ISBN: | 978-5-5112-8474-3 |
High Quality Content by WIKIPEDIA articles! A Universal indicator is a pH indicator composed of a blend of several compounds that exhibits several smooth colour changes over a pH value range from 1-14 to indicate the acidity or basicity of solutions. Although there are a number of commercially available universal pH indicators, most are a variation of a formula patented by Yamada in 1923. Details of this patent can be found in Chemical Abstracts.