Polarography of Green S

Abstract

The food dye Green S, 4-[4-dimethylammoniocyclohexa-2,5-dienylidene-(4-dimethylaminophenyl)methyl]-3-hydroxynaphthalene-2,7-disulphonic acid, monosodium salt, is reduced at the dropping-mercury electrode from 50% ethanolic solutions with the total consumption of two electrons. Polarograms follow theoretical predictions in the pH range 2.7–8.75. The reduction mechanism involves two electron transfer steps that are sufficiently differentiated at higher pH for separate waves to appear.