How, then, does it happen that these coal tar colors have been so long
and so seriously maligned by the general public? Apart from the fact
that public opinion has been based upon an imperfect knowledge of the
subject, we shall find a further explanation when we examine the
diagrams showing the "direct dyes" obtained from coal tar. According
to their mode of application I have here arranged them in three large
groups, viz., basic, acid, and Congo colors. A fourth group,
comprising comparatively few, is made up of those colors which are
directly produced upon the fiber itself.

The "basic colors" have a well known type in magenta. They are usually
applied to wool and silk in a neutral or slightly alkaline bath; on
cotton they are fixed by means of 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 which was discovered,
viz., Congo red. They are applicable to wool, silk, and cotton,
usually in a neutral or slightly alkaline bath. Of the dyes produced
directly upon the fiber itself, one may take aniline black and also
primulin as a type, the latter a dye somewhat recently introduced by
Mr. A.G. Green, of this city.

Our first impression, in looking at these "direct dyes," is that they
are more numerous and more brilliant than the "mordant dyes," and that
they are for the most part fugitive. Still, if we examine the
different series in detail, we shall find here and there, on the
different fibers, colors quite equal in fastness to any of the