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The Commercial Products of the Vegetable Kingdom by P. L. Simmonds

P >> P. L. Simmonds >> The Commercial Products of the Vegetable Kingdom




Under the third head, he examined, in a general way, the chemistry
of the colorific and coloring matters of the lichens and the results
to which it has led, avoiding as much as possible the technicalities
inseparable from such a subject, and giving a short _vise_ of the
researches of Heeren, Kane, Rochleder, and Heldt, Stenhouse,
Schunck, Laurent, and Gerhardt, and others. "Our untaught senses
should undoubtedly lead us to expect the lichens, whose thallus
exhibits the brightest tints, to yield the finest dyes, and these,
too, of a color similar to that of the thallus, but experience
teaches us that the beautiful reddish or purplish coloring-matters
are producible in the greatest abundance by the very species from
which we should least expect to derive any, viz., in those most
devoid of external color. This, though at first sight very
remarkable, is easily explicable, when we remember that, in most of
the so-called dye-lichens, colorific principles exist in a colorless
form, and only become converted into colored substances under a
peculiar combination of circumstances.

"Some lichens contain coloring matters, ready formed, and these
exhibit themselves in the tint of the thallus of the plants, _e.g._
chrysophanic [or parietinic] acid in _Parmelia parietina_, and
vulpinic acid in _Evernia vulpina_. In other species we find
principles, which, while in the plant, and unacted on by chemical
re-agents, are colorless, but which, when the lichens are exposed to
the combined influence of atmospheric air, water, and ammonia, yield
colored substances. This series of colored products is usually
comprehended more for convenience sake than on account of chemical
identity, under the generic term orceine."

The whole subject of the chemistry of these bodies is at present in
a most unsatisfactory condition, demanding fresh investigation and
research, in illustration of which, the author exhibited tables of
the colorific and coloring principles, so far as they are at present
known, showing their chemical formulae and the authority therefor,
and various relative information. "It is highly probable that when
the chemistry of the lichens has been more fully studied, and the
whole subject of their color-educts and products better understood,
we shall begin to reduce the present confused mass of complex
substances, and find the same principles more extensively diffused
through different lichen species." Dr. L. entered somewhat minutely
on the chemical reactions of the better known colorific and coloring
principles, and their derivatives, so far at least as these throw
any light on the production and transmutation of the red or purple
colors extracted from what may be termed _par excellence_, the
_dye-lichens_. After a few remarks on the chemical constitution of
orchil and litmus, as given by Kane, Gelis, Pereira, and others, he
discussed the subject of decolorisation of weak infusions of orchil
and litmus by exclusion of atmospheric air, and by various
deoxidising agents, and the different theories as to the causation
of this phenomenon. "I have repeatedly had occasion to notice that,
when weak infusions of these substances are excluded for some time
from atmospheric air, in a bottle, with a tightly fitting cork, they
gradually lose color, but rapidly regain it on re-exposure. It is
curious that both orchil and litmus are what are called transient or
false colors, _i.e._, they slowly lose their bloom and tint by long
exposure to the atmosphere; the coloring matter, therefore, appears
to be decolorised both by exposure to, and exclusion from the air,
phenomena apparently of very opposite characters. The cause of the
latter phenomenon has never, so far as I am aware, been quite
satisfactorily explained; but it has been variously supposed to be
due:--

1. To the mere negation of oxygen.

2. To the development, in the liquids, of various substances,
capable of exerting a decolorising influence on the coloring matter.

3. To deoxidation of the coloring matter by substances, which have a
great tendency to become oxidised or peroxised; _e.g._ hydrogen, in
the case of decolorisation by sulphuretted hydrogen, nascent
hydrogen, and the protoxides of iron and tin, &c.

4. To the fixation of an additional amount of hydrogen in a new
colorless body, formed by the union of the sulphuretted hydrogen or
other substances with the coloring matter of the liquid. This view
is chiefly supported by Kane, who says, "that precisely as the
coloring matters combine with water, to form different shades of
red-colored bodies--with ammonia to produce a series of bodies,
which are blue and purple--so they combined with sulphuretted
hydrogen to form colorless compounds in solution, which, if solid,
very probably would be white." He supposes, in a word, that for
every colored substance existing in orchil and litmus, there is a
corresponding white one, producible by the action of sulphuretted
hydrogen, &c.; and, in proof of this theory, he mentions having
obtained from Azolitmine and Betaorceine colorless bodies, to which
he gave the respective names of Leuco-litmine and Leuco-orceine.

