Methyl orange


Methyl orange is a pH indicator frequently used in titration because of its clear and distinct color variance at different pH values. Methyl orange shows red color in acidic medium and yellow color in basic medium. Because it changes color at the pKa of a mid strength acid, it is usually used in titration for acids. Unlike a universal indicator, methyl orange does not have a full spectrum of color change, but it has a sharp end point. In a solution becoming less acidic, methyl orange changes from red to orange and, finally, to yellow—with the reverse process occurring in a solution of increasing acidity.

Indicator colors

In a solution becoming less acidic, methyl orange moves from red to orange and finally to yellow with the reverse occurring for a solution increasing in acidity. The entire color change occurs in acidic conditions.
In an acid, it is reddish and in alkali, it is yellow. Methyl orange has a pKa of 3.47 in water at.

Other indicators

Modified methyl orange, an indicator consisting of a solution of methyl orange and xylene cyanol, changes from grey-violet to green as the solution becomes more basic.

Safety

Methyl orange has mutagenic properties. Direct contact should be avoided. It is a hazardous substance.