Among the most venerable of natural dye-stuffs is indigo, the substance
from which Unverdorben first obtained aniline in 1826. The colouring
matter is found in a number of leguminous (see Fig. 7), cruciferous, and
other plants, some of which are largely cultivated in India, China, the
Malay Archipelago, South America, and the West Indies; while others, such
as woad (see Fig. 8), are grown in more temperate European climates. The
tinctorial value of these plants was known in India and Egypt long before
the Christian era. Egyptian mummy-cloths have been found dyed with indigo.
The dye was known to the Greeks and Romans; its use is described by the
younger Pliny in his Natural History. Indigo was introduced into Europe
about the sixteenth century, but its use was strongly opposed by the woad
cultivators, with whose industry the dye came into competition. In France
the opposition was strong enough to secure the passing of an act in the
time of Henry IV. inflicting the penalty of death upon any person found
using the dye. The importance of indigo as an article of commerce is
sufficiently known at the present time; more than 8000 tons are produced
annually, corresponding in money value to about four million pounds. It is
of importance to us as rulers of India to remember that the cultivation
and manufacture of indigo is one of the staple industries of that country,
from which the European markets derive the greater part of their supply.
[Illustration: FIG. 7.--INDIGO PLANT (_Indigofera tinctoria_).]
Imagine the industrial revolution which would be caused by the discovery
of a process for obtaining indigo synthetically from a coal-tar
hydrocarbon, at a price which would compare favourably with that of the
natural product. This has not actually been done as yet, but chemists have
attempted to compete with Nature in this direction, and the present state
of the competition is that the natural product can be cultivated and made
more cheaply. Nevertheless the dye can be synthesised from a coal-tar
hydrocarbon, and this is one of the greatest achievements of modern
chemistry in connection with the tar-products. For more than half a
century indigo had been undergoing investigation by chemists, and at
length the work culminated in the discovery of a method for producing it
artificially. This discovery was the outcome of the labour of Adolf v.
Baeyer, who commenced his researches upon the derivatives of indigo in
1866, and who in 1880 secured the first patents for the manufacture of the
colouring-matter. It is to the laborious and brilliant investigations of
this chemist that we owe nearly all that is at present known about the
chemistry of indigo and allied compounds.
[Illustration: FIG. 8.--WOAD (_Isatis tinctoria_).]
Two methods have been used for the production of artificial indigo--benzal
chloride being the starting-point in one of these, and nitrobenzoic
aldehyde in the other. The generating hydrocarbon is therefore toluene. By
heating benzal chloride with dry sodium acetate there is formed an acid
known as cinnamic acid, a fragrant compound which derives its name from
cinnamon, because the acid was prepared by the oxidation of oil of
cinnamon by Dumas and Peligot in 1834. The acid and its ethers occur also
in many balsams, so that we have here another instance of the synthesis of
a natural vegetable product from a coal-tar hydrocarbon. The subsequent
steps are--(1) the nitration of the acid to produce nitrocinnamic acid;
(2) the addition of bromine to form a dibromide of the nitro-acid; (3) the
action of alkali on the dibromide to produce what is known as "propiolic
acid." The latter, under the influence of mild alkaline reducing agents,
is transformed into indigo-blue. The process depending on the use of
nitrobenzoic aldehyde is much simpler; but the particular nitro-derivative
of the aldehyde which is required is at present difficult to make, and
therefore expensive. If the production of this compound could be
cheapened, the competition between artificial and natural indigo would
assume a much more serious aspect.[5]
The light oil of the tar-distiller has now been sufficiently dealt with so
far as regards colouring-matters; let us pass on to the next fraction of
the tar, the carbolic oil. The important constituents of this portion are
carbolic acid and naphthalene. The carbolic oil is in the first place
separated into two distinct portions by washing with an alkaline solution.
Carbolic acid or phenol belongs to a class of compounds derived from
hydrocarbons of the benzene and related series by the substitution of the
residue of water for hydrogen. This water-residue is known to chemists as
"hydroxyl"--it is water less one atom of hydrogen. Carbolic acid or phenol
is hydroxybenzene; and all analogous compounds are spoken of as "phenols."
It will be understood in future that a phenol is a hydroxy-derivative of a
benzenoid hydrocarbon. Now these phenols are all more or less acid in
character by virtue of the hydroxyl-group which they contain. For this
reason they dissolve in aqueous alkaline solutions, and are precipitated
therefrom by acids. This will enable us to understand the purification of
the carbolic oil.
The two layers into which this oil separates after washing with alkali are
(1) the aqueous alkaline solution of the carbolic acid and other phenols,
and (2) the undissolved naphthalene contaminated with oily hydrocarbons
and other impurities. Each of these portions has its industrial history.
The alkaline solution, on being drawn off and made acid, yields its
mixture of phenols in the form of a dark oil from which carbolic acid is
separated by a laborious series of fractional distillations. The
undissolved hydrocarbon is similarly purified by fractional distillation,
and furnishes the solid crystalline naphthalene. The tar from one ton of
Lancashire coal yields about 1-1/2 lbs. of carbolic acid, equal to about 1
per cent. by weight of the tar, and about 6-1/4lbs. of naphthalene, so
that this last hydrocarbon is one of the chief constituents of the tar, of
which it forms from 8 to 10 per cent. by weight.
The crude carbolic acid as separated from the alkaline solution is a
mixture of several phenolic compounds, and all of these but the carbolic
acid itself are gradually removed during the process of purification.
Among the compounds associated with the carbolic acid are certain phenols
of higher boiling-point, which bear the same relationship to carbolic acid
that toluene bears to benzene. That is to say, that while phenol itself
is hydroxybenzene, these other compounds, which are called "cresols," are
hydroxytoluenes. The cresols form an oily liquid largely used for
disinfecting purposes under the designation of "liquid carbolic acid," or
"cresylic acid." Carbolic acid is a white crystalline solid possessing
strongly antiseptic properties, and is therefore of immense value in all
cases where putrefaction or decay has to be arrested. It was discovered in
coal-tar by Runge in 1834, and was obtained pure by Laurent in 1840.
The gradual establishment of the germ-theory of disease, chiefly due to
the labours of Pasteur, has led to a most important application of
carbolic acid. Once again we find the coal-tar industry brought into
contact with another department of science. Arguing from the view that
putrefactive change is brought about by the presence of the germs of
micro-organisms ever present in the atmosphere, Sir Joseph Lister proposed
that during surgical operations the incised part should be kept under a
spray of the germicidal carbolic acid to prevent subsequent mortification.
No operation upon portions of the body exposed to the air is at present
conducted without this precaution, and many a human life must have been
saved by Lister's treatment. To this result the chemist and technologist
have contributed, not only by the discovery of the carbolic acid in the
tar, but also by the development of the necessary processes for its
purification. It should be added that the phenol used must be of the
greatest possible purity, and the requirements of the surgeon have been
met by chemical and technological skill.
From surgery back to colouring-matters, and from these to pharmaceutical
preparations and perfumes, are we led in following up the cycles of
chemical transformation which these tar-products have undergone in the
hands of the technologist, guided by the researches of the chemist. It was
observed by Runge in 1834 that crude carbolic acid, on treatment with
lime, gave a red, acid colouring-matter which he separated and named
"rosolic acid." The observation was followed up, and many other chemists
obtained red colouring-matters by the oxidation of crude phenol. In 1859,
the colour-giving property of carbolic acid acquired industrial importance
from a discovery made by Kolbe and Schmitt in Germany, and by Persoz in
France. These chemists found that a good yield of the colouring-matter was
obtained by heating phenol with oxalic and sulphuric acids. Under the
names of "corallin" and "aurin" the dye-stuff was introduced into
commerce, and it is still used for certain purposes, especially for the
preparation of coloured lakes for paper-staining.
The scientific development of the history of this phenol dye is full of
interest, but we can only give it a passing glance. Its interest lies
chiefly in the circumstance that it is related to magenta, as was first
pointed out by Caro and Wanklyn in 1866. In fact they obtained rosolic
acid from magenta by the action of nitrous acid on the latter. We now know
that a diazo-salt is first formed under these circumstances, and that the
decomposition of this unstable compound in the presence of water gives
rise to the rosolic acid. Later researches have shown that by heating
rosolic acid with ammonia it is converted into rosaniline. It is also
known that the commercial corallin, like the commercial magenta, is a
mixture of closely related colouring-matters. The close analogy between
magenta and rosolic acid was further shown by Caro in 1866. In the same
way that Hofmann found that magenta could not be produced by the oxidation
of _pure_ aniline, Caro found that a mixture of phenol and cresol was
necessary for the production of rosolic acid when inorganic oxidizers were
used. It is indeed this series of investigations upon the phenol
dyes--investigations which have been taken part in not only by the
chemists named, but also by Graebe, Dale and Schorlemmer, and the
Fischers--which led up to the discovery of the constitution of the
colouring-matters of the rosaniline group, and, through this, to the
far-reaching industrial developments of the discovery as traced in the
last chapter. It is evident, from what has been said, that rosolic acid
and its related colouring-matters are members of the triphenylmethane
group. They are in fact the hydroxylic or acid analogues of the
amido-containing or basic dyes of the rosaniline series.
In the fragrant blossom of the meadowsweet (_Spiraea ulmaria_) there is
contained an acid which is found also as an ether in the oil of
wintergreen (_Gautheria procumbens_). This is salicylic acid, a white
crystalline compound which has been known to chemists since 1839. In 1860
Kolbe prepared the sodium salt of this acid by passing carbon dioxide gas
into phenol in which metallic sodium had been dissolved. It was found
subsequently that the same transformation was brought about by heating the
dry sodium salt of carbolic acid in an atmosphere of carbon dioxide. This
process of Kolbe's is now worked on a manufacturing scale for the
preparation of artificial salicylic acid. The acid and its salts and
ethers find numerous applications as antiseptics, for the preservation of
food, and in pharmacy.
Salicylic acid is employed also for the manufacture of certain azo-dyes in
a way that it will be very instructive to consider, because the process
used may be taken as typical of the general method of preparing such
compounds. Solutions of diazo-salts act not only upon amido- and
diamido-compounds, as we have seen in the case of aniline yellow and
chrysoidine, but also upon phenols, forming acid azo-colours. This
important fact was made known in 1870 by the German chemists Kekule and
Hidegh, but more than six years elapsed before this discovery was taken
advantage of by the technologist. Large numbers of these acid azo-dyes are
now made from various diazotised amido-compounds combined with different
phenols and phenolic acids. The mode of procedure is to diazotise the
amido-compound by sodium nitrite and hydrochloric acid in the manner
already described, and then add the diazo-salt solution to the phenolic
compound dissolved in alkali. The colouring-matter is at once formed.
Salicylic acid possesses the characters both of an acid and a phenol. It
combines readily with diazo-salts under the circumstances described, and
gives rise to azo-dyes, some of which are of technical value.
The manufacture of azo-dyes from salicylic acid brings us into contact
with certain amidic compounds which figure so largely in the tinctorial
industry that they may be conveniently dealt with here. These bases are
not azo-compounds themselves, but they are prepared from azo-compounds,
viz. from the azobenzene and azotoluene which were spoken about in the
last chapter. When these are reduced by acid reducing-agents, they become
converted into diamido-bases which are known as benzidine and tolidine
respectively. These bases can be diazotised, and as they contain two
amido-groups, they form double diazo-salts, _i.e._ tetrazo-salts, which
are capable of combining with amido-compounds, or phenols, in the usual
way. Thus diazotised benzidine and tolidine combine with salicylic acid to
form valuable yellow azo-dyes known as "chrysamines." The dyes of this
class obviously contain two azo-groups.
Some other uses of carbolic acid must next be considered. Of the
colouring-matters derived from coal-tar, none is more widely known than
the oldest artificial yellow dye, picric acid. This is a phenol
derivative, and was first obtained as long ago as 1771 by Woulfe, by
acting upon indigo with nitric acid. Laurent in 1842 was the first to
obtain this dye from carbolic acid, from which compound it is still
manufactured by acting upon the sulpho-acid with nitric acid. Chemically
considered, it is trinitrophenol. It has a very wide application as a dye,
and has been used as an explosive agent. A similar colouring-matter was
made from cresol in 1869, and introduced under the name of "Victoria
yellow," which is dinitro-cresol. Other dyes derived directly or
indirectly from phenol will take us back once again to toluene.
A new diazotisable diamido-compound was obtained from this last
hydrocarbon, and introduced in 1886 by Leonhardt & Co. One of the three
isomeric nitrotoluenes furnishes a sulpho-acid which, on treatment with
alkali, gives a compound derived from a hydrocarbon known as stilbene, and
this, on reduction, is converted into the diamido-compound referred to.
The latter, which is a disulpho-acid as well as a diamido-compound, can be
diazotised and combined with phenols, &c. The stilbene azo-dyes thus
prepared from phenol and salicylic acid, like the chrysamines, are yellow
colouring-matters, containing two azo-groups. It is a valuable
characteristic of these secondary azo-dyes that they all possess a special
affinity for vegetable fibre, and their introduction has exerted a great
influence upon the art of cotton-dyeing. We shall have to return to these
cotton-dyes again shortly.
