Acid Orange 7

Chemical properties

Orange-red powder

The Uses of Acid Orange 7

Acid Orange 7 (CAS# 633-96-5) is used as an azo dye pH indicator, it is an environmental pollutant.

Preparation

Acid Orange 7, commonly known as acidic orange II. 4-Aminobenzenesulfonic acid diazo, and Naphthalen-2-ol coupling. It is produced by azo coupling of β-naphthol and diazonium derivative of sulfanilic acid.

Definition

ChEBI: Acid orange 7 is a member of naphthalenes. Orange allergenic extract is used in allergenic testing.

Preparation

Acid orange 7 is produced by azo coupling of β-naphthol and diazonium derivative of sulfanilic acid.

fig. Synthesis of Acid Orange 7

Flammability and Explosibility

Non flammable

Purification Methods

Purification is as for Orange I. Its solubility in H2O is 40g/L at 25o. [Müller et al. Helv Chim Acta 35 2579 1952.] Also purify it by extracting it with a small volume of cold water, then crystallising it by dissolving in boiling water, cooling to ca 80o, adding two volumes of EtOH and cooling. When cold, the precipitate is filtered off, washed with a little EtOH and dried in air. It can be salted out from aqueous solution with sodium acetate, then repeatedly extracted with EtOH. Meggy and Sims [J Chem Soc 2940 1956], after crystallising the sodium salt twice from water, dissolved it in cold water (11mL/g) and added conc HCl to precipitate the acid dye which was separated by centrifugation, redissolved and again precipitated with acid. After washing the precipitate three times with 0.5M acid, it was dried over NaOH, recrystallised twice from absolute EtOH, washed with a little Et2O, dried over NaOH and stored over conc H2SO4 in the dark. It can then be converted to the pure salt with the calculated amount of NaOH or Na2CO3. [Beilstein 16 IV 408.]

Properties and Applications

red light orange. Golden yellow powder. Soluble in water is red light yellow, orange soluble in alcohol. The strong sulfuric acid for quality in red, dilute create tan precipitation; In a golden of nitric acid; In the thick of sodium hydroxide solution not dissolve. Its water solution with hydrochloric acid generation tan precipitation; Add sodium hydroxide solution brown. In dyeing copper ions trend dark red in colour and lustre of iron ion shallow and dark. Discharge the gender is good. Mainly used for silk and wool dyeing, widely used in wool dyeing, can be used for wool, silk and polyamide fiber fabric of direct printing, leather and paper color, can also be used in indicator and biological shading. Is tasted can be used as a food dye, heavy metal salt used in organic pigments.