Disappearing rainbow indicator

Disappearing Rainbow Indicator is a pH indicator that has different colors to indicate the range of the pH of the solution it is in. This is opposed to indicators like phenolphthalein which have only two different colors and are able to indicate only whether the pH is above or below a certain point by using the various pH values of the indicators. It usually has the following composition:

• Ethyl Alcohol
• Phenolphthalein
• Thymolphthalein
• p-Nitrophenol

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Essential Laboratory Skills Guide

Disappearing rainbow indicator is a flammable liquid. It is moderately toxic by inhalation or ingestion, and is an irritant.

Colors and meanings

• Red - pH 1
• Orange - pH 2
• Yellow - pH 3
• Pale green - pH 4
• Forest Green - pH 5
• Blue-green - pH 6
• Blue - pH 7

The colors follow those of the visible spectrum of light. The pH number is compared with the color. Anything below 7 is acidic (the lower the pH, the more acidic it is), 7 is neutral (neither acidic or alkali) & anything above 7 is alkali (the higher the pH, the more alkali it is)

More details

• Physical state: Liquid
• Appearance: dark
• Odour: alcohol-like
• 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