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FAMILIAR LETTERS ON CHEMISTRY,
AND ITS RELATION TO COMMERCE, PHYSIOLOGY, AND AGRICULTURE,
BY JUSTUS LIEBIG, M.D., PH. D., F.R.S.,
PROFESSOR OF CHEMISTRY IN THE UNIVERSITY OF GIESSEN.
EDITED BY
JOHN GARDNER, M.D.,
MEMBER OF THE CHEMICAL SOCIETY.
Second Edition, Corrected.
LONDON:
MDCCCXLIV.
PREFACE
The Letters contained in this little Volume embrace some of the most
important points of the science of Chemistry, in their application
to Natural Philosophy, Physiology, Agriculture, and Commerce. Some
of them treat of subjects which have already been, or will hereafter
be, more fully discussed in my larger works. They were intended to
be mere sketches, and were written for the especial purpose of
exciting the attention of governments, and an enlightened public, to
the necessity of establishing Schools of Chemistry, and of
promoting, by every means, the study of a science so intimately
connected with the arts, pursuits, and social well-being of modern
civilised nations.
For my own part I do not scruple to avow the conviction, that ere
long, a knowledge of the principal truths of Chemistry will be
expected in every educated man, and that it will be as necessary to
the Statesman, the Political Economist, and the Practical
Agriculturist, as it is already indispensable to the Physician, and
the Manufacturer.
In Germany, such of these Letters as have been already published,
have not failed to produce some of the results anticipated. New
professorships have been established in the Universities of
Goettingen and Wuertzburg, for the express purpose of facilitating
the application of chemical truths to the practical arts of life,
and of following up the new line of investigation and research--the
bearing of Chemistry upon Physiology, Medicine, and Agriculture,--which
may be said to be only just begun.
My friend, Dr. Ernest Dieffenbach, one of my first pupils, who is
well acquainted with all the branches of Chemistry, Physics, Natural
History, and Medicine, suggested to me that a collection of these
Letters would be acceptable to the English public, which has so
favourably received my former works.
I readily acquiesced in the publication of an English edition, and
undertook to write a few additional Letters, which should embrace
some conclusions I have arrived at, in my recent investigations, in
connection with the application of chemical science to the
physiology of plants and agriculture.
My esteemed friend, Dr. Gardner, has had the kindness to revise the
manuscript and the proof sheets for publication, for which I cannot
refrain expressing my best thanks.
It only remains for me to add a hope, that this little offering may
serve to make new friends to our beautiful and useful science, and
be a remembrancer to those old friends who have, for many years
past, taken a lively interest in all my labours.
JUSTUS LIEBIG
Giessen, Aug. 1843.
CONTENTS
LETTER I
The Subject proposed. Materials employed for Chemical Apparatus:--
GLASS--CAOUTCHOUC--CORK--PLATINUM. THE BALANCE. The "Elements" of
the Ancients, represent the forms of matter. Lavoisier and his
successors. Study of the materials composing the Earth. Synthetic
production of Minerals--LAPIS LAZULI. Organic Chemistry.
LETTER II
Changes of Form which every kind of Matter undergoes. Conversion of
Gases into Liquids and Solids. Carbonic Acid--its curious properties
in a solid state. Condensation of Gases by porous bodies. By Spongy
Platinum. Importance of this property in Nature.
LETTER III
The Manufacture of Soda from Culinary Salt; its importance in the
Arts and in Commerce. Glass--Soap--Sulphuric Acid. Silver Refining.
Bleaching. TRADE IN SULPHUR.
LETTER IV
Connection of Theory with Practice. Employment of MAGNETISM as a
moving power--its impracticability. Relation of Coals and Zinc as
economic sources of Force. Manufacture of Beet-root Sugar--its
impolicy. Gas for illumination.
LETTER V
ISOMERISM, or identity of composition in bodies with different
chemical and physical properties. CRYSTALLISATION. AMORPHISM.
ISOMORPHISM, or similarity of properties in bodies totally different
in composition.
LETTER VI
ALLIANCE OF CHEMISTRY WITH PHYSIOLOGY. Division of Food into
nourishment, and materials for combustion. Effects of Atmospheric
Oxygen. Balance of CARBON and OXYGEN.
LETTER VII
ANIMAL HEAT, its laws and influence on the Animal Functions. Loss
and SUPPLY. Influence of Climate. Fuel of Animal Heat. Agency of
Oxygen in Disease. Respiration.
LETTER VIII
ALIMENTS. Constituents of the Blood. Fibrine, Albumen. Inorganic
Substances. Isomerism of Fibrine, Albumen, and elements of
nutrition. Relation of animal and vegetable organisms.
LETTER IX
Growth of Animals. Uses of Butter and Milk. Metamorphoses of
Tissues. Food of Carnivora, and of the Horse.
LETTER X
Application of the preceding facts to Man. Division of human Food.
Uses of Gelatine.
LETTER XI
CIRCULATION OF MATTER IN THE ANIMAL AND VEGETABLE KINGDOMS. The
Ocean. AGRICULTURE. RESTITUTION OF AN EQUILIBRIUM IN THE SOIL.
