w Substances may be tried, whether they are serviceable
in Dyeing, from Hopson's Translation of Weigleb's Chemistry.

"In order to discover if any vegetable contains a colouring principle
fit for dyeing, it should be bruised and boiled in water, and a bit of
cotton, linen, or woollen stuff, which has previously been well cleaned,
boiled in this decoction for a certain time, and rinsed out and dried.
If the stuff becomes coloured, it is a sign that the colour may be
easily extracted; but if little or no colour be perceived, we are not
immediately to conclude that the body submitted to the trial has no
colour at all, but must first try how it will turn out with the addition
of saline substances. It ought, therefore, to be boiled with pot-ash,
common salt, sal ammoniac, tartar, vinegar, alum, or vitriol, and then
tried upon the stuff: if it then exhibit no colour, it may safely be
pronounced to be unfit for dyeing with. But if it yields a dye or
colour, the nature of this dye must then be more closely examined, which
may be done in the following manner:--

Let a saturated decoction of the colouring substance be well clarified,
distributed into different glass vessels, and its natural colour
observed. Then to one portion of it let there be added a solution of
common salt; to the second, some sal ammoniac; and to the third, alum;
to the fourth, pot-ash; to the fifth, vitriolic or marine acid; and to
the sixth, some green vitriol: and the mixtures be suffered to stand
undisturbed for the space of twenty-four hours. Now in each of these
mixtures the change of colour is to be observed, as likewise whether it
yields a precipitate or not.

If the precipitate by the pure acid dissolve in an alkaline lixivium
entirely, and with a colour, they may be considered as resino-
mucilaginous particles, in which the tingeing property of the
body must be looked for, which, in its natural state, subsists in an
alkalino-saponaceous compound. But if the precipitate be only partly
dissolved in this manner, the dissolved part will then be of the nature
of a resinous mucilage, which in the operation has left the more earthy
parts behind. But if nothing be precipitated by the acids, and the
colour of the decoction is rendered brighter, it is a mark of an
acido-mucilaginous compound, which cannot be separated by acids. In this
there are mostly commonly more earthy parts, which are soon made to
appear by the addition of an alkali.

When, in t