Methyl orange
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| Methyl orange | |
|---|---|
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| Systematic name | p-dimethylamino- azobenzenesulfonic acid |
| Chemical formula | C14H15N3O3S |
| Molecular mass | 305.35 g/mol |
| Density | 1.28 g/cm3 |
| Melting point | xx.x °C |
| Boiling point | xx.x °C |
| CAS number | [547-58-0] |
| SMILES | CN(C)C(C=C2)=CC=C2N=N C1=CC=C(S(=O)(O[Na])=O)C=C1 |
| pKa | 3.39 |
| Disclaimer and references | |
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 as a mid-strength acid, it is usually used in titrations between strong acids and weak bases. Unlike universal indicator, methyl orange does not have a full spectrum of colour change, but has a sharper end point.
[edit] Indicator Colours
| Methyl orange (pH indicator) | ||
| below pH 3.1 | above pH 4.4 | |
| 3.1 | ↔ | 4.4 |
| Methyl orange in xylene cyanole 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. It should be noted that the entire color change occurs in acidic conditions.
[edit] Other Indicators
- Modified 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.
- Phenolphthalein is another indicator frequently used in acid-base titration reactions because of its very sharp color change.
- A number of other common indicators are tabulated in the article on pH indicators.
