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Conductometric and Potentiometric Titration of Exchangeable Aluminum
Author(s) -
Rich C. I.
Publication year - 1970
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1970.03615995003400010014x
Subject(s) - potentiometric titration , chemistry , titration , conductometry , inorganic chemistry , ion exchange , salt (chemistry) , hydrolysis , aluminate , adsorption , ion , organic chemistry , materials science , cement , metallurgy
Conductometric and potentiometric titrations of an AlCl 3 solution and AlCl 3 ‐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 AlCl 3 or AlCl 3 ‐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 Na 2 B 4 O 7 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.