Produced by Louise Hope
[Transcriber’s Note:
DO NOT TRY THIS AT HOME.
This e-text comes in three different forms: unicode (UTF-8), Latin-1 and
ascii-7. Use the one that works best on your text reader.
--If “œ” displays as a single character, and apostrophes and quotation
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part of this paragraph displays as garbage, try changing your text
reader’s “character set” or “file encoding”. If that doesn’t work,
proceed to:
--In the Latin-1 version, “œ” is two letters, but the word “aëriform”
is usually written with dieresis (dots) over the “e”, and “æ” is a
single letter. Apostrophes and quotation marks will be straight
(“typewriter” form). Again, if you see any garbage in this paragraph
and can’t get it to display properly, use:
--The ASCII-7 or rock-bottom version. All necessary text will still be
there; it just won’t be as pretty.
The full caption of each Plate is given after its first mention in the
text--generally a few pages before the Plate’s physical appearance, as
specified in the caption.
Many terms used in this book are different from today’s standard
terminology. Note in particular:
oxy-muriatic acid = the element chlorine
phosphat of lime = calcium diphosphate _or_ the element calcium
glucium = the element beryllium
muriatic acid = hydrochloric acid
muriat of lime = calcium chloride
oxymuriate of potash = potassium chlorate
carbonic acid = carbon dioxide
Further details and more examples are at the end of the e-text.
Each Volume had its own table of contents. They have been merged for
this e-text, but the Vol. II title page was retained. Some Conversations
were renumbered between the 4th and 5th edition, resulting in the
apparent disappearance of Conversations XI and XII.
Typographical errors are listed at the end of the text.]
* * * * *
* * * *
* * * * *
CONVERSATIONS
ON
CHEMISTRY;
In Which
The Elements Of That Science
Are
_Familiarly Explained_
And
Illustrated By Experiments.
IN TWO VOLUMES.
_The Fifth Edition, revised, corrected,_
_and considerably enlarged._
VOL. I.
ON SIMPLE BODIES.
_London:_
Printed For Longman, Hurst, Rees, Orme, and Brown,
Paternoster-Row.
1817.
Printed by A. Strahan, Printers-Street, London.
ADVERTISEMENT.
_The Author, in this fifth edition, has endeavoured to give an account
of the principal discoveries which have been made within the last four
years in Chemical Science, and of the various important applications,
such as the gas-lights, and the miner’s-lamp, to which they have given
rise. But in regard to doctrines or principles, the work has undergone
no material alteration._
_London_, _July_, 1817.
PREFACE.
In venturing to offer to the public, and more particularly to the female
sex, an Introduction to Chemistry, the author, herself a woman,
conceives that some explanation may be required; and she feels it the
more necessary to apologise for the present undertaking, as her
knowledge of the subject is but recent, and as she can have no real
claims to the title of chemist.
On attending for the first time experimental lectures, the author found
it almost impossible to derive any clear or satisfactory information
from the rapid demonstrations which are usually, and perhaps
necessarily, crowded into popular courses of this kind. But frequent
opportunities having afterwards occurred of conversing with a friend on
the subject of chemistry, and of repeating a variety of experiments, she
became better acquainted with the principles of that science, and began
to feel highly interested in its pursuit. It was then that she
perceived, in attending the excellent lectures delivered at the Royal
Institution, by the present Professor of Chemistry, the great advantage
which her previous knowledge of the subject, slight as it was, gave her
over others who had not enjoyed the same means of private instruction.
Every fact or experiment attracted her attention, and served to explain
some theory to which she was not a total stranger; and she had the
gratification to find that the numerous and elegant illustrations, for
which that school is so much distinguished, seldom failed to produce on
her mind the effect for which they were intended.
Hence it was natural to infer, that familiar conversation was, in
studies of this kind, a most useful auxiliary source of information; and
more especially to the female sex, whose education is seldom calculated
to prepare their minds for abstract ideas, or scientific language.
As, however, there are but few women who have access to this mode of
instruction; and as the author was not acquainted with any book that
could prove a substitute for it, she thought that it might be useful for
beginners, as well as satisfactory to herself, to trace the steps by
which she had acquired her little stock of chemical knowledge, and to
record, in the form of dialogue, those ideas which she had first derived
from conversation.
