Meter needle: pH 0 to 14Flask: tint is the share of indicator in its pink formBurette: level falls by the volume added25.0 cm³ of 0.100 mol/dm³ hydrochloric acid with phenolphthalein is titrated with 0.100 mol/dm³ sodium hydroxide at 25 °C: a strong acid and a strong base, with ideal behaviour assumed (concentrations stand for activities, Kw = 1.0 × 10⁻¹⁴, volumes add). The pH comes from the charge balance with dilution. It climbs slowly from 1.00, jumps from 3.7 to 10.3 between 24.90 and 25.10 cm³ around the equivalence point at 25.00 cm³ (pH 7.00), and levels off at 12.52 by 50 cm³. Phenolphthalein's range is pH 8.2 (colourless) to about 10 (pink), so the end point (first permanent pink) comes within one drop of the equivalence point (pH 7.00); in practice it is read at the first faint pink that stays on swirling. The electrode's bulb sits below the liquid surface at every volume; the tint follows 1/(1 + 10^(9.3 − pH)). Glassware not to scale.