Bijdrage tot de kennis van de kationen- en anionen-adsorptie van tropische en Nederlandsche gronden

When percolating a soil with neutral or weakly alkaline normal solutions (pH about 8.3) of different acetates, the order of cation adsorption, Mg>Ca>Ba>Na, follows that of solubility of the hydroxides. However cation adsorption for NH 4 , K, Ba and Na when percolating thereafter with the chloride solutions are alike.
The above constant cation value (in m-equiv./100 g) does not change with repeated exchanges neither does it change when acid or alkaline solutions are used such as 0.05 N HCl, 0.5 N FeCl 3 , 0.5 N AICI 3 , about 0.2 N Ba(OH) 2 . Tropical soils may contain much material inactive or hardly active in cation exchange (quartz, iron-, aluminium hydroxides, silicic acid and kaolinite) which disturb the relation between total surface (particles < 2μ) and cation value.

After treating soil with HCl sp.gr. 1.035 for 0.5 h at 55°C, cation value decreases slightly but still remains proportional to the surface of the soil particles. The amount of silica in excess of (or less than) the amount of Fe 2 O 3 + Al 2 O 3 (in m- equiv.) dissolved by HQ sp.gr. 1.035 for 1 h at 55°C and the SiO 2 /Fe 2 O 3 + Al 2 O 3 ) quotient are correlated with the amount of PO4 3-which is fixed from Ca (H 2 P0 4 ) 2 solution. The amount fixed depends also on temperature, duration of the reaction and concentration of the components (soil and Ca (H 2 PO 4 ) 2 solution). Cl -and SO 42-are bound to the soil as iron and aluminium hydroxide compounds which, however, are easily hydrolyzed.