Product Short Description: HYDROXY NAPHTHOL BLUE (ACS GRADE) Product Description: HYDROXY NAPHTHOL BLUE ACS GRADE excellent quality manufacturer, exporter and supplier. Hydroxynaphthol blue, disodium salt is used for determining the endpoint in metal complexation titrations. Hydroxynaphthol blue is an azo dye. HYDROXY NAPHTHOL BLUE ACS GRADE excellent quality manufacturer, exporter and supplier. Hydroxynaphthol blue, disodium salt is used for determining the endpoint in metal complexation titrations. Hydroxynaphthol blue is an azo dye.