Acids, Bases & pH

Sources and simplifications

Every reference cited on this site, and every place a figure idealizes the real system.

References

  1. NIST Physical Measurement Laboratory (2018). CODATA value: Avogadro constant. NIST. standard (The pH scale)
  2. E. W. Lemmon, I. H. Bell, M. L. Huber, M. O. McLinden (NIST Chemistry WebBook, SRD 69) (2023). Thermophysical properties of fluid systems: water (IAPWS-95 formulation). NIST. dataset (The pH scale)
  3. R. P. Buck, S. Rondinini, A. K. Covington, F. G. K. Baucke, et al. (2002). Measurement of pH. Definition, standards, and procedures (IUPAC Recommendations 2002). Pure and Applied Chemistry 74, 2169–2200. doi:10.1351/pac200274112169. standard (The pH scale)
  4. D. Harvey (2016). Analytical Chemistry 2.1, chapter 6: Equilibrium chemistry (6.7 Solving equilibrium problems; 6.8 Buffer solutions; 6.9 Activity effects). DePauw University (open textbook, LibreTexts edition). textbook (The pH scale)
  5. J. B. Dressman, R. R. Berardi, L. C. Dermentzoglou, et al. (1990). Upper gastrointestinal (GI) pH in young, healthy men and women. Pharmaceutical Research 7, 756–761. doi:10.1023/A:1015827908309. primary (The pH scale)
  6. U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition (2007). Approximate pH of foods and food products. FDA/CFSAN, Acidified and Low-Acid Canned Foods (April 2007 list; copy hosted by RiverStone Health). institutional (The pH scale)
  7. U.S. Environmental Protection Agency (2025). What is acid rain?. EPA. institutional (The pH scale)
  8. H. Arcis and A. H. Harvey (2025). Ionization constant of water (tables for the CRC Handbook of Chemistry and Physics, 106th edition). National Institute of Standards and Technology / CRC Press. dataset Values computed from the IAPWS R11-24 formulation; we use the saturated-liquid table, 0–100 °C. (The pH scale)
  9. I. Shaw and K. Gregory (2022). Acid–base balance: a review of normal physiology. BJA Education 22(10), 396–401. doi:10.1016/j.bjae.2022.06.003. review (The pH scale)
  10. National Oceanic and Atmospheric Administration (2025). Ocean acidification (education resource collection). NOAA. institutional (The pH scale)
  11. R. N. Goldberg, N. Kishore, R. M. Lennen (2002). Thermodynamic quantities for the ionization reactions of buffers. Journal of Physical and Chemical Reference Data 31, 231–370 (NIST). doi:10.1063/1.1416902. dataset Section 8: selected pK values at 298.15 K and 0.1 MPa, used for every pKa on this site. (The pH scale)
  12. H. Arcis, M. Bachet, S. Dickinson, et al. (2024). Revised parameters for the IAPWS formulation for the ionization constant of water over a wide range of temperatures and densities, including near-critical conditions. Journal of Physical and Chemical Reference Data 53, 023103. doi:10.1063/5.0198792. primary (The pH scale)
  13. R. A. Robinson, R. H. Stokes (1959). Electrolyte Solutions, 2nd ed. (revised). Butterworths, London; reprinted Dover 2002 (Debye–Hückel constant, ch. 7; activity coefficients of HCl, Appendix 8.10). ISBN 9780486422251. book (The pH scale)
  14. S. P. L. Sørensen (1909). Enzymstudien. II. Mitteilung. Über die Messung und die Bedeutung der Wasserstoffionenkonzentration bei enzymatischen Prozessen. Biochemische Zeitschrift 21, 131–304 (published simultaneously in French in Comptes-rendus des travaux du Laboratoire de Carlsberg 8, 1–168). primary (The pH scale)
  15. J. G. Nørby (2000). The origin and the meaning of the little p in pH. Trends in Biochemical Sciences 25, 36–37. doi:10.1016/S0968-0004(99)01517-0. scholarship (The pH scale)
  16. S. Arrhenius (1887). Über die Dissociation der in Wasser gelösten Stoffe. Zeitschrift für Physikalische Chemie 1, 631–648. doi:10.1515/zpch-1887-0164. primary (Strong and weak acids)
  17. J. N. Brønsted (1923). Einige Bemerkungen über den Begriff der Säuren und Basen. Recueil des Travaux Chimiques des Pays-Bas 42, 718–728. doi:10.1002/recl.19230420815. primary (Strong and weak acids)
