ll readily comprehend that the thorough appreciation and use
of that highest and best method of classification, particularly in the
case of the coal-tar dyes, will be, more or less, a sealed book except
to the student of organic chemistry. But it may be asked, "How does that
highest and best method of classifying the dyestuffs affect the users,
the dyers, in their processes?" In reply, I would say, "I believe that
the dyer who so understands the chemical principles involved in the
processes he carries out, and in the best methods of classifying the
dyes as chemical substances, so as to be able to act independently of
the prescriptions and recipes given him by the dye manufacturers, and so
be master of his own position, will, _ceteris paribus_, be the most
economical and successful dyer." Many manufacturers of dyestuffs have
said the very same thing to me, but, independently of this, I know it,
and can prove it with the greatest ease. Let me now, by means of an
experiment or two, prove to you that at least some classification is
necessary to begin with. So different and varied are the substances used
as colouring matters by the dyer, both as regards their chemical and
physical properties, that they even act differently towards the same
fibre. I will take four pieces of cotton fabric; three of them are
simple white cotton, whilst the fourth cotton piece has had certain
metallic salts mixed with thickening substances like gum, printed on it
in the form of a pattern, which at present cannot readily be discerned.
We will now observe and note the different action on these pieces of
cotton--(i.) of a Turmeric bath, (ii.) a Magenta bath, and (iii.) a
madder or Alizarin bath. The Turmeric dyes the cotton a fast yellow, the
Magenta only stains the cotton crimson, and on washing with water alone,
almost every trace of colour is removed again; the madder, however,
stains the cotton with no presentable shade of colour at all, produces a
brownish-yellow stain, removed at once by a wash in water. But let us
take the printed piece of cotton and dye that in the Alizarin bath, and
then we shall discover the conditions for producing colours with such a
dyestuff as madder or Alizarin. Different coloured stripes are
produced, and the colours are conditioned by the kind of metallic salts
used. Evidently the way in which, the turmeric dyes the cotton is
different from that in which the madder dyes it. The first is a yellow
dyestuff, but it woul