But to do this with sufficient method, and to fix upon a mode of
arrangement, was an object of some difficulty. After much hesitation,
and a degree of embarrassment, which, probably, the most competent
chemical writers have often felt in common with the most superficial,
a mode of division was adopted, which, though the most natural, does not
always admit of being strictly pursued--it is that of treating first of
the simplest bodies, and then gradually rising to the most intricate
compounds.
It is not the author’s intention to enter into a minute vindication of
this plan. But whatever may be its advantages or inconveniences, the
method adopted in this work is such, that a young pupil, who should
occasionally recur to it, with a view to procure information on
particular subjects, might often find it obscure or unintelligible; for
its various parts are so connected with each other as to form an
uninterrupted chain of facts and reasonings, which will appear
sufficiently clear and consistent to those only who may have patience to
go through the whole work, or have previously devoted some attention to
the subject.
It will, no doubt, be observed, that in the course of these
Conversations, remarks are often introduced, which appear much too acute
for the young pupils, by whom they are supposed to be made. Of this
fault the author is fully aware. But, in order to avoid it, it would
have been necessary either to omit a variety of useful illustrations, or
to submit to such minute explanations and frequent repetitions, as would
have rendered the work tedious, and therefore less suited to its
intended purpose.
In writing these pages, the author was more than once checked in her
progress by the apprehension that such an attempt might be considered by
some, either as unsuited to the ordinary pursuits of her sex, or
ill-justified by her own recent and imperfect knowledge of the subject.
But, on the one hand, she felt encouraged by the establishment of those
public institutions, open to both sexes, for the dissemination of
philosophical knowledge, which clearly prove that the general opinion no
longer excludes women from an acquaintance with the elements of science;
and, on the other, she flattered herself that whilst the impressions
made upon her mind, by the wonders of Nature, studied in this new point
of view, were still fresh and strong, she might perhaps succeed the
better in communicating to others the sentiments she herself
experienced.
The reader will soon perceive, in perusing this work, that he is often
supposed to have previously acquired some slight knowledge of natural
philosophy, a circumstance, indeed, which appears very desirable. The
author’s original intention was to commence this work by a small tract,
explaining, on a plan analogous to this, the most essential rudiments of
that science. This idea she has since abandoned; but the manuscript was
ready, and might, perhaps, have been printed at some future period, had
not an elementary work of a similar description, under the tide of
“Scientific Dialogues,” been pointed out to her, which, on a rapid
perusal, she thought very ingenious, and well calculated to answer its
intended object.
Contents Of
_The First Volume_.
ON SIMPLE BODIES.
CONVERSATION I.
Page
ON THE GENERAL PRINCIPLES OF CHEMISTRY. 1
Connexion between Chemistry and Natural Philosophy. --Improved State
of modern Chemistry. --Its use in the Arts. --The general Objects of
Chemistry. --Definition of Elementary Bodies. --Definition of
Decomposition. --Integrant and Constituent Particles. --Distinction
between Simple and Compound Bodies. --Classification of Simple
Bodies. --Of Chemical Affinity, or Attraction of Composition.
--Examples of Composition and Decomposition.
CONVERSATION II.
ON LIGHT AND HEAT. 26
Light and Heat capable of being separated. --Dr. Herschel’s
Experiments. --Phosphorescence. --Of Caloric. --Its two
Modifications. --Free Caloric. --Of the three different States of
Bodies, solid, fluid, and aeriform. --Dilatation of solid Bodies.
--Pyrometer. --Dilatation of Fluids. --Thermometer. --Dilatation of
Elastic Fluids. --Air Thermometer. --Equal Diffusion of Caloric.
--Cold a Negative Quality. --Professor Prevost’s Theory of the
Radiation of Heat. --Professor Pictet’s Experiments on the Reflexion
of Heat. --Mr. Leslie’s Experiments on the Radiation of Heat.
CONVERSATION III.
CONTINUATION OF THE SUBJECT. 70
Of the different Power of Bodies to conduct Heat. --Attempt to
account for this Power. --Count Rumford’s Theory of the
non-conducting Power of Fluids. --Phenomena of Boiling. --Of
Solution in general. --Solvent Power of Water. --Difference between
Solution and Mixture. --Solvent Power of Caloric. --Of Clouds, Rain,
Dr. Wells’ theory of Dew, Evaporation, &c. --Influence of
Atmospherical Pressure on Evaporation. --Ignition.
CONVERSATION IV.
ON COMBINED CALORIC, COMPREHENDING SPECIFIC HEAT
AND LATENT HEAT. 122
Of Specific Heat. --Of the different Capacities of Bodies for Heat.