Before leaving this branch of the subject, the following scheme is
presented to show the relationships and inter-relationships of the
products thus far dealt with in the present chapter--
Tar
|
---------------------------------------------------------
| |
Light Oil Carbolic Oil
/ \ /-> Benzal Chloride |
/ \ / | \ |
/ \ / | Benzaldehyde |
/ \ / Cinnamic acid | |
Benzene Toluene | Nitrobenzaldehyde |
| | Nitrocinnamic acid (+ acetone) |
| | | / |
| | | / |-----------|
Nitrobenzene Nitrotoluene Propiolic acid / | |
| | \ | / Phenols Naphthalene
| | \ | / | \
| | \ | / | \
| | \ | / | ->Cresols
Azobenzene Azotoluene \ Indigo<--/ Phenol |
| | Stilbene- | Victoria
| | derivative <------------------- yellow
| | (Diazotised)\ | \
Benzidine Tolidine Salicylic Picric Corallin
\ / acid acid & Aurin
(Diazotised) \/
--------------------------------
The existence of naphthalene in coal-tar was made known in 1820 by Garden,
who gave it this name because the oils obtained from the tar by
distillation went under the general designation of naphtha. The greater
portion of the hydrocarbon is contained in the carbolic oil, and is
separated and purified in the manner described. A further quantity of
impure naphthalene separates out from the next fraction--the creosote oil,
and this is similarly washed and purified by distillation. The large
quantity of naphthalene existing in tar has already been referred to, but
although it is such an important constituent, it was only late in the
history of the colour industry that it found any extensive application. In
early times it was regarded as a nuisance, and was burnt as fuel, or for
the production of a dense soot, which was condensed to form lampblack. It
will be remembered that the first of the coal-tar colours made required
only the light oils. There are at present only a few direct uses for
naphthalene, but one of its applications is sufficiently important to be
mentioned.
The hydrocarbon is a white crystalline solid melting at 80 deg. C., and
boiling at 217 deg. C. Although it has a high boiling-point, it passes readily
into vapour at lower temperatures, and the vapour on condensation forms
beautiful silvery crystalline scales. This product is "sublimed
naphthalene." The vapour of naphthalene burns with a highly luminous
flame, and if mixed with coal-gas, it considerably increases the
luminosity of the flame. Advantage is taken-of this in the so-called
"albo-carbon light," which is the flame of burning coal-gas saturated with
naphthalene vapour. The burner is constructed so that the gas passes
through a reservoir filled with melted naphthalene kept hot by the flame
itself (Fig. 9).
[Illustration: FIG. 9.--ALBO-CARBON BURNER.]
To appreciate properly the value of those discoveries which have enabled
manufacturers to utilize this hydrocarbon, it is only necessary to recall
to mind the actual quantity produced in this country. Supposing that ten
million tons of coal are used annually for gas-making, and that the
500,000 tons of tar resulting therefrom contain only eight per cent. of
naphthalene, there would be available about 40,000 tons of this
hydrocarbon annually. Great as have been the recent advancements in the
utilization of naphthalene derivatives, there is still a larger quantity
of this hydrocarbon produced than is necessary to supply the wants of the
colour-manufacturer. From this last statement it will be inferred that
naphthalene is now a source of colouring-matters. Let us consider how this
has been brought about.
The phenols of naphthalene are called naphthols--they bear the same
relationship to naphthalene that carbolic acid bears to benzene. Owing to
the structure of the naphthalene molecule there are two isomeric
naphthols, whereas there is only one phenol. The naphthols--known as
alpha- and beta-naphthol, respectively--are now made on a large scale from
naphthalene, by heating the latter with sulphuric acid; at a low
temperature the alpha sulpho-acid is produced, and at a higher temperature
the beta sulpho-acid, and these acids on fusion with caustic soda furnish
the corresponding naphthols. Similarly there are two amidonaphthalenes,
known as alpha- and beta-naphthylamine respectively. As aniline is to
benzene, so are the naphthylamines to naphthalene. The alpha-compound is
made in precisely the same way as aniline, viz. by acting upon naphthalene
with nitric acid so as to form nitronaphthalene, and then reducing the
latter with iron dust and acid. Beta-napthylamine cannot be made in this
way; it is prepared from beta-naphthol by heating the latter in presence
of ammonia, when the hydroxyl becomes replaced by the amido-group in
accordance with a process patented in 1880 by the Baden Aniline Company.
The principle thus utilized is the outcome of the scientific work of two
Austrian chemists, Merz and Weith. Setting out from the naphthols and
naphthylamines we shall be led into industrial developments of the
greatest importance.
The first naphthalene colour was a yellow dye, discovered by Martius in
1864, and manufactured under the name of "Manchester yellow." It is,
chemically speaking, dinitro-alpha-naphthol; but it was not at first made
from naphthol, as the latter was not at the time a technical product. It
was made from alpha-naphthylamine by the action of nitrous and nitric
acids. When a good method for making the naphthol was discovered in 1869,
the dye was made from this. The process is just the same as that employed
in making picric acid; the naphthol is converted into a sulpho-acid, and
this when acted upon by nitric acid, gives the colouring-matter.
Manchester yellow is now largely used for colouring soap, but as a
dye-stuff it has been improved upon in a manner that will be readily
understood. The original colouring-matter being somewhat fugitive, it was
found that its sulpho-acid was much faster. This sulpho-acid cannot be
made by the direct action of sulphuric acid upon the colouring-matter--as
in the case of acid yellow or acid magenta--but by acting upon the
naphthol with very strong sulphuric acid, three sulphuric acid residues or
sulpho-groups enter the molecule, and then on nitration only two of these
are replaced by nitro-groups, and there results a sulpho-acid of
dinitro-alpha-naphthol. This was discovered in 1879 by Caro, and
introduced as "acid naphthol yellow." It is now one of the standard yellow
dyes.
The history of another important group of colouring-matters dependent on
naphthalene begins with A. v. Baeyer in 1871 and with Caro in 1874. Two
products formerly known only as laboratory preparations were called into
requisition by this discovery. One of these compounds, phthalic acid, is
obtained from naphthalene, and the other, resorcin or resorcinol, is
prepared from benzene. Phthalic acid, which was discovered in 1836 by
Laurent, is a product of the oxidation of many benzenoid compounds.
Chemically considered it is a di-derivative of benzene, _i.e._ two of the
hydrogen atoms of benzene are replaced by certain groups of carbon,
oxygen, and hydrogen atoms. We have seen how the replacement of hydrogen
by an ammonia-residue, amidogen, gives rise to bases such as amidobenzene
(aniline), or diamidobenzene. Similarly, the replacement of hydrogen by a
water-residue, hydroxyl, gives rise to a phenol. The group of carbon,
oxygen, and hydrogen atoms which confers the property of acidity upon an
organic compound is a half-molecule of oxalic acid--it is known as the
carboxyl group. Thus benzoic acid is the carboxyl-derivative of benzene,
and the phthalic acid with which we are now concerned is a
dicarboxyl-derivative of benzene. It is related to benzoic acid in the
same way that diamidobenzene is related to aniline. Three isomeric
phthalic acids are known, but only one of these is of use in the present
branch of manufacture. The acid in question, although a derivative of
benzene, is most economically prepared by the oxidation of certain
derivatives of naphthalene which, when completely broken down by energetic
oxidizing agents, furnish the acid. Thus the dinitronaphthol described as
Manchester yellow, if heated for some time with dilute nitric acid,
furnishes phthalic acid. The latter is made on a large scale by the
oxidation of a compound which naphthalene forms with chlorine, and known
as naphthalene tetrachloride, because it contains four atoms of chlorine.
The other compound, resorcinol, was known to chemistry ten years before it
was utilized as a source of colouring-matters. It was originally prepared
by fusing certain resins, such as galbanum, asafoetida, &c., with
caustic alkali. Soon after its discovery, viz. in 1866, it was shown by
Koerner to be a derivative of benzene, and from this hint the technical
process for the preparation of the compound on a large scale has been
developed. Resorcinol is a phenolic derivative of benzene containing two
hydroxyl groups; it is therefore related to phenol in the same way that
diamidobenzene is related to aniline or phthalic acid to benzoic acid. The
relationships can be expressed in a tabular form thus--
Amidobenzene or Aniline. Benzoic acid. Carbolic acid or Phenol.
Diamidobenzene. Phthalic acid. Resorcinol.
Resorcinol is now made by heating benzene with very strong sulphuric acid
so as to convert it into a disulpho-acid, and the sodium salt of the
latter is then fused with alkali. As a technical operation it is one of
great delicacy and skill, and the manufacture is confined to a few
Continental factories.
When phthalic acid is heated it loses water, and is transformed into a
white, magnificently crystalline substance known as phthalic anhydride,
_i.e._ the acid deprived of water. In 1871, A. v. Baeyer, the eminent
chemist who subsequently synthesised indigo, published the first of a
series of investigations describing the compounds produced by heating
phthalic anhydride with phenols. To these compounds he gave the name of
"phthaleins." Baeyer's work, like that of so many other chemists who have
contributed to the advancement of the coal-tar colour industry, was of a
purely scientific character at first, but it soon led to technological
developments. The phthaleins are all acid compounds possessing more or
less tinctorial power. One of the first discovered was produced by heating
phthalic anhydride with an acid known as gallic acid, which occurs in
vegetable galls, and in the form of tannin in many vegetable extracts
which are used by the tanner. The acid is a phenolic derivative of benzoic
acid, viz. trihydroxybenzoic acid, and on heating it readily passes into
trihydroxybenzene, which is the "pyrogallic acid" or pyrogallol familiar
as a photographic developer. The phthalein formed from gallic acid and
phthalic anhydride really results from the union of the latter with
pyrogallol. It is now manufactured under the name of "gallein," and is
largely used for imparting a bluish grey shade to cotton fabrics. By
heating gallein with strong sulphuric acid, it is transformed into another
colouring-matter which gives remarkably fast olive-green shades when dyed
on cotton fibre with a suitable mordant. This derivative of gallein is
used to a considerable extent under the name of "coerulein." These two
colouring-matters were the first practical outcome of v. Baeyer's
researches. There is another possible development in this direction which
chemistry may yet accomplish, and another natural colouring-matter may be
threatened, even as the indigo culture was threatened by the later work of
the same chemist. There is reason for believing that the colouring-matter
of logwood, known to chemists as haematein, is related to or derived in
some way from the phthaleins, and the synthesis of this compound may
ultimately be effected.
The dye introduced by Caro in 1874 is the brominated phthalein of
resorcinol. The phthalein itself is a yellow dye, and the solutions of its
salts show a splendid and most intense greenish yellow fluorescence, for
which reason it is called "fluorescein." When brominated, the latter
furnishes a beautiful red colouring-matter known as "eosin" (Gr. [Greek:
eos], dawn), and the introduction of this gave an industrial impetus to
the phthaleins which led to the discovery of many other related
colouring-matters now largely used under various trade designations.
About a dozen distinct compounds producing different shades of pink,
crimson and red, and all derived from fluorescein, are at present in the
market, and a few other phthaleins formed by heating phthalic anhydride
with other phenolic compounds instead of resorcinol or pyrogallol (_e.g._
diethylamidophenol), are also of industrial importance. By converting
nitrobenzene into a sulpho-acid, reducing to an amido-sulpho-acid, and
then fusing with alkali, an amido-phenol is produced, the ethers of which,
when heated with phthalic anhydride, give rise to red phthaleins of most
intense colouring power introduced by the Baden Aniline Company as
"rhodamines."
It remains to point out that the scientific spirit which prompted the
investigation of the phthaleins in the first instance has followed these
compounds throughout their technological career. The researches started by
v. Baeyer were taken up by various chemists, whose work together with that
of the original discoverer has led to the elucidation of the constitution
of these colouring-matters. The phthaleins are members of the
triphenylmethane group, and are therefore related to magenta, corallin,
malachite green, methyl violet, and the phosgene dyes.
It has been said that the phenolic and amidic derivatives of naphthalene,
_i.e._ the naphthols and naphthylamines, are of the greatest importance to
the colour industry. One of the first uses of alpha-naphthylamine has
already been mentioned, viz. for the production of the Manchester yellow,
which was afterwards made more advantageously from alpha-naphthol. A red
colouring-matter possessing a beautiful fluorescence was afterwards (1869)
made from this naphthylamine and introduced as "Magdala red." The latter
was discovered by Schiendl of Vienna in 1867. It was prepared in precisely
the same way as induline was prepared from aniline yellow. The latter,
which is amido-azobenzene, and which is prepared, broadly speaking, by the
action of nitrous acid on aniline, has its analogue in
amido-azonaphthalene, which is similarly prepared by the action of nitrous
acid on naphthylamine. Just as aniline yellow when heated with aniline and
an aniline salt gives induline, so amido-azonaphthalene when heated with
naphthylamine and a salt of this base gives Magdala red. The latter is,
therefore, a naphthalene analogue of induline, as was shown by Hofmann in
1869, and the knowledge of the constitution of the azines which has been
gained of late years, enables us to relegate the colouring-matter to this
group. This knowledge has also enabled the manufacture to be conducted on
more rational principles, viz. by the method employed for the production
of the saffranines, as previously sketched.
The introduction of azo-dyes, formed by the action of a diazotised
amido-compound on a phenol or another amido-compound, marks the period
from which the naphthols and naphthylamines rose to the first rank of
importance as raw materials for the colour manufacturer. The introduction
of chrysoidine in 1876 was immediately followed by the manufacture of acid
azo-dyes obtained by combining diazotised amido-sulpho-acids with phenols
of various kinds, or with bases, such as dimethylaniline and
diphenylamine. From what has been said in the foregoing portion of this
volume, it is evident that all such azo-compounds result from the
combination of two things, viz. (1) a diazotised amido-compound, and (2) a
phenolic or amidic compound. Either (1) or (2) or both may be a
sulpho-acid, and the resulting dye will then also be a sulpho-acid.
