Shepherdstown register. [volume] (Shepherdstown, Va. [W. Va.]) 1849-1955, 1913-03-27
Ancient Purple Dye.

The source ofthe purple pigment which
the ancients priced so highly that il was
actually sold for its weight in gold and is
said to have been the basis OF the CON-
mercial prosperity of Tyre and Sidon,
has been long in doubt. although it was
known to have been derived from certain
marine gastropodS or "snails." Protes-
sor Raphael Dubois, the physiological
chemist OF the University OF Lyons in
France, has succeeded recently in repro
ducing this pigment.
The purple is derived from SnailS OF
two genera, purpura and murex, the lat
ter bristling periwinkle sometimes cali
ed the rock snail. The species OF the
former genus used was Purpura lapilluS,
while of the Murex there are two species
available, brandaris and trunculus. The
three species yielded coloring matter OF
three distinct shades. The brandaris
corresponds probably to that produced at
Tyre. The species trunculus furnished
amethyst purple and was chiefly prepared
at Sidon. The pigment from lapillus is
of a deep violet, more red than blue,
having shade intermediate between the
other two.
II is not at all improbable that the dy-
ers of olden times added coloring matter
extracted from the madder plant or from
the cochineal insect, even in large pro-
portions. This seems TO have been a
common practice in Toulon, where there
are still the remains OF an ancient Roman
dyeing establishment, but where no
traces OF the shells of these snails can be
found.
In the cavity enclosed by the mantle
of the snail there is found, in addition TO
the gillS and other organs, a small whit
ish gland which secretes colorleSs fluid.
Under certain conditions this fluid ac-
uuires pink or violet tint, and this was
the basis for the highly priced dye.
The changes in color seem to be the
result of Preventative action like SO
many physiological processes. In the
gland and in the secretion Professor Du-
bois finds an insoluble ferment or "zy-
mase," which he calls purpuraSe. This
ferment is present in all three species and
is identical in all. Dissolved in the Sc
cretion there is substance which he calls
purpurine. This is different in each spe-
cies and is acted upon by the terment m
such a way that there results conversion
of the purpurine into chromogene or
color maker.
Tine chromogene then changes into
pigmented substance, becoming at hrst
yellow, then green, and finally purple,
under the influence OF heat or light. Ac-
companying this change from the chro-
mogene 10 the pigment there is an elm
ination OF a peculiar substance with a
strong, disagreeabIe odor resembling ash
fetda. The pigment produced from the
ch-omogene is quite lnSoluole III wafer
which accounts for its permanence wher
used as dye.
The color becomes even more brilliant
from long exposure TO the light OF tht
sun.
The method OF dyeing followed by tht
ancients has not been understood, but thu
researches Of Professor Dubois make
clear. According 10 Pliny, The linens
were dipped in juice that was yellow
or green and the light and the air did I'M
rest. II is also known that the ancient'
placed the glands Of the animals, as soor
as removed, into salt or flour. We car
now see that this not only prevented th'
putrefaction OF the precious material, bu
also retarded the secretion OF the juice:
and inhibited the fermentation OF the pur'
purase, since the salt or flour rapidly re-
moves the water in the tissues.
|