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Soil Science Society of America Journal Abstract -

Field Estimation of Amorphous Aluminum with 4M Potassium Hydroxide1


This article in SSSAJ

  1. Vol. 48 No. 6, p. 1378-1382
    Received: Dec 16, 1983
    Accepted: June 27, 1984

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  1. G. G. S. Holmgren and
  2. J. M. Kimble2



A procedure is described that provides the field scientist with a rapid, quantitative measure of a form of amorphous Al characteristic of Spodosols and Andepts. The proposed procedure is as follows: React 0.2 g of soil for 10 min with 2 mL of 4M KOH. Dilute to 20 mL and neutralize with HCl to a phenolphthalein end point. Add 2 mL of 1M KF and re-titrate the suspension to the same end point with drop count additions of 0.1M HCl. Studies of the procedures' sensitivity to reagent concentration, soil/solution ratio and time are presented. Evidence is also presented to demonstrate that this method does not extract Al from crystalline clay minerals. KOH extractable Al values compare well with acid ammonium oxalate extractable Al for amounts 20 g kg−1(2%). Above this, ammonium oxalate Al generally exceeds KOH aluminum by an amount equivalent to the silica extracted by ammonium oxalate.

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