The first of these colouring-matters derived from the naphthols, was
introduced in 1876-77 by Roussin and Poirrier, and by O. N. Witt. They
were prepared by converting aniline into a sulpho-acid (sulphanilic acid),
diazotising this and combining the diazo-compound with alpha- or
beta-naphthol. The compounds formed are brilliant orange dyes, the latter
being still largely consumed as "naphthol orange." Other dye-stuffs of a
similar nature were introduced by Caro about the same time, and were
prepared from the diazotised sulpho-acid of alpha-naphthylamine combined
with the naphthols. By this means alpha-naphthol gives what is known as
"acid brown," or "fast brown," and beta-naphthol a fine crimson, known as
"fast red," or "roccellin." Diazotised compounds combine also with this
same sulpho-acid of alpha-naphthylamine (known as naphthionic acid), the
first colouring-matter formed in this way having been introduced by
Roussin and Poirrier in 1878. It was prepared by diazotising a
nitro-derivative of aniline, and acting with the diazo-salt on napthionic
acid, and this dye is still used to some extent under the name of "archil
substitute." In 1878, the firm of Meister, Lucius & Bruening of
Hoechst-on-the-Main gave a further impetus to the utilization of
naphthalene by discovering two isomeric disulpho-acids of beta-naphthol
formed by heating that phenol with sulphuric acid. By combining various
diazotised bases with these sulpho-acids, a splendid series of acid
azo-dyes ranging in shade from bright orange to claret-red, and to
scarlets rivalling cochineal in brilliancy were given to the tinctorial
industry.
The colouring-matters introduced in 1878 by the Hoechst factory under the
names of "Ponceaux" of various brands, and "Bordeaux," although to some
extent superseded by later discoveries, still occupy an important
position. Their discovery not only increased the consumption of
beta-naphthol, but also that of the bases which were used for diazotising.
These bases are alpha-naphthylamine and those of the aniline series. The
intimate relationship which exists between chemical science and
technology--a relationship which appears so constantly in the foregoing
portions of this work--is well brought out by the discovery under
consideration. A little more chemistry will enable this statement to be
appreciated.
Going back for a moment to the hydrocarbons obtained from light oil, it
will be remembered that benzene and toluene have thus far been considered
as the only ones of importance to the colour-maker. Until the discovery
embodied in the patent specification of 1878, the portions of the light
oil boiling above toluene were of no value in the colour industry. Benzene
and toluene are related to each other in a way which chemists describe by
saying that they are "homologous." This means that they are members of a
regularly graduated series, the successive terms of which differ by the
same number of atoms of carbon and hydrogen. Thus toluene contains one
atom of carbon and two atoms of hydrogen more than benzene. Above toluene
are higher homologues, viz. xylene, cumene, &c., which occur in the light
oil, the former being related to toluene in the same way that toluene is
related to benzene, while cumene again contains one atom of carbon and two
atoms of hydrogen more than xylene. This relationship between the members
of homologous series is expressed in other terms by saying that the weight
of the molecule increases by a constant quantity as we ascend the series.
The homology existing among the hydrocarbons extends to all their
derivatives. Thus phenol is the lower homologue of the cresols. Also we
have the homologous series--
Benzene. Nitrobenzene. Aniline.
Toluene. Nitrotoluene. Toluidine.
Xylene. Nitroxylene. Xylidine.
Cumene. Nitrocumene. Cumidine.
The bases of the third column when diazotised and combined with the
disulpho-acids of beta-naphthol give a graduated series of dyes beginning
with orange and ending with bluish scarlet. Thus it was observed that the
toluidine colour was redder than the aniline colour, and it was a natural
inference that the xylidine colour would be still redder. At the time of
this discovery no azo-colour of a true scarlet shade had been manufactured
successfully. A demand for the higher homologues of benzene was thus
created, and the higher boiling-point fractions of the light oil, which
had been formerly used as solvent naphtha, became of value as sources of
colouring-matters. The isolation of coal-tar xylene (which is a mixture of
three isomeric hydrocarbons) is easily effected by fractional distillation
with a rectifying column, and by nitration and reduction, in the same way
as in the manufacture of aniline, xylidine is placed at the disposal of
the colour-maker.
Xylidine scarlet, although at the time of its introduction the only true
azo-scarlet likely to come into competition with cochineal, was still
somewhat on the orange side. The cumidine dye would obviously be nearer
the desired shade. To meet this want, cumidine had to be made on a large
scale, but here practical difficulties interposed themselves. The quantity
of cumene in the light oil is but small, and it is associated with other
hydrocarbons which are impurities from the present point of view, and from
which it is separated only with difficulty. A new source of the base had
therefore to be sought, and here again we find chemical science
ministering to the wants of the technologist.
It was explained in the last chapter that aniline and similar bases can be
methylated by heating their dry salts with methyl alcohol under pressure.
In this way dimethylaniline is made, and dimethyltoluidine or
dimethylxylidine can similarly be prepared. Now it was shown by Hofmann in
1871, that if this operation is conducted at a very high temperature, and
under very great pressure, the methyl-alcohol residue, _i.e._ the
methyl-group, does not replace the amidic hydrogen or the hydrogen of the
ammonia residue, but the methylation takes place in another way, resulting
in the formation of a higher homologue of the base started with. For
example, by heating aniline salt and pure wood-spirit to a temperature
considerably above that necessary for producing dimethylaniline, toluidine
is formed. In a similar way, by heating xylidine hydrochloride and methyl
alcohol for some time in a closed vessel at about 300 deg. C. cumidine is
produced. Hofmann's discovery was thus utilized in 1882, and by its means
the base was manufactured, and cumidine scarlet, very similar in shade to
cochineal, became an article of commerce.
While the development of this branch of the colour industry was taking
place by means of the new naphthol disulpho-acids, the cultivation of the
fertile field of the azo-dyes was being carried on in other directions. It
came to be realized that the fundamental discovery of Griess was capable
of being extended to all kinds of amido-compounds. The azo-dyes hitherto
introduced had all been derived from amido-compounds containing only one
amido-group, and they accordingly contained only one azo-group; they were
_primary_ azo-compounds. It was soon found that aniline yellow, which
already contains one azo-group as well as an amido-group, could be again
diazotised and combined with phenols so as to produce compounds containing
two azo-groups, _i.e._ _secondary_ azo-compounds. The sulpho-acid of
aniline yellow--Graessler's "acid yellow"--was the first source of azo-dyes
of this class. By diazotising this amidoazo-sulpho-acid, and combining it
with beta-naphthol, a fine scarlet dye was discovered by Nietzki in 1879,
and introduced under the name of "Biebrich scarlet." Two years later a new
sulpho-acid of beta-naphthol was discovered by Bayer & Co. of Elberfeld,
and this gave rise, when combined with diazotised acid yellow and
analogous compounds, to another series of brilliant dyes introduced as
"Crocein scarlets."
From these beginnings the development of the azo-dyes has been steadily
carried on to the present time--year by year new diazotisable
amido-compounds or new sulpho-acids of the naphthols and naphthylamines
are being discovered, and this branch of the colour industry has already
assumed colossal dimensions. An important departure was made in 1884 by
Boettiger, who introduced the first secondary azo-colours derived from
benzidine. As already explained in connection with salicylic acid, this
base and its homologue tolidine form tetrazo-salts, which combine with
phenols and amines or their sulpho-acids. One of the first
colouring-matters of this group was obtained by combining diazotised
benzidine with the sulpho-acid of alpha-naphthylamine (naphthionic acid),
and was introduced under the name of "Congo red." Then came the discovery
(Pfaff, 1885), that the tetrazo-salts of benzidine and tolidine combine
with phenols, amines, &c., in two stages, one of the diazo-groups first
combining with one-half of the whole quantity of phenol to form an
intermediate compound, which then combines with the other half of the
phenol to form the secondary azo-dye. In the hands of the
"Actiengesellschaft fuer Anilinfabrikation" of Berlin this discovery has
been utilized for the production of a number of such azo-colours
containing two distinct phenols, or amines, or sulpho-acids. Tolidine has
been found to give better colouring-matters in most cases than benzidine,
and it is scarcely necessary to point out that an increased demand for the
nitrotoluene from which this base is made is the necessary consequence of
this discovery.
It is impossible to attempt to specify by name any of these recent
benzidine and tolidine dyes. Their introduction has been the means of
finding new uses for the naphthylamines and naphthols and their
sulpho-acids, and has thus contributed largely to the utilization of
naphthalene. An impetus has been given to the investigation of these
sulpho-acids, and chemical science has profited largely thereby. The
process by which beta-naphthylamine is prepared from beta-naphthol,
already referred to, viz. by heating with ammonia under pressure, has been
extended to the sulpho-acids of beta-naphthol, and by this means new
beta-naphthylamine sulpho-acids have been prepared, and figure largely in
the production of these secondary azo-colours. The latter, as previously
stated, possess the most valuable property of dyeing cotton fibre
directly, and by their means the art of cotton dyeing has been greatly
simplified. The shades given by these colours vary from yellow through
orange to bright scarlet, violet, or purple.
In addition to benzidine and tolidine, other diazotisable amido-compounds
have of late years been pressed into the service of the
colour-manufacturer. The derivative of stilbene, already mentioned as
being prepared from a sulpho-acid of one of the nitrotoluenes, forms
tetrazo-salts, which can be combined with similar or dissimilar phenols,
amines, or sulpho-acids, as in the case of benzidine and tolidine.
Various shades of red and purple are thus obtained from the diazotised
compound, when the latter is combined with the naphthylamines, naphthols,
or their sulpho-acids. These, again, are all cotton dyes. The
nitro-derivatives of the ethers of phenol and cresol, when reduced in the
same way that nitrobenzene and nitrotoluene are reduced to azobenzene and
azotoluene, also furnish azo-compounds which, on further reduction, give
bases analogous to benzidine and tolidine. Secondary azo-colours derived
from these bases and the usual naphthalene derivatives are also
manufactured. It is among the secondary azo-dyes that we meet with the
first direct dyeing blacks, the importance of which will be realized when
it is remembered that the ordinary aniline-black is not adapted for wool
dyeing. The azo-blacks are obtained by combining diazotised sulpho-acids
of amidoazo-compounds of the benzene or naphthalene series with naphthol
sulpho-acids or other naphthalene derivatives.
One other series of azo-compounds must be briefly referred to. It has long
been known that aniline and toluidine when heated with sulphur evolve
sulphuretted hydrogen and give rise to thio-bases, that is, aniline or
toluidine in which the hydrogen is partly replaced by sulphur. One of the
toluidines treated in this way is transformed into a thiotoluidine which,
when diazotised and combined with one of the disulpho-acids of
beta-naphthol, forms a red azo-dye, introduced by Dahl & Co. in 1885 as
"thiorubin." By modifying the conditions of reaction between the sulphur
and the base, it was found in 1887 by Arthur Green, that a complicated
thio-derivative of toluidine could be produced which possessed very
remarkable properties. The sulpho-acid of the thio-base is a yellow dye,
which was named by its discoverer "primuline." Not only is primuline a
dye, but it contains an amido-group which can be diazotised. If therefore
the fabric dyed with primuline is passed through a nitrite bath, a
diazo-salt is formed in the fibre, and on immersing the latter in a second
bath containing naphthol or other phenol or an amine, an azo-dye is
precipitated in the fibre. By this means there are produced valuable
"ingrain colours" of various shades of red, orange, purple, &c.
So much for the azo-dyes, one of the most prolific fields of industrial
enterprise connected with coal-tar technology. From the introduction of
aniline yellow in 1863 to the present time, about 150 distinct compounds
of this group have been given to the tinctorial industry. Of these over
thirty are cotton dyes containing two azo-groups. Sombre shades, rivalling
logwood black, bright yellows, orange-reds, browns, violets, and brilliant
scarlets equalling cochineal, have been evolved from the refuse of the
gas-works. The artificial colouring-matters have in this last case once
again threatened a natural product, and with greater success than the
indigo synthesis, for the introduction of the azo-scarlets has caused a
marked decline in the cochineal culture.
In addition to the azo-colours, there are certain other products which
claim naphthalene as a raw material. In 1879 it was found that one of the
sulpho-acids of beta-naphthol when treated with nitrous acid readily gave
a nitroso-sulpho-acid. A salt of this last acid, containing sodium and
iron as metallic bases, was introduced in 1884, under the name of
"naphthol green." It is used both as a dye for wool and as a pigment. It
may be mentioned here that other nitroso-derivatives of phenols, such as
those of resorcinol and the naphthols, under the name of "gambines," are
largely used for dyeing purposes, owing to the facility with which they
combine with metallic mordants to form coloured salts in the fibre. In
this same year, 1879, it was found that by heating nitrosodimethylaniline
with beta-naphthol in an appropriate solvent, a violet colouring-matter
was formed. This is now manufactured under the name of "new blue," or
other designations, and is largely used for producing an indigo-blue shade
on cotton prepared with a suitable mordant. The discovery of this
colouring-matter gave an impetus to further discoveries in the same
direction. It was found that nitrosodimethylaniline reacted in a similar
way with other phenolic or with amidic compounds. In 1881 Koechlin
introduced an analogous dye-stuff prepared by the action of the same
nitroso-compound on gallic acid. Gallocyanin, as it is called, imparts a
violet blue shade to mordanted cotton. Other colouring-matters of the same
group are in use; some of them, like "new blue," being derivatives of
naphthalene. These compounds all belong to a series of which the parent
substance is constructed on a type similar to azine; it contains a
nitrogen and oxygen atom linking together the hydrocarbon residues, and is
therefore known as "oxazine." The researches of Nietzki in 1888 first
established the true constitution of the oxazines.