Causes of the exhaustion of Land. Virginia. England. Relief gained
by importation of bones. Empirical farming unsatisfactory. Necessity
for scientific principles. Influence of the atmosphere. Of Saline
and Earthy matters of the soil.
LETTER XII
SCIENCE AND ART OF AGRICULTURE. NECESSITY OF CHEMISTRY. Rationale of
agricultural processes. Washing for gold.
LETTER XIII
ILLUSTRATION OF THE NECESSITY OF CHEMISTRY TO ADVANCE AND PERFECT
AGRICULTURE. Manner in which FALLOW ameliorates the soil. Uses of
Lime. Effects of Burning. Of Marl.
LETTER XIV
NATURE AND EFFECTS OF MANURES. Animal bodies subject to constant
waste. Parts separating--exuviae--waste vegetable matters--together
contain all the elements of the soil and of food. Various value of
excrements of different animals as manure.
LETTER XV
SOURCE OF THE CARBON AND NITROGEN OF PLANTS. Produce of Carbon in
Forests and Meadows supplied only with mineral aliments prove it to
be from the atmosphere. Relations between Mineral constituents, and
Carbon and Nitrogen. Effects of the Carbonic Acid and Ammonia of
Manures. Necessity of inorganic constituents to the formation of
aliments, of blood, and therefore of nutrition. NECESSITY OF
INQUIRIES by ANALYSIS to advance AGRICULTURE.
LETTER XVI
RESULTS OF THE AUTHOR'S LATEST INQUIRIES. Superlative importance of
the PHOSPHATES OF LIME and ALKALIES to the cultivation of the
CEREALIA. Sources of a SUPPLY of these MATERIALS.
LETTERS ON CHEMISTRY
LETTER I
My dear Sir,
The influence which the science of chemistry exercises upon human
industry, agriculture, and commerce; upon physiology, medicine, and
other sciences, is now so interesting a topic of conversation
everywhere, that it may be no unacceptable present to you if I trace
in a few familiar letters some of the relations it bears to these
various sciences, and exhibit for you its actual effect upon the
present social condition of mankind.
In speaking of the present state of chemistry, its rise and
progress, I shall need no apology if, as a preliminary step, I call
your attention to the implements which the chemist employs--the
means which are indispensable to his labours and to his success.
These consist, generally, of materials furnished to us by nature,
endowed with many most remarkable properties fitting them for our
purposes; if one of them is a production of art, yet its adaptation
to the use of mankind,--the qualities which render it available to
us,--must be referred to the same source as those derived
immediately from nature.
Cork, Platinum, Glass, and Caoutchouc, are the substances to which I
allude, and which minister so essentially to modern chemical
investigations. Without them, indeed, we might have made some
progress, but it would have been slow; we might have accomplished
much, but it would have been far less than has been done with their
aid. Some persons, by the employment of expensive substances, might
have successfully pursued the science; but incalculably fewer minds
would have been engaged in its advancement. These materials have
only been duly appreciated and fully adopted within a very recent
period. In the time of Lavoisier, the rich alone could make chemical
researches; the necessary apparatus could only be procured at a very
great expense.
And first, of Glass: every one is familiar with most of the
properties of this curious substance; its transparency, hardness,
destitution of colour, and stability under ordinary circumstances:
to these obvious qualities we may add those which especially adapt
it to the use of the chemist, namely, that it is unaffected by most
acids or other fluids contained within it. At certain temperatures
it becomes more ductile and plastic than wax, and may be made to
assume in our hands, before the flame of a common lamp, the form of
every vessel we need to contain our materials, and of every
apparatus required to pursue our experiments.
Then, how admirable and valuable are the properties of Cork! How
little do men reflect upon the inestimable worth of so common a
substance! How few rightly esteem the importance of it to the
progress of science, and the moral advancement of mankind!--There is
no production of nature or art equally adapted to the purposes to
which the chemist applies it. Cork consists of a soft, highly
elastic substance, as a basis, having diffused throughout a matter
with properties resembling wax, tallow, and resin, yet dissimilar to
all of these, and termed suberin. This renders it perfectly
impermeable to fluids, and, in a great measure, even to gases. It is
thus the fittest material we possess for closing our bottles, and
retaining their contents. By its means, and with the aid of
Caoutchouc, we connect our vessels and tubes of glass, and construct
the most complicated apparatus. We form joints and links of
connexion, adapt large apertures to small, and thus dispense
altogether with the aid of the brassfounder and the mechanist. Thus
the implements of the chemist are cheaply and easily procured,
immediately adapted to any purpose, and readily repaired or altered.
Again, in investigating the composition of solid bodies,--of
minerals,--we are under the necessity of bringing them into a liquid
state, either by solution or fusion. Now vessels of glass, of
porcelain, and of all non-metallic substances, are destroyed by the
means we employ for that purpose,--are acted upon by many acids, by
alkalies and the alkaline carbonates. Crucibles of gold and silver
would melt at high temperatures. But we have a combination of all
the qualities we can desire in Platinum. This metal was only first
adapted to these uses about fifty years since. It is cheaper than
gold, harder and more durable than silver, infusible at all
temperatures of our furnaces, and is left intact by acids and
alkaline carbonates. Platinum unites all the valuable properties of
gold and of porcelain, resisting the action of heat, and of almost
all chemical agents.
