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Buffer Curves and Acid Strength of Humic Acid and Two Resins
Author(s) -
Gilmour J. T.,
Coleman N. T.
Publication year - 1971
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/sssaj1971.03615995003500050024x
Subject(s) - chemistry , titration curve , titration , humic acid , salt (chemistry) , ion exchange , adsorption , buffer solution , buffer (optical fiber) , chromatography , nuclear chemistry , ion , inorganic chemistry , organic chemistry , fertilizer , telecommunications , computer science
Two humic acids, Cellex‐CM, and IRC‐50 were placed in 10 ‐1 , 10 ‐2 , and 10 ‐3 M NaCl or CaCl 2 and titrated potentiometrically with NaOH or Ca(OH) 2 , respectively. Titration curves of Cellex‐CM and IRC‐50 in the NaOH‐NaCl system showed parallel 1 pH unit displacements for a 10‐fold change in NaCl concentration, while humic acid showed a 0.5 pH unit displacement. Buffer curves of humic acid, Cellex‐CM, and IRC‐50 in the Ca(OH) 2 ‐CaCl 2 system showed a 0.4 pH unit displacement for a 10‐fold change in CaCl 2 concentration. The regular displacement of buffer curves led to development of a theory using ion exchange and surface ionization of H that described the buffer curves and assigned a salt independent pK a to the weak acid adsorbents.