White indigo

Supplement (combined with Volumes XXIV and 1936 3458-3793 methane, 25. Pyrimidine, 89. Pyrazine, 91. Nicotine, 110. Dipyridyl, 199. Phenanthroline, 227. Hydroxy compounds, 348 Cinchonine, 424. Quinine, 511. Indigo white, i... 

Tndig-rot. n. — Indigorot. -stein, m. indicolite (blue tourmaline), -weiss, n. indigo white. 

Chemically, conversion into a vat consists in a 1 6-addition of hydrogen and recalls exactly the conversion of quinone into quinol. Like quinol, indigo white , also a dihydric phenol , is a weak add, the alkali salts of which are coloured intensely yellow. 

From its alkali salt, which is partially hydrolysed, the large indigo white molecule is adsorbed by the fibre and then, in this finely divided condition, dehydrogenated by the oxygen of the air, so that the dye now remains as a fast blue pigment. The oxidation is analogous to that of indoxyl. 

Indigo is readily reduced by various reducing agents such as zinc dust, sodium dithionite, hydroxyacetone, and hydrogen, or by electrochemical means. In an alkaline medium, a salt (for example the sodium salt) of leuco indigo is produced (3), which can be converted by acids to so-called indigo white (2). 

An interesting application of electrolytic reduction to vat-dyeing is the process of the Farbwerke vorm. Meister Lucius and Briining, in which alkali sulphite is electro-lytically reduced in the presence of indigo. In an acid solution, indigo white is precipitated.2... 

Wiistenberg, P., Kohler, G., and Stammwitz, U. 1999. Efficacy and mode of action of an immunomodulator herbal preparation containing Echinacea, wild indigo, white cedar. Adv. Ther. 16, 51-70. 

Indigo solution reduced to the colourless leuco compound, known as indigo white. 

Indigotin dissolves in hot concentrated caustic potash solution with an orange-yellow colom , indigo white and isatic acid being probably formed. 

On reduction in alkaline solution indigo blue takes up two atoms of hydrogen, forming indigo white, which possesses phe-noloid properties and dissolves in the alkaline liquid. 

In the air, indigo white solution oxidises immediately, insoluble indigo blue separating. This property is extensively employed in dyeing with indigo, and also serves for the isolation of pure indigo from the commercial product. 

From the derivatives of indigo blue (sulphonic acids, c.), substitution-derivatives of indigo white are obtained on reduction. 

Cotton fabrics impregnated with grape-sugar solutions are printed with a mixture of finely divided indigo and strong caustic soda suitably thickened. On steaming the indigo white produced... 

Indigotin reduces to the leuco compound, known as Indigo White, (6) ... 

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