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Guidelines for Potentiometric Measurements in Suspensions

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Chemistry International -- Newsmagazine for IUPAC
From the journal Chemistry International -- Newsmagazine for IUPAC Volume 29 Issue 4

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Making an imPACt|Recent IUPAC technical reports and recommendations that affect the many fields of pure and applied chemistry.

See also www.iupac.org/publications/pac

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Guidelines for Potentiometric Measurements in Suspensions

Srecko F. Oman, M. Filomena Camões, Kipton J. Powell, Raj Rajagopalan, and Petra Spitzer

Part A. The Suspension Effect (IUPAC Technical Report)

Pure and Applied Chemistry

Vol. 79, No. 1, pp. 67–79, 2007

doi:10.1351/pac200779010067

Part B. Guidelines for Practical pH Measurements in Soil Suspensions (IUPAC Recommendations 2006)

Pure and Applied Chemistry

Vol. 79, No. 1, pp. 81–86, 2007

doi:10.1351/pac200779010081

An explanation of the origin and interpretation of the suspension effect (SE) is presented in accordance with “pH Measurement: IUPAC Recommendations 2002” [Pure Appl. Chem.74, 2169 (2002)]. It is based on an analysis of detailed schemes of suspension potentiometric cells and confirmed with experimental results. Historically, the term “suspension effect” evolved during attempts to determine electrochemically the thermodynamically defined activity of H+ (aq) in suspensions. The experimental SE arises also in determining other pIon values, analogous to pH values.

The SE relates to the observation that for the potential generated when a pair of electrodes (e.g., reference electrode (RE) and glass electrode) is placed in a suspension, the measured cell voltage is different from that measured when they are both placed in the separate equilibrium solution (eqs). The SE is defined here as the sum of (1) the difference between the mixed potential of the indicator electrode (IE) in a suspension and the IE potential placed in the separated eqs; and (2) the anomalous liquid junction potential of the RE placed in the suspension. It is not the consequence of a boundary potential between the sediment and its eqs in the suspension potentiometric cells as is stated in the current definition of the SE.

Within Part A the measured cell potentials for suspension potentiometric cells are interpreted and explained in detail. With some former disagreements among investigations clarified, a new unambiguous operational definition of the SE is presented in Part B. It is defined as the difference in cell potential for two suspension potentiometric cells, one with both electrodes in the separated eqs and the other with both electrodes in the sediment or suspension. This potential difference is the sum of the change in the IE potential and the change in the liquid junction potential of the RE, when the electrodes are used for measurement, once in the sediment of the suspension and then in its eqs.

www.iupac.org/publications/pac/2007/7901/7901x0067.html

www.iupac.org/publications/pac/2007/7901/7901x0081.html

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Page last modified 10 July 2007.

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Published Online: 2009-09-01
Published in Print: 2007-07

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https://doi.org/10.1515/ci.2007.29.4.27b

Articles in the same Issue

  1. Masthead
  2. From the Editor
  3. Contents
  4. Streamlining IUPAC Operations
  5. Mendeleev’s Triumph
  6. Where Does Chemistry Fit?
  7. A Three-Point Primer
  8. The Eurobachelor: An Update
  9. Adjustment, Estimation, and Uses of Equilibrium Reaction Constants in Aqueous Solution
  10. Resolving Ambiguous Naming for an Ionic Liquid Anion
  11. 2007 IUPAC Prizes for Young Chemists
  12. Election of IUPAC Officers
  13. Highlights of the Executive Committee Meeting
  14. ChemZoo Announces the Release of the ChemSpider Service
  15. Young Ambassadors for Chemistry in Grahamstown, South Africa
  16. Principles of Chemical Nomenclature
  17. Metal-Focussed –omics: Guidelines for Terminology and Critical Evaluation of Analytical Approaches
  18. Altered Crop Protection Agent Residues in Transgenic Crops
  19. Provisional Recommendations
  20. Glossary of Terms Used in Photochemistry, 3rd edition (IUPAC Recommendations 2006)
  21. Chemical Speciation of Environmentally Significant Metals with Inorganic Ligands Part 2: The Cu2+-OH-, Cl-, CO32-, SO42-, and PO4 3- Systems (IUPAC Technical Report)
  22. Properties and Units in the Clinical Laboratory Sciences Part XX. Properties and Units in Clinical and Environmental Human Toxicology (IUPAC Technical Report)
  23. Guidelines for Potentiometric Measurements in Suspensions
  24. PAC is CrossRef Enabled
  25. Natural Products and Biodiversity
  26. Advanced Polymers for Emerging Technologies
  27. Thermodynamics, Solubility and Environmental Issues
  28. Chemistry for Water–CHEMRAWN XV Perspectives and Recommendations
  29. Coordination Chemistry
  30. Polymers for Advanced Applications
  31. Advanced Materials and Polymer Characterization
  32. OPCW Academic Forum
  33. Pharmaceutical Chemistry
  34. FTIR Applied to Biological Systems
  35. ISRANALYTICA 2008
  36. Mark Your Calendar
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