Oct. 16, 1916 
Acidity and Adsorption in Soils 
133 
A study of the foregoing data makes it evident that in all cases there 
has been a distinct increase in the H-ion concentration, when either 
potassium chlorid, sodium chlorid, or barium chlorid was added to the 
suspension in the quantities indicated. The increase does not vary 
greatly for the three salts used, but on the whole the barium chlorid has 
a somewhat greater effect. In soil 14 we have an interesting case in 
which a change of reaction from alkaline to acid has taken place, as a 
result of the addition of neutral salts of sodium, potassium, or barium. 
It is obvious that such a soil would probably be adjudged acid by the 
potassium-nitrate method, although its normal reaction is, in fact, 
slightly alkaline. In a more normal type of soil (No. i), however, 
no change in the reaction is found. The use of calcium chlorid in the 
above experiment was found to be impracticable on account of the 
difficulty in obtaining a perfectly neutral salt. 
ADSORPTION OF OH IONS BY SOILS IN SUSPENSIONS OF VARIOUS 
BASES 
So far the H-ion concentration of soil suspensions, the factors affect¬ 
ing it, and the possible use of an electrometric titration method for 
determining the lime requirement have been the chief topics considered. 
We shall now consider another phase of the general problem, involving 
the question of the adsorption of OH ions by the soil. The hydrogen 
electrode has proved useful for this purpose. 
Changes of the OH-ion concentration of soil suspensions were measured 
when varying quantities of different hydrates were added. In addition 
the removal of Ca from a solution of hydrate in contact with two of the 
soils studied was noted. The data obtained from these experiments are 
incorporated in Tables VIII and IX. 
To suspensions of soils that pass through a 200-mesh sieve the hydrates 
were added, a small portion at a time, until the neutral point was just 
passed; then further additions of hydrate were made until an arbitrarily 
selected OH-ion concentration was maintained over a considerable 
period of time, as noted in Table VIII. After each addition of the 
hydrate the soil suspension was given a prolonged shaking. The bases 
added have been calculated for convenience of comparison to the equiva¬ 
lent OH expressed in grams. The above data enable us to estimate the 
approximate quantity of OH ions removed from the solution by the soil, 
and in two cases where calcium hydroxid was added the removal of Ca 
has also been determined by the usual analytical method. 
