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This article in SSSAJ

  1. Vol. 34 No. 1, p. 31-38
    Received: Apr 11, 1969
    Accepted: Sept 23, 1969

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Conductometric and Potentiometric Titration of Exchangeable Aluminum1

  1. C. I. Rich2



Conductometric and potentiometric titrations of an AlCl3 solution and AlCl3-treated Dowex-50, trioctahedral vermiculite, and two montmorillonites were compared with the Al and acidity removed from these systems with neutral chloride salts. The endpoints of potentiometric titrations of AlCl3 or AlCl3-treated exchangers in neutral salt solution were lowered by these salts and adsorption of partially neutralized hydroxy-Al groups on the exchangers. Titrations of solutions to pH 8.0 gave better estimates of the acidity present than did inflection points. Hydrolysis of Al on the exchanger during exchange may produce H+ ions not originally present. Conductometric titrations with Na2B4O7 and NaOH were confounded by incomplete exchange and reaction with Al. The formation of aluminate in the titration with NaOH and Ba(OH)2 decreased the conductivity and caused “high” results. It is proposed that conductometric titrations should be continued until the change in conductivity with added base approaches that of a blank. A method for correcting for aluminate formation is proposed.

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