Methyl Orange - Indicator Colours

Indicator Colours

Methyl orange (pH indicator)
below pH 3.1 above pH 4.4
3.1 ↔ 4.4
Methyl orange in xylene cyanol solution (pH indicator)
below pH 3.2 above pH 4.2
3.2 ↔ 4.2

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 colour 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 25 degrees Celsius.

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