The main use of litmus is to test whether a solution is acidic or basic. Light-blue litmus paper turns red under acidic conditions, and red litmus paper turns blue under basic or alkaline conditions, with the color change occurring over the pH range 4.5–8.3 at 25 °C (77 °F). Neutral litmus paper is purple.

1. The main use of litmus is to test whether a solution is acidic or basic. Light-blue litmus paper turns red under acidic conditions, and red litmus paper turns blue under basic or alkaline conditions, with the color change occurring over the pH range 4.5–8.3 at 25 °C (77 °F). Neutral litmus paper is purple

1. Litmus turns red in acidic solutions and blue in alkaline solutions and is the oldest and most commonly used indicator of whether a substance is an acid or a base.

1.  Litmus indicator solution turns red in acidic solutions and blue in alkaline solutions. It turns purple in neutral solutions. Litmus paper is usually more reliable, and comes as red litmus paper and blue litmus paper. The table shows the colour changes it can make
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LITMUS INDICATOR LR