668

DYEING AND CALICO PRINTING.

of the vermillion remains. Subsequent treatment with an alkali does notaffedt the red or restore the original shade.

In all these diredtions it must be understood that madder comprehendsgarancin and alizarin, natural or artificial. Cochineal must, in like manner,be taken to include lac.

The nature of the fibre often gives a clue to the colour, which should not beoverlooked. Thus among yellows, picric acid is not to be expected upon Ncotton, nor is iron-buff often found upon wool. Reds upon cotton are rarelycochineal,—usually madder, or the woods. Upon woollen or worsted, cochi-neal or magenta is more probable. Upon cotton, aniline blues are less likelythan upon wool and silk.