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.
Read more about this topic: Methyl Orange
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