The author then gave a short summary of Dr. Westring's experiments
on the dyeing powers of the Swedish lichens, which he found might be
conveniently divided into four classes, according to the degree of
heat employed in their maceration, viz.:--

1. Lichens, whose coloring matter was easily extractable by _cold_
water alone.

2. Those which required for the elimination of their coloring
matter, maceration in _tepid_ water (_i.e._ below 258 degs. Swedish
thermometer).

3. Those which required maceration in _warm_ water (_i.e._between 50
and 60 degs. Swedish thermometer).

4. Those requiring _boiling_ water alone, or with the aid of
solvents.

"It must be admitted that our knowledge of the true nature of the
colorofic and coloring principles of the lichens is, as yet, very
imperfect and confused, and one great cause of the dubity and
obscurity overhanging the subject, is the fact that different
analysts have arrived at most opposite results, even in the
examination of the same species. For instance, in _Rocella
tinctoria_, which has, of all the dye-Lichens, been most frequently
selected for analytical investigation, on account of its important
product orchil, the discrepancies between the results obtained are
very striking. In it Heeren discovered his _Erythrine_; Kane his
_Erythriline_; Schunk his _Erythric acid_; and Stenhouse three
different substances in as many varieties of the plant; all of these
bodies differing more or less from each other in composition and
properties (at least, if we are to assume, as correct, the
descriptions given of them by their respective discoverers").

"I have already hinted that there is no ratio between the external
and internal color or structure of a lichen, and the kind or amount
of coloring matter it will be found to yield. It is exceedingly
natural to suppose that such a ratio should exist; but, proceeding
for some time on this supposition, I was frequently disappointed in
my results--the most showy and brilliantly colored lichens often
furnishing the dullest and most worthless colors. For instance, the
bright yellow thallus of _Parmelia parietina_, and the beautiful
scarlet apothecia of _Scyphophorus cocciferus_, instead of producing
a rich yellow in the one case, and a deep crimson in the other,
yielded, respectively, only dirty greenish-yellow and brownish
colors. As a general rule I should almost be inclined to say that
the finer the color of the thallus of any given lichen, the more is
that lichen to be suspected of poverty in valuable coloring matters;
and that, on the other hand, the palest pulverulent or crustaceous
species, especially such as are saxicolous, may be expected to yield
the most beautiful and valuable pigments (_e.g._ the Rocellas and
Lecanoras). In such circumstances it is necessary to have some test,
of easy applicability, of the kind and amount of colorific
properties of any lichen, and this fortunately is readily
attainable."

The fourth section of the paper was devoted to the consideration of
the various tests of colorific power, which have been recommended by
different authors. "Of these, the greater number proceed on the
principle of developing the coloring matter by some alkali, in
conjunction with the decomposing action of atmospheric oxygen and
water; others are founded on the reaction between colorific
principles of certain of the dye lichens and some of our ordinary
chemical re-agents." The author noticed in particular--

1. Helot's test, }
2. Westring's tests, }qualitative.
3. Stenhouse's test, }
4. " quantitative.

Helot's test consists in digesting the dried and powdered lichen or
a few hours, at a temperature of 130 degs., in a weak solution of
ammonia, sufficiently strong, however, to be tolerably pungent. One
that is fit for the dyer will yield a rich violet red liquor.

Dr. Westring recommended simply macerating three or four drachms of
the lichen in cool spring water, assisting, perhaps, the solvent
action of the water by minute quantities of common salt, nitre,
quicklime, sulphate of copper or iron, or similar re-agents. If
these means failed, after a sufficient length of time had been
allowed for the development of color, he digested a fresh portion of
the pulverised lichen in water, containing small quantities of
sal-ammoniac and quicklime [in the proportion of 25 parts of water,
1-10th lime, and 1-20th sal-ammoniac for every part of lichen], for
a period varying from eight to fourteen days, and by this process,
he says, he never failed to develop all the color which the plant
was capable of yielding.