--Specific Heat not perceptible by the Senses. --How to be
ascertained. --Of Latent Heat. --Distinction between Latent and
Specific Heat. --Phenomena attending the Melting of Ice and the
Formation of Vapour. --Phenomena attending the Formation of Ice, and
the Condensation of Elastic Fluids. --Instances of Condensation, and
consequent Disengagement of Heat, produced by Mixtures, by the
Slaking of Lime. --General Remarks on Latent Heat. --Explanation of
the Phenomena of Ether boiling, and Water freezing, at the same
Temperature. --Of the Production of Cold by Evaporation.
--Calorimeter. --Meteorological Remarks.
CONVERSATION V.
ON THE CHEMICAL AGENCIES OF ELECTRICITY. 160
Of Positive and Negative Electricity. --Galvani’s Discoveries.
--Voltaic Battery. --Electrical Machine. --Theory of Voltaic
Excitement.
CONVERSATION VI.
ON OXYGEN AND NITROGEN. 181
The Atmosphere composed of Oxygen and Nitrogen in the State of Gas.
--Definition of Gas. --Distinction between Gas and Vapour. --Oxygen
essential to Combustion and Respiration. --Decomposition of the
Atmosphere by Combustion. --Nitrogen Gas obtained by this Process.
--Of Oxygenation in general. --Of the Oxydation of Metals. --Oxygen
Gas obtained from Oxyd of Manganese. --Description of a Water-Bath
for collecting and preserving Gases. --Combustion of Iron Wire in
Oxygen Gas. --Fixed and volatile Products of Combustion. --Patent
Lamps. --Decomposition of the Atmosphere by Respiration.
--Recomposition of the Atmosphere.
CONVERSATION VII.
ON HYDROGEN. 214
Of Hydrogen. --Of the Formation of Water by the Combustion of
Hydrogen. --Of the Decomposition of Water. --Detonation of Hydrogen
Gas. --Description of Lavoisier’s Apparatus for the formation of
Water. --Hydrogen Gas essential to the Production of Flame.
--Musical Tones produced by the Combustion of Hydrogen Gas within a
Glass Tube. --Combustion of Candles explained. --Gas lights.
--Detonation of Hydrogen Gas in Soap Bubbles. --Air Balloons.
--Meteorological Phenomena ascribed to Hydrogen Gas. --Miner’s Lamp.
[Transcriber’s Note:
The final two pages of the Table of Contents for Volume I were
missing; everything after “Decomposition of Water” was supplied
from earlier and later editions, compared against the body text.
The section marked “Diamond” (Conv. IX) was called “Diamond is
Carbon(e) in a state of perfect purity” in the 4th edn., “Diamond”
alone in later editions.]
CONVERSATION VIII.
ON SULPHUR AND PHOSPHORUS. 256
Natural History of Sulphur. --Sublimation. --Alembic. --Combustion
of Sulphur in Atmospheric Air. --Of Acidification in general.
--Nomenclature of the Acids. --Combustion of Sulphur in Oxygen Gas.
--Sulphuric Acid. --Sulphurous Acid. --Decomposition of Sulphur.
--Sulphurated Hydrogen Gas. --Harrogate, or Hydro-sulphurated
Waters. --Phosphorus. --History of its Discovery. --Its Combustion
in Oxygen Gas. --Phosphoric Acid. --Phosphorus Acid. --Eudiometer.
--Combination of Phosphorus with Sulphur. --Phosphorated Hydrogen
Gas. --Nomenclature of Binary Compounds. --Phosphoret of Lime
burning under Water.
CONVERSATION IX.
ON CARBON. 282
Method of obtaining pure Charcoal. --Method of making common
Charcoal. --Pure Carbon not to be obtained by Art. --Diamond.
--Properties of Carbon. --Combustion of Carbon. --Production of
Carbonic Acid Gas. --Carbon susceptible of only one Degree of
Acidification. --Gaseous Oxyd of Carbon. --Of Seltzer Water and
other Mineral Waters. --Effervescence. --Decomposition of Water by
Carbon. --Of Fixed and Essential Oils. --Of the Combustion of Lamps
and Candles. --Vegetable Acids. --Of the Power of Carbon to revive
Metals.
CONVERSATION X.
