Monatshefte für Chemie / Chemical Monthly

, Volume 126, Issue 8–9, pp 819–837 | Cite as

The ionic product of water in highly concentrated aqueous electrolyte solutions

  • I. Kron
  • S. L. Marshall
  • P. M. May
  • G. Hefter
  • E. Königsberger
Anorganische Und Physikalische Chemie


The ionic product of water,\(K_w = [H^ + ][OH^ - ] = 10^{ - pK_w } \), has been determined in aqueous NaCl (0.5–5.0M), KCl (3.0M), NaNO3 (3.0 and 5.0M), and KNO3 (2.5M) at 25 °C from high-precision potentiometric titrations carried out in cells with liquid junction using either glass or hydrogen electrodes. Measurements ofKw provide a set of self-consistent data that can be used in the estimation of activity coefficient changes and liquid junction potentials in the study of extremely concentrated electrolyte solutions. Where comparison is possible, results obtained by hydrogen electrode measurements are in excellent agreement (ca ± 0.005 inpKw) with other reliable experimental values and the predictions of thePitzer activity-coefficient model. The glass electrode results are, as expected, routinely lower (by 0.03–0.05pKw units), owing to interference by Na+ ions. This effect virtually disappears in solutions of potassium salts. Comparison of the experimental results with thePitzer predictions shows that knowledge of the ternary interaction parameters is essential to account for specific ionic effects in the concentration dependence ofpKw.


Aqueous electrolyte solutions Glass electrode Hydrogen electrode Ionic product of water Pitzer model Potentiometric titration 

Das Ionenprodukt des Wassers in hochkonzentrierten wäßrigen Elektrolytlösungen


Das Ionenprodukt des Wassers,\(K_w = [H^ + ][OH^ - ] = 10^{ - pK_w } \), wurde in wässerigen Lösungen von NaCl (0.5–5.0M), KCl (3.0M), NaNO3 (3.0 and 5.0M) und KNO3 (2.5M) bei 25 °C gemessen. Dazu wurden potentiometrische Titrationen unter Verwendung von Glas- oder Wasserstoffelektroden in Zellen mit Überführung durchgeführt. Mit diesenpKw-Werten kann man Änderungen der Aktivitätskoeffizienten in hochkonzentrierten Elektrolytlösungen ermitteln sowie Diffusionspotentiale abschätzen. Die mit Wasserstoffelektroden erhaltenenpKw-Werte stimmen mit verläßlichen Literaturdaten innerhalb vonca. ± 0.005 überein. Bei Messungen mit Glaselektroden führt der Na+-Fehler zu um 0.03–0.05 kleinerenpKw-Werten. Dieser Effekt wurde in Kaliumsalzlösungen nicht beobachtet. Der Vergleich der experimentellen Resultate mit Voraussagen desPitzer-Modells unterstreicht die Bedeutung ternärer Wechselwirkungsparameter für die exakte Berechnung des Ionenproduktes.