Dr. Stenhouse, of London, one of our latest and best authorities on
the chemistry of the lichens, adds to an alcoholic infusion of the
lichen, a solution of common bleaching powder (chloride of lime),
whereby, if it contain certain colorific principles capable of
developing, under the joint action of air, water, and ammonia, red
coloring matters, a fugitive but distinct _blood-red color_ will be
exhibited. The amount of this colorific matter may be estimated
quantitatively by noting the quantity of the chloride of lime
solution required to destroy this blood-red color in different
cases: or the same result may be obtained by macerating for a short
period in milk of lime--filtering--precipitating the filtered liquor
by acetic or muriatic acid--collecting this precipitate on a weighed
filter--drying at ordinary temperatures and again weighing.

The author entered into a full analysis of these tests and
processes--pointing out their respective advantages and
disadvantages--and showing their practical value and applications.
He stated that he had made use of these, and various other tests, in
upwards of 300 experiments, and the one which he employed to the
greatest extent, because most uniformly applicable, was Helot's
ammonia test. The following combination is that most favorable for
the development of the coloring matter of the lichens--viz., the
presence

1. Of _water_ as a solvent menstruum.
2. Of atmospheric _oxygen_.
3. Of _ammonia_, in the state of vapor or in solution, and
4. Of a moderate degree of _heat_;

And according as the proportion of these combining elements varies,
so do the kind and amount of color educed by them. This combination
is the foundation of all the processes for the manufacture of the
lichen dyes throughout the world, however different these may appear
to be in detail or results.

I believe it may come to be a matter of great commercial importance
to discover, at home or abroad, some cheap and easily-procurable
substitute for the _Roccellas_, which are gradually becoming scarce,
and consequently valuable in European commerce, having sometimes
fetched, in times of scarcity, no less than L1,000 per ton. No
plants can be so easily collected and preserved as
lichens--requiring merely to be cleaned, dried, pulverised, and
packed; and if their bulk be an objection to transport, their whole
colorific matter may be collected in the way I have already
mentioned. Ascending to the verge of eternal snows, and descending
to the ocean level--with a geographical diffusion that is
co-extensive with the surface of our earth, it is difficult to say
where lichens shall not be found. There are myriads of small rocky
islets in the boundless ocean, and there are thousands of miles of
barren rocky coast and sterile mountain range in every part of the
world, which, though at present unfit to bear any of the higher
members of the vegetable kingdom, are yet carpeted and adorned with
a rich covering of lichens, and of those very species too, which I
have already spoken of as prolific in colorific materials. I
sincerely believe, therefore, that a more general attention to the
very simple tests just enumerated, would ultimately result in a
greatly extended use of the lichens as dye agents. What renders it
very probable that efforts in this direction are likely to meet with
success is the great similarity of species found all over the world.
It has been repeatedly noticed that the European species, which, of
course, are best known, differ little from those of North America.
Dr. Robert Brown remarked the same fact with regard to New Holland
species, and Humboldt also recognised the similarity in natives of
the South American Andes. Of a large collection made by Professor
Royle, in the Himalayas, Don pronounced almost every one to be
identical with European species. From examining the raw vegetable
products, sent by different countries to the Great Exhibition of
1851, I am satisfied that, even now, there are many fields open for
the establishment of an export trade in _Roccellas_ and other
so-called orchella weeds." I there saw specimens of good dye lichens
from almost every part of the world, including our own young
colonies; and as a single instance of their probable value, I may
introduce here the copy of a note appended to a specimen of orchella
weed from the island of Socotra, contained in the Indian collection
of that exhibition, "_abundant_, but _unknown_ as an article of use
or commerce. Also abundant on the hills around (Aden) and _might_ be
made an article of trade." Roccellas from this source are estimated
as worth L190 to L380 per ton. I believe that a similar statement
might be made with regard to the countless islands of the broad
Atlantic and Pacific, which may, at some future period, perhaps not
far distant, be found to be rich depots of orchella weeds, just as
some of them are, at present, rich fields of guano, and may, as
such, become new nuclei of British commerce and enterprise. Even at
home, in the immediate vicinity of Edinburgh, or, to restrict our
limits still more narrowly, within the compass of Arthur's Seat,
there are not a few very good dye-lichens, which require merely to
be scraped with an old knife or similar instrument, from the rocks
to which they adhere, and subjected to the ammonia process already
mentioned. Of twelve specimens thus collected at random one morning,
I found no less than three yielded beautiful purple-red colors,
apparently as fine as orchil or cudbear, while the others furnished
rich and dark tints of brownish-red, brown and olive-green.

