By Professor CHARLES O'NEILL.
Twenty-eight years ago Mr. Perkin discovered the first of the aniline
dyes. It was the shade of purple called mauve, and the chief agent in its
production was bichromate of potash. This salt is not actively poisonous,
and no one thought of attributing injurious properties to materials dyed
with the aniline mauve. Next in chronological order came magenta red. It
was first made from aniline by the agency of mercurial salts, and
afterward by that form of arsenic known to chemists as arsenic acid. The
fact that this at one time fashionable color was prepared by means of an
arsenical compound was spread through the country in a very impressive
manner by the great trial as to whether the patent was valid or not, all
turning upon the expression in the specification of "dry arsenic acid,"
and the disputes of scientists whether this expression meant arsenic acid
with or without water. The public mind had been for some time previously
exercised and alarmed by accounts of sickness and debility caused by
arsenical paper-hangings; it was, therefore, easy for pseudo scientists to
create an opinion that the magenta dye must be also poisonous, and that
persons wearing materials dyed with this color were liable to absorb
arsenic and suffer from its action. Ever since there have been, at
intervals, statements more or less circumstantial, that individuals have
suffered from wearing materials dyed with some of the artificial dyes. At
the present time these statements are emphasized by the exhibition at the
Healtheries of models of skin diseases said to be actually produced by the
wearing of dyed garments. Whether it be true or not that any form of skin
disease has been produced by the wearing of dyed articles of clothing is
simply a question of evidence, and there is evidence enough to show that
individuals have experienced ill effects who have worn clothing dyed with
artificial colors. But, as far as we know, there is an entire want of any
evidence that will satisfactorily show that the inconvenience suffered by
wearers of these dyed goods has been owing to the dyeing material. Years
must elapse before chemists or physicians can hope to become thoroughly
informed of the physiological action produced by the cutaneous absorption
of the thousands of new products which the ingenuity and industry of
technological chemists have made available for the manufacture of colors;
they are also new to science, most of them very complex in their
constitution, and so dissimilar to previously studied compounds used by
the dyer, that it may be said we have nearly everything to learn
concerning their action upon the human economy. With respect to dyed
woolen and silk goods it is almost entirely a question as to the innocence
or otherwise of the coloring matter itself, which in nine cases out of ten
is an organic body containing no mineral matter of any sort, and not
requiring the assistance of any mordant to enable it to dye.
Considerations of arsenic, or antimony, or mercury existing in the dyed
stuffs are absolutely excluded. In a few cases the dyestuff is a zinc
compound, and zinc in small traces may possibly be fixed by the material,
but this metal is not known to be actively noxious. Textiles made from
fibers of animal origin do not require, and as a rule do not tolerate, the
addition of any metal in dyeing with the artificial colors, and if the
manufacture of the color require the use of a metal, such as arsenic,
which by unskillfulness or carelessness is left in it when delivered to
the dyer, the tendency of the animal fiber is to reject it.
But the case with regard to textiles made from vegetables fibers is quite
different; upon materials made from cotton, flax, jute, or other fiber of
the vegetable kingdom, the new aniline colors cannot be fixed without the
assistance of other bodies acting the part of mordants. Some of these
bodies are actively poisonous in their nature, and introduce a possible
element of danger to the wearer of the dyed article. For many years,
almost the only method of dyeing cotton goods with the aniline colors
consisted in a preliminary steeping in sumac or tannic acid, followed by a
passage in some suitable compound of tin, and subsequent dyeing in the
coloring matter. Sumac and tin have been used for two hundred years or
more as the dyer's basis for a considerable number of shades of color from
old dye-stuffs; there never has been the least suspicion that there was
anything hurtful in colors so dyed. Sumac or tannic acid, in combination
with alumina, may be held to be equally inoffensive; now it is a fact that
the great bulk of cotton goods are dyed with the aniline colors by the
agency of these harmless chemicals. But of late years the dyers of certain
goods, and the calico printers generally, have found an advantage in the
use of tartar emetic, and other compounds of antimony, to fix aniline
colors; besides this, some colors are fixed in calico printing by means of
an arsenical alumina mordant; it need not be mentioned that antimony, as
well as arsenic, is, when administered internally, an active poison in
even small quantities, and that externally both are injurious under
certain conditions. An alarmist would require nothing further than this
statement to feel himself justified in attributing everything bad to
fabrics so colored; but the practical dyer or calico printer knows that
though he employs these poisonous bodies in his business, and that some
portion of them does actually accompany the dyed material in its finished
state, not only is the quantity excessively small, but that it is in such
a state of combination as to be completely inert and innoxious. In the
case of tartar emetic, it is the tannate of antimony which remains upon
the cloth, a compound of considerable stability, and almost perfectly
insoluble in water; in the case of a few colors fixed by the arsenical
alumina mordant, the arsenic is in an insoluble state of combination with
the alumina, in fact, the poisons are in the presence of their antidotes,
and not even the most scrupulous manufacturer has any fear that he is
turning out goods which can be hurtful to the wearer. Persons quite
unacquainted with the process of dyeing are apt to think that goods are
dyed by simply immersing them in a colored liquid and then drying them
with all the color on them and all that the color contains; they do not
know that in all usual cases of dyeing a careful washing in a plentiful
supply of water is the final process in the dye-house, and that nothing
remains upon the cloth which can be washed out by water, the color being
retained by a sort of attraction or affinity between it and the fiber, or
mordant on the fiber. Dyeing is not like painting or even the printing or
staining of paper for hangings, where the vehicle and color in its
entirety is applied and remains. It follows, therefore, that many
chemicals used in dyeing have only a transitory use, and are washed away
completely--such as oil of vitriol, much used in woolen dyeing--and that
of others only a very minute quantity is finally left on the cloth, as is
the case in antimony and arsenic in cotton dyeing and printing.
There is evidently among working dyers, as among all other classes, an
unknown amount of carelessness, ignorance, and stupidity, from which
employers are constantly suffering in the shape of spoiled colors and
rotted cloth. It is not for us to say that the public may not at times
have to suffer also from neglect of the most common treatments which
should remove injurious matters from dyed goods; what can be said is, that
if the dyeing processes for aniline colors be followed out with ordinary
care and intelligence, it is extremely improbable that anything left in
the material should be injurious to human health.--_Manchester Textile
Recorder._
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