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Methyl orange

Methyl orange
Methyl-orange-2D-skeletal.png
Methyl-orange-3D-vdW.png
Methyl-orange-sample.jpg
Names
Preferred IUPAC name
Sodium 4-{[4-(dimethylamino)phenyl]diazenyl}benzene-1-sulfonate
Other names
Sodium 4-[(4-dimethylamino)phenylazo]benzenesulfonate
Identifiers
547-58-0 YesY
3D model (Jmol) Interactive image
ChemSpider 16736152 YesY
ECHA InfoCard 100.008.115
Properties
C14H14N3NaO3S
Molar mass 327.33 g·mol−1
Density 1.28 g/cm3, solid
Melting point >300 °C (572 °F; 573 K)
not precisely defined
Boiling point decomposes
0.5 g/100 mL (20 °C)
Solubility insoluble in diethyl ether
Hazards
Main hazards Toxic (T)
GHS pictograms The skull-and-crossbones pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word Danger
H301
P308, P310
Toxic T
R-phrases R25
S-phrases S37, S45
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Lethal dose or concentration (LD, LC):
LD50 (median dose)
 60 mg/kg (rat, oral)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY  (what is YesYN ?)
Infobox references

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. Methyl orange shows red colour in acidic medium and yellow colour in basic medium.

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.

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).

Modified (or screened) methyl orange, an indicator consisting of a solution of methyl orange and xylene cyanol, changes from grey-violet to green as the solution becomes more basic.

Methyl orange has mutagenic properties. Direct contact should be avoided.


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Wikipedia

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