Determination of Aluminum Ion Activity in Soil Extracts

Abstract

A method is presented for calculating the Al3+ ion activity from measurements of the concentration of Al, pH, and the ionic strength of the soil extract. The colorimetric method for determining the concentration of Al in soil extracts makes use of the aluminon reagent with provisions for removing organic matter and silica and for preventing the interference of Fe by the addition of thioglycollic acid.The validity of the method was established by verifying the existence of a theoretical equilibrium relationship between the Al3+ and the H+ activities in soil extracts. The value of (pH — ⅓ pAl) for CaCl2 extracts of three acid soils was found to remain remarkably constant as the concentration of CaCl2 in the extracting solution was increased from 0.001 to 0.10M. This constancy of (pH — ⅓ pAl) for soil extracts can be predicted from the Donnan and Gouy theories and does not necessarily indicate the presence in the soil of some crystalline form of hydrous aluminum oxide having a definite solubility product.

The Toxic Effect of Aluminium on Barley Plants in Relation to Ionic Composition of the Nutrient Solution

“…The relationship pH-1/3 pAl increases after lime application in both soils. Similar results were found by Lindsay et al (1959). They stated that a value of 2.75 should be expected on the basis of the solubility product of gibbsite.…”

“…A phenol disulphonic method was applied for nitrate determination and a gravimetrical method for sulphate. The aluminon method, as discribed by Lindsay et al (1959), was used for Al determinations. In this procedure the acid cation extracts from the resin were evaporated to dryness, burned at 40094C after addition of nitric acid and then taken up again in hydrochloric acid solution.…”

Soil Minerals in the Al2O3-SiO2-H2O System and a Theory of Their Formation

“…It is encouraging to note, however, that much of the rather limited aluminum hydroxide potential data on soils and sediments do fall in the range indicated in Fig. 2 (see for example Lindsay, Peech, and Clark, 1959).…”

Yellow Mottles in Some Poorly Drained Soils of the Lower Fraser Valley, British Columbia

“…Since the tubular formations and, in some cases, the yellow flecks, could be soparated from the soil, a study was The locations of the four soils used for this study are shorvn in the map in Figure 3 and detailed descriptions of the soils are given in the apdendix. "The samples for analysir t"ere selected from a_depth of 16 the ortho-phenanthroline merhod (18) and aluminium by the aluminon method (9). After separation of iron and aluminium by piecipitation with NH-OH and NHnCl, and of sulphate with an anion exchairse iesin, calcium rvas determined rvith the flame photometer.…”