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.

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