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.
[1] https://en.wikipedia.org/wiki/Methyl_orange
[2] Mohammed Bassim Alqaragully (2014) International Journal of Advanced Research in Chemical Science, 1, 48-59
Orange-yellow powder. Soluble in hotwater; insoluble in alcohol.
Methyl orange is a pH indicator frequently used in titrations, also used for histological microscopy.
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.
4-Aminobenzenesulfonic acid diazo, and N,N-dimethylaniline coupling.
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.
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.
Azo dyes can be explosive when suspended in air at specific concentrations. Insoluble in water.
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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Soaping
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Oxygen bleaching
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Fading
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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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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.]