Closely related to this group is a colouring-matter introduced by Koechlin
and Witt in 1881 under the name of "indophenol." It is prepared in the
same way as the azines of the "neutral red" group; viz. by the action of
nitrosodimethylaniline on alpha-naphthol, or by oxidizing
amidodimethylaniline in the presence of alpha-naphthol. Indophenol belongs
to that group of blue compounds formed as intermediate products in the
manufacture of azines, as mentioned in connection with "neutral red." But
while these intermediate blues resulting from the oxidation of a diamine
in the presence of another amine are unstable, and pass readily into red
azines, indophenol is stable, and can be used for dyeing and printing in
the same way as indigo. The shades which it produces are very similar to
this last dye, but for certain practical reasons it has not been able to
compete with the natural dye-stuff.
The story of naphthalene is summarized in the schemes on pp. 164, 165.
Light Oil:
Benzene->Disulpho-acid-->Resorcinol.[6]
\
\-->Nitrobenzene} } Sulphanilic acid.[7]
} Aniline} Amidoazobenzene and sulpho-acid.[7]
} } Nitrosodimethylaniline[8] and
} } amidodimethylaniline.[8]
} Sulpho-acid-->Amidosulpho-acid-->Amidophenol
} and ethers.[6]
} Azobenzene-->Benzidine.[7]
}Toluidines[7] Sulpho-acids.[7]
} Amidoazotoluene[7]
} and sulpho-acid.[7]
} Thiotoluidine and primuline.[7]
Toluene-->Nitrotoluenes} Azotoluene-->Tolidine.[7]
} Sulpho-acid and Stilbene-derivative.[7]
} Sulpho-acids.[7]
Xylene->Nitroxylenes->Xylidines[7]} Amidoazoxylene[7] and sulpho-acid.[7]
} Cumidine.[7]
Carbolic Oil:
Phenol-->Nitrophenol and ethers } Azophenol ethers-->Diamidic bases[9]
} analogous to benzidine.
} Amidophenol[9] and ethers.[9]
Cresols-->Nitrocresols and ethers-->Amidocresols[9] and ethers.[9]
|>Nitronaphthalene
| |
| |>[Greek: a]-Naphthylamine[9][10]{Naphthionic acid.[9][10]
| {Amidoazonaphthalene
| |
| {Magdala red.
| {Sulpho-acid.[9]
|
Naphthalene>|>Tetrachloride-->Phthalic acid and anhydride.
|
| } {Manchester yellow.
| }[Greek: a]-Naphthol {Acid naphthol yellow.
| } {Sulpho-acids.[10]
|>Sulpho-acids}
| } {[Greek: b]-Naphthylamine
| } { and sulpho-acids.[9][10]
| }[Greek: b]-Naphthol{Sulpho-acids &
| } { [Greek: b]-naphthylamine
| } { sulpho-acids.[9][10]
| } {Nitrososulpho-acid and
{ naphthol green.
The fraction of coal-tar succeeding the carbolic oil, viz. the creosote
oil, does not at present supply the colour manufacturer with any raw
materials beyond the small proportion of naphthalene which separates from
it in a very impure condition as "creosote salts." This oil consists of a
mixture of the higher homologues of phenol with various hydrocarbons and
basic compounds. It is the oil used for creosoting timber in the manner
already described; and among its other applications may be mentioned its
use as an illuminating agent and as a source of lampblack. In order to
burn the oil effectively as a source of light, a specially-constructed
burner is used, which is fed by a stream of oil raised from a reservoir at
its foot by means of compressed air, which also aids the combustion of the
oil. There is produced by this means a great body of lurid flame, which
is very serviceable where building or other operations have to be carried
on at night (see Fig. 10). For lampblack the oil is simply burnt in iron
pans set in ovens, and the sooty smoke conducted into condensing chambers.
The creosote oil constitutes more than 30 per cent. by weight of the
tar--the time may come when this fraction, like the light oil and carbolic
oil, may be found to contain compounds of value to the colour-maker or to
other branches of chemical manufacture.
[Illustration: FIG. 10.--VERTICAL BURNER FOR HEAVY COAL OIL BY THE LUCIGEN
LIGHT CO.]
[Illustration: FIG. 11.--THE MADDER PLANT (_Rubia tinctoria_).]
The utilization of the next fraction, anthracene oil, is one of the
greatest triumphs which applied chemical science can lay claim to since
the foundation of the coal-tar colour industry. This discovery dates from
1868, when it was shown by two German chemists, Graebe and Liebermann,
that the colouring-matter of madder was derived from the hydrocarbon
anthracene. Like indigo, madder may be regarded as one of the most ancient
of natural dye-stuffs. It consists of the powdered roots of certain plants
of the genus _Rubia_, such as _R. tinctoria_ (see Fig. 11), _R.
peregrina_, and _R. munjista_, which were at one time cultivated on an
enormous scale in various parts of Europe and Asia. It is estimated that
at the time of Graebe and Liebermann's discovery, 70,000 tons of madder
were produced annually in the madder-growing countries of the world. At
that time we were importing madder into this country at the rate of 15,000
to 16,000 tons per annum, at a cost of L50 per ton. In ten years the
importation had fallen to about 1600 tons, and the price to L18 per ton.
At the present time the cultivation of madder is practically extinct.
There is no better gauge of the practical utility of a scientific
discovery than the financial effect. In addition to madder, a more
concentrated extract containing the colouring-matter itself was largely
used by dyers and cotton printers under the name of "garancin." In 1868 we
were importing, in addition to the 15,000 to 16,000 tons of madder, about
2000 tons of this extract annually, at a cost of L150 per ton. By 1878 the
importation of garancin had sunk to about 140 tons, and the price had
been lowered to L65 per ton. The total value of the imports of madder and
garancin in 1868 was over one million pounds sterling; in ten years the
value of these same imports had been reduced to about L38,000.
Concurrently with this falling off in the demand for the natural
colouring-matter, the cultivation of the madder plant had to be abandoned,
and the vast tracts of land devoted to this purpose became available for
other crops. A change amounting to a revolution was produced in an
agricultural industry by a discovery in chemistry.
In the persons of two Frenchmen, Messrs. Robiquet and Colin, science laid
hands on the colouring-matter of the _Rubia_ in 1826. These chemists
isolated two compounds which they named alizarin and purpurin. It is now
known that there are at least six distinct colouring-matters in the madder
root, all of these being anthracene derivatives. It is known also that the
colouring-matters do not exist in the free state in the plant, but in the
form of compounds known as glucosides, _i.e._ compounds consisting of the
colouring-matter combined with the sugar known as glucose. It may be
mentioned incidentally that the colouring-matter of the indigo plant also
exists as a glucoside in the plant. During a period of more than forty
years from the date of its isolation, alizarin was from time to time
submitted to examination by chemists, but its composition was not
completely established till 1868, when Graebe and Liebermann, by heating
it with zinc-dust, obtained anthracene. This was the discovery which gave
the death-blow to the madder culture, and converted the last fraction of
the tar-oil from a waste product into a material of the greatest value.
The large quantity of madder consumed for tinctorial purposes is
indicative of the value of this dye-stuff. It produces shades of red,
purple, violet, black, or deep brown, according to the mordant with which
the fabric is impregnated. The colours obtained by the use of madder are
among the fastest of dyes, the brilliant "Turkey red" being one of the
most familiar shades. The discovery of the parent hydrocarbon of this
colouring-matter which had been in use for so many ages--a
colouring-matter capable of furnishing both in dyeing and printing many
distinct shades, all possessed of great fastness--was obviously a step
towards the realization of an industrial triumph, viz. the chemical
synthesis of alizarin. Within a year of their original observation, this
had been accomplished by Graebe and Liebermann, and almost simultaneously
by W. H. Perkin in this country. From that time the anthracene, which had
previously been burnt or used as lubricating grease, rose in value to an
extraordinary extent. In two years a material which could have been bought
for a few shillings the ton, rose at the touch of chemical magic to more
than two hundred times its former value.
Anthracene is a white crystalline hydrocarbon, having a bluish
fluorescence, melting at 213 deg. C. and boiling above 360 deg. C. It was
discovered in coal-tar by Dumas and Laurent in 1832, and its composition
was determined by Fritzsche in 1857. It separates in the form of crystals
from the anthracene oil on cooling, and is removed by filtration. The
adhering oil is got rid of by submitting the crystals to great pressure in
hydraulic presses. Further purification is effected by powdering the crude
anthracene cake and washing with solvent naphtha, _i.e._ the mixture of
the higher homologues of benzene left after the rectification of the light
oil. Another coal-tar product, viz. the pyridine base referred to in the
last chapter, has been recently employed for washing anthracene with great
success. It is used either by itself or mixed with the solvent naphtha.
The anthracene by washing with these solvents is freed from more soluble
impurities, and may then contain from 30 to 80 per cent. of the pure
hydrocarbon. The washing liquid, which is recovered by distillation,
contains, among other impurities dissolved out of the crude anthracene, a
hydrocarbon isomeric with the latter, and known as phenanthrene, for which
there is at present but little use, but which may one day be turned to
good account. The actual amount of anthracene contained in coal-tar
corresponds to about 1/2 lb. per ton of coal distilled, _i.e._ from 1/4 to
1/2 per cent. by weight of the tar. Owing to the great value of alizarin
and the large quantity of this colouring-matter annually consumed,
anthracene is now by far the most important of the coal-tar hydrocarbons.
Alizarin, purpurin, and the other colouring-matters of madder are hydroxyl
derivatives of a compound derived from anthracene by the replacement of
two atoms of hydrogen by two atoms of oxygen. These oxygen derivatives of
benzenoid hydrocarbons form a special group of compounds known as
quinones. Thus there is quinone itself, or benzoquinone, which is benzene
with two atoms of oxygen replacing two atoms of hydrogen. There are also
isomeric quinones of the naphthalene series known as naphthaquinones. A
dihydroxyl derivative of one of the latter is in use under the somewhat
misappropriate name of "alizarin black." With this exception no other
quinone derivative is used in the colour industry till we come to the
hydrocarbons of the anthracene oil. Phenanthrene forms a quinone which
has been utilized as a source of colouring-matters, but these are
comparatively unimportant. The quinone with which we are at present
concerned is anthraquinone.
The latter is prepared by oxidizing the anthracene--previously reduced by
sublimation to the condition of a very finely-divided crystalline
powder--with sulphuric acid and potassium dichromate. The quinone is
purified, converted into a sulpho-acid, and the sodium salt of the latter
on fusion with alkali gives alizarin, which is dihydroxy-anthraquinone. It
is of interest to note that in this case a monosulpho-acid gives a
dihydroxy-derivative. During the process of fusion potassium chlorate is
added, by which means the yield of alizarin is considerably increased. In
the original process of Graebe and Liebermann, dibromanthraquinone was
fused with alkali; but this method was soon improved upon by the discovery
of the sulpho-acid by Caro and Perkin in 1869, and from this period the
manufacture of artificial alizarin became commercially successful.
In addition to alizarin, other anthracene derivatives are of industrial
importance. The purpurin, discovered among the colouring-matters of madder
in 1826, is a trihydroxy-anthraquinone; it can be prepared by the
oxidation of alizarin, as shown by De Lalande in 1874. Isomeric compounds
known as "flavopurpurin" and "anthrapurpurin" are also made from the
disulpho-acids of anthraquinone by fusion with alkali and potassium
chlorate. These two disulpho-acids are obtained simultaneously with the
monosulpho-acid by the action of fuming sulphuric acid on the quinone, and
are separated by the fractional crystallization of their sodium salts from
the monosulpho-acid (which gives alizarin) and from each other. The
purpurins give somewhat yellower shades than alizarin. Another
trihydroxy-anthraquinone, although not obtained directly from anthracene,
must be claimed as a tar-product. It is prepared by heating gallic acid
with benzoic and sulphuric acids, or with phthalic anhydride and zinc
chloride, and is a brown dye known as "anthragallol" or
"anthracene-brown." The anthracene derivative is in this process built up
synthetically. A sulpho-acid of alizarin has been introduced for wool
dyeing under the name of alizarin carmine, and a nitro-alizarin under the
name of alizarin orange. The latter on heating with glycerin and sulphuric
acid is transformed into a remarkably fast colouring-matter known as
alizarin blue, which is used for dyeing and printing. By heating alizarin
blue with strong sulphuric acid, it is converted into alizarin green.
The great industry arising out of the laboratory work of two German
chemists has influenced other branches of chemical manufacture, and has
reacted upon the coal-tar colour industry itself. A new application for
caustic soda and potassium chlorate necessitated an increased production
of these materials. The first demand for fuming sulphuric acid on a large
scale was created by the alizarin manufacture in 1873, when it was found
that an acid of this strength gave better results in the preparation of
sulpho-acids from anthraquinone. The introduction of this acid into
commerce no doubt exerted a marked influence on the production of other
valuable sulpho-acids, such as acid magenta in 1877, acid yellow in 1878,
and acid naphthol yellow in 1879. The introduction of artificial alizarin
has also simplified the art of colour printing on cotton fabrics to such
an extent that other colouring-matters, also derived from coal-tar, are
largely used in combination with the alizarin to produce parti-coloured
designs. The manufacture of one coal-tar colouring-matter has thus
assisted in the consumption of others.
