392 EK. P. Deatrick 
The soils treated with calcium hydroxide precipitated more manganese 
than did the untreated soils. In the case of soil C, one liter of the solution 
was passed thru it before any appreciable amount of manganese appeared 
in the percolate. On air-drying these soils, C and D were found to have 
an intensive oxidizing power as compared with A and B. 
Soils treated with 1000 parts per million of manganese in the form of 
pulverized pyrolusite were found not to have a strong oxidizing power. 
A solution of aloin, however, is rapidly oxidized when some of the pyrolusite 
is added toit. Colloidal manganese dioxide (from potassium permanganate 
and hydrochloric acid, purified by decantation) oxidizes aloin immediately. 
These phenomena, added to the fact that soils C and D developed the 
oxidizing power immediately in the presence of calcium, have led the 
writer to believe that the oxidation in soils due to manganese is due to 
the presence of manganese dioxide. In a solution of a manganese salt, 
manganic hydroxide is readily formed on the addition of an alkali. The 
formation of the oxide in soil to which a soluble manganese salt has been 
added, is directly proportional to the lime content, that is, the basicity 
of the soil. In the absence of an excess of an alkali form of calcium, 
the formation of the oxide of manganese is slower, for the stability of the 
soluble salts, as the sulfate and the chloride, is of course greatest in an 
acid solution. The salts of the weak acids, however, are not so stable, 
and when adsorption phenomena play a part, the salts are unstable even 
in neutral media. Thus, if pure, fine sand is treated with a solution of 
manganese citrate, this instability is soon demonstrated by the browning 
of the sand. This has been found to be the case with sand so treated 
and stored in a jar. On exposure to air, sand treated with the acetate 
and the citrate has developed a shght brown color. 
Schreiner, Sullivan, and Reid (1910) apparently tested their soils 
immediately after adding the manganese salts. These soils were prob- 
ably deficient in lime, and therefore the addition of manganese did not 
increase oxidation. The increase noted when hydroxy acids were added 
to these soils may have been due to the formation of the organic salt of 
manganese and the subsequent precipitation of the oxide from the less 
stable salt. 
The formation of the dioxide, and the oxidation phenomena in soils 
as described, are analogous to the formation of calcium manganite (CaO. 
