Chemical indicators such as methyl orange, bromothymol blue, phenolphthalein and litmus are often used to determine the acidic or basic nature of a substance. The indicators change colour over a pH range.

 

Indicator

pH range

Type of indicator

Picture

Methyl orange

3.1 to 4.4
Red to Yellow

Acidic indicator

 

Bromothymol blue

6.0 to 7.6
Yellow to Blue

Neutral indicator

 

Phenolphthalein

8.3 to 10.0
Colourless to Pink

Basic indicator

 

Litmus

5 to 8
Pink to Blue

General indicator

 

Molar Mass
 

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