Artificial alizarin is used in the form of a paste, which consists of the
colouring-matter precipitated from its alkaline solution by acid, and
mixed with water so as to form a mixture containing from 10 to 20 per
cent. of alizarin. The magnitude of the industry will be gathered from the
estimate that the whole quantity of anthracene annually made into
alizarin corresponds to a daily production of about 65 tons of 10 per
cent. paste, of which only about one-eighth is made in this country, the
remainder being manufactured on the Continent. The total production of
alizarin corresponds in money value to about L2,000,000 per annum. One
pound of dry alizarin has the tinctorial power of 90 pounds of madder.
Seeing therefore that the raw material anthracene was at one time a waste
product, and that the quantity of alizarin produced in the factory
corresponds to nearly five pounds of 20 per cent. paste for one pound of
anthracene, it is not surprising that the artificial has been enabled to
compete successfully with the natural product.
The industrial history of anthracene is thus summarized. (See opposite.)
Anthracene
|
Anthraquinone
|
| } Sulpho-acid (Alizarin carmine)
|->Monosulpho-acid-->Alizarin----------} Purpurin
| } Nitro-alizarin-->Alizarin blue
|->[Greek: a]-Disulpho-acid-->Flavopurpurin |
| |
|->[Greek: b]-Disulpho-acid-->Anthrapurpurin |
Alizarin green.
The black, viscid residue left in the tar-still after the removal of the
anthracene oil is the substance known familiarly as pitch. From the
latter, after removal of all the volatile constituents, there is prepared
asphalte, which is a solution of the pitchy residue in the heavy tar-oils
from which all the materials used in the colour industry have been
removed. Asphalte is used for varnish-making, in the construction of hard
pavements, and for other purposes. A considerable quantity of pitch is
used in an industry which originated in France in 1832, and which is
still carried out on a large scale in that country, and to a smaller
extent in this and other tar-producing countries. The industry in question
is the manufacture of fuel from coal-dust by moulding the latter in
suitable machines with pitch so as to form the cakes known as "briquettes"
or "patent fuel." By this means two waste materials are disposed of in a
useful way--the pitch and the finely-divided coal, which could not
conveniently be used as fuel by itself. From two to three million tons of
this artificial fuel are being made annually here and on the Continent.
The various constituents of coal-tar have now been made to tell their
story, so far as relates to the colouring-matters which they furnish. If
the descriptive details are devoid of romance to the general reader, the
results achieved in the short period of thirty-five years, dating from the
discovery of mauve by Perkin, will assuredly be regarded as falling but
little short of the marvellous. Although the most striking developments
are naturally connected with the colouring-matters, whose history has been
sketched in the foregoing pages, and whose introduction has revolutionized
the whole art of dyeing, there are other directions in which the coal-tar
industry has in recent times been undergoing extension. Certain
tar-products are now rendering good service in pharmacy. Salicylic acid
and its salts have long been used in medicine. By distilling a mixture of
the dry lime salts of benzoic and acetic acids there is obtained a
compound known to chemists as acetophenone, which is used for inducing
sleep under the name of hypnone. The acetyl-derivative of aniline and of
methylaniline are febrifuges known as "antifebrine" and "exalgine." Ethers
of salicylic acid and its homologues, prepared from these acids and
phenol, naphthols, &c., are in use as antiseptics under the general
designation of "salols."
In 1881 there was introduced into medicine the first of a group of
antipyretics derived from coal-tar bases of the pyridine series. It has
already been explained that this base is removed from the light oil by
washing with acid. Chemically considered, it is benzene containing one
atom of nitrogen in place of a group consisting of an atom of carbon and
an atom of hydrogen. The quantity of pyridine present in coal-tar is very
small, and no use has as yet been found for it excepting as a solvent for
washing anthracene or for rendering the alcohol used for manufacturing
purposes undrinkable, as is done in this country by mixing in crude
wood-spirit so as to form methylated spirit. The salts of pyridine were
shown by McKendrick and Dewar to act as febrifuges in 1881, but they have
not hitherto found their way into pharmacy. The chief interest of the base
for us centres in the fact that it is the type of a group of bases related
to each other in the same way as the coal-tar hydrocarbons. Thus in
coal-tar, in addition to pyridine, there is another base known as
quinoline, which is related to pyridine in the same way that naphthalene
is related to benzene. Similarly there is a coal-tar base known as
acridine, which is found associated with the anthracene, and which is
related to quinoline in the same way that anthracene is related to
naphthalene. The three hydrocarbons are comparable with the three bases,
which may be regarded as derived from them in the same manner that
pyridine is derived from benzene--
Benzene ... ... ... Pyridine
Naphthalene ... ... Quinoline
Anthracene ... ... ... Acridine
Some of these bases and their homologues are found in the evil-smelling
oil produced by the destructive distillation of bones (Dippel's oil, or
bone oil), and the group is frequently spoken of as the pyridine group.
The colouring-matter described as phosphine, obtained as a by-product in
the manufacture of magenta (p. 94), is a derivative of acridine, and a
yellow colouring-matter discovered by Rudolph in 1881, and obtained by
heating the acetyl derivative of aniline with zinc chloride, is a
derivative of a homologue of quinoline. This dye-stuff, known as
"flavaniline," is no longer made; but it is interesting as having led to
the discovery of the constitution of phosphine by O. Fischer and Koerner in
1884.
The antipyretic medicines which we have first to consider are derivatives
of quinoline. This base was discovered in coal-tar by Runge in 1834, and
was obtained by Gerhardt in 1842 by distilling cinchonine, one of the
cinchona alkaloids, with alkali. Now it is of interest to note that the
quinoline of coal-tar is of no more use to the technologist than the
aniline; these bases are not contained in the tar in sufficient quantity
to enable them to be separated and purified with economical advantage. If
the colour industry had to depend upon this source of aniline only, its
development would have been impossible. But as chemistry enabled the
manufacturer to obtain aniline in quantity from benzene, so science has
placed quinoline at his disposal. This important discovery was made in
1880 by the Dutch chemist Skraup, who found that by heating aniline with
sulphuric acid and glycerin in the presence of nitrobenzene, quinoline is
produced. The nitrobenzene acts only as an oxidizing agent; the
amido-group of the aniline is converted into a group containing carbon,
hydrogen, and nitrogen, _i.e._ the pyridine group. The discovery of
Skraup's method formed the starting-point of a series of syntheses, which
resulted in the formation of many products of technical value. In all
these syntheses the fundamental change is the same, viz. the conversion
of an amidic into a pyridine group. We may speak of the amido-group as
being "pyridised" in such processes. Thus alizarin blue, which is formed
by heating nitro-alizarin with glycerin and sulphuric acid, results from
the pyridisation of the nitro-group. By an analogous method Doebner and v.
Miller prepared a homologue of quinoline (quinaldine) in 1881, by the
action of sulphuric acid and a certain modification of aldehyde known as
paraldehyde on aniline.
Quinoline and its homologue quinaldine have been utilized as sources of
colouring-matters. A green dye-stuff, known as quinoline green, was
formerly made by the same method as that employed for producing the
phosgene colours by Caro and Kern's process (p. 106). The phthalein of
quinaldine was introduced by E. Jacobsen in 1882 under the name of
quinoline yellow, a colouring-matter which forms a soluble sulpho-acid by
the action of sulphuric acid.
To return to coal-tar pharmaceutical preparations. At the present time
seven distinct derivatives of quinoline, all formed by pyridising the
amido-group in aniline, amido-phenols, &c., are known in medicine under
such names as kairine, kairoline, thalline, and thermifugine. The mode of
preparation of these compounds cannot be entered into here, Kairine, the
first of the artificial alkaloids, is a derivative of hydroxy-quinoline,
which was discovered in 1881 by Otto Fischer. All these quinoline
derivatives have the property of lowering the temperature of the body in
certain kinds of fevers, and may therefore be considered as the first
artificial products coming into competition with the natural alkaloid,
quinine. There is reason for believing that the latter alkaloid, the most
valuable of all febrifuges, is related to the quinoline bases, so that if
its synthesis is accomplished--as may certainly be anticipated--we shall
have to look to coal-tar as a source of the raw materials.
Another valuable artificial alkaloid, discovered in 1883 by Ludwig Knorr,
claims aniline as a point of departure. When aniline and analogous bases
are diazotised, and the diazo-salts reduced in the cold with a very gentle
reducing agent, such as stannous chloride, there are formed certain basic
compounds, containing one atom of nitrogen and one atom of hydrogen more
than the original base. These bases were discovered in 1876 by Emil
Fischer, and they are known as hydrazines, the particular compound thus
obtained from aniline being phenylhydrazine. By the action of this base on
a certain compound ether derived from acetic acid, which is known as
aceto-acetic ether, there is formed a product termed "pyrazole," and this
on methylation gives the alkaloid in question, which is now well known in
pharmacy under the name of "antipyrine."
While dealing with this first industrial application of a hydrazine, it
must be mentioned that the original process by which Fischer prepared
these bases was improved upon by Victor Meyer and Lecco in 1883, who
discovered the use of a cold solution of stannous chloride for reducing
the diazo-chloride to the hydrazine. By this method the manufacture of
phenylhydrazine and other hydrazines is effected on a large scale--all
kinds of amido-compounds and their sulpho-acids can be diazotised and
reduced to their hydrazines. Out of this discovery has arisen the
manufacture of a new class of colouring-matters related to the azo-dyes.
The hydrazines combine with quinones and analogous compounds with the
elimination of water, the oxygen coming from the quinone, and the hydrogen
from the hydrazine. The resulting products are coloured compounds very
similar in properties to the azo-dyes, and one of these was introduced in
1885 by Ziegler, under the name of "tartrazine." The latter is obtained by
the action of a sulpho-acid of phenylhydrazine on dioxytartaric acid, and
is a yellow dye, which is of special interest on account of its
extraordinary fastness towards light.
Another direction in which coal-tar products have been utilized is in the
formation of certain aromatic compounds which occur in the vegetable
kingdom. Thus the artificial production of bitter-almond oil from toluene
has already been explained. By heating phenol with caustic alkali and
chloroform, the aldehyde of salicylic acid, _i.e._ salicylic aldehyde, is
formed, and this, on heating with dry sodium acetate and acetic anhydride,
passes into _coumarin_, the fragrant crystalline substance which is
contained in the Tonka bean and the sweet-scented woodruff. Furthermore,
the familiar flavour and scent of the vanilla bean, which is due to a
crystalline substance known as vanillin, can be obtained from coal-tar
without the use of the plant. The researches of Tiemann and Haarman having
shown that vanillin is a derivative of benzene containing the aldehyde
group, one hydroxyl- and one methoxy-group, the synthesis of this compound
soon followed (Ulrich, 1884). The starting-point in this synthesis is
nitrobenzoic aldehyde, so that here again we begin with toluene as a raw
material. A mixture of vanillin and benzoic aldehyde when attenuated to a
state of extreme dilution in a spirituous solvent, gives the perfume known
as "heliotrope."
Not the least romantic chapter of coal-tar chemistry is this production of
fragrant perfumes from the evil-smelling tar. Be it remembered that these
products--which Nature elaborates by obscure physiological processes in
the living plant--are no more contained in the tar than are the hundreds
of colouring-matters which have been prepared from this same source. It is
by chemical skill that these compounds have been built up from their
elemental groups; and the artificial products, as in the case of indigo
and alizarin, are chemically identical with those obtained from the plant.
Among the late achievements in the synthesis of vegetable products from
coal-tar compounds is that of juglone, a crystalline substance found in
walnut-shell. It was shown by Bernthsen in 1884 that this compound was
hydroxy-naphthaquinone, and in 1887 its synthesis from naphthalene was
accomplished by this same chemist in conjunction with Dr. Semper.
Another recent development in the present branch of chemistry brings a
coal-tar product into competition with sugar. In 1879 Dr. Fahlberg
discovered a certain derivative of toluene which possessed an intensely
sweet taste. By 1884 the manufacture of this product had been improved to
a sufficient extent to enable it to be introduced into commerce as a
flavouring material in cases where sweetness is wanted without the use of
sugar, such as in the food of diabetic patients. Under the name of
"saccharin," Fahlberg thus gave to commerce a substance having more than
three hundred times the sweetening power of cane-sugar--a substance not
only possessed of an intense taste, but not acted upon by ferments, and
possessing distinctly antiseptic properties. The future of coal-tar
saccharin has yet to be developed; but its advantages are so numerous that
it cannot fail to become sooner or later one of the most important of
coal-tar products. In cases where sweetening is required without the
possibility of the subsequent formation of alcohol by fermentation,
saccharin has been used with great success, especially in the manufacture
of aerated waters. Its value in medicine has been recognized by its recent
admission into the Pharmacopoeia.