As no mineral analysis could be made perfectly without platinum
vessels, had we not possessed this metal, the composition of
minerals would have yet remained unknown; without cork and
caoutchouc we should have required the costly aid of the mechanician
at every step. Even without the latter of these adjuncts our
instruments would have been far more costly and fragile. Possessing
all these gifts of nature, we economise incalculably our time--to us
more precious than money!
Such are our instruments. An equal improvement has been accomplished
in our laboratory. This is no longer the damp, cold, fireproof vault
of the metallurgist, nor the manufactory of the druggist, fitted up
with stills and retorts. On the contrary, a light, warm, comfortable
room, where beautifully constructed lamps supply the place of
furnaces, and the pure and odourless flame of gas, or of spirits of
wine, supersedes coal and other fuel, and gives us all the fire we
need; where health is not invaded, nor the free exercise of thought
impeded: there we pursue our inquiries, and interrogate Nature to
reveal her secrets.
To these simple means must be added "The Balance," and then we
possess everything which is required for the most extensive
researches.
The great distinction between the manner of proceeding in chemistry
and natural philosophy is, that one weighs, the other measures. The
natural philosopher has applied his measures to nature for many
centuries, but only for fifty years have we attempted to advance our
philosophy by weighing.
For all great discoveries chemists are indebted to the
"balance"--that incomparable instrument which gives permanence to
every observation, dispels all ambiguity, establishes truth, detects
error, and guides us in the true path of inductive science.
The balance, once adopted as a means of investigating nature, put an
end to the school of Aristotle in physics. The explanation of
natural phenomena by mere fanciful speculations, gave place to a
true natural philosophy. Fire, air, earth, and water, could no
longer be regarded as elements. Three of them could henceforth be
considered only as significative of the forms in which all matter
exists. Everything with which we are conversant upon the surface of
the earth is solid, liquid, or aeriform; but the notion of the
elementary nature of air, earth, and water, so universally held, was
now discovered to belong to the errors of the past.
Fire was found to be but the visible and otherwise perceptible
indication of changes proceeding within the, so called, elements.
Lavoisier investigated the composition of the atmosphere and of
water, and studied the many wonderful offices performed by an
element common to both in the scheme of nature, namely, oxygen: and
he discovered many of the properties of this elementary gas.
After his time, the principal problem of chemical philosophers was
to determine the composition of the solid matters composing the
earth. To the eighteen metals previously known were soon added
twenty-four discovered to be constituents of minerals. The great
mass of the earth was shown to be composed of metals in combination
with oxygen, to which they are united in one, two, or more definite
and unalterable proportions, forming compounds which are termed
metallic oxides, and these, again, combined with oxides of other
bodies, essentially different to metals, namely, carbon and
silicium. If to these we add certain compounds of sulphur with
metals, in which the sulphur takes the place of oxygen, and forms
sulphurets, and one other body,--common salt,--(which is a compound
of sodium and chlorine), we have every substance which exists in a
solid form upon our globe in any very considerable mass. Other
compounds, innumerably various, are found only in small scattered
quantities.
The chemist, however, did not remain satisfied with the separation
of minerals into their component elements, i.e. their analysis; but
he sought by synthesis, i.e. by combining the separate elements and
forming substances similar to those constructed by nature, to prove
the accuracy of his processes and the correctness of his
conclusions. Thus he formed, for instance, pumice-stone, feldspar,
mica, iron pyrites, &c. artificially.
But of all the achievements of inorganic chemistry, the artificial
formation of lapis lazuli was the most brilliant and the most
conclusive. This mineral, as presented to us by nature, is
calculated powerfully to arrest our attention by its beautiful
azure-blue colour, its remaining unchanged by exposure to air or to
fire, and furnishing us with a most valuable pigment, Ultramarine,
more precious than gold!
The analysis of lapis lazuli represented it to be composed of
silica, alumina, and soda, three colourless bodies, with sulphur and
a trace of iron. Nothing could be discovered in it of the nature of
a pigment, nothing to which its blue colour could be referred, the
cause of which was searched for in vain. It might therefore have
been supposed that the analyst was here altogether at fault, and
that at any rate its artificial production must be impossible.
Nevertheless, this has been accomplished, and simply by combining in
the proper proportions, as determined by analysis, silica, alumina,
soda, iron, and sulphur. Thousands of pounds weight are now
manufactured from these ingredients, and this artificial ultramarine
is as beautiful as the natural, while for the price of a single
ounce of the latter we may obtain many pounds of the former.
With the production of artificial lapis lazuli, the formation of
mineral bodies by synthesis ceased to be a scientific problem to the
chemist; he has no longer sufficient interest in it to pursue the
subject. He may now be satisfied that analysis will reveal to him
the true constitution of minerals. But to the mineralogist and
geologist it is still in a great measure an unexplored field,
offering inquiries of the highest interest and importance to their
pursuits.
