Eriochrome black T is used as an indicator in analytical chemistry. It is also used in the detection of rare earth metals. It finds application in dyeing and printing of wool fabric dyeing of silk and nylon as well as in leather dyeing. It can be used in the spectrophotometric determination of diphenhydramine hydrochloride in pharmaceutical preparations. As a complexometric indicator it is useful in the determination of hardness of water.

Its main purpose is to undergo color changes (blue free form to red wine-red metal complex) at the titration endpoint signaling complete chelation of metal ions by EDTA in ammoniacal buffers.

Eriochrome Black T is used as an indicator for complexometric titrations. It functions as an acid-base indicator. Eriochrome Black T forms complex with Ca2 and Mg2 but it binds more strongly to Mg2 ions.