Universal indicator

Universal Indicator is a pH indicator that transitions through numbers 3-12 (on the pH chart) to indicate the acidity and alkaline 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]

Additional recommended knowledge

Safe Weighing Range Ensures Accurate Results

How to quickly check pipettes?

What is the Correct Way to Check Repeatability in Balances?

Potential hazards

Yamada's Universal Indicator is a flammable liquid. The indicator dyes should be considered toxic by ingestion and skin contact should also be avoided^{[citation needed]}.

More details

• Physical state: Liquid
• Appearance: light green in water solvent; dark green alone
• Odour: alcohol-like, occasionally likened to vanilla.
• pH value: Approximately 7
• Vapour pressure: 25 mmHg (3.3 kPa)
• Vapour Density: 1.3 kg/m³
• Boiling point: 80 °C
• Solubility: Soluble in water.
• Specific gravity/Density: 0.93 g/cm³
• Molecular formula: Mixture

"A universal indicator is typically composed of water, methanol, propan-1-ol, phenolphthallien sodium salt, methyl red sodium salt, phenol,4,4'-(3h-2,1-benzoxathiol-3-ylidene)bis2-bromo--methy l-6-(1-methylethyl)-, s,s-dioxide, monosodium salt, and phenol,4,4'-(3h-2,1-benzoxathiol-3-ylidene)bis5-methyl2-(1-m ethylethyl)-, s,s-dioxide, monosodium salt."^[4]

See also

• Litmus paper

References