After becoming acquainted with the constituent elements of all the
substances within our reach and the mutual relations of these
elements, the remarkable transmutations to which the bodies are
subject under the influence of the vital powers of plants and
animals, became the principal object of chemical investigations, and
the highest point of interest. A new science, inexhaustible as life
itself, is here presented us, standing upon the sound and solid
foundation of a well established inorganic chemistry. Thus the
progress of science is, like the development of nature's works,
gradual and expansive. After the buds and branches spring forth the
leaves and blossoms, after the blossoms the fruit.
Chemistry, in its application to animals and vegetables, endeavours
jointly with physiology to enlighten us respecting the mysterious
processes and sources of organic life.
LETTER II
My dear Sir,
In my former letter I reminded you that three of the supposed
elements of the ancients represent the forms or state in which all
the ponderable matter of our globe exists; I would now observe, that
no substance possesses absolutely any one of those conditions; that
modern chemistry recognises nothing unchangeably solid, liquid, or
aeriform: means have been devised for effecting a change of state in
almost every known substance. Platinum, alumina, and rock crystal,
it is true, cannot be liquified by the most intense heat of our
furnaces, but they melt like wax before the flame of the
oxy-hydrogen blowpipe. On the other hand, of the twenty-eight
gaseous bodies with which we are acquainted, twenty-five may be
reduced to a liquid state, and one into a solid. Probably, ere long,
similar changes of condition will be extended to every form of
matter.
There are many things relating to this condensation of the gases
worthy of your attention. Most aeriform bodies, when subjected to
compression, are made to occupy a space which diminishes in the
exact ratio of the increase of the compressing force. Very
generally, under a force double or triple of the ordinary
atmospheric pressure, they become one half or one third their former
volume. This was a long time considered to be a law, and known as
the law of Marriotte; but a more accurate study of the subject has
demonstrated that this law is by no means of general application.
The volume of certain gases does not decrease in the ratio of the
increase of the force used to compress them, but in some, a
diminution of their bulk takes place in a far greater degree as the
pressure increases.
Again, if ammoniacal gas is reduced by a compressing force to
one-sixth of its volume, or carbonic acid is reduced to one
thirty-sixth, a portion of them loses entirely the form of a gas,
and becomes a liquid, which, when the pressure is withdrawn, assumes
again in an instant its gaseous state--another deviation from the
law of Marriotte.
Our process for reducing gases into fluids is of admirable
simplicity. A simple bent tube, or a reduction of temperature by
artificial means, have superseded the powerful compressing machines
of the early experimenters.
The cyanuret of mercury, when heated in an open glass tube, is
resolved into cyanogen gas and metallic mercury; if this substance
is heated in a tube hermetically sealed, the decomposition occurs as
before, but the gas, unable to escape, and shut up in a space
several hundred times smaller than it would occupy as gas under the
ordinary atmospheric pressure, becomes a fluid in that part of the
tube which is kept cool.
When sulphuric acid is poured upon limestone in an open vessel,
carbonic acid escapes with effervescence as a gas, but if the
decomposition is effected in a strong, close, and suitable vessel of
iron, we obtain the carbonic acid in the state of liquid. In this
manner it may be obtained in considerable quantities, even many
pounds weight. Carbonic acid is separated from other bodies with
which it is combined as a fluid under a pressure of thirty-six
atmospheres.
The curious properties of fluid carbonic acid are now generally
known. When a small quantity is permitted to escape into the
atmosphere, it assumes its gaseous state with extraordinary
rapidity, and deprives the remaining fluid of caloric so rapidly
that it congeals into a white crystalline mass like snow: at first,
indeed, it was thought to be really snow, but upon examination it
proved to be pure frozen carbonic acid. This solid, contrary to
expectation, exercises only a feeble pressure upon the surrounding
medium. The fluid acid inclosed in a glass tube rushes at once, when
opened, into a gaseous state, with an explosion which shatters the
tube into fragments; but solid carbonic acid can be handled without
producing any other effect than a feeling of intense cold. The
particles of the carbonic acid being so closely approximated in the
solid, the whole force of cohesive attraction (which in the fluid is
weak) becomes exerted, and opposes its tendency to assume its
gaseous state; but as it receives heat from surrounding bodies, it
passes into gas gradually and without violence. The transition of
solid carbonic acid into gas deprives all around it of caloric so
rapidly and to so great an extent, that a degree of cold is produced
immeasurably great, the greatest indeed known. Ten, twenty, or more
pounds weight of mercury, brought into contact with a mixture of
ether and solid carbonic acid, becomes in a few moments firm and
malleable. This, however, cannot be accomplished without
considerable danger. A melancholy accident occurred at Paris, which
will probably prevent for the future the formation of solid carbonic
acid in these large quantities, and deprive the next generation of
the gratification of witnessing these curious experiments. Just
before the commencement of the lecture in the Laboratory of the
Polytechnic School, an iron cylinder, two feet and a half long and
one foot in diameter, in which carbonic acid had been developed for
experiment before the class, burst, and its fragments were scattered
about with the most tremendous force; it cut off both the legs of
the assistant and killed him on the spot. This vessel, formed of the
strongest cast-iron, and shaped like a cannon, had often been
employed to exhibit experiments in the presence of the students. We
can scarcely think, without shuddering, of the dreadful calamity
such an explosion would have occasioned in a hall filled with
spectators.
