SAFFLOWER OR CARTHAMINE RED.
The safflower or bastard saffron (_Carthamus tinctoria_) grows wild
in Southern Europe, and is also cultivated. It contains two colouring
matters, yellow and red. The former is not used in dyeing, but is
employed for colouring liqueurs, since it is innocuous. The red
colouring matter is used for colouring artificial flowers and for fine
cosmetics; formerly it was employed in dyeing, but is now rarely used
for this purpose, since carthamine red has little permanence and can be
replaced by cheaper dyes.
The yellow colouring matter, which is not used, is generally removed
by treating the corolla of the safflower, which contains the colouring
matter, with water. After this treatment it is known as washed
safflower. In the dried corolla of the flower up to 36 per cent. of the
yellow colouring matter is found, whilst only 0·4 to 0·6 per cent. of
the red is contained.
It appears that the colouring matter of the safflower has been used
from the most ancient times. The Chinese employ it to obtain a handsome
cosmetic, the Tyrians are said to have used it in dyeing. In Europe it
was not cultivated before the seventeenth century, when it came into
use for dyeing.
In order to obtain pure carthamine red—and this is the form in which
it is generally used—safflower is treated for a long time with water
containing a little acetic acid until a yellow solution no longer
results. The residue is then treated with soda solution for several
hours, when the colouring matter dissolves; the solution is filtered
and neutralised with acetic acid. Cotton is then introduced. Carthamine
red is a colouring matter which at once dyes animal and vegetable
fibres when these are brought in contact with its solution. Thus the
whole of the colouring matter is precipitated on the cotton, which is
coloured a deep red. After twenty-four hours the cotton is taken out,
washed, and treated with soda solution, in which the colouring matter
dissolves. When this solution is carefully neutralised with citric acid
the colouring matter separates in the form of fine flocks. These are
collected, dissolved in strong alcohol, the solution evaporated to a
small volume, the colouring matter again precipitated by the addition
of a large quantity of water, and washed with pure water until the wash
waters begin to be coloured red. The pure carthamine thus obtained is
spread upon small cups, in which it dries to a beautiful red mass which
in somewhat thicker layers has a fine green lustre. It is brought into
commerce as ”cup red” or ”plate red”.
The small quantity of colouring matter contained in the safflower,
as well as the complicated process for obtaining it, make it evident
that this colouring matter will be among the most expensive found
in commerce. The high price is, however, neutralised by its great
colouring power, and by the fact that nothing can in all cases replace
it for colouring the best artificial flowers.
=Safflower Carmine.=—This substance, used by dyers, is a solution of
carthamine red in soda solution. It is only necessary to add an acid
after once introducing the fabric in order to fix the colouring matter
at once upon the fibre.
The shades produced by carthamine red are distinguished by a delicacy
of tint not produced by other dyes; all shades between the deepest red
and the palest rose-red may be obtained from it. Unfortunately it is
very susceptible to the action of alkalis; one careless washing of an
article dyed with carthamine is sufficient to remove the greater part
of the colour.
On account of its cost and little durability carthamine red is not
used in painting. It is principally employed in the artificial flower
industry for colouring flowers. Pure carthamine or a mixture with
finely powdered steatite is applied by rubbing.
=Alkanet.=—The roots of alkanet (_Alkanna tinctoria_) contain in the
bark a fine red colouring matter, from which also a violet lake can
be obtained, though this is rarely made. The plant is largely grown
in Southern Europe and also around Vienna. The colouring matter is
obtained pure by macerating the root for a long time with water and
then treating with strong alcohol, which dissolves the colouring
matter, together with a large quantity of resin. The alcohol is
distilled off, the residue extracted with ether, and the ethereal
extract treated with a large quantity of water, which extracts the
colouring matter. This is left in the pure state, when the solution is
slowly evaporated.
According to Carnelutti and R. Nasini alkannin is obtained by
extracting the root of _Anchusa tinctoria_ with petroleum ether,
evaporating, treating the residue with weak caustic potash, filtering,
and shaking the filtrate several times with ether. The solvent is
removed, the colouring matter precipitated by carbonic acid, dried over
sulphuric acid, and dissolved in ether. The filtered solution is then
allowed to evaporate. Alkannin is then obtained as a dark brownish-red
mass, which is easily powdered. It has a metallic lustre, and readily
dissolves in alcohol, glacial acetic acid and chloroform.
When alum is added to the aqueous solution of the colouring matter a
beautiful violet precipitate separates, which when dry is very suitable
for artistic purposes. Alkanet is little used. It is completely
replaced by much cheaper colouring matters.