|Molar mass||327.33 g·mol−1|
|Density||1.28 g/cm3, solid|
|Melting point||>300 °C (572 °F; 573 K)
not precisely defined
|0.5 g/100 mL (20 °C)
soluble in hot water
|Solubility||insoluble in diethyl ether|
|Main hazards||Toxic (T)|
|GHS signal word||Danger|
LD50 (Median lethal dose)
|60 mg/kg (rat, oral)|
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
Methyl orange is a pH indicator frequently used in titrations because of its clear and distinct colour change. Because it changes colour at the pH of a midstrength 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.
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.
|Methyl orange (pH indicator)|
|below pH 3.1||above pH 4.4|
In an acid, it is reddish and in alkali, it is yellow. Methyl orange has a pKa of 3.47 in water at 25 °C (77 °F).
|Methyl orange in xylene cyanol solution (pH indicator)|
|below pH 3.2||above pH 4.2|
Modified (or screened) methyl orange, an indicator consisting of a solution of methyl orange and xylene cyanol, changes from grey to green as the solution becomes more basic.
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