- An orange-red crystalline substance, C8H5NO2, obtained by
the oxidation of indigo blue. It is also produced from certain
derivatives of benzoic acid, and is one important source of artificial
indigo.
- A peculiar substance obtained from the wool of sheep,
consisting largely of potash mixed with fatty and earthy matters. It is
used as a source of potash and also for the manufacture of gas.
- A glucoside obtained from woad (indigo plant) and other
plants, as a yellow or light brown sirup. It has a nauseous bitter
taste, a decomposes or drying. By the action of acids, ferments, etc.,
it breaks down into sugar and indigo. It is the source of natural
indigo. - An indigo-forming substance, found in urine, and other
animal fluids, and convertible into red and blue indigo (urrhodin and
uroglaucin). Chemically, it is indoxyl sulphate of potash, C8H6NSO4K,
and is derived from the indol formed in the alimentary canal. Called
also uroxanthin.