<P> A universal indicator is a pH indicator composed of a solution of several compounds that exhibits several smooth colour changes over a pH value range from 0 to 14 to indicate the acidity or alkalinity of solutions, where 7 indicates neutral . Although there are several commercially available universal pH indicators, most are a variation of a formula patented by Yamada in 1933 . Details of this patent can be found in Chemical Abstracts . Experiments with Yamada's universal indicator are also described in the Journal of Chemical Education . </P> <P> A universal indicator is typically composed of water, propan - 1 - ol, phenolphthalein sodium salt, sodium hydroxide, methyl red, bromothymol blue monosodium salt, and thymol blue monosodium salt . The colours that indicate the pH of a solution, after adding a universal indicator, are: </P>

What is the composition of a universal indicator