二甲酚橙是一个配位滴定指示剂，能与金属离子（铝，铁，铋，锌等）生成紫色的络合物。其优点在于同时还能指示pH值，pH＜6.3时显亮黄色，pH＞6.3时显红色。

Xylenol orange is an organic reagent, most commonly used as a tetrasodium salt as an indicator for metal titrations. When used for metal titrations it will appear red in the titrand and yellow once it reaches its endpoint. Historically, commercial preparations of it have been notoriously impure, sometimes consisting of as little as 20% xylenol orange, and containing large amounts of semi-xylenol orange and iminodiacetic acid. Purities as high as 90% are now available.