phthalein indicator

例句：

1. 1. Thechemical test uses a solution of phthalocyanine as the indicator.
   这种化学测试使用一种溶液作为指示剂。
2. 2.The color change of the indicator is usedto indicate the presence of the substance.
   指示剂的颜色变化用于指示该物质的存在。
3. 3.The pH value of the solution was determinedby measuring the intensity of the indicator's color change.
   通过测量指示剂颜色变化的强度来确定溶液的pH值。