The remarkable achievements of modern chemistry in connection with
coal-tar products do not end with the formation of colouring-matters,
medicines, and perfumes. The introduction of the beautiful dyes has had an
influence in other directions, and has led to results quite unsuspected
until the restless spirit of investigation opened out new fields for their
application. A few of these secondary uses are sufficiently important to
be chronicled here. In sanitary engineering, for example, the intense
colouring power of fluorescein is frequently made use of to test the
soundness of drains, or to find out whether a well receives drainage from
insanitary sources. In photography also coal-tar colouring-matters are
playing an important part by virtue of a certain property which some of
these compounds possess.
The ordinary photographic plate is, as is well known, much more sensitive
to blue and violet than to yellow or red, so that in photographing
coloured objects the picture gives a false impression of colour intensity,
the violets and blues impressing themselves too strongly, and the yellows
and reds too feebly. It was discovered by Dr. H. W. Vogel in 1873 that if
the sensitive film is slightly tinted with certain colouring-matters, the
sensitiveness for yellow and red can be much increased, so that the
picture is a more natural representation of the object. Plates thus dyed
are said to be "isochromatic" or "orthochromatic," and by their use
paintings or other coloured objects can be photographed with much better
results than by the use of ordinary plates. The boon thus conferred upon
photographic art is therefore to be attributed to coal-tar chemistry.
Among the numerous colouring-matters which have been experimented with,
the most effective special sensitizers are erythrosin, one of the
phthaleins, quinoline red, a compound related to the same group, and
cyanin, a fugitive blue colouring-matter obtained from quinoline in 1860
by Greville Williams.
In yet another way has photography become indebted to the tar chemist. Two
important developers now in common use are coal-tar products, viz.
hydroquinone and eikonogen. The history of these compounds is worthy of
narration as showing how a product when once given by chemistry to the
world may become applicable in quite unexpected directions. Chloroform is
a case in point. This compound was discovered by Liebig in 1831, but its
use as an anaesthetic did not come about till seventeen years after its
discovery. It was Sir James Simpson who in 1848 first showed the value of
chloroform in surgical operations. A similar story can be told with
respect to these photographic developers.
Towards the middle of the last century a French chemist, the Count de la
Garaye, noticed a crystalline substance deposited from the extract of
Peruvian bark, then, as now, used in medicine. This substance was the lime
salt of an acid to which Vauquelin in 1806 gave the name of quinic acid
(_acide quinique_). In 1838 Woskresensky, by oxidizing quinic acid with
sulphuric acid and oxide of manganese, obtained a crystalline substance
which he called quinoyl. The name was changed to quinone by Woehler, and,
as we have already seen (p. 172), the term has now become generic,
indicating a group of similarly constituted oxygen derivatives of
hydrocarbons. Hydroquinone was obtained by Caventou and Pelletier by
heating quinic acid, but these chemists did not recognize its true nature.
It was the illustrious Woehler who in 1844 first prepared the compound in a
state of purity, and established its relationship to quinone. This
relationship, as the name given by Woehler indicates, is that of the nature
of a hydrogenised quinone. The compound is readily prepared by the action
of sulphurous acid or any other reducing agent on the quinone.
It has long been known in photography, that a developer must be of the
nature of a reducing agent, either inorganic or organic, and many
hydroxylic and amidic derivatives of hydrocarbons come under this
category. Thus, pyrogallol, which has already been referred to as a
trihydroxybenzene (p. 146), when dissolved in alkali rapidly absorbs
oxygen--it is a strong reducing agent, and is thus of value as a
developer. But although pyrogallol is a benzene derivative, and could if
necessary be prepared synthetically, it can hardly be claimed as a tar
product, as it is generally made from gallic acid. Now hydroquinone when
dissolved in alkali also acts as a reducing agent, and in this we have the
first application of a true coal-tar product as a photographic developer.
Its use for this purpose was suggested by Captain Abney in 1880, and it
was found to possess certain advantages which caused it to become
generally adopted.
As soon as a practical use is found for a chemical product its manufacture
follows as a matter of course. In the case of hydroquinone, the original
source, quinic acid, was obviously out of question, for economical
reasons. In 1877, however, Nietzki worked out a very good process for the
preparation of quinone from aniline by oxidation with sulphuric acid and
bichromate of soda in the cold. This placed the production of quinone on a
manufacturing basis, so that when a demand for hydroquinone sprung up, the
wants of the photographer were met by the technologist. Eikonogen is
another organic reducing agent, discovered by the writer in 1880, and
introduced as a developer by Dr. Andresen in 1889. It is an
amido-derivative of a sulpho-acid of beta-naphthol, so that naphthalene is
the generating hydrocarbon of this substance.
The thio-derivative of toluidine described as "primuline" (p. 160), has
recently been found by its discoverer to possess a most remarkable
property which enables this compound to be used for the photographic
reproduction of designs in azo-colours. Diazotised primuline, as already
explained, combines in the usual way with amines and phenols to form
azo-dyes. Under the influence of light, however, the diazotised primuline
is decomposed with the loss of nitrogen, and the formation of a product
which does not possess the properties of a diazo-compound. The product of
photochemical decomposition no longer forms azo-colours with amines or
phenols. If, therefore, a fabric is dyed with primuline, then diazotised
by immersion in a nitrite bath, and exposed under a photographic negative,
those portions of the surface to which the light penetrates lose the power
of giving a colour with amines or phenols. The design can thus be
developed by dipping the fabric into a solution of naphthol,
naphthylamine, &c. By this discovery another point of contact has been
established between photography and coal-tar products. Nor is this the
only instance of its kind, for it has also been observed that a
diazo-sulpho-acid of one of the xylenes does not combine with phenols to
form azo-dyes excepting under the influence of light. A fabric can
therefore be impregnated with the mixture of diazo-sulpho-acid and
naphthol, and exposed under a design, when the azo-colour is developed
only on those portions of the surface which are acted upon by light.
The last indirect application of coal-tar colouring-matters to which
attention must be called is one of great importance in biology. The use of
these dyes as stains for sections of animal and vegetable tissue has long
been familiar to microscopists. Owing to the different affinities of the
various components of the tissue for the different colouring-matters,
these components are capable of being differentiated and distinguished by
microscopical analysis. Furthermore, the almost invisible organisms which
in recent times have been shown to play such an important part in
diseases, have in many cases a special affinity for particular
colouring-matters, and their presence has been revealed by this means. The
micro-organism of tubercle, for example, was in this way found by Koch to
be readily stained by methylene blue, and its detection was thus rendered
possible with certainty. Many of the dyes referred to in the previous
pages have rendered service in a similar way. To the pure utilitarian such
an application of coal-tar products will no doubt compensate for any
defects which they may be supposed to possess from the aesthetic point of
view.[11]
From a small beginning there has thus developed in a period of
five-and-thirty years an enormous industry, the actual value of which at
the present time it is very difficult to estimate. We shall not be far out
if we put down the value of the coal-tar colouring-matters produced
annually in this country and on the Continent at L5,000,000 sterling. The
products which half a century or so ago were made in the laboratory with
great difficulty, and only in very small quantities, are now turned out by
the hundredweight and the ton.[12] To achieve these results the most
profound chemical knowledge has been combined with the highest
technological skill. The outcome has been to place at the service of man,
from the waste products of the gas-manufacturer, a series of
colouring-matters which can compete with the natural dyes, and which in
many cases have displaced the latter. From this source we have also been
provided with explosives such as picric acid; with perfumes and flavouring
materials like bitter-almond oil and vanillin; with a sweetening principle
like saccharin--compared with which the product of the sugar-cane is but
feeble; with dyes which tint the photographic film, and enable the most
delicate gradations of shade to be reproduced; with developers such as
hydroquinone and eikonogen; with disinfectants which contribute to the
healthiness of our towns; with potent medicines which rival the natural
alkaloids; and with stains which reveal the innermost structure of the
tissues of living things, or which bring to light the hidden source of
disease. Surely if ever a romance was woven out of prosaic material it has
been this industrial development of modern chemistry.
But although the results are striking enough when thus summed up, and
although the industrial importance of all this work will be conceded by
those who have the welfare of the country in mind, the paths which the
pioneers have had to beat out can unfortunately be followed but by the
few. It is not given to our science to strike the public mind at once with
the magnitude of its achievements, as is the case with the great works of
the engineer. Nevertheless the scientific skill which enables a Forth
Bridge to be constructed for the use of the travelling public of this
age--marvellous as it may appear to the uninstructed--is equalled, if not
surpassed, by the mastery of the intricate atomic groupings which has
enabled the chemist to build up the colouring-matters of the madder and
indigo plants.
A great industry needs no excuse for its existence provided that it
supplies something of use to man, and finds employment for many hands. The
coal-tar industry fulfils these conditions, as will be gathered from the
foregoing pages. If any further justification is required from a more
exalted standpoint than that of pure utilitarianism it can be supplied. It
is well known to all who have traced the results of applying any
scientific discovery to industrial purposes, that the practical
application invariably reacts upon the pure science to the lasting benefit
of both. In no department of applied science is this truth more forcibly
illustrated than in the branch of technology of which I have here
attempted to give a popular account. The pure theory of chemical
structure--the guiding spirit of the modern science--has been advanced
enormously by means of the materials supplied by and resulting from the
coal-tar industry. The fundamental notion of the structure of the benzene
molecule marks an epoch in the history of chemical theory of which the
importance cannot be too highly estimated. This idea occurred, as by
inspiration, to August Kekule of Bonn in the year 1865, and its
introduction has been marked by a quarter century of activity in research
such as the science of chemistry has never experienced at any previous
period of its history. The theory of the atomic structure of the benzene
molecule has been extended and applied to all analogous compounds, and it
is in coal-tar that we have the most prolific source of the compounds of
this class.
It was scarcely to be wondered at that an idea which has been so prolific
as a stimulator of original investigation should have exerted a marked
influence on the manufacture of tar-products. All the brilliant syntheses
of colouring-matters effected of late years are living witnesses of the
fertility of Kekule's conception. In the spring of 1890 there was held in
Berlin a jubilee meeting commemorating the twenty-fifth anniversary of the
benzene theory. At that meeting the representative of the German coal-tar
colour industry publicly declared that the prosperity of Germany in this
branch of manufacture was primarily due to this theoretical notion. But if
the development of the industry has been thus advanced by the theory, it
is no less true that the latter has been helped forward by the industry.
The verification of a chemical theory necessitates investigations for
which supplies of the requisite materials must be forthcoming. Inasmuch as
the very materials wanted were separated from coal-tar and purified on a
large scale for manufacturing purposes, the science was not long kept
waiting. The laborious series of operations which the chemist working on a
laboratory scale had to go through in order to obtain raw materials, could
be dispensed with when products which were at one time regarded as rare
curiosities became available by the hundredweight. It is perhaps not too
much to say that the advancement of chemical theory in the direction
started by Kekule has been accelerated by a century owing to the
circumstance that coal-tar products have become the property of the
technologist. In other words, we might have had to wait till 1965 to reach
our present state of knowledge concerning the theory of benzenoid
compounds if the coal-tar industry had not been in existence. And this is
not the only way in which the industry has helped the science, for in the
course of manufacture many new compounds and many new chemical
transformations have been incidentally discovered, which have thrown great
light on chemical theory. From the higher standpoint of pure science, the
industry has therefore deservedly won a most exalted position.
With respect to the value of the coal-tar dyes as tinctorial agents, there
is a certain amount of misconception which it is desirable to remove.
There is a widely-spread idea that these colours are fugitive--that they
rub off, that they fade on exposure to light, that they wash out, and, in
short, that they are in every way inferior to the old wood or vegetable
dyes. These charges are unfounded. One of the best refutations is, that
two of the oldest and fastest of natural colouring-matters, viz. alizarin
and indigo, are coal-tar products. There are some coal-tar dyes which are
not fast to light, and there are many vegetable dyes which are equally
fugitive. If there are natural colouring-matters which are fast and which
are aesthetically orthodox, these are rivalled by tar-products which fulfil
the same conditions. Such dyes as aniline black, alizarin blue, anthracene
brown, tartrazine, some of the azo-reds and naphthol green resist the
influence of light as well as, if not better than, any natural
colouring-matter. The artificial yellow dyes are as a whole faster than
the natural yellows. There are at the present time some three hundred
coal-tar colouring-matters made, and about one-tenth of that number of
natural dyes are in use. Of the latter only ten--let us say 33 per
cent.--are really fast. Of the artificial dyes, thirty are extremely fast,
and thirty fast enough for all practical requirements, so that the fast
natural colours have been largely outnumbered by the artificial ones. If
Nature has been beaten, however, this has been rendered possible only by
taking advantage of Nature's own resources--by studying the chemical
properties of atoms, and giving scope to the play of the internal forces
which they inherently possess--
"Yet Nature is made better by no mean,
But Nature makes that mean: so, o'er that art,
Which, you say, adds to Nature, is an art
That Nature makes."
The story told in this chapter is chronologically summarized below--
1820. Naphthalene discovered in coal-tar by Garden.
1832. Anthracene discovered in coal-tar by Dumas and Laurent.
1834. Phenol discovered in coal-tar by Runge.
1842. Picric acid prepared from phenol by Laurent; manufactured in
Manchester in 1862.
1845. Benzidine discovered by Zinin.
1859. Corallin and aurin discovered by Kolbe and Schmitt and by Persoz;
leading to manufacture from oxalic acid and phenol.
1860. Synthesis of salicylic acid by Kolbe.
1864. Manchester yellow discovered by Martius, leading to manufacture of
alpha-naphthylamine and then to alpha-naphthol.