When we had ascertained the fact of gases becoming fluid under the
influence of cold or pressure, a curious property possessed by
charcoal, that of absorbing gas to the extent of many times its
volume,--ten, twenty, or even as in the case of ammoniacal gas or
muriatic acid gas, eighty or ninety fold,--which had been long
known, no longer remained a mystery. Some gases are absorbed and
condensed within the pores of the charcoal, into a space several
hundred times smaller than they before occupied; and there is now no
doubt they there become fluid, or assume a solid state. As in a
thousand other instances, chemical action here supplants mechanical
forces. Adhesion or heterogeneous attraction, as it is termed,
acquired by this discovery a more extended meaning; it had never
before been thought of as a cause of change of state in matter; but
it is now evident that a gas adheres to the surface of a solid body
by the same force which condenses it into a liquid.
The smallest amount of a gas,--atmospheric air for instance,--can be
compressed into a space a thousand times smaller by mere mechanical
pressure, and then its bulk must be to the least measurable surface
of a solid body, as a grain of sand to a mountain. By the mere
effect of mass,--the force of gravity,--gaseous molecules are
attracted by solids and adhere to their surfaces; and when to this
physical force is added the feeblest chemical affinity, the
liquifiable gases cannot retain their gaseous state. The amount of
air condensed by these forces upon a square inch of surface is
certainly not measurable; but when a solid body, presenting several
hundred square feet of surface within the space of a cubic inch, is
brought into a limited volume of gas, we may understand why that
volume is diminished, why all gases without exception are absorbed.
A cubic inch of charcoal must have, at the lowest computation, a
surface of one hundred square feet. This property of absorbing gases
varies with different kinds of charcoal: it is possessed in a higher
degree by those containing the most pores, i.e. where the pores are
finer; and in a lower degree in the more spongy kinds, i.e. where
the pores are larger.
In this manner every porous body--rocks, stones, the clods of the
fields, &c.,--imbibe air, and therefore oxygen; the smallest solid
molecule is thus surrounded by its own atmosphere of condensed
oxygen; and if in their vicinity other bodies exist which have an
affinity for oxygen, a combination is effected. When, for instance,
carbon and hydrogen are thus present, they are converted into
nourishment for vegetables,--into carbonic acid and water. The
development of heat when air is imbibed, and the production of steam
when the earth is moistened by rain, are acknowledged to be
consequences of this condensation by the action of surfaces.
But the most remarkable and interesting case of this kind of action
is the imbibition of oxygen by metallic platinum. This metal, when
massive, is of a lustrous white colour, but it may be brought, by
separating it from its solutions, into so finely divided a state,
that its particles no longer reflect light, and it forms a powder as
black as soot. In this condition it absorbs eight hundred times its
volume of oxygen gas, and this oxygen must be contained within it in
a state of condensation very like that of fluid water.
When gases are thus condensed, i.e. their particles made to
approximate in this extraordinary manner, their properties can be
palpably shown. Their chemical actions become apparent as their
physical characteristic disappears. The latter consists in the
continual tendency of their particles to separate from each other;
and it is easy to imagine that this elasticity of gaseous bodies is
the principal impediment to the operation of their chemical force;
for this becomes more energetic as their particles approximate. In
that state in which they exist within the pores or upon the surface
of solid bodies, their repulsion ceases, and their whole chemical
action is exerted. Thus combinations which oxygen cannot enter into,
decompositions which it cannot effect while in the state of gas,
take place with the greatest facility in the pores of platinum
containing condensed oxygen. When a jet of hydrogen gas, for
instance, is thrown upon spongy platinum, it combines with the
oxygen condensed in the interior of the mass; at their point of
contact water is formed, and as the immediate consequence heat is
evolved; the platinum becomes red hot and the gas is inflamed. If we
interrupt the current of the gas, the pores of the platinum become
instantaneously filled again with oxygen; and the same phenomenon
can be repeated a second time, and so on interminably.
In finely pulverised platinum, and even in spongy platinum, we
therefore possess a perpetuum mobile--a mechanism like a watch which
runs out and winds itself up--a force which is never
exhausted--competent to produce effects of the most powerful kind,
and self-renewed ad infinitum.
Many phenomena, formerly inexplicable, are satisfactorily explained
by these recently discovered properties of porous bodies. The
metamorphosis of alcohol into acetic acid, by the process known as
the quick vinegar manufacture, depends upon principles, at a
knowledge of which we have arrived by a careful study of these
properties.
LETTER III
My dear Sir,
The manufacture of soda from common culinary salt, may be regarded
as the foundation of all our modern improvements in the domestic
arts; and we may take it as affording an excellent illustration of
the dependence of the various branches of human industry and
commerce upon each other, and their relation to chemistry.
