Now the woolen dyer has largely adopted an excellent mordant in
bichromate of potash; it is cheap, easily applied, and not perceptibly
injurious to the fiber. It is his desire, therefore, to have a good
range of red, yellow, blue, and other coloring matters, all giving
fast dyes with this mordant. This action and desire on the part of the
dyer has more and more placed the problem of producing fast colors
upon the shoulders of the color manufacturer or chemist, and right
well has the demand been met, for in the diagram on the wall we see
how, in the alizarin colors and their allies, he has already furnished
the dyer with a goodly number of dyestuffs yielding fast dyes with
this chosen mordant of the woolen dyer. Since, however, they yield
fast colors with other useful mordants, and upon other fibers than
wool, these alizarin colors prove of the greatest value to the dyer of
textile fabrics generally. Let us not forget the fact, then, that it
is among the "mordant dyes," the very class to which belong most of
the natural coloring matters, that we find our fastest coal tar dyes.

When we examine the results of actual exposure experiments, such as
are here shown on these four diagram sheets, surely we have no
hesitation in declaring how utterly false is the popular opinion that
all coal tar colors are fugitive to light, while the good
old-fashioned natural dyes are all fast. The very opposite indeed is
here shown to be the case. For myself, I feel persuaded that at the
present time the dyer has at his command a greater number of fast dyes
derived from coal tar than from any other source, and I believe it
possible to produce with dyes obtained from this source alone, if need
be, tapestries, rugs, carpets, and other textile fabrics which shall
vie successfully in point of color and duration of color with the best
productions of the East, either of this or any other age.