Abstract
Formation constants for silver thiolates were obtained by titration of the ligand in a constant temperature, ionic strength and pH medium and measuring the potential change at a Ag2S electrode. A non-linear equation was derived from which the first and second silver formation constants, β1 and β2′, and the sulfide group acid dissociation constant, Ka′, were determined. An overall estimate of the uncertainty in the derived parameters was obtained using a Monte Carlo approach. The procedure was compared to a previous work on AgHS°. Log β1′, log β2′ and - log Ka′ results were obtained for cysteine (11.9 ± 0.5, 15.2 ± 0.4, 7.8 ± 0.1), glutathione (12.3 ± 0.3, 14.3 ± 0.8, 8.8 ± 0.3) and 3-mercaptopropanoic acid (12.0± 0.4, 14.0 ± 0.4, 10.5 ± 0.3) at 20 °C and 0.01 m ionic strength.
Similar content being viewed by others
References
Adams N. W. H. and Kramer J. R. (1998) Reactivity of Ag+ ion with thiol ligands in the presence of iron sulfide. Environ. Toxicol. Chem. 17, 625-629.
Cline J.D. (1969) Spectrophotometric determination of hydrogen sulfide in natural waters. Limnol. Oceanograph. 14, 454-458. Martell A. E. and Smith R. M. (1977) Critical Stability Constants. Vol. 3: Other Organic Ligands, Plenum Press, New York.
Morf, W. E. (1981) The Principles of Ion Selective Electrodes and of Membrane Transport, Elsevier, NY.
Morf W.E., Kahr G. and Simon W. (1974) Theoretical treatment of the selectivity and detection limit of silver compound membrane electrodes. Anal. Chem. 46, 1538-1543.
Motulsky H. J. and Ransnas L. A. (1987) Fitting curves to data using nonlinear regression: a practical and nonmathematical review. FASEB J. 1, 365-374.
Schwarzenbach G. and Widmer M. (1966) Die Löslichkeit von Metallsulfiden II. Silbersulfid [1]. Helv. Chim. Acta 49, 111-123.
Shea D. and MacCrehan W. A. (1988) Determination of hydrophilic thiols in sediment porewater using ion-pair liquid chromatography coupled to electrochemical detection. Anal. Chem. 60, 1449-1454.
Smith R. M. and Martell A. E. (1997) NIST Critically selected stability constants of metal constants databases. NIST Database 46, vers. 3.0, Std. Ref. Pgm., Gaithersburg, MD 20899.
Stumm, Werner, and Morgan, James J. (1996) Aquatic Chemistry. 3rd Ed., Wiley Interscience.
Tseng P. K. C. and Gutnecht W. F. (1975) Direct potentiometric measurement of several thiols. Anal. Chem. 47, 2316-2319.
Tunaboylu K. and Schwarzenbach G. (1971) Silbermercaptide und-mercaptokomplexe. Helv. Chim. Acta 54, 2166-2185.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Adams, N.W.H., Kramer, J.R. Potentiometric Determination of Silver Thiolate Formation Constants Using a Ag2S Electrode. Aquatic Geochemistry 5, 1–11 (1999). https://doi.org/10.1023/A:1009699617808
Issue Date:
DOI: https://doi.org/10.1023/A:1009699617808