5,5’-Indigo disulfonic acid

Indigo disulfonic acid (indigo carmine) 0.29 -0.12 Indigo Blue Colorless <9... 

Chromium compounds catalyze the oxidation of indigocarmine (indigo-disulfonic acid) by hydrogen peroxide. The addition of 2,2 -dipyridyl increases the sensitivity of the reaction. This behavior forms the basis of a very sensitive test for hexavalent chromium. 

Indigo-5,5 -disulfonic acid (Na salt) 0.291 -0.125 <9 Colorless to blue... 

Likewise, P.B.63 is an aluminum lake. It is derived from the indigo structure, which is sulfonated to afford indigo-5,5 -disulfonic acid. For indigo syntheses, please see [1]. 

Indigo-5,5 -disulfonic acid, disodium salt, C.I. Acid Blue 74, 73015 [860-22-0, Indigotin I, indigo carmine, is approved almost worldwide as a food colorant, and has gained some significance as a dye for foodstuffs, cosmetics, and pharmaceuticals. 

Synonyms Blue X Ceruleinum Cl 73015 2-(1,3-Dihydro-3-oxo-5-sulfo-2H-indol-2-ylidene)-2,3-dihydro-3-oxo-1 H-indole-5-sulfonic acid disodium salt Disodium indigo-5,5-disulfonate FD C Blue No. 2 Food blue 1 Indigo carmine Indigo carmine disodium salt 5,5 -lndigotin disulfonic acid... 

Disodium 3-hydroxy-4-((2,4,5-trimethylphenyl) azo)-2,7-naphthalenedisulfonate Disodium 3-hydroxy-4-((2,4,5-trimethylphenyl) azo)-2,7-naphthalenedisulfonic acid. See Ponceau 3R Disodium IMP. See Disodium inosinate Disodium indigo-5,5-disulfonate. See FD C Blue No. 2 Acid blue 74 Disodium inosinate CAS 4691-65-0... 

Key CL, chemiluminescence UV, ultraviolet IDS, indigo-5,5 -disulfonate ITS, indigo-5,5, 7-trisulfonate ACVK, Acid Chrome Violet K (Alizarin Violet 3R) n.a., For batch methods, sampling time (s) is shown in parentheses. 

Two isomers occur within indigo carmine, reflecting different sulfonation points on the molecule disodium 3,3 -dioxo-[d -biindoline]-5,5 -disulfonate and disodium 3,3 -dioxo-[D -biin-doline]-5,7 -disulfonate (also given as 2-(l,3-dihydro-3-oxo-5-sulfo-2H-indol-2-ylidene)-2,3-dihydro-3-oxo-lH-indole-5-sulphonic acid disodium salt Merck Index, 1992). It is prepared by treatment of indigo with sulfuric acid. 

---