ON METALS. 314
Natural History of Metals. --Of Roasting, Smelting, &c. --Oxydation
of metals by the Atmosphere. --Change of Colours produced by
different degrees of Oxydation. --Combustion of Metals. --Perfect
Metals burnt by Electricity only. --Some Metals revived by Carbon
and other Combustibles. --Perfect Metals revived by Heat alone. --Of
the Oxydation of certain Metals by the Decomposition of Water. Power
of Acids to promote this Effect. --Oxydation of Metals by Acids.
--Metallic Neutral Salts. --Previous oxydation of the Metal
requisite. --Crystallisation. --Solution distinguished from
Dissolution. --Five metals susceptible of acidification. --Meteoric
Stones. --Alloys, Soldering, Plating, &c. --Of Arsenic, and of the
caustic Effects of Oxygen. --Of Verdigris, Sympathetic Ink, &c. --Of
the new Metals discovered by Sir H. Davy.
Contents Of
_The Second Volume_.
ON COMPOUND BODIES.
CONVERSATION XIII.
Page
ON THE ATTRACTION OF COMPOSITION. 1
Of the laws which regulate the Phenomena of the Attraction of
Composition. --1. It takes place only between Bodies of a different
Nature. --2. Between the most minute Particles only. --3. Between 2,
3, 4, or more Bodies. --Of Compound or Neutral Salts. --4. Produces
a Change of Temperature. --5. The Properties which characterise
Bodies in their separate State, destroyed by Combination. --6. The
Force of Attraction estimated by that which is required by the
Separation of the Constituents. --7. Bodies have amongst themselves
different Degrees of Attraction. --Of simple elective and double
elective Attractions. --Of quiescent and divellent Forces. --Law of
definite Proportions. --Decomposition of Salts by Voltaic
Electricity.
CONVERSATION XIV.
ON ALKALIES. 19
Of the Composition and general Properties of the Alkalies. --Of
Potash. --Manner of preparing it. --Pearlash. --Soap. --Carbonat of
Potash. --Chemical Nomenclature. --Solution of Potash. --Of Glass.
--Of Nitrat of Potash or Saltpetre. --Effect of Alkalies on
Vegetable Colours. --Of Soda. --Of Ammonia or Volatile Alkali.
--Muriat of Ammonia. --Ammoniacal Gas. --Composition of Ammonia.
--Hartshorn and Sal Volatile. --Combustion of Ammoniacal Gas.
CONVERSATION XV.
ON EARTHS. 44
Composition of the Earths. --Of their Incombustibility. --Form the
Basis of all Minerals. --Their Alkaline Properties. --Silex; its
Properties and Uses in the Arts. --Alumine; its Uses in Pottery, &c.
--Alkaline Earths. --Barytes. --Lime; its extensive chemical
Properties and Uses in the Arts. --Magnesia. --Strontian.
CONVERSATION XVI.
ON ACIDS. 69
Nomenclature of the Acids. --Of the Classification of Acids. --1st
Class --Acids of simple and known Radicals, or Mineral Acids.
--2d Class --Acids of double Radicals, or Vegetable Acids.
--3d Class --Acids of triple Radicals or Animal Acids. --Of the
Decomposition of Acids of the 1st Class by Combustible bodies.
CONVERSATION XVII.
OF THE SULPHURIC AND PHOSPHORIC ACIDS: OR, THE COMBINATIONS OF
OXYGEN WITH SULPHUR AND WITH PHOSPHORUS; AND OF THE SULPHATS
AND PHOSPHATS. 80
Of the Sulphuric Acid. --Combustion of Animal or Vegetable Bodies by
this Acid. --Method of preparing it. -- The Sulphurous Acid obtained
in the Form of Gas. --May be obtained from Sulphuric Acid. --May be
reduced to Sulphur. --Is absorbable by Water. --Destroys Vegetable
Colours. --Oxyd of Sulphur. --Of Salts in general. --Sulphats.
--Sulphat of Potash, or Sal Polychrest. --Cold produced by the
melting of Salts. --Sulphat of Soda, or Glauber’s Salt. --Heat
evolved during the Formation of Salts. --Crystallisation of Salts.
--Water of Crystallisation. --Efflorescence and Deliquescence of
Salts. --Sulphat of Lime, Gypsum or Plaister of Paris. --Sulphat of
Magnesia. --Sulphat of Alumine, or Alum. --Sulphat of Iron. --Of
Ink. --Of the Phosphoric and Phosphorous Acids. --Phosphorus
obtained from Bones. --Phosphat of Lime.
