Since solution A turns China rose colour to dark pink hence Solution A is an acidic solution. solution B turns China rose colour to green colour hence Solution B is a basic solution. Since Solution C did not change the colour of the china rose Solution it is a neutral solution.
Indicators are chemical compounds that tell us whether a substance is acidic or basic by changing its colour. When added to an acidic solution or a basic solution, indicators change their colour and this change in colour is different for the acids and bases. The indicator thus helps us to decide whether a given solution is acidic or basic in nature.
The indicators that are obtained from plants are known as natural indicators.
Examples of natural indicators
- Turmeric compound is a naturally occurring yellow colour compound. It is an acid-base indicator, turmeric compound remains yellow when acid or neutral solutions are added to it. When basic solutions such as sodium hydroxide are added to it, the solution turns pinkish-red.
- China rose converts acidic solution to dark pink, basic solutions to green colour and has no colour change for neutral solutions.