Soda has been used from time immemorial in the manufacture of soap
and glass, two chemical productions which employ and keep in
circulation an immense amount of capital. The quantity of soap
consumed by a nation would be no inaccurate measure whereby to
estimate its wealth and civilisation. Of two countries, with an
equal amount of population, the wealthiest and most highly civilised
will consume the greatest weight of soap. This consumption does not
subserve sensual gratification, nor depend upon fashion, but upon
the feeling of the beauty, comfort, and welfare, attendant upon
cleanliness; and a regard to this feeling is coincident with wealth
and civilisation. The rich in the middle ages concealed a want of
cleanliness in their clothes and persons under a profusion of costly
scents and essences, whilst they were more luxurious in eating and
drinking, in apparel and horses. With us a want of cleanliness is
equivalent to insupportable misery and misfortune.
Soap belongs to those manufactured products, the money value of
which continually disappears from circulation, and requires to be
continually renewed. It is one of the few substances which are
entirely consumed by use, leaving no product of any worth. Broken
glass and bottles are by no means absolutely worthless; for rags we
may purchase new cloth, but soap-water has no value whatever. It
would be interesting to know accurately the amount of capital
involved in the manufacture of soap; it is certainly as large as
that employed in the coffee trade, with this important difference as
respects Germany, that it is entirely derived from our own soil.
France formerly imported soda from Spain,--Spanish sodas being of
the best quality--at an annual expenditure of twenty to thirty
millions of francs. During the war with England the price of soda,
and consequently of soap and glass, rose continually; and all
manufactures suffered in consequence.
The present method of making soda from common salt was discovered by
Le Blanc at the end of the last century. It was a rich boon for
France, and became of the highest importance during the wars of
Napoleon. In a very short time it was manufactured to an
extraordinary extent, especially at the seat of the soap
manufactories. Marseilles possessed for a time a monopoly of soda
and soap. The policy of Napoleon deprived that city of the
advantages derived from this great source of commerce, and thus
excited the hostility of the population to his dynasty, which became
favourable to the restoration of the Bourbons. A curious result of
an improvement in a chemical manufacture! It was not long, however,
in reaching England.
In order to prepare the soda of commerce (which is the carbonate)
from common salt, it is first converted into Glauber's salt
(sulphate of soda). For this purpose 80 pounds weight of
concentrated sulphuric acid (oil of vitriol) are required to 100
pounds of common salt. The duty upon salt checked, for a short time,
the full advantage of this discovery; but when the Government
repealed the duty, and its price was reduced to its minimum, the
cost of soda depended upon that of sulphuric acid.
The demand for sulphuric acid now increased to an immense extent;
and, to supply it, capital was embarked abundantly, as it afforded
an excellent remuneration. The origin and formation of sulphuric
acid was studied most carefully; and from year to year, better,
simpler, and cheaper methods of making it were discovered. With
every improvement in the mode of manufacture, its price fell; and
its sale increased in an equal ratio.
Sulphuric acid is now manufactured in leaden chambers, of such
magnitude that they would contain the whole of an ordinary-sized
house. As regards the process and the apparatus, this manufacture
has reached its acme--scarcely is either susceptible of improvement.
The leaden plates of which the chambers are constructed, requiring
to be joined together with lead (since tin or solder would be acted
on by the acid), this process was, until lately, as expensive as the
plates themselves; but now, by means of the oxy-hydrogen blowpipe,
the plates are cemented together at their edges by mere fusion,
without the intervention of any kind of solder.
And then, as to the process: according to theory, 100 pounds weight
of sulphur ought to produce 306 pounds of sulphuric acid; in
practice 300 pounds are actually obtained; the amount of loss is
therefore too insignificant for consideration.
Again; saltpetre being indispensable in making sulphuric acid, the
commercial value of that salt had formerly an important influence
upon its price. It is true that 100 pounds of saltpetre only are
required to 1000 pounds of sulphur; but its cost was four times
greater than an equal weight of the latter.
Travellers had observed near the small seaport of Yquiqui, in the
district of Atacama, in Peru, an efflorescence covering the ground
over extensive districts. This was found to consist principally of
nitrate of soda. Advantage was quickly taken of this discovery. The
quantity of this valuable salt proved to be inexhaustible, as it
exists in beds extending over more than 200 square miles. It was
brought to England at less than half the freight of the East India
saltpetre (nitrate of potassa); and as, in the chemical manufacture
neither the potash nor the soda were required, but only the nitric
acid, in combination with the alkali, the soda-saltpetre of South
America soon supplanted the potash-nitre of the East. The
manufacture of sulphuric acid received a new impulse; its price was
much diminished without injury to the manufacturer; and, with the
exception of fluctuations caused by the impediments thrown in the
way of the export of sulphur from Sicily, it soon became reduced to
a minimum, and remained stationary.
Potash-saltpetre is now only employed in the manufacture of
gunpowder; it is no longer in demand for other purposes; and thus,
if Government effect a saving of many hundred thousand pounds
annually in gunpowder, this economy must be attributed to the
increased manufacture of sulphuric acid.