  18. T. M. Lowry (1923). The uniqueness of hydrogen. Journal of the Society of Chemical Industry 42, 43–47. doi:10.1002/jctb.5000420302. primary (Strong and weak acids)
  19. G. N. Lewis (1923). Valence and the Structure of Atoms and Molecules. Chemical Catalog Company (American Chemical Society Monograph Series), New York. primary (Strong and weak acids)
  20. D. Harvey (2016). Analytical Chemistry 2.1, chapter 9.2: Acid–base titrations. DePauw University (open textbook, LibreTexts edition). textbook (Strong and weak acids)
  21. R. de Levie (1993). Explicit expressions of the general form of the titration curve in terms of concentration: writing a single closed-form expression for the titration curve for a variety of titrations without using approximations or segmentation. Journal of Chemical Education 70, 209. doi:10.1021/ed070p209. primary (Titration)
  22. L. J. Henderson (1908). Concerning the relationship between the strength of acids and their capacity to preserve neutrality. American Journal of Physiology 21, 173–179. doi:10.1152/ajplegacy.1908.21.2.173. primary (Buffers)
  23. H. N. Po and N. M. Senozan (2001). The Henderson–Hasselbalch equation: its history and limitations. Journal of Chemical Education 78, 1499. doi:10.1021/ed078p1499. scholarship (Buffers)
  24. C. W. Davies (1962). Ion Association. Butterworths, London (the Davies equation for activity coefficients, ch. 3). ISBN 9780408119002. book (Buffers)
  25. D. D. Van Slyke (1922). On the measurement of buffer values and on the relationship of buffer value to the dissociation constant of the buffer and the concentration and reaction of the buffer solution. Journal of Biological Chemistry 52, 525–570. doi:10.1016/S0021-9258(18)85845-8. primary (Buffers)
  26. R. Sander (2023). Compilation of Henry's law constants (version 5.0.0) for water as solvent. Atmospheric Chemistry and Physics 23, 10901–12440. doi:10.5194/acp-23-10901-2023. dataset Recommended Hcp for CO2 at 298.15 K: 3.4 × 10⁻⁴ mol m⁻³ Pa⁻¹ (henrys-law.org, entry 124-38-9). (Blood, rain and ocean)
  27. NOAA Global Monitoring Laboratory (2026). Trends in atmospheric carbon dioxide: global monthly means. NOAA GML. dataset (Blood, rain and ocean)
  28. R. E. Zeebe, D. A. Wolf-Gladrow (2001). CO2 in Seawater: Equilibrium, Kinetics, Isotopes. Elsevier Oceanography Series 65 (chapter 1 and appendix A). ISBN 978-0-444-50946-8. textbook (Blood, rain and ocean)
  29. A. G. Dickson, C. L. Sabine, J. R. Christian (eds.) (2007). Guide to Best Practices for Ocean CO2 Measurements (chapter 5: physical and thermodynamic data). PICES Special Publication 3 (IOCCP Report 8), North Pacific Marine Science Organization. standard (Blood, rain and ocean)
  30. R. F. Weiss (1974). Carbon dioxide in water and seawater: the solubility of a non-ideal gas. Marine Chemistry 2, 203–215. doi:10.1016/0304-4203(74)90015-2. primary (Blood, rain and ocean)
  31. T. J. Lueker, A. G. Dickson, C. D. Keeling (2000). Ocean pCO2 calculated from dissolved inorganic carbon, alkalinity, and equations for K1 and K2: validation based on laboratory measurements of CO2 in gas and seawater at equilibrium. Marine Chemistry 70, 105–119. doi:10.1016/S0304-4203(00)00022-0. primary (Blood, rain and ocean)
  32. A. G. Dickson (1990). Thermodynamics of the dissociation of boric acid in synthetic seawater from 273.15 to 318.15 K. Deep-Sea Research 37, 755–766. doi:10.1016/0198-0149(90)90004-F. primary (Blood, rain and ocean)
  33. F. J. Millero (1995). Thermodynamics of the carbon dioxide system in the oceans. Geochimica et Cosmochimica Acta 59, 661–677. doi:10.1016/0016-7037(94)00354-O. primary (Blood, rain and ocean)
  34. J. E. Dore, R. Lukas, D. W. Sadler, M. J. Church, D. M. Karl (2009). Physical and biogeochemical modulation of ocean acidification in the central North Pacific. Proceedings of the National Academy of Sciences 106, 12235–12240. doi:10.1073/pnas.0906044106. primary (Blood, rain and ocean)
  35. NOAA Global Monitoring Laboratory (2026). Mauna Loa CO2 annual mean data. NOAA GML. dataset (Blood, rain and ocean)

Simplifications