Dr. Lindley's communication was illustrated with specimens of
coloring matters yielded by various lichens collected in the
neighbourhood of Edinburgh, &c.


BARKS FOR TANNING.

Let us now take a brief review of the sources from whence tanning
materials may be obtained, which will also enable us to form a fair
estimate of the prospect of future supplies. Only one medal was
awarded, at the Great Exhibition, for tanning substances, viz., to
Messrs. Curtis, Brothers (United Kingdom, No. 126), but honorable
mention was made of the following competitors:--One from Tunis, one
from Van Diemen's Land, one from New Zealand, one from Belgium, one
from the Cape of Good Hope, one from Canada, and one from the United
Kingdom.

The substance from which pure tannin is most frequently obtained for
chemical purposes is nutgalls, for tannin constitutes above 40 per
cent, of their weight. It may be procured also from several other
sources, such as oak, horse chestnut, sumach, and cinchona barks,
catechu, kino, &c.

The basis of the skins of animals is composed of a substance to which
the name of gelatine is given. One of the properties of this substance
is, that when combined with tannin, it forms the compound of tannate
of gelatine, or leather, a substance which is so useful to mankind.
From time immemorial, the substance employed to furnish the tannin to
the hides of animals, in order to convert them into leather, has been
oak bark. But as the purpose for which oaks are grown is their timber,
and not their bark, the supply of oak bark cannot be calculated upon,
and this is, perhaps, one of the causes why tanning as an art is in
such a backward state.

The consumption of tannin required in the leather manufacture may be
estimated from the fact that more than 672,000 cwts. of raw hides were
imported in 1851, besides the hides of the cattle, &c., consumed in
the United Kingdom. On the Continent and in the United States the
consumption of bark for this purpose is also considerable.

The imports of bark for the use of tanners and dyers has amounted
yearly to the very large quantity of 380,674 cwt., besides what we
obtain at home. Oak bark contains usually the largest proportion of
tannin, and according to Davy's experiments eight-and-a-half pounds of
oak bark are equivalent for tanning purposes to two-and-a-quarter of
galls, three of sumach, seven-and-a-half of Leicester willow, eleven
of Spanish chesnut, eighteen of elm, and twenty-one of common willow
bark. Tannin obtained from these sources, however, differs materially
in some of its characters. The tannin of nutgalls, which is that
generally employed for chemical purposes, is sometimes called
gallo-tannic acid, to distinguish it from other species.

Notwithstanding the number of different substances which have from
time to time been introduced for the use of tanners, it is,
nevertheless, pretty generally acknowledged that there is nothing
superior, or even equal, to good oak bark, and that all attempts to
hurry the process beyond a certain point by the use of concentrated
solutions of tan, &c., are for the most part failures, as the
manufacture of good leather, to a great extent, depends on the process
being conducted in a slow and gradual, but--at the same time--thorough
and complete matter.

Oak bark is, however, by no means the only astringent bark well suited
to the use of the tanner, and in various parts of the world other
similar substances are used with very great success. All these tanning
materials, though they may not be considered by the English tanner
equal to the best oak bark, are, nevertheless, of great value to him;
they may be employed in conjunction with oak bark, or even as a
substitute in times of scarcity, or when the price of oak bark is
high; in fact the very existence of such substances tends to keep down
and equalise the price of bark, and to prevent it from undergoing
those great fluctuations in value which would necessarily occur were
it the only tanning material available to our manufacture--("Prof.
Solly in Jury Reports of Great Exhibition.")