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  1. [1]
    Harned HS, Hamer WJ (1933) The ionization constant of water and the dissociation of water in potassium chloride solutions from electromotive forces of cells without liquid junctions. J Am Chem Soc55: 2194–2205Google Scholar
  2. [2]
    Harned HS, Copson HR (1933) The dissociation of water in lithium chloride solutions. J Am Chem Soc55: 2206–2215Google Scholar
  3. [3]
    Harned HS, Mannweiler GE (1935) The thermodynamics of ionized water in sodium chloride solutions. J. Am Chem Soc57: 1873–1877Google Scholar
  4. [4]
    Carpéni G, Boitard E, Pilard R, Poize S, Sabiani N (1973) Sur la détermination potentiometrique des concentrations des ions H+ et du produit ionique d'un solvant donné. J Chim Phys69: 1445–1447Google Scholar
  5. [5]
    Fischer R, Byé J (1964) Étude de l'influence des sels de fond sur le produit ionique apparent de l'eau et la constante apparente de la deuxième alcalinité de l'éthylène diamine. Bull Soc Chim Fr: 2920–2929Google Scholar
  6. [6]
    Jameson RF, Wilson MF (1972) Apparent molar ionic products of water in potassium nitrate solutions and calibration of the glass electrode as a wide-range proton concentration probe. J Chem Soc Dalton Trans: 2607–2610Google Scholar
  7. [7]
    Eilbeck WJ, Holmes F, Phillips GC, Underhill AE (1967) Heterocyclic chelating agents. 1. Metal complexes of 4,2′-pyrimidylimidazole. J Chem Soc (A): 1161–1166Google Scholar
  8. [8]
    Näsänen R, Meriläinen P (1960) Potentiometric determination of the solubility product of silver (I) oxide in potassium nitrate and sodium perchlorate solutions. Suomen KemB33: 197–199Google Scholar
  9. [9]
    Dyrssen D, Hansson I (1972) Ionic medium effects in sea water — a comparison of acidity constants of carbonic acid and boric acid in sodium chloride and sea water. Marine Chem1: 137–149Google Scholar
  10. [10]
    Näsänen R, Meriläinen P (1960) Thermodynamic properties of lead hydroxide iodide Pb(OH) I. Suomen KemB33: 149–151Google Scholar
  11. [11]
    Ferse A (1965) Die mittleren Aktivitätskoeffizienten von NaOH in NaCl-Lösungen. Z Phys Chem (Leipzig)229: 51–57Google Scholar
  12. [12]
    Sjöberg S, Hägglund Y, Nordin A, Ingri N (1983) Equilibrium and structural studies of silicon (IV) and aluminium (III) in aqueous solution. Marine Chem13: 35–44Google Scholar
  13. [13]
    Santschi PH, Schindler PW (1974) Complex formation in the ternary systems Ca(II)-H4SiO4-H2O and Mg(II)-H4SiO4-H2O. J Chem Soc Dalton Trans: 181–184Google Scholar
  14. [14]
    Ingri N, Lagerstrom G, Frydman M, Sillén L-G (1957) Equilibrium studies of polyanions. II. Polyborates in sodium perchlorate medium. Acta Chem Scand11: 1034–48.Google Scholar
  15. [15]
    Carell B, Olin Å (1960) Studies on the hydrolysis of metal ions. 31. The complex formation between Pb2+ and OH in Na+ (OH, ClO4) medium. Acta Chem Scand14: 1999–2008Google Scholar
  16. [16]
    Burkov KA, Bus'ko EA, Zinevich NI (1975) Determination of the water ionization product in solutions with high ionic strength at 0–60 degrees. Vestn Leningr Univ Fiz Khim (1): 144–145Google Scholar
  17. [17]
    Hugel R (1965) Etude de l'hydrolyse de l'ion Pb2+ dans les solutions de nitrate de sodium. Bull Soc Chim Fr: 968–971Google Scholar
  18. [18]
    Ågren A (1955) The complex formation between iron (III) ion and some phenols. III. Salicylaldehyde, o-hydroxyacetophenone, salicylamide, and methyl salicylate. Acta Chem Scand9: 39–48Google Scholar
  19. [19]
    Teder A (1972) Equilibrium between hydrogen sulfite and sulfite ions. Sv Papperstidn75: 704–706; Chem Abs77: 157079vGoogle Scholar
  20. [20]
    Verhoeven P, Hefter GT, May PM (1990) Dissociation constant of hydrogen cyanide in saline solutions. Minerals and Metall Proc5: 185Google Scholar
  21. [21]
    Persson H (1971) Complex formation in the zinc cyanide and cadmium cyanide systems. Acta Chem Scand25: 543–550Google Scholar
  22. [22]
    Hefter G (1972) The use of ion-selective electrodes in the determination of mixed stability constants. J Electroanal Chem39: 345Google Scholar
  23. [23]
    McTigue PT (personal communication)Google Scholar
  24. [24]
    May PM, Murray K, Williams DR (1988) The use of glass electrodes for the determination of formation constants — III. Optimization of titration data: the ESTA library of computer programs. Talanta35: 825–830Google Scholar
