A single pH indicator used as an indicator paper or in solution. It is red in acidic solutions, purple in neutral solutions, and blue in alkaline solutions.
The table shows the colours of litmus paper in acidic, neutral and alkaline solutions.
| acidic solutions | neutral solutions | alkaline solutions | |
|---|---|---|---|
| red litmus | stays red | stays red | turns blue |
| blue litmus | turns red | stays blue | stays blue |
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