REVERSIBILITY OF THE COLLOIDAL CONDITION OF SOILS 495 
TABLE 3. Avsorprion oF Metuytenr Buur (Bastc Dy) anp DIAMINE SKY-BLUE 
(Acip Dyk) By Sori-Forminc MINERALS 
(Relative intensities of solutions after adsorption shown) 
: Methylene Diamine 
Lease blue sky-biue 
Growmel ome SORE ies occ aereielas © caine seen ee eae 23.0+0.8 22.5+0.4 
Heloysibe pads Sie Ort Oki tes a oly accede. a clone anlange 355.0+4.0 40.0-40.0 
aynopiyllhitestoAts (SiOs) calms ate oe tiictilcie as. se Nase ae 46 .0-++0.0 23.0+0.8 
kaolinite 2SKOp NO pws Oseee cea sees esueesee sen sone ase. Clear 120.0+4.3 
Here lammbeplls an Alo (SIOsenr ss yal ohne Laetoli | S 27.5+0.4 26.5+0.4 
NatroliteyNasAlysisOrs2HoOl i) ca. fe eg ale de 26.5-++0.4 25.0+0.0 
SUGGS We Oa sc Fei Pas era sues REE A ae are ate etic henna 24.0-+0.8 34.0+0.0 
Hemmentitemie: Ocmene rin e  laccs a wees se ulate (meta) Ser poe 34.0-40.0 29.0+0.8 
MimmomiberAhe> Osco Om srer cS tin Pe oats OM MAket a ALS Ste 23.0+0.8 75.0+0.0 
@alciommsuitate CaSO. 2.54 snes ck 2 ah Does a 22.0+0.0 38.0+0.8 
(alcrumpcanoonate; Ca Ose st.) a sn oe yr ais 22.0+1.7 45.0+0.8 
CalciumeyhydraterCa (OM) oie 655 fy Se *16.0+1.7 Clear 
Chie oo 010 eis 45/6 S75 Seah a aie nee I Recon are ee OR 25.0 25.0 
* Purplish tinge. Difficult to read. 
~ 
It can be seen that, in general, the adsorption of methylene blue is 
greater by the acid minerals. 
Kaolinite shows the greatest adsorption 
of this dye, and acts more lke colloidal silica than does ground quartz, 
which adsorbs very little. 
With diamine sky-blue the correlation between chemical composition 
and dye adsorption is less well marked. 
most basic, is also the most adsorptive of this dye. 
than would be suspected from its composition. 
However, calcium hydrate, the 
In this case floccula- 
tion probably plays a part. Kaolinite adsorbs this dye more strongly 
It is very likely that the 
ereat amount of internal surface of this mineral overrides any chemical 
effect on adsorption. 
Rohland (1914) has pointed out that certain classes of dyes are adsorbed 
by certain kinds of soils. 
Effect of lower forms of plant life on dye adsorption.— In the course of 
the experiment some results were obtained indicating that the plant life 
which had grown in the soil was affecting the adsorption of dyes. It 
was known that certain dyes are used by plant physiologists and bac- 
teriologists in staining organisms. In order to get definite data on this 
point an experiment was run, using a fungus and an alga. That the 
possible effect of the soluble matter on the dye might be done away with, 
