Color Characteristics of Certain Acid-Base Indicators

It was found that students have difficulty in observing end points when titrating with methyl red and methyl orange as indicators, because of the comparatively large volume of solution necessary to cause a definite color change. Methyl orange-xylene cyanole was purchased from Eastman Kodak Company to overcome this difficulty. However, it was found that the color change of this mixed indicator was not completely satisfactory. A study has been made to obtain an indicator which presented the best possible color characteristics combined with the lowest pH interval for the titration of strong acids and bases. Four indicators were studied. They were methyl red, methyl red-xylene cyanole, methyl red plus methyl orange-xylene cyanole, and methyl orange-xylene cyanole