There are a vast number of bark and other substances useful for
tanning purposes, which are found in the tropics, that are
comparatively unknown or little regarded in Europe; but which might be
readily obtained in large quantities and at a trifling cost. The bark
of many species of _Acacia_ furnishes the tanning principle in a great
degree, particularly that of _A. arabica_, which, under the name of
Babul wood, is largely used about Scinde, Biliary, Gruzerat, and other
parts of India; where it is regarded as a powerful tonic. The fruit of
_A. vera_, termed Egyptian and Senegal "bablah," has been employed in
tanning and dyeing. Numerous species of this tribe are found abundant
in New South Wales and the Cape Colony, and these, particularly the
wattle bark of Australia, are in common use for tanning, from their
astringent properties. The bark and rind of the fruit of the
pomegranate (_Pumica Granata_) have similar properties.

The bark of _Avicenna tomentosa_ is in great use in the Brazils for
tanning. So are the curved pods of _Caesalpinia Coriari_, in the East
and West Indies, under the name of Divi-divi. _Coriaria myrtifolia_ is
not only used in tanning leather, but also for staining black. It is
worth L9 to L10 per ton. _Pterocarpus marsupium_ furnishes about
Tellicherry the concrete exudation called kino, a powerful astringent
used for tanning.

The plants of the mangrove tribe, _Rhizophora Mangle_, and other
allied species, have frequently an astringent bark, which is in many
cases used for tanning and dyeing black. This tree is very common in
most tropical countries, where it forms dense thickets on the muddy
banks of rivers and the sea shores. The bark of _Bauhinia variegata_,
is made use of in Scinde and other parts of Asia. The bitter
astringent bark and the galls of several of the Tamarisk tribe are
also well suited for the purpose.

_Mesembryanthemum nodiflorum_, one of the numerous indigenous species
of the Cape, is used in making morocco leather.

The extract procured from the bark of the _Butea_, that of the
_Buchanania latifolia_, the _Scyzgium_ (_Calyptranthes_), _Jambolana_,
&c., are likely to be of consequence to the tanners, and could be
produced in India in large quantities. Specimens of these, and of the
bark of the Saul tree, of _Nychanthes arbortrista, Terminalia
angustifolia_, and of the gaub fruit (_Diospyros glutinosa_), were
shown by the East India Company. The bark of the hemlock tree is
extensively employed for tanning in New Brunswick.

The bark of yellow hercules (_Xanthoxylum ochroxylon_), and the pods
of _Acacia tortuosa_ are used for tanning in the West Indies.

In the instructions given by the Admiralty to Sir James Boss, when
proceeding on his Antarctic Expedition, his attention was particularly
called to the astringent substances adapted for tanning, and to the
various extracts of barks, &c., imported into England from our
Australian settlements, and which are employed by the tanner. Little
sterling information has as yet been obtained as to the qualities of
the astringent gums, barks, and dyes, yielded in such abundance by the
trees of those colonies, and the proportion of tannin they contained.

In 1846, 563 tons of bark for tanning were exported from Port Phillip.

A large quantity of tannin is extracted from various species of
Eucalyptus, the gigantic gum trees in Australia and Van Diemen's Land
(of which quarter all the species are natives), and sent to the
English market; it is said to be twice as powerful in its operations
as oak bark. Some of these trees attain a height of 200 feet. Their
bark separates remarkably into layers. A sort of kino gum, an
astringent resinous-like substance, is also extracted from _E.
resinifera_, the brown gum-tree of New Holland, which is sold in the
medicine bazaars of India. It exudes in the form of red juice from
incisions in the bark. A single tree will often yield 60 gallons. In
Brazil they use the bark of _Luhea panicata_, an evergreen climber,
for tanning leather; and in Peru the bark of some species of
_Weinmaunia_ serve the same purpose. Among other powerful astringents
I may notice the root of a species of Sea Lavender (_Statice
Caroliniana_), _Myrica cerifera_, and _Heuchera Americana_, all
natives of North America. Also the petals of _Hibiscus Rosa-sinensis_,
a native of Asia.

The sea-side grape (_Coccolaba uvifera_) yields an astringent
substance, known as Jamaica kino.

The bark of the _Cassia auriculata_, and the milky juice of the
_Asclepias gigantea_, are used for tanning in India.

The red astringent gum obtained from _Butea frondosa_, a middling
size tree, common in Bengal and the mountainous parts of India, is
used by the natives for tanning. English tanners, however, object to
its use on account of the color which it communicates to the leather.

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