Phenol red is a water-soluble dye used as a pH indicator, changing from yellow to red over pH 6.6 to 8.0, and then turning a bright pink color above pH 8.1. As such, phenol red can be used as a pH indicator dye in various medical and cell biology tests.

Application

Phenol Red Indicator Solution: Dissolve 0.1 g of phenol red in 2.82 ml of 0.1 M sodium hydroxide and 20 ml of ethanol (95 percent). After the solution is effected, add sufficient water to produce 100 ml.