one instance, that of 

 the comparatively strong solution of N/50 NaCl, is the influence 

 of the added salt sufficient to flocculate completely the colloidal 

 matter of the NaCl + HoO soil. 



Furthermore, it .seemed possible that the transformations 

 manifestly occurring in the physical condition of the soil might 

 also be reflected in some measure in the chemical composition of 

 the variously treated soils and of their colloidal substances. Ac- 

 cordingly these materials were subjected to analysis by the strong 

 hydrochloric-acid digestion method, as recommended by Hilgard 

 for chemical soil studies. However, the results secured up to 

 the present time have not confirmed the above presumption. But 

 to what extent future analytical work will enable us to decipher 

 the relationship of the various factors involved in producing the 

 condition under consideration, is still an open question. 