1867. Magdala red discovered by Schiendl.
1868. Synthesis of alizarin by Graebe and Liebermann, leading to the
utilization of anthracene, caustic soda, potassium chlorate and
bichromate, and calling into existence the manufacture of fuming
sulphuric acid.
1870. Gallein, the first of the phthaleins, discovered by A. v. Baeyer,
followed in 1871 by coerulein, and in 1874 by the eosin dyes
(Caro). These discoveries necessitated the manufacture of phthalic
acid and resorcinol.
1873. Orthochromatic photography discovered by Vogel.
1876. Azo-dyes from the naphthols introduced by Roussin and Poirrier and
Witt, leading to the manufacture of the naphthols, sulphanilic
acid, &c.
1877. Preparation of quinone from aniline by Nietzki, utilized in
photography in 1880 for manufacture of hydroquinone.
1878. Disulpho-acids of beta-naphthol introduced by Meister, Lucius, and
Bruening, leading to azo-dyes from aniline, toluidine, xylidine,
and cumidine.
1879. Acid naphthol yellow introduced by Caro.
" Biebrich scarlet, the first secondary azo-colour, introduced by
Nietzki.
" Nitroso-sulpho acid of beta-naphthol discovered by the writer;
followed in 1883 by naphthol green (O. Hoffmann), and in 1889 by
eikonogen (Andresen).
" Beta-naphthol violet, the first of the oxazines, discovered by the
writer; followed in 1881 by gallocyanin.
" Coal-tar saccharin discovered by Fahlberg; manufacture made
practicable in 1884.
1880. Synthesis of indigo by A. v. Baeyer.
" Quinoline synthesised by Skraup's process.
1881. Kairine introduced by O. Fischer, the first artificial febrifuge.
" Indophenol discovered by Koechlin and Witt.
" Azo-dyes from new sulpho-acid of beta-naphthol introduced by Bayer
& Co.
1883. Antipyrine introduced by L. Knorr, leading to manufacture of
phenylhydrazine.
1884. Congo red, the first secondary azo-colour from benzidine,
introduced by Boettiger. Beginning of manufacture of cotton
azo-dyes, and leading to the production of benzidine and tolidine
on a large scale.
1885. Secondary azo-dyes from benzidine and tolidine containing two
dissimilar amines, phenols, &c., introduced by Pfaff.
" Tartrazine discovered by Ziegler; manufacture of sulpho-acid of
phenylhydrazine and of dioxytartaric acid.
1885. Thiorubin introduced by Dahl & Co., leading to manufacture of
thiotoluidine; followed by primuline, discovered by A. G. Green in
1887.
1886. Secondary azo-dyes of stilbene series introduced by Leonhardt & Co.
ADDENDUM.
By passing steam over red-hot carbon, a mixture of carbon monoxide and
hydrogen is formed. This mixture of inflammable gases is known as
"water-gas," and in the preparation of the gas on a large scale, coke is
used as a source of carbon. If, therefore, water-gas became generally
used, another use for coke would be added to those already referred to (p.
47).
With reference to the consumption of coal in London (p. 46), it appears
from the Report of a Committee of the Corporation of London, issued at the
end of 1890, that the present rate of consumption in the Metropolis is
9,709,000 tons per annum. This corresponds to 26,600 tons per diem. It has
been proved by experiment, that when coal is burnt in an open grate, from
one to three per cent. of the coal escapes in the form of unburnt solid
particles, or "soot," and about 10 per cent. is lost in the form of
volatile compounds of carbon. It has been estimated that the total amount
of coal annually wasted by imperfect combustion in this country is
45,000,000 tons, corresponding to about L12,000,000, taking the value of
coal at the pit's mouth. Taking the unconsumed solid particles at the very
lowest estimate of 1 per cent., it will be seen that, in London alone, we
are sending forth carbonaceous and tarry matter into the atmosphere at the
rate of about 266 tons daily; and volatile carbon compounds at the daily
rate of 2660 tons (see p. 32). At the price of coal in London this means
that, in solid combustibles alone, we are absolutely squandering about
L10,000 annually, to say nothing of the damage caused by the presence of
this sooty pall. Such facts as these require no comment; they speak for
themselves in sombre gloom, and in the sickliness of our town
vegetation--they give a new meaning to the term "in darkest London," and
they plead eloquently for science and legislation to show us "the way
out."
INDEX.
Accum, condensation of tar-oils, 69
Acetic acid, 64
Acetophenone, 178
Acid brown, 151
Acid greens, 106
Acid magenta, 92
Acid naphthol yellow, 143
Acid yellow, 120
Acridine, 180
Air, composition of, 24
Albo-carbon light, 140
Alizarin black, 172
Alizarin blue, 174
Alizarin carmine, 174
Alizarin green, 174
Alizarin orange, 174
Alkali blue, 93
Amidodimethylaniline, 112
Ammonia in gas-liquor, 64
Ammonia, origin in gas-liquor, 65
Analyses of coal, 23
Aniline black, 114
Aniline, history, 75
Aniline, manufacture, 87
Aniline yellow, 116
Annual production of ammonia, 68
Anthracene, 171
Anthracene brown, 174
Anthracene oil, 81, 167
Anthragallol, 174
Anthrapurpurin, 174
Anthraquinone, 173
Antifebrine, 179
Antipyrine, 183
Archil substitute, 151
Arctic coal, 12
Arsenic acid process, 90
Arsenic acid, recovery, 94
Artificial alizarin, 173
Artificial purpurin, 173
Asphalte, 176
Auramine, 106
Aurin, 132
Azines, 109
Azo-blacks, 159
Azo-colours, 118
Azo-dyes for cotton, 158
Azobenzene, 119
Azo-dyes from salicylic acid, 135
Azotoluene, 119
Baeyer, A. v., indigo, 127
Baeyer, A. v., phthaleins, 146
Basle blue, 111
Becher, early experiments, 34
Beet-sugar cultivation, 67
Benzal chloride, 102
Benzaldehyde, 103
Benzene, discovery, 73
Benzene, final purification, 86
Benzene in tar-oil, 73
Benzene theory, 196
Benzidam, 75
Benzidine, 136
Benzoic acid, manufacture, 104
Benzotrichloride, 102
Benzyl chloride, 102
Bernthsen, methylene blue, 113
Bethell, timber preserving, 70
Biebrich scarlet, 156
Biology, dyes used in, 192
Bismarck brown, 116
Bitter-almond oil, 103
Bone oil, 180
Boettiger, Congo-red, 157
Breant, timber pickling, 70
Briquettes, 178
Burning naphtha, 86
Calorific value of carbon, 25
Calorific value of coal, 20
Carbolic acid, 129
Carbolic oil, 23, 80, 129
Carbon dioxide, 24
Carboniferous period, 11
Caro and Kern, phosgene dyes, 106
Caro and Wanklyn, rosolic acid, 133
Caro, fluorescein and eosin, 147
Caro, methylene blue, 112
Chemical washing, 83
Chlorophyll, 29
Chrysamines, 136
Chrysoidine, 116
Cinnamic acid, 128
Clayton, Dean, distils coal, 35
Clegg, Samuel, gas-engineer, 40
Coal, amount raised, 59
Coal-fields of United Kingdom, 60
Coal-gas, composition, 56
Coal-gas, manufacture, 42
Coal-mining, history, 57
Coal, origin, 9
Coal, supply, 59
Coerulein, 147
Coke, composition of, 48
Coke from gas-retorts, 45
Coke-oven tar, 49
Coke, uses of, 47
Combustion, 23
Composition of coal, 23
Congo red, 157
Conservation of energy, 18
Constitution of molecules, 95
Corallin, 132
Cotton dyes, 137
Coumarin, 185
Coupier's process, 91
Creosote oil, 163
Creosoting of timber, 70
Cresols, 131
Cresylic acid, 131
Cretaceous coal, 12
Crocein scarlets, 156
Crystal violet, 106
Cumidine, 155
Cyanin, 188
Dale and Caro, induline, 120
Destructive distillation, 33
Diazo-compounds, 116
Diazotype, 191
Dimethylaniline, 100
Dinitrobenzene, 120
Diphenylamine, 101
Diphenylamine blue, 101
Distillation, fractional, 78
Doebner, malachite green, 102
Dover, coal under, 60
Dumas and Laurent, anthracene, 171
Dundonald, Earl, early experiments, 39
Eikonogen, 189
Electricity as an illuminating agent, 62
Eocene coal, 12
Eosin, 147
Erythrosin, 188
Essence of mirbane, 74
Exalgine, 179
Fahlberg, saccharin, 186
Faraday, discovers benzene, 73
Fast red, 151
Fertilization by ammonia, 66
Fire-damp, 32
First runnings, 80
Fischer, E. and O., rosaniline, 97
Fischer, hydrazines, 183
Fischer, malachite green, 103
Flavaniline, 180
Flavopurpurin, 174
Fluorescein, 147
Foot-pound, 19
Fractional distillation, 78
Fritzsche, aniline, 75
Gallein, 146
Gallic acid, 146
Gallocyanin, 162
Gambines, 161
Garancin, 168
Garden, naphthalene, 139
Gas producers, 57
Gas, quantity obtained from coal, 45
Girard and De Laire, rosaniline blues, 92
Glucosides, 169
Goethe, visit to coke-burner, 48
Graebe and Liebermann, alizarin, 170
Graphite, 12
Graessler, acid yellow, 120
Green, A. G., primuline, 160
Griess, diazo-compounds, 116
Hales, Rev. Stephen, distils coal, 37
Hofmann, benzene in tar-oil, 73
Hofmann, red from aniline, 89
Hofmann's violets, 93
Homologous series, 152
Horse-power, 22
Hull, Prof., coal supply, 59
Hydrazines, 183
Hydrocarbons of benzene series, 82
Hydrogen, calorific value, 25
Hydroquinone, 189
Hypnone, 179
Indigo plants, 124
Indigo, syntheses, 126
Indophenol, 162
Indulines, 121
Ingrain colours, 160
Iodine green, 94
Iron smelting, 16
Iron swarf, 87
Isochromatic plates, 188
Isomerism, 88
Joule, mechanical equivalent of heat, 19
Juglone, 186
Jurassic coal, 12
Kairine, 182
Kekule, benzene theory, 196
Kekule and Hidegh, azo-dyes, 135
Koch, tubercle, 193
Koechlin, gallocyanin, 162
Koechlin and Witt, indophenol, 162
Kolbe, salicylic acid, 134
Kolbe and Schmitt, phenol dye, 132
Kyanol, 75
Lampblack, 139, 166
Laurent, phenol, 131
Laurent, phthalic acid, 143
Laurent, picric acid, 136
Lauth, methyl violet, 98
Lauth's violet, 111
Leonhardt & Co., stilbene dyes, 137
Lightfoot, aniline black, 114
Light oil, 80
Light oils, early uses, 71
Lister, antiseptic surgery, 131
London, coal introduced, 58
London, illuminated by gas, 40
Lucigen burner, 163
Madder, 168
Magdala red, 149
Magenta, history, 89
Malachite green, 102
Manchester brown, 116
Manchester yellow, 142
Mansfield, isolation of benzene, 73
Mansfield's still, 77
Manures, 66
Marsh gas, 32
Mauve, discovery, 74
Mechanical value of coal, 22
Medlock, magenta process, 90
Methyl chloride, 99
Methylene green, 113
Methyl green, 101
Methyl violet, 98
Mirbane, essence, 74
Murdoch, introduces coal-gas, 40
Naphthalene, annual production, 141
Naphthalene in carbolic oil, 130
Naphthionic acid, 151
Naphthol green, 161
Naphthol orange, 151
Naphthols, 141
Naphthylamines, 142
Natanson, aniline red, 89
Neutral red, 111
Neutral violet, 111
New blue, 161
Nicholson blue, 93
Nicholson, magenta process, 90
Nietzki, azines, 109
Nietzki, Biebrich scarlet, 156
Nietzki, quinone, 191
Night blue, 106
Nigrosine, 121
Nitrification, 66
Nitrobenzene process, 91
Nitrosodimethylaniline, 111
Non-Carboniferous coal, 11
Number of compounds in tar, 81
Old Red Sandstone, coal in, 12
Oligocene brown coal, 12
Orthochromatic plates, 188
Oxazines, 162
Oxide of iron for gas purifying, 44
Paraffin oil and wax, 50
Patent fuel, 178
Perfumes, 185
Perkin, alizarin, 170
Perkin, discovers mauve, 74
Permanence of dyes, 198
Permian coal, 12
Persoz, phenol dye, 132
Pharmaceutical preparations, 178
Phenanthrene, 172
Phenols, 129
Phosgene dyes, 106
Phosphine, 94, 180
Photographic developers, 189
Phthaleins, 146
Phthalic acid, 143
Picric acid, 136
Pitch, 81, 176
Plants, growth of, 26
Ponceaux, 151
Primary azo-dyes, 156
Primuline, 160
Propiolic acid, 128
Purpurin, 169
Pyrazole, 183
Pyridine, 87
Pyridine bases, 179
Pyrogallol, 146
Quinaldine, 182
Quinic acid, 189
Quinoline, 180
Quinoline green, 182
Quinoline red, 188
Quinoline yellow, 182
Quinones, 172
Read Holliday's lamp, 72
Rectification of hydrocarbons, 84
Resorcinol, 145
Rhodamines, 148
Roccellin, 151
Roman coal-mining, 57
Rosaniline blues, 92
Rosaniline from rosolic acid, 133
Rosolic acid, 132
Runge, kyanol, 75
Runge, phenol in tar, 131
Saccharin, 186
Saffranine, 108
Salicylic acid, 134
Salicylic aldehyde, 185
Salols, 179
Schiendl, Magdala red, 149
Scotland, shale-oil industry, 53
Sea coal, 58
Secondary azo-dyes, 156
Shale, nature of, 51
Shale-oil industry, 50
Skraup, quinoline, 181
Sodium nitrite, 119
Solar energy, 28
Soluble blue, 93
Solvent naphtha, 86
Steam-engines, 20
Stilbene azo-dyes, 137
Structure of coal, 15
Sulphanilic acid, 150
Sulphuric acid, 45
Sunlight, source of energy in coal, 30
Surgery, antiseptic, 131
Tar distilling, 77
Tar, first utilization, 69
Tar from coke-ovens, 49
Tar, quantity obtained from coal, 45
Tartrazine, 184
Tertiary coal, 12
Thalline, 182
Thermifugine, 182
Thiazines, 113
Thiodiphenylamine, 113
Thiorubin, 160
Timber pickling, 70
Tolidine, 136
Toluene from tar, 81
Torbane Hill coal, 52
Transformation of wood into coal, 31
Triassic coal, 12
Trimethylamine, 99
Trinitrophenol, 136
Triphenylmethane, 97
Tubercle bacillus, 193
Turkey red, 170
Underclay, 13
Unverdorben, crystallin, 75
Uses of coal, 16
Vanillin, 185
Vegetable deposits, recent, 13
Verguin, red from aniline, 90
Victoria blue, 106
Victoria yellow, 137
Vinasse, 99
Vincent, methyl chloride, 100
Violaniline, 121
Wasteful use of coal, 32, 203
Water, composition of, 25
Water gas, 203
Watson, Bishop, coke-oven tar, 50
Watson, Bishop, distils coal, 37
Wealden iron industry, 17
Whitaker, W., coal in S.-E. England, 60
Winsor, promotes introduction of gas, 41
Witt, azines, 109
Witt, chrysoidine, 116
Witt, naphthol orange, 150
Wood vinegar, 64
Woody fibre, 26
Woulfe, picric acid, 136
Xylenes from tar, 81
Xylidine scarlet, 153
Young, James, burning-oil, 51
Ziegler, tartrazine, 184
Zinin, benzidam, 75
THE END.