CONVERSATION XVIII.
OF THE NITRIC AND CARBONIC ACIDS: OR THE COMBINATION OF
OXYGEN WITH NITROGEN AND WITH CARBON; AND OF THE NITRATS AND
CARBONATS. 100
Nitrogen susceptible of various Degrees of Acidification. --Of the
Nitric Acid. --Its Nature and Composition discovered by
Mr. Cavendish. --Obtained from Nitrat of Potash. --Aqua Fortis.
--Nitric Acid may be converted into Nitrous Acid. --Nitric Oxyd Gas.
--Its Conversion into Nitrous Acid Gas. --Used as an Eudiometrical
Test. --Gaseous Oxyd of Nitrogen, or exhilarating Gas, obtained from
Nitrat of Ammonia. --Its singular Effects on being respired.
--Nitrats. --Of Nitrat of Potash, Nitre or Saltpetre. --Of
Gunpowder. --Causes of Detonation. --Decomposition of Nitre.
--Deflagration. --Nitrat of Ammonia. --Nitrat of Silver. --Of the
Carbonic Acid. --Formed by the Combustion of Carbon. --Constitutes a
component Part of the Atmosphere. --Exhaled in some Caverns.
--Grotto del Cane. --Great Weight of this Gas. --Produced from
calcareous Stones by Sulphuric Acid. --Deleterious Effects of this
Gas when respired. --Sources which keep up a Supply of this Gas in
the Atmosphere. --Its Effects on Vegetation. --Of the Carbonats of
Lime; Marble, Chalk, Shells, Spars, and calcareous Stones.
CONVERSATION XIX.
ON THE BORACIC, FLUORIC, MURIATIC, AND OXYGENATED MURIATIC ACIDS;
AND ON MURIATS. 131
On the Boracic Acid. --Its Decomposition by Sir H. Davy. --Its Basis
Boracium. --Its Recomposition. --Its Uses in the Arts. --Borax or
Borat of Soda. --Of the Fluoric Acid. --Obtained from Fluor;
corrodes Siliceous Earth; its supposed Composition. --Fluorine; its
supposed Basis. --Of the Muriatic Acid. --Obtained from Muriats.
--Its gaseous Form. --Is absorbable by Water. --Its Decomposition.
--Is susceptible of a stronger Degree of Oxygenation. --Oxygenated
Muriatic Acid. --Its gaseous Form and other Properties. --Combustion
of Bodies in this Gas. --It dissolves Gold. --Composition of Aqua
Regia. --Oxygenated Muriatic Acid destroys all Colours. --Sir H.
Davy’s Theory of the Nature of Muriatic and Oxymuriatic Acid.
--Chlorine. --Used for Bleaching and for Fumigations. --Its
offensive Smell, &c. --Muriats. --Muriat of Soda, or common Salt.
--Muriat of Ammonia. --Oxygenated Muriat of Potash. --Detonates with
Sulphur, Phosphorus, &c. --Experiment of burning Phosphorus under
Water by means of this Salt and of Sulphuric Acid.
CONVERSATION XX.
ON THE NATURE AND COMPOSITION OF VEGETABLES. 162
Of organised Bodies. --Of the Functions of Vegetables. --Of the
Elements of Vegetables. --Of the Materials of Vegetables. --Analysis
of Vegetables. --Of Sap. --Mucilage, or Gum. --Sugar. --Manna, and
Honey. --Gluten. --Vegetable Oils. --Fixed Oils, Linseed, Nut, and
Olive Oils. --Volatile Oils, forming Essences and Perfumes.
--Camphor. --Resins and Varnishes. --Pitch, Tar, Copal, Mastic, &c.
--Gum Resins. --Myrrh, Assafœtida, &c. --Caoutchouc, or Gum Elastic.
--Extractive colouring Matter; its Use in the Arts of Dyeing and
Painting. --Tannin; its Use in the Art of preparing Leather. --Woody
Fibre. --Vegetable Acids. --The Alkalies and Salts contained in
Vegetables.
CONVERSATION XXI.
