Universal indicator
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| Universal indicator | |
|---|---|
| Properties | |
| Molar mass | 98.078 g/mol |
| Appearance | light green in water solvent; dark green alone, alcohol-like, occasionally likened to vanilla odour liquid |
| Density | 0.93 g cm−3, liquid |
| Boiling point |
80 °C, 353 K, 176 °F |
| Solubility in water | fully miscible (exothermic) |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
|
Universal indicator is a pH indicator that transitions through numbers 3-12 (on the pH chart) to indicate the acidity or alkalinity of solutions. Although there are a number of commercially available universal pH indicators, most are a variation of a formula patented by Yamada in 1923.[1] Details of this patent can be found in Chemical Abstracts.[2]
Experiments with Yamada's Universal Indicator are also described in the Journal of Chemical Education.[3]
[edit] Details
- pH value: Approximately 7
- Vapour pressure: 25 mmHg (3.3 kPa)
- Vapour density: 1.3 kg/m³
- Molecular formula: Mixture
A universal indicator is typically composed of water, methanol, propan-1-ol, phenolphthalein sodium salt, methyl red sodium salt, bromothymol blue monosodium salt, and thymol blue monosodium salt [4]
Here are the colours that indicate the adicity of a solution, after adding UI:
1. Very acidic - Red
2. Acidic - Orange/Yellow
3. Neutral - Green
4. Basic/base/alkali - Blue
5. Very basic/base/alkali - Purple
[edit] See also
[edit] References
- ^ Jap. Pat. 99,664, Feb 21, 1933
- ^ Chem Abstr, 28, 2258 (1934)
- ^ For a discussion of these experiments, as well as recipes for Yamada and other universal indicators, see Foster, S.F. and Gruntfest, J.Chem.Educ., 14, 274(1937)
- ^ "Universal Indicator". ISCID Encyclopedia of Science and Philosophy.
