INDICATOR PAPER With colour scale pH2.0-4.5

A universal indicator is collectively a mixture of indicators which show a colour change in a solution, which interprets how acidic or basic a solution is. A universal indicator can be in paper form or present in a form of a solution.[5]

Paper form: It is a strip of coloured paper which changes colour to red if the solution is acidic and to blue, if the solution is basic. The strip can be placed directly onto a surface of a wet substance or few drops of the solution can be dropped onto the universal indicator using dropping equipment. If the test solution is of a dark colour, it is preferable to use a paper universal indicator.

Solution: The main components of a universal indicator, in the form of a solution, are thymol blue, methyl red, bromothymol blue, and phenolphthalein. This mixture is important because each component loses or gains protons depending upon the acidity or alkalinity of the solution being tested. It is beneficial to use this type of universal indicator in a colourless solution. This will increase the accuracy level of indication.