"mordant dyes."

Among the "basic colors" we search in vain, however, for a really fast
dye on any fiber. Still, Magdala red, perhaps, appears faster than the
rest on silk, and among the greens and blues we find a few dull blues
on cotton, which, for this fiber, have been recommended as substitutes
for indigo, viz., Indophenin, paraphenylene, blue, cinerein, Meldola's
blue, etc. The azine greens, also, appear tolerably fast on cotton and
on silk, but although possessing some body of color, after exposure,
the original dark green has changed to a decided drab.

When we examine the "acid colors," however, we meet with a number of
scarlets, crimsons, and clarets, possessing considerable fastness both
on wool and on silk. Some, indeed, appear almost, if not entirely, as
fast as cochineal scarlet, e.g., Biebriech scarlet, brilliant crocein,
etc.

Among the "acid oranges and yellows," we also find a goodly number
which are of medium fastness. About ten, either on wool or on silk,
may even be accounted really fast, and are fit, apparently, to rank
with alizarin colors. Note, for example, on wool: Crocein orange,
aurantia, orange crystal, tartrazin, milling yellow, palatine orange;
on silk, acid yellow D, brilliant yellow, azo acid yellow, metanil
yellow, curcumin S, etc. I may remark that these are some of the
fastest yellows on wool and silk with which we are acquainted. It is
interesting to note the decided fugitive character, on silk, of
tartrazin, aurantia, orange crystal, etc., compared with their great
fastness on wool. Observe, also, how, on wool, the pale lemon yellow
of picric acid has changed to a full reddish brown.