广用试剂，又名通用指示剂或广范试剂。一般用来指示溶液的酸碱性，并可以指示酸性和碱性范围内的各种pH值，其变色之 pH 范围如下表：　　　

pH值<4，颜色皆为红色

pH值>10，颜色皆为紫色

广范试剂是pH指示剂的一种，其适用范围为pH3~12，可用以显示不同溶液之酸碱度。虽然市面上有多种不同的广范试剂，但大部分都是从山田所获得专利的配方变化而来的。 这个专利细节可以在化学文摘找到。 有关山田的广范试剂之实验也刊登在化学教育学报。

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 1 to 14 to indicate the acidity or alkalinity of solutions. 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.