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A potentiometric back‐titration method for determining sulfate in seawater and marine pore waters
Author(s) -
Mucci Alfonso
Publication year - 1991
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1991.36.2.0409
Subject(s) - potentiometric titration , seawater , chemistry , titration , sulfate , elution , chromatography , precipitation , inorganic chemistry , mercury (programming language) , environmental chemistry , electrode , geology , physics , organic chemistry , meteorology , computer science , programming language , oceanography
Sulfate concentrations can be determined accurately by potentiometric back‐titration of excess Ba 2+ with a mercury electrode following precipitation of BaSO 4 . The filtered seawater solution is eluted through a cation exchange column and the eluate reacted with excess BaCl 2 . The BaSO 4 precipitate is removed by filtration and the solution titrated potentiometrically with EGTA. The method applies over a wide range of salinities and in the presence of 0.001 M HgCl 2 which is used to inhibit bacterial activity during preservation. The oxidation of sulfides may interfere, but several remedial procedures can be adopted. The potentiometric titration and endpoint determination can be automated easily. The method determines the SO 4 2− concentration in 1 ml or less of seawater with a SD of <0.6% (28.26±0.16 mmol kg −1 seawater, n = 28).