_Richard Clay & Sons, Limited, London & Bungay._
Footnotes:
[1] "An experiment concerning the Spirit of Coals," _Phil. Trans._
(abridged), vol. viii. p. 295.
[2] _Report of the Coal Commissioners_ (1866-71), vol. i.
[3] In a paper read before the Royal Statistical Society by Mr.
Price-Williams in 1889, this author points out that, owing to the
introduction of the Bessemer process and other economical improvements,
the amount of coal used in the iron and steel manufacture had fallen in
1867 to about sixteen and a half per cent. of the total quantity raised.
[4] This remark does not apply to Great Britain; our Excise regulations
have practically killed those branches of manufacture requiring the use of
pure wood-spirit.
[5] Since the above was written, new synthetical processes for the
production of indigo have been made known in Germany by Karl Heumann. Of
the commercial aspect of these discoveries it is of course impossible at
present to form an opinion.
[6] With phthalic anhydride gives fluorescein and dyes of eosin and
rhodamin series.
[7] Diazotised and combined with naphthylamines, naphthols, or their
sulpho-acids give azo-dyes.
[8] With naphthols give oxazines and indophenol.
[9] Diazotised and combined with phenols, amines, or sulpho-acids to form
azo-dyes.
[10] Combined with diazotised amido-compounds to form azo-dyes.
[11] Since the above was written the continuation of Koch's researches
upon the tubercle bacillus has culminated in the discovery of his now
world-renowned lymph for the inoculation of patients suffering from
tubercular disease.
[12] In one large factory in Yorkshire there is a set of stills kept
constantly at work making pure aniline at the rate of two hundred tons per
month. The monthly consumption of coal in this factory is two thousand
tons, equal to twenty-four thousand tons per annum.
PUBLICATIONS OF THE
Society for Promoting Christian Knowledge.
THE ROMANCE OF SCIENCE.
A series of books which will show that science has for the masses as great
interest and more edification than the romances of the day.
_Small Post 8vo, Cloth boards._
The Birth and Growth of Worlds. A Lecture by Professor A. H. GREEN, M.A.,
F.R.S. 1_s._
Soap-Bubbles, and the Forces which Mould Them. A course of Lectures by C.
V. BOYS, A.R.S.M., F.R.S. With numerous diagrams. 2_s._ 6_d._
Spinning Tops. By Professor J. PERRY, M.E., D.Sc., F.R.S. With numerous
diagrams. 2_s._ 6_d._
Diseases of Plants. By Professor MARSHALL WARD. With Numerous
Illustrations. 2_s._ 6_d._
The Story of a Tinder-Box. A course of Lectures by CHARLES MEYMOTT TIDY,
M.B., M.S., F.C.S. With Numerous Illustrations. 2_s._
Time and Tide. A Romance of the Moon. By Sir ROBERT S. BALL, LL.D., Royal
Astronomer of Ireland. With Illustrations. 2_s._ 6_d._
MANUALS OF HEALTH.
_Fcap. 8vo, 128 pp., limp cloth, price 1s. each._
Health and Occupation. By B. W. RICHARDSON, Esq., F.R.S., M.D.
Habitation in Relation to Health (The). By F. S. B. CHAUMONT, M.D., F.R.S.
On Personal Care of Health. By the late E. A. PARKES, M.D., F.R.S.
Water, Air, and Disinfectants. By W. NOEL HARTLEY, Esq., King's College.
MANUALS OF ELEMENTARY SCIENCE.
_Fcap. 8vo, 128pp., with Illustrations, limp cloth, 1s. each._
Physiology. By F. LE GROS CLARKE, F.R.S., St. Thomas's Hospital.
Geology. By the Rev. T. G. BONNEY, M.A., F.G.S., Fellow and late Tutor of
St. John's College, Cambridge.
Chemistry. By ALBERT J. BERNAYS.
Astronomy. By W. H. M. CHRISTIE, M.A., the Royal Observatory, Greenwich.
Botany. By ROBERT BENTLEY, Professor of Botany in King's College, London.
Zoology. By ALFRED NEWTON, M.A., F.R.S., Professor of Zoology and
Comparative Anatomy in the University of Cambridge.
Matter and Motion. By the late J. CLERK MAXWELL, M.A., Trinity College,
Cambridge.
Spectroscope and its Work (The). By the late RICHARD A. PROCTOR.
Crystallography. By HENRY PALIN GURNEY, M.A., Clare College, Cambridge.
Electricity. By the late Professor FLEEMING JENKIN.
NATURAL HISTORY RAMBLES.
_Fcap. 8vo, with numerous Woodcuts, Cloth boards, 2s. 6d. each._
IN SEARCH OF MINERALS. By the late D. T. ANSTED, M.A., F.R.S.
LAKES AND RIVERS. By C. O. GROOM NAPIER, F.G.S.
LANE AND FIELD. By the late Rev. J. G. WOOD, M.A.
MOUNTAIN AND MOOR. By J. E. TAYLOR, F.L.S., F.G.S., Editor of
"Science-Gossip."
PONDS AND DITCHES. By M. C. COOKE, M.A., LL.D.
THE SEA-SHORE. By Professor P. MARTIN DUNCAN, M.B. (London), F.R.S.
THE WOODLANDS. By M. C. COOKE, M.A., LL.D.
UNDERGROUND. By J. E. TAYLOR, F.L.S.
SERIES OF PHOTO-RELIEVO MAPS.
_(Patented) Size 19 in. by 14 in._
ENGLAND AND WALES.--SCOTLAND.--EUROPE.
Names of places and rivers left to be filled in by _s._ _d._
scholars _each_ 0 6
With rivers and names of places " 0 9
With names of places, and county and country
divisions in colours " 1 0
ASIA.
Names of places and rivers left to be filled in by
scholars " 0 6
With rivers and names of places " 0 9
SOUTH LONDON.
With names of places, &c. " 0 6
Wall Map.--ENGLAND AND WALES.
(Size 56 in. by 46 in.) Mounted on canvas, roller
and varnished " 12 0
These Maps present each country as if in actual relief, and thus afford an
accurate picture of the configuration of the earth's surface.
MISCELLANEOUS PUBLICATIONS.
_s._ _d._
_Animal Creation (The)._ A popular Introduction to Zoology.
By the late THOMAS RYMER JONES, F.R.S. With 488 Woodcuts.
Post 8vo. _Cloth boards_ 7 6
_Beauty in Common Things._ Illustrated by 12 Drawings from
Nature, by Mrs. J. W. Whymper, and printed in Colours, with
descriptions by the Author of "Life Underground," &c. 4to.
_Cloth boards_ 10 6
_Birds' Nests and Eggs._ With 22 coloured plates of Eggs.
Square 16mo. _Cloth boards_ 3 0
_British Birds in their Haunts._ By the late Rev. C. A.
JOHNS, B.A., F.L.S. With 190 engravings by Wolf and Whymper.
Post 8vo. _Cloth boards_ 6 0
_Evenings at the Microscope_; or, Researches among the
Minuter Organs and Forms of Animal Life. By PHILIP H.
GOSSE, F.R.S. With 112 woodcuts. Post 8vo. _Cloth boards_ 4 0
_Fern Portfolio (The)._ By FRANCIS G. HEATH, Author of
"Where to find Ferns," &c. With 15 plates, elaborately drawn
life-size, exquisitely coloured from Nature, and accompanied
with descriptive text. _Cloth boards_ 8 0
_Fishes, Natural History of British_: their Structure,
Economic Uses, and Capture by Net and Rod. By the late FRANK
BUCKLAND. With numerous illustrations. Crown 8vo. _Cloth
boards_ 5 0
_Flowers of the Field._ By the late Rev. C. A. JOHNS, B.A.,
F.L.S. With numerous woodcuts. Post 8vo. _Cloth boards_ 5 0
_Forest Trees (The) of Great Britain._ By the late Rev.
C. A. Johns, B.A., F.L.S. With 150 woodcuts. Post 8vo.
_Cloth boards_ 5 0
_Freaks and Marvels of Plant Life_; or, Curiosities of
Vegetation. By M. C. COOKE, M.A., LL.D. With numerous
illustrations. Post 8vo. _Cloth boards_ 6 0
_Man and his Handiwork._ By the late Rev. J. G. WOOD,
Author of "Lane and Field," &c. With about 500
illustrations. Large Post 8vo. _Cloth boards_ 10 6
_Natural History of the Bible (The)._ By the Rev. CANON
TRISTRAM, Author of "The Land of Israel," &c. With
numerous illustrations. Crown 8vo. _Cloth boards_ 5 0
_Nature and her Servants_; or, Sketches of the Animal
Kingdom. By the Rev. THEODORE WOOD. With numerous woodcuts.
Large Post 8vo. _Cloth boards_ 5 0
_Ocean (The)._ By PHILIP HENRY GOSSE, F.B.S., Author of
"Evenings at the Microscope." With 51 illustrations and
woodcuts. Post 8vo. _Cloth boards_ 3 0
_Our Bird Allies._ By the Rev. THEODORE WOOD. With numerous
illustrations. Fcap. 8vo. _Cloth boards_ 2 6
_Our Insect Allies._ By the Rev. THEODORE WOOD. With
numerous illustrations. Fcap. 8vo. _Cloth boards_ 2 6
_Our Insect Enemies._ By the Rev. THEODORE WOOD. With
numerous illustrations. Fcap. 8vo. _Cloth boards_ 2 6
_Our Island Continent._ A Naturalist's Holiday in
Australia. By J. E. TAYLOR, F.L.S., F.G.S. With Map.
Fcap. 8vo. _Cloth boards_ 2 6
_Our Native Songsters._ By ANNE PRATT, Author of "Wild
Flowers." With 72 coloured plates. 16mo. _Cloth boards_ 6 0
_Selborne (The Natural History of)._ By the Rev. GILBERT
WHITE. With Frontispiece, Map, and 50 woodcuts. Post 8vo.
_Cloth boards_ 2 6
_Toilers in the Sea._ By M. C. COOKE, M.A., LL.D. Post 8vo.
With numerous illustrations. _Cloth boards_ 5 0
_Wayside Sketches._ By F. EDWARD HULME, F.L.S., F.S.A. With
numerous illustrations. Crown 8vo. _Cloth boards_ 5 0
_Where to find Ferns._ By FRANCIS G. HEATH, Author of "The
Fern Portfolio," &c. With numerous illustrations. Fcap.
8vo. _Cloth boards_ 1 6
_Wild Flowers._ By ANNE PRATT, Author of "Our Native
Songsters," &c. With 192 coloured plates. In two volumes.
16mo. _Cloth boards_ 12 0
LONDON:
NORTHUMBERLAND AVENUE, CHARING CROSS, W.C.;
43, QUEEN VICTORIA STREET, E.C.
BRIGHTON: 135, NORTH STREET.
Transcriber's Notes:
Passages in italics are indicated by _italics_.
Punctuation has been corrected without note.
Spelling and hyphenation variants have been retained from the original.
The original text includes Greek characters. For this text version these
letters have been replaced with transliterations.
The diagrams in this text are rough approximations of images provided in
the html version.