Among the "Congo oranges and yellows," we find some of the fastest on
cotton of this class of colors. Still they deserve only the rank of
medium fastness. They are Mikado orange 4 R, R, G. Hessian yellow,
curcumin S, chrysophenin. On wool, we have about half a dozen of
medium fastness, viz., benzo-orange, Congo orange R, chrysophenin G,
chrysamin R, brilliant yellow. On silk, however, we find in this group
about a dozen of the fastest oranges and yellows with which we are
acquainted for this fiber, viz., Congo orange R, chrysophenin G,
diamine yellow N, brilliant yellow, curcumin W, benzo orange, Hessian
yellow, chrysamin R and G, cresotin yellow R and G, cotton yellow G,
and carbazol yellow.
Does it not appear somewhat remarkable that we should find among this
generally fugitive group of coloring matters colors which are so
eminently fast on silk, and which we entirely fail to meet with among
those groups which usually furnish our fast colors, e.g., the alizarin
group?
Passing on to the "Congo violets, blues, and purples," we find few
colors worthy of particular notice for fastness. Diamine violet N
appears, perhaps, of medium fastness on wool and silk, while
sulphonazurin, benzo-black blue, and direct gray may claim the same
distinction on silk.
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