i8o 
Journal of Agricultural Research 
Vol. I, No. 3 
to litmus and attributed this to the fact that a selective concentration 
of the dissolved substance—an adsorption of the base—had taken place. 
E. C. Sullivan 1 2 repeated these experiments and obtained the same 
result, accounting for it by an exchange of the sodium and magnesium 
of these salts in part for the iron and aluminium of the kaolin, the salts 
of the latter undergoing extensive hydrolysis in dilute solution. 
Similarly, the acidity of a salt solution after treating a soil with it is 
explained by some as a hydrolysis of aluminium and iron salts after the 
replacement by the base of the salts and by others as a selective ad¬ 
sorption of the base of the salt. 
It has been found by many experimenters that on quantitatively de¬ 
termining the replaced bases present in a salt solution after treating a 
soil, kaolin, various silicates, etc., with the solution the replaced bases are 
equivalent or very nearly equivalent, within the limits of experimental 
error, to the loss of the base of salt. 
Van Bemmelen 3 treated ioo grams of soil with 200 c. c. portions of 
solutions containing 8 and 40 mg. equivalents of potassium chlorid. 
After filtration the solutions were analyzed, and it was found that an 
almost complete exchange of potassium for sodium, calcium, and mag¬ 
nesium had taken place. Chlorin was determined in one experiment and 
had not changed. 
Sullivan 3 found that by treating kaolin and various other silicates 
with salt solutions a quantity of bases almost equivalent to the loss of 
the base from the salt was dissolved in each case. 
Wiegner 4 found that on treating an artificial amorphous water- 
containing (hydrated) so-called double silicate with a neutral salt solu¬ 
tion the cation of the neutral salt was taken in part from the solution, 
and in its place the cations of the silicate-gel in nearly equivalent amounts 
entered the solution. The anion of the neutral salt remained unchanged, 
provided secondary reaction did not take place. 
From many similar investigations with the same general result— 
namely, that the bases dissolved are very nearly equivalent to the loss 
of the base of the salt in solution—it would seem and is concluded by 
many experimenters that an exchange of bases takes place in the soil 
according to the following reaction: 
KC 1 (for example) + X n silicate,^ X n Cl + K silicate m 
From the -standpoint of fertilizer practice, however, on applying 
potassium chlorid to the soil it is very unlikely that the above reaction 
takes place and that the potassium is held in the soil as a relatively 
insoluble silicate and in a form highly unavailable for plants. 
1 Sullivan, E. C. The interaction between minerals and water solutions. U. S. Geol. Survey, Bui. 312, 
1907. 
2 Bemmelen, J. M. van. Das Absorptionsvermogen der Ackererde. Landw. Vers. Stat., Bd. 21, p. 
I 35 -I 9 I* 1877 * 
8 Sullivan, E. C. Op. cit. 
4 Wiegner, Georg. Zum Basenaustausch in der Ackererde. Jour. Eandw., Bd. 60, p. 111-1:50, 197-222, 
1912. 