ON THE DECOMPOSITION OF VEGETABLES. 202
Of Fermentation in general. --Of the Saccharine Fermentation, the
Product of which is Sugar. --Of the Vinous Fermentation, the Product
of which is Wine. --Alcohol, or Spirit of Wine. --Analysis of Wine
by Distillation. --Of Brandy, Rum, Arrack, Gin, &c. --Tartrit of
Potash, or Cream of Tartar. --Liqueurs. --Chemical Properties of
Alcohol. --Its Combustion. --Of Ether. --Of the Acetous
Fermentation, the Product of which is Vinegar. --Fermentation of
Bread. --Of the Putrid Fermentation, which reduces Vegetables to
their Elements. --Spontaneous Succession of these Fermentations.
--Of Vegetables said to be petrified. --Of Bitumens: Naphtha,
Asphaltum, Jet, Coal, Succin, or Yellow Amber. --Of Fossil Wood,
Peat, and Turf.
CONVERSATION XXII.
HISTORY OF VEGETATION. 243
Connexion between the Vegetable and Animal Kingdoms. --Of Manures.
--Of Agriculture. --Inexhaustible Sources of Materials for the
Purposes of Agriculture. --Of sowing Seed. --Germination of the
Seed. --Function of the Leaves of Plants. --Effects of Light and Air
on Vegetation. --Effects of Water on Vegetation. --Effects of
Vegetation on the Atmosphere. --Formation of Vegetable Materials by
the Organs of Plants. --Vegetable Heat. --Of the Organs of Plants.
--Of the Bark, consisting of Epidermis, Parenchyma, and Cortical
Layers. --Of Alburnum, or Wood. --Leaves, Flowers, and Seeds.
--Effects of the Season on Vegetation. --Vegetation of Evergreens in
Winter.
CONVERSATION XXIII.
ON THE COMPOSITION OF ANIMALS. 276
Elements of Animals. --Of the principal Materials of Animals, viz.
--Gelatine, Albumen, Fibrine, Mucus. --Of Animal Acids. --Of Animal
Colours, Prussian Blue, Carmine, and Ivory Black.
CONVERSATION XXIV.
ON THE ANIMAL ECONOMY. 297
Of the principal Animal Organs. --Of Bones, Teeth, Horns, Ligaments,
and Cartilage. --Of the Muscles, constituting the Organs of Motion.
--Of the Vascular System, for the Conveyance of Fluids. --Of the
Glands, for the Secretion of Fluids. --Of the Nerves, constituting
the Organs of Sensation. --Of the Cellular Substance which connects
the several Organs. --Of the Skin.
CONVERSATION XXV.
ON ANIMALISATION, NUTRITION, AND RESPIRATION. 314
Digestion. --Solvent Power of the Gastric Juice. --Formation of a
Chyle. --Its Assimilation, or Conversion into Blood. --Of
Respiration. --Mechanical Process of Respiration. --Chemical Process
of Respiration. --Of the Circulation of the Blood. --Of the
Functions of the Arteries, the Veins, and the Heart. --Of the Lungs.
--Effects of Respiration on the Blood.
CONVERSATION XXVI.
ON ANIMAL HEAT; AND OF VARIOUS ANIMAL PRODUCTS. 336
Of the Analogy of Combustion and Respiration. --Animal Heat evolved
in the Lungs. --Animal Heat evolved in the Circulation. --Heat
produced by Fever. --Perspiration. --Heat produced by Exercise.
--Equal Temperature of Animals at all Seasons. --Power of the Animal
Body to resist the Effects of Heat. --Cold produced by Perspiration.
--Respiration of Fish and of Birds. --Effects of Respiration on
Muscular Strength. --Of several Animal Products, viz. Milk, Butter,
and Cheese; Spermaceti; Ambergris; Wax; Lac; Silk; Musk; Civet;
Castor. --Of the putrid Fermentation. --Conclusion.
CONVERSATIONS
ON
CHEMISTRY.
CONVERSATION I.
ON THE GENERAL PRINCIPLES OF CHEMISTRY.
MRS. B.
As you have now acquired some elementary notions of NATURAL PHILOSOPHY,
I am going to propose to you another branch of science, to which I am
particularly anxious that you should devote a share of your attention.
This is CHEMISTRY, which is so closely connected with Natural
Philosophy, that the study of the one must be incomplete without some
knowledge of the other; for, it is obvious that we can derive but a very
imperfect idea of bodies from the study of the general laws by which
they are governed, if we remain totally ignorant of their intimate
nature.
CAROLINE.
To confess the truth, Mrs. B., I am not disposed to form a very
favourable idea of chemistry, nor do I expect to derive much
entertainment from it. I prefer the sciences which exhibit nature on a
grand scale, to those that are confined to the minutiæ of petty details.
