B13 Indigo Dye

Description
Reduced indigo is a soluble pale yellow compound. A cloth is immersed in the solution which penetrates the fibers. When the cloth is removed and exposed to air, a blue insoluble oxidation product forms. This is an ancient dyeing process.

Equation
4 RC-O-R' + O2 + 2 H2O --> 4 OH-+ 4 RC=OR'

yellow reduced form blue oxidized form

Reference
L. R. Summerlin, C. L. Borgford, and J. B. Ealy,"Chemical Demonstrations A Sourcebook for Teachers",Vol. 2, American Chemical Society, Washington, DC, (1987) p.208.