We may form an idea of the amount of sulphuric acid consumed, when
we find that 50,000 pounds weight are made by a small manufactory,
and from 200,000 to 600,000 pounds by a large one annually. This
manufacture causes immense sums to flow annually into Sicily. It has
introduced industry and wealth into the arid and desolate districts
of Atacama. It has enabled us to obtain platina from its ores at a
moderate and yet remunerating price; since the vats employed for
concentrating this acid are constructed of this metal, and cost from
1000l. to 2000l. sterling. It leads to frequent improvements in the
manufacture of glass, which continually becomes cheaper and more
beautiful. It enables us to return to our fields all their potash--a
most valuable and important manure--in the form of ashes, by
substituting soda in the manufacture of glass and soap.
It is impossible to trace, within the compass of a letter, all the
ramifications of this tissue of changes and improvements resulting
from one chemical manufacture; but I must still claim your attention
to a few more of its most important and immediate results. I have
already told you, that in the manufacture of soda from culinary
salt, it is first converted into sulphate of soda. In this first
part of the process, the action of sulphuric acid produces muriatic
acid to the extent of one-and-a-half the amount of the sulphuric
acid employed. At first, the profit upon the soda was so great, that
no one took the trouble to collect the muriatic acid: indeed it had
no commercial value. A profitable application of it was, however,
soon discovered: it is a compound of chlorine, and this substance
may be obtained from it purer than from any other source. The
bleaching power of chlorine has long been known; but it was only
employed upon a large scale after it was obtained from this
residuary muriatic acid, and it was found that in combination with
lime it could be transported to distances without inconvenience.
Thenceforth it was used for bleaching cotton; and, but for this new
bleaching process, it would scarcely have been possible for the
cotton manufacture of Great Britain to have attained its present
enormous extent,--it could not have competed in price with France
and Germany. In the old process of bleaching, every piece must be
exposed to the air and light during several weeks in the summer, and
kept continually moist by manual labour. For this purpose, meadow
land, eligibly situated, was essential. Now a single establishment
near Glasgow bleaches 1400 pieces of cotton daily, throughout the
year. What an enormous capital would be required to purchase land
for this purpose! How greatly would it increase the cost of
bleaching to pay interest upon this capital, or to hire so much land
in England! This expense would scarcely have been felt in Germany.
Besides the diminished expense, the cotton stuffs bleached with
chlorine suffer less in the hands of skilful workmen than those
bleached in the sun; and already the peasantry in some parts of
Germany have adopted it, and find it advantageous.
Another use to which cheap muriatic acid is applied, is the
manufacture of glue from bones. Bone contains from 30 to 36 per
cent. of earthy matter--chiefly phosphate of lime, and the remainder
is gelatine. When bones are digested in muriatic acid they become
transparent and flexible like leather, the earthy matter is
dissolved, and after the acid is all carefully washed away, pieces
of glue of the same shape as the bones remain, which are soluble in
hot water and adapted to all the purposes of ordinary glue, without
further preparation.
Another important application of sulphuric acid may be adduced;
namely, to the refining of silver and the separation of gold, which
is always present in some proportion in native silver. Silver, as it
is usually obtained from mines in Europe, contains in 16 ounces, 6
to 8 ounces of copper. When used by the silversmith, or in coining,
16 ounces must contain in Germany 13 ounces of silver, in England
about 14 1/2. But this alloy is always made artificially by mixing
pure silver with the due proportion of the copper; and for this
purpose the silver must be obtained pure by the refiner. This he
formerly effected by amalgamation, or by roasting it with lead; and
the cost of this process was about 2l. for every hundred-weight of
silver. In the silver so prepared, about 1/1200 to 1/2000th part of
gold remained; to effect the separation of this by nitrio-hydrochloric
acid was more expensive than the value of the gold; it was therefore
left in utensils, or circulated in coin, valueless. The copper, too,
of the native silver was no use whatever. But the 1/1000th part of
gold, being about one and a half per cent. of the value of the silver,
now covers the cost of refining, and affords an adequate profit to
the refiner; so that he effects the separation of the copper, and
returns to his employer the whole amount of the pure silver, as well
as the copper, without demanding any payment: he is amply remunerated
by that minute portion of gold. The new process of refining is a most
beautiful chemical operation: the granulated metal is boiled in
concentrated sulphuric acid, which dissolves both the silver and the
copper, leaving the gold nearly pure, in the form of a black powder.
The solution is then placed in a leaden vessel containing metallic
copper; this is gradually dissolved, and the silver precipitated in
a pure metallic state. The sulphate of copper thus formed is also a
valuable product, being employed in the manufacture of green and
blue pigments.
Other immediate results of the economical production of sulphuric
acid, are the general employment of phosphorus matches, and of
stearine candles, that beautiful substitute for tallow and wax.
Twenty-five years ago, the present prices and extensive applications
of sulphuric and muriatic acids, of soda, phosphorus, &c., would
have been considered utterly impossible. Who is able to foresee what
new and unthought-of chemical productions, ministering to the
service and comforts of mankind, the next twenty-five years may
produce?
