520 A. B. Beaumont 
Experiments with the adsorption of diamine sky-blue showed that less 
of the dye was adsorbed than of methylene blue. The only point that 
stood out clearly, as regards moisture changes, was that ignition decreased 
the adsorption of this dye. 
Drying a soil decreased the amount of it that would go into suspension 
in distilled water and in 4-per-cent ammonium hydroxide. Drying thirty- 
two times as compared with drying one time decreased the amount of 
suspended matter. 
Extractions of humus with 4-per-cent ammonium hydroxide showed no 
effect on humus due to drying. 
Extractions with distilled water showed an increase in the solubility 
of the coloring matter of humus due to drying. 
Oven-drying soils previous to their standing in an excess of water 
increased the amount of iron soluble in weak hydrochloric acid. Ster- 
ilization checked the formation of this easily soluble colloidal material. 
Judged by the consistency of the results, the water-vapor-adsorption 
method is better than the dye-adsorption method for measuring the total 
surface of soils. ; 
GENERAL CONCLUSIONS 
Drying a surface soil once produces as much effect on the colloidal 
material as repeated dryings alternated with moistenings. 
With a subsoil there is a cumulative effect due to alternate drying and 
wetting. 
Drying a soil once or many times produces a change in the colloidal 
material from which it does not immediately recover on being wetted. 
Drying a soil affects indirectly the reversibility of its colloidal condition, 
the changes being directly produced thru biological and chemical action. 
