Physical Pharmacy
Physical pharmacy explains why the same drug behaves differently in the stomach than it does in plasma. These two calculators handle the Henderson–Hasselbalch relationship — solving either for pH or for the conjugate ratio needed to reach a target pH — and the degree of ionisation of a weak acid or weak base at a given pH, with an interactive curve showing how that fraction shifts across the physiological range. Ionisation governs absorption, distribution, and renal handling, so these underpin much of the rest of the site.
Henderson–Hasselbalch equation
Relate pH, pKa, and the ratio of conjugate species for a weak acid or weak base buffer system — solving for pH or for the ratio needed to reach a target pH.
Percentage ionisation
Calculate what fraction of a weak acid or weak base is ionised at a given pH, with an interactive curve showing how it changes across the physiological range.
Where to go next
- Practice problems — one worked problem for every calculator, solutions hidden until you open them.
- Reference tables and formula sheet — every constant and conversion factor used here, with citations.
- All 58 calculators — the full index, filterable by category.
Other categories
Also known as
henderson hasselbalch · pH · pKa · buffer · salt acid ratio · buffer capacity · percent ionization · ionisation · ionized fraction · absorption · ion trapping · urine alkalinisation