References & Constants
The constants and molecular weights used throughout this site, plus the buffer systems available in the experiments and a short list of further reading. All figures are standard textbook values at about 25 °C unless noted.
Physical constants
| Symbol | Quantity | Value |
|---|---|---|
| Kw | Ion product of water (25 °C) | 1.0 × 10⁻¹⁴ |
| R | Molar gas constant | 8.314 J·mol⁻¹·K⁻¹ |
| F | Faraday constant | 96 485 C·mol⁻¹ |
| 2.303·RT/F | Nernst slope (25 °C) | 59.16 mV per pH unit |
| ln 10 | Natural log of 10 | 2.3026 |
Buffer pKa & molar mass
| Buffer | pKa (region) | All pKa | Acid form | MW | Base form | MW | Notes |
|---|---|---|---|---|---|---|---|
| Loading buffer data… | |||||||
Further reading
- Good, N. E., Winget, G. D., Winter, W., Connolly, T. N., Izawa, S. & Singh, R. M. M. (1966). Hydrogen ion buffers for biological research. Biochemistry, 5(2), 467–477. — the origin of the “Good’s buffers.”
- Nelson, D. L. & Cox, M. M. Lehninger Principles of Biochemistry — the chapter on water, weak acids and buffering (Henderson–Hasselbalch, buffer capacity, physiological buffers).
- Sigma-Aldrich / Thermo Fisher Buffer Reference tables — practical pKa, temperature coefficients and recipes for common laboratory buffers.
- CRC Handbook of Chemistry and Physics — authoritative pKa values and their temperature dependence for acids and bases.
Important: every value on this page is a standard textbook constant
provided for teaching. The site treats activity as equal to concentration and ignores
ionic-strength effects, and polyprotic buffers are represented by a single relevant
pKa. For any real laboratory work you must confirm pKa, molecular
weight, hydration state and purity against the reagent's own certificate of analysis,
and verify pH against a freshly calibrated meter at your working temperature.