  25. [25]
    May PM, Murray K (1988) The use of glass electrodes for the determination of formation constants — IV. Matters of weight. Talanta35: 927–932Google Scholar
  26. [26]
    May PM, Murray K (1988) The use of glass electrodes for the determination of formation constants — V. Monte-Carlo analysis of error propagation. Talanta35: 933–941Google Scholar
  27. [27]
    Bockris JO'M, Reddy AKN (1971) Modern Electrochemistry, vol 1. Plenum Press, New YorkGoogle Scholar
  28. [28]
    Zemaitis JF, Jr, Clark DM, Rafal M, Scrivner NC (1986) Handbook of Aqueous Electrolyte Thermodynamics. American Institute of Chemical Engineers, New YorkGoogle Scholar
  29. [29]
    Pitzer KS (1979) Theory — Ion Interaction Approach. In: Pytkowicz RM (ed) Activity Coefficients in Electrolyte Solutions. CRC Press, Boca Raton, FLGoogle Scholar
  30. [30]
    Harvie CE, Weare JH (1980) The prediction of mineral solubilities in natural waters: the Na-K-Mg-Ca-Cl-SO4-H2O system from zero to high concentration at 25°C. Geochim Cosmochim Acta44: 981–997Google Scholar
  31. [31]
    Königsberger E, Schuster E, Gamsjäger H, God C, Hack K, Kowalski M, Spencer PJ (1992) Thermochemical data and software for the optimization of processes and materials. Netsu Sokutei19: 135–144Google Scholar
  32. [32]
    Maeda M, Hisada O, Kinjo Y, Ito K (1987) Estimation of salt and temperature effects on ion product of water in aqueous solutions. Bull Chem Soc Jpn60: 3233–3239Google Scholar
  33. [33]
    Smith WR, Missen RW (1982) Chemical Reaction Equilibrium Analysis. Wiley, New York, p 67Google Scholar
  34. [34]
    National Bureau of Standards, Washington DC (1982) J Phys Chem Ref Data 11 [Supplement 2]Google Scholar
  35. [35]
    Eriksson G, Hack K (1990) ChemSage — a computer program for the calculation of complex chemical equilibria. Metall Trans21B: 1013Google Scholar
  36. [36]
    Harvie CE, Moeller NE, Weare JH (1984) The prediction of mineral solubilities in natural waters: the Na-K-Mg-Ca-H-Cl-SO4-OH-HCO3-CO2-H2O system to high ionic strengths. Geochim Cosmochim Acta48: 723–751Google Scholar
  37. [37]
    Königsberger E, Schuster E, Eriksson G (1993) A new optimization routine for ChemSage. Paper presented at CALPHAD XXII, Catalonia, SpainGoogle Scholar
  38. [38]
    Millero F (1972) The partial molal volumes of electrolytes in aqueous solutions. In: Horne RA (ed) Water and Aqueous Solutions: Structure, Thermodynamics and Transport Properties. Wiley-Interscience, New YorkGoogle Scholar
  39. [39]
    Ives DJG, Janz GJ (eds) (1961) Reference Electrodes. Theory and Practice, Academic Press, New YorkGoogle Scholar
  40. [40]
    Hamer WJ, Wu, Y-C (1972) Osmotic coefficients and mean activity coefficients of uni-univalent electrolytes in water at 25°C. J Phys Chem Ref Data1: 1047–1099Google Scholar
  41. [41]
    Kim H-T, Frederick WJ (1988) Evaluation of Pitzer ion interaction parameters of aqueous electrolytes at 25°C. 1. Single salt parameters. J Chem Eng Data33: 177–184Google Scholar
  42. [42]
    Kim H-T, Frederick WJ (1988) Evaluation of Pitzer ion interaction parameters of aqueous mixed electrolytes at 25°C. 2. Ternary mixing parameters. J Chem Eng Data33: 278–283Google Scholar
  43. [43]
    Gonçalves FA, Kestin J (1977) The viscosity of NaCl and KCl solutions in the range 25–50°C. Ber Bunsenges Phys Chem81: 1156Google Scholar
  44. [44]
    Halasey ME (1941) Partial molal volumes of potassium salts of the Hofmeister series. J Phys Chem45: 1252Google Scholar
  45. [45]
    Hölemann P, Kohner H (1931) The dependence of equivalent refraction of strong electrolytes in solution upon temperature. Z Physik ChemB13: 338Google Scholar
  46. [46]
    Isono T (1985) Densities, viscosities, and electrolytic conductivities of concentrated aqueous solutions of 31 solutes in the range 15–55°C and empirical equations for the relative viscosity. Rikagaku Kenkyusho Hokoku61: 53Google Scholar

Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • I. Kron
    • 1
  • S. L. Marshall
    • 1
  • P. M. May
    • 1
  • G. Hefter
    • 1
  • E. Königsberger
    • 1
  1. 1.A. J. Parker Cooperative Research Centre for Hydrometallurgy, School of Mathematical and Physical SciencesMurdoch UniversityMurdochAustralia

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