The pK* of TRISH+ in Na-K-Mg-Ca-Cl-SO4 brines-pH scales

Frank J. Millero, J. Peter Hershey, Marino Fernandez

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56 Scopus citations


The stoichiometric dissociation constant, pK* of TRISH+ has been determined in NaCl, KCl, MgCl2 and CaCl2 solutions to an ionic strength of 6 molal. The results have been used to derive Pitzer coefficients for the interactions of TRIS with Na+, K+, Mg2+ and Ca2+ ions. These results can be used to determine the pK* of TRISH+ in mixed brines which can be used to calibrate pH electrodes. Measurements of pK* of TRISH+ in mixtures of NaCl-MgCl2, NaCl-CaCl2, NaCl-Na2SO4, KCl-MgCl2 and KCl-CaCl2, artificial seawater and Dead Sea waters were made to determine the reliability of the Pitzer coefficients. The estimated values were found to be in good agreement with the measured values provided corrections were made for the interactions of H+ with SO2-4. It now is possible to use dilute solutions of TRIS and TRISH+ to make buffers that can be used to make reproducible pH measurements in brines.

Original languageEnglish (US)
Pages (from-to)707-711
Number of pages5
JournalGeochimica et Cosmochimica Acta
Issue number3
StatePublished - Mar 1987

ASJC Scopus subject areas

  • Geochemistry and Petrology


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