Methyl orange

Structural formula
General
Surname	Methyl orange
other names	Sodium 4 - {[4- (dimethylamino) phenyl] diazenyl} benzenesulfonate ( IUPAC ); CI Acid Orange 52; CI 13025; Helianthin; Orange III; Golden orange; Tropaeolin D;
Molecular formula	C 14 H 14 N 3 NaO 3 S
Brief description	orange solid with a faint odor
External identifiers / databases
EC number	208-925-3
ECHA InfoCard	100.008.115
PubChem	23673835
ChemSpider	16736152
Wikidata	Q409196
properties
Molar mass	327.34 g mol −1
Physical state	firmly
density	1.28 g cm −3
Melting point	> 300 ° C
solubility	poor in water (approx. 5 g l −1 at 20 ° C)
safety instructions
GHS labeling of hazardous substances danger
H and P phrases	H: 301
	P: 301-330-331-310
Toxicological data	60 mg kg −1 ( LD 50 , rat , oral )
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Methyl orange is an azo dye from the application group of acid dyes . It is present as the sodium salt of 4- [4- (dimethylamino) phenylazo] benzenesulfonic acid and is mostly used as a pH indicator .

presentation

Sulphanilic acid is diazotized with nitrous acid :

The diazonium salt is then coupled with N , N -dimethylaniline ( green ), converted into the sodium salt with sodium hydroxide solution and precipitated :

properties

Methyl orange forms orange crystals.

Powdered methyl orange.

In the strongly acidic pH range, the azo group is protonated and a mesomeric quinoid system is obtained . When base is added, the group deprotonates in the pH range 3.0 to 4.4 and the color changes from red to yellow-orange.

Color changes from red to yellow-orange with increasing pH.

Web links

Commons : Methyl Orange - Collection of images, videos, and audio files

www.seilnacht.com (methyl orange)

Individual evidence

↑ ^a ^b ^c ^d ^e Entry on sodium 4- (4-dimethylaminophenylazo) benzenesulfonate in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .

↑ Applicher: Safety data sheet methyl orange (CI 13025) ( Memento of the original from September 16, 2016 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. As of August 5, 2016, accessed on September 12, 2016 @1@ 2

↑ Data sheet methyl orange (PDF) from Merck , accessed December 9, 2010.

^ Author collective: Organikum . 21st edition. Wiley-VCH, 2001, ISBN 3-527-29985-8 , p. 645.

↑ Indicator Reagents . In: Ullmann's Encyclopedia of Industrial Chemistry (engl.).

[GESTIS-1] Entry on sodium 4- (4-dimethylaminophenylazo) benzenesulfonate in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .