... tannate of antimony or tin. The "acid colors" are only suitable for wool and silk, to which they are applied in an acid bath. A typical representative of this group is furnished by any one of the ordinary azo scarlets which in recent years have come into prominence as competitors of cochineal. The "Congo colors" are comparatively new, and are conveniently so named from the first coloring matter of the group ... — Scientific American Supplement, No. 810, July 11, 1891 • Various