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Under the deep-furrowed, brown surface bark is a yellow layer, rich in tannin, and a dyestuff called quercitron.

The American quercitron bark gives us also a useful additional yellow dye.

A very minute proportion of quercetin, a principle yielded by quercitron bark, has been obtained from catechu.

Brown.—Prepare a bath with 20 lb. cutch, 2 lb. copper sulphate, 4 lb. quercitron extract.

Similarly the dyer proceeds to dye black upon a deep blue basis of indigo, with the ruddy colour of madder and the yellow of quercitron, &c.