Description
Methyl orange is an orange, azoic dye. It has a transition range from 3.1 to 4.4. Methyl orange does not have a full spectrum of color change, but has a sharper end point. Methyl orange shows red color in acidic medium (pH < 3.1) and yellow color in basic medium (pH > 4.4).
It is used as a pH-indicator in 0.1% aqueous solution for the titration of mineral acids (not organic acids) and strong bases. Methyl orange is also used in dyeing and printing textiles as a dyestuff.
References
[1] https://en.wikipedia.org/wiki/Methyl_orange
[2] Mohammed Bassim Alqaragully (2014) International Journal of Advanced Research in Chemical Science, 1, 48-59
Chemical Properties
Orange-yellow powder. Soluble in hotwater; insoluble in alcohol.
Uses
Methyl orange is a pH indicator frequently used in titrations, also used for histological microscopy.
Uses
As indicator in 0.1% aqueous solution. pH: 3.1 red, 4.4 yellow. Employed for titrating most mineral acids, strong bases, estimating alkalinity of waters; useless for organic acids. In dyeing and printing of textiles.
Preparation
4-Aminobenzenesulfonic acid diazo, and N,N-dimethylaniline coupling.
Definition
An acid–base indicator
that is red in solutions below a pH of 3 and
yellow above a pH of 4.4. As the transition
range is clearly on the acid side, methyl orange
is suitable for the titration of an acid
with a moderately weak base, such as
sodium carbonate.
Definition
methyl orange: An organic dyeused as an acid–base indicator. Itchanges from red below pH 3.1 toyellow above pH 4.4 (at 25°C) and isused for titrations involving weakbases.
General Description
Orange powder.
Air & Water Reactions
Azo dyes can be explosive when suspended in air at specific concentrations. Insoluble in water.
Reactivity Profile
Methyl Orange is an azo compound. Azo, diazo, azido compounds can detonate. This applies in particular to organic azides that have been sensitized by the addition of metal salts or strong acids. Toxic gases are formed by mixing materials of this class with acids, aldehydes, amides, carbamates, cyanides, inorganic fluorides, halogenated organics, isocyanates, ketones, metals, nitrides, peroxides, phenols, epoxides, acyl halides, and strong oxidizing or reducing agents. Flammable gases are formed by mixing materials in this group with alkali metals. Explosive combination can occur with strong oxidizing agents, metal salts, peroxides, and sulfides.
Properties and Applications
orange. The strong sulfuric acid for green light yellow, diluted into red orange. The dye solution to join strong hydrochloric acid for orange red; Add thick sodium hydroxide solution for green light yellow.
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Standard
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Light Fastness
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Soaping
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Persperation Fastness
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Oxygen bleaching
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Fastness to seawater
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Fading
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Stain
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Fading
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Stain
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Fading
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Stain
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ISO
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AATCC
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Purification Methods
Recrystallise it twice from hot water, then wash it with a little EtOH followed by diethyl ether. It is an indicator: pH 3.1 (red) and pH 4.4 (yellow). [Beilstein 16 IV 510.]
