1-naphthalene sulfonic acid, 7-Hydroxy-, sodium

Naphthol Yellow S (citronin A, flavianic acid sodium salt, 8-hydroxy-5,7-dinitro-2-naphthalene sulfonic acid disodium salt) [846-70-8] M 358.2, m dec on heating. Greenish yellow powder soluble in H2O. The free sulfonic acid can be recrystd from dil HCl (m 150°) or AcOH-EtOAc (m 148-149.5°). The disodium salt is then obtained by dissolving the acid in two equivalents of aqueous NaOH... 

CAS 1658-56-6 EINECS/ELINCS 216-760-3 Synonyms Cl 15620 Ext. D C Red. no. 8 Fast red A 4-(2-Hydroxynaphthalen-1-ylazo) naphthalene-1-sulfonic acid, sodium salt 4-((2-Hydroxy-1 -naphthalenyl) azo)-1 -naphthalene sulfonic acid sodium salt 1-Naphthalenesulfonic acid, 4-((2-hydroxy-1-naphthalenyl) azo)-, monosodium salt Red no. 506 Rocceline Roccelline Solid red A Classification Azobenzene Empiricai C2oHi4N2Na04S Properties M.w. 401.41 m.p. 280 C Toxicoiogy Mutagen TSCA listed Storage Store in cool, dry place keep container closed when not in use... 

Hydroxynaphthalen-1 -ylazo) naphthalene-1 -sulfonic acid, sodium salt 4-((2-Hydroxy-1-naphthalenyl) azo)-1-naphthalene sulfonic acid... 

In our laboratory, this method was appUed to the purification of food mono-azo dyes. Amaranth, New Coccine, and Sunset Yellow FCF were purified at 99.7%, 99.5%, and 99.3%, respectively, from 1-23 g of commercial dyes. Continued research has led to the purification of impurities present in commercial Sunset Yellow FCF that include RS-SA (trisodium salt of 3-hydroxy-4-[sulfophenyl] azo-2,7-naphthalene disulfonic acid), GS-S A (1 -[4-sulfophenyl]azo)-2-naphthol-6,8-disulfonic acid), DONS (disodium salt of 6,6 -oxybis-2-naphthalene sulfonic acid), and 2N-SA (sodium salt of 4-[(2-hydroxy-l-naphthalenyl)azo]benzenesulfonic add). The method successfully isolated GS-SA from Sunset Yellow FCF. " ... 

H-acid, l-hydroxy-3,6,8-ttisulfonic acid, which is one of the most important letter acids, is prepared as naphthalene is sulfonated with sulfuric acid to ttisulfonic acid. The product is then nitrated and neutralized with lime to produce the calcium salt of l-nitronaphthalene-3,6,8-ttisulfonic acid, which is then reduced to T-acid (Koch acid) with Fe and HCl modem processes use continuous catalytical hydrogenation with Ni catalyst. Hydrogenation has been performed in aqueous medium in the presence of Raney nickel or Raney Ni—Fe catalyst with a low catalyst consumption and better yield (51). Fusion of the T-acid with sodium hydroxide and neutralization with sulfuric acid yields H-acid. Azo dyes such as Direct Blue 15 [2429-74-5] (17) and Acid... 

CAS 5858-39-9 EINECS/ELINCS 227-490-0 Synonyms Acid red 4, monosodium salt Cl 14710 4-Hydroxy-3-(2-methoxyphenylazo) naphthalene-1-sulfonic acid, sodium salt 1-Naphthalenesulfonic acid, 4-hydroxy-3-((2-methoxyphenyl) azo)-, monosodium salt Classification Azobenzene Empirical Ci7Hi4N2Na05S Properties M.w. 381.35 Toxicology TSCA listed Uses Dye for wool, paper Manuf./Distnb. Aldrich http //www.sigma-aidrich.com, Sigma... 

Hydroxy-3-(2-methoxyphenylazo) naphthalene-1-sulfonic acid, sodium salt. See Acid red 4... 

Naphthalenesulfonic acid, 6-amino-4-hydroxy-5-((2-(trifluoromethyl) phenyl) azo)-, monosodium salt. See Acid red 337 Naphthalenesulfonic acid, bis-(l-methylethyl)-, sodium salt. See Sodium isopropyl naphthalene sulfonate... 

Allura red AC (E 129, FD C Red No. 40, Cl Eood Red 17) is a mono azo dye that consists essentially of 6-hydroxy-5-(2-methoxy-5-methyl-4-sulfophenyl) azo-2-naphtalenesulfonic acid sodium salt (or disodium 2-hydroxy-l-(2-methoxy-5-methyl-4sufonato-phenylazo)-naphthalene-6-sulfonate). The calcium and potassium salts are also permitted. 

---