Acid Blue 19 is an organic dye used in toner transfer electrophotographic and urban telecommunication cables for insulation. Used as acid-base indicator and coloring agent Use acid-base indicator, Chemicalbook biological staining, petroleum analysis, nitrogen fertilizer analysis. Acid-base indicator, pH discoloration range 9.4 (blue) ~ 14.0 (red); used to determine the pH of petroleum; biological staining.