Methyl orange is a pH indicator frequently used in titrations.
It is often chosen to be used in titrations because of its clear colour change. Because it changes colour at the pH of a mid-strength acid, it is usually used in titrations for acids. Unlike a universal indicator, methyl orange does not have a full spectrum of colour change, but has a sharper end point.
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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. It should be noted that the entire colour change occurs in acidic conditions.
In an acid it is reddish and in alkali it is yellow.
- Modified (or screened) methyl orange, an indicator consisting of a solution of methyl orange and xylene cyanol, changes from gray to green as the solution becomes more basic.
- A number of other common indicators are tabulated in the article on pH indicators.