518 A. B. BEAUMONT 
of the soils inhibited the formation of these easily soluble compounds. 
These results agree with the appearance of the soils. 
One way to account for these effects is by bacterial activity. Some 
investigators have shown that oven-drying a soil increases the solubility 
of the organic matter but does not appreciably affect the iron compounds. 
Oven-drying does not kill all bacteria. Owing to the increased food 
in the water with the oven-dried soil, the bacteria may work more vigor- 
ously and destroy the organic matter. Thus adsorbed iron compounds 
may be liberated directly, or indirectly as products of excretion. In any 
event, more iron compounds may be brought into solution thru bacterial 
destruction of the organic matter. These may hydrolyze and form col- 
loidal ferric hydrate. : 
Ellis (1915) has observed this formation of ferric hydrate in many 
waters and has accounted for its formation by the action of special iron- 
bacteria. He admits, however, that the action is not limited strictly to 
these iron-bacteria, but that others may bring it about. It seems more 
reasonable to assume, therefore, that the part the bacteria play is in 
regard to breaking down the organic matter. This was suggested by 
Brown (quoted by Ellis, 1915). 
That the iron compound probably first appears as crystalloidal is indi- 
eated by the manner in which it usually forms in the supernatant liquid. 
Its crystalloidal character was further indicated by an experiment in 
which some of the dried soil was placed in a collodion dialyzing sack with 
some distilled water, the sack then being immersed in distilled water. 
The colloidal precipitate was later found outside the sack as well as inside. 
The assumption is that part of the iron compound must have gone thru 
the membrane as a crystalloid and later was hydrolyzed and precipitated, 
for the colloidal form will not pass thru the membrane. The identity of 
the colloidal ferric oxide outside the membrane was established by dis- 
solving it in weak hydrochloric acid and testing qualitatively. 
SUMMARY 
The experimental work here presented may be summarized as follows: 
Variations of from 5 to 10 degrees between 15° and 40° C. did not 
materially affect the adsorption of water vapor. 
The chemical composition of certain soil-forming minerals affected the 
adsorption of dyes. Acid dyes, as a rule, were more strongly adsorbed 