After these remarks you will perceive that it is no exaggeration to
say, we may fairly judge of the commercial prosperity of a country
from the amount of sulphuric acid it consumes. Reflecting upon the
important influence which the price of sulphur exercises upon the
cost of production of bleached and printed cotton stuffs, soap,
glass, &c., and remembering that Great Britain supplies America,
Spain, Portugal, and the East, with these, exchanging them for raw
cotton, silk, wine, raisins, indigo, &c., &c., we can understand why
the English Government should have resolved to resort to war with
Naples, in order to abolish the sulphur monopoly, which the latter
power attempted recently to establish. Nothing could be more opposed
to the true interests of Sicily than such a monopoly; indeed, had it
been maintained a few years, it is highly probable that sulphur, the
source of her wealth, would have been rendered perfectly valueless
to her. Science and industry form a power to which it is dangerous
to present impediments. It was not difficult to perceive that the
issue would be the entire cessation of the exportation of sulphur
from Sicily. In the short period the sulphur monopoly lasted,
fifteen patents were taken out for methods to obtain back the
sulphuric acid used in making soda. Admitting that these fifteen
experiments were not perfectly successful, there can be no doubt it
would ere long have been accomplished. But then, in gypsum,
(sulphate of lime), and in heavy-spar, (sulphate of barytes), we
possess mountains of sulphuric acid; in galena, (sulphate of lead),
and in iron pyrites, we have no less abundance of sulphur. The
problem is, how to separate the sulphuric acid, or the sulphur, from
these native stores. Hundreds of thousands of pounds weight of
sulphuric acid were prepared from iron pyrites, while the high price
of sulphur consequent upon the monopoly lasted. We should probably
ere long have triumphed over all difficulties, and have separated it
from gypsum. The impulse has been given, the possibility of the
process proved, and it may happen in a few years that the
inconsiderate financial speculation of Naples may deprive her of
that lucrative commerce. In like manner Russia, by her prohibitory
system, has lost much of her trade in tallow and potash. One country
purchases only from absolute necessity from another, which excludes
her own productions from her markets. Instead of the tallow and
linseed oil of Russia, Great Britain now uses palm oil and cocoa-nut
oil of other countries. Precisely analogous is the combination of
workmen against their employers, which has led to the construction
of many admirable machines for superseding manual labour. In
commerce and industry every imprudence carries with it its own
punishment; every oppression immediately and sensibly recoils upon
the head of those from whom it emanates.
LETTER IV
My dear Sir,
One of the most influential causes of improvement in the social
condition of mankind is that spirit of enterprise which induces men
of capital to adopt and carry out suggestions for the improvement of
machinery, the creation of new articles of commerce, or the cheaper
production of those already in demand; and we cannot but admire the
energy with which such men devote their talents, their time, and
their wealth, to realise the benefits of the discoveries and
inventions of science. For even when these are expended upon objects
wholly incapable of realisation,--nay, even when the idea which
first gave the impulse proves in the end to be altogether
impracticable or absurd, immediate good to the community generally
ensues; some useful and perhaps unlooked-for result flows directly,
or springs ultimately, from exertions frustrated in their main
design. Thus it is also in the pursuit of science. Theories lead to
experiments and investigations; and he who investigates will
scarcely ever fail of being rewarded by discoveries. It may be,
indeed, the theory sought to be established is entirely unfounded in
nature; but while searching in a right spirit for one thing, the
inquirer may be rewarded by finding others far more valuable than
those which he sought.
At the present moment, electro-magnetism, as a moving power, is
engaging great attention and study; wonders are expected from its
application to this purpose. According to the sanguine expectations
of many persons, it will shortly be employed to put into motion
every kind of machinery, and amongst other things it will be applied
to impel the carriages of railroads, and this at so small a cost,
that expense will no longer be matter of consideration. England is
to lose her superiority as a manufacturing country, inasmuch as her
vast store of coals will no longer avail her as an economical source
of motive power. "We," say the German cultivators of this science,
"have cheap zinc, and, how small a quantity of this metal is
required to turn a lathe, and consequently to give motion to any
kind of machinery!"
Such expectations may be very attractive, and yet they are
altogether illusory! they will not bear the test of a few simple
calculations; and these our friends have not troubled themselves to
institute.
With a simple flame of spirits of wine, under a proper vessel
containing boiling water, a small carriage of 200 to 300 pounds
weight can be put into motion, or a weight of 80 to 100 pounds may
be raised to a height of 20 feet. The same effects may be produced
by dissolving zinc in dilute sulphuric acid in a certain apparatus.
This is certainly an astonishing and highly interesting discovery;
but the question to be determined is, which of the two processes is
the least expensive?
In order to answer this question, and to judge correctly of the
hopes entertained from this discovery, let me remind you of what
chemists denominate "equivalents." These are certain unalterable
ratios of effects which are proportionate to each other, and may
therefore be expressed in numbers. Thus, if we require 8 pounds of
oxygen to produce a certain effect, and we wish to employ chlorine
for the same effect, we must employ neither more nor less than 35
1/2 pounds weight. In the same manner, 6 pounds weight of coal are
equivalent to 32 pounds weight of zinc. The numbers representing
chemical equivalents express very general ratios of effects,
comprehending for all bodies all the actions they are capable of
producing.