Can the studies which we have lately pursued, the general properties of
matter, or the revolutions of the heavenly bodies, be compared to the
mixing up of a few insignificant drugs? I grant, however, there may be
entertaining experiments in chemistry, and should not dislike to try
some of them: the distilling, for instance, of lavender, or rose
water . . . . . .
MRS. B.
I rather imagine, my dear Caroline, that your want of taste for
chemistry proceeds from the very limited idea you entertain of its
object. You confine the chemist’s laboratory to the narrow precincts of
the apothecary’s and perfumer’s shops, whilst it is subservient to an
immense variety of other useful purposes. Besides, my dear, chemistry is
by no means confined to works of art. Nature also has her laboratory,
which is the universe, and there she is incessantly employed in chemical
operations. You are surprised, Caroline, but I assure you that the most
wonderful and the most interesting phenomena of nature are almost all of
them produced by chemical powers. What Bergman, in the introduction to
his history of chemistry, has said of this science, will give you a more
just and enlarged idea of it. The knowledge of nature may be divided, he
observes, into three periods. The first was that in which the attention
of men was occupied in learning the external forms and characters of
objects, and this is called _Natural History_. In the second, they
considered the effects of bodies acting on each other by their
mechanical power, as their weight and motion, and this constitutes the
science of _Natural Philosophy_. The third period is that in which the
properties and mutual action of the elementary parts of bodies was
investigated. This last is the science of CHEMISTRY, and I have no doubt
you will soon agree with me in thinking it the most interesting.
You may easily conceive, therefore, that without entering into the
minute details of practical chemistry, a woman may obtain such a
knowledge of the science as will not only throw an interest on the
common occurrences of life, but will enlarge the sphere of her ideas,
and render the contemplation of nature a source of delightful
instruction.
CAROLINE.
If this is the case, I have certainly been much mistaken in the notion I
had formed of chemistry. I own that I thought it was chiefly confined to
the knowledge and preparation of medicines.
MRS. B.
That is only a branch of chemistry which is called Pharmacy; and, though
the study of it is certainly of great importance to the world at large,
it belongs exclusively to professional men, and is therefore the last
that I should advise you to pursue.
EMILY.
But, did not the chemists formerly employ themselves in search of the
philosopher’s stone, or the secret of making gold?
MRS. B.
These were a particular set of misguided philosophers, who dignified
themselves with the name of Alchemists, to distinguish their pursuits
from those of the common chemists, whose studies were confined to the
knowledge of medicines.
But, since that period, chemistry has undergone so complete a
revolution, that, from an obscure and mysterious art, it is now become a
regular and beautiful science, to which art is entirely subservient. It
is true, however, that we are indebted to the alchemists for many very
useful discoveries, which sprung from their fruitless attempts to make
gold, and which, undoubtedly, have proved of infinitely greater
advantage to mankind than all their chimerical pursuits.
The modern chemists, instead of directing their ambition to the vain
attempt of producing any of the original substances in nature, rather
aim at analysing and imitating her operations, and have sometimes
succeeded in forming combinations, or effecting decompositions, no
instances of which occur in the chemistry of Nature. They have little
reason to regret their inability to make gold, whilst, by their
innumerable inventions and discoveries, they have so greatly stimulated
industry and facilitated labour, as prodigiously to increase the
luxuries as well as the necessaries of life.
EMILY.
But, I do not understand by what means chemistry can facilitate labour;
is not that rather the province of the mechanic?
MRS. B.
There are many ways by which labour may be rendered more easy,
independently of mechanics; but even the machine, the most wonderful in
its effects, the Steam-engine, cannot be understood without the
assistance of chemistry. In agriculture, a chemical knowledge of the
nature of soils, and of vegetation, is highly useful; and, in those arts
which relate to the comforts and conveniences of life, it would be
endless to enumerate the advantages which result from the study of this
science.
CAROLINE.
But, pray, tell us more precisely in what manner the discoveries of
chemists have proved so beneficial to society?
MRS. B.
That would be an injudicious anticipation; for you would not comprehend
the nature of such discoveries and useful applications, as well as you
will do hereafter. Without a due regard to method, we cannot expect to
make any progress in chemistry. I wish to direct your observations
chiefly to the chemical operations of Nature; but those of Art are
certainly of too high importance to pass unnoticed. We shall therefore
allow them also some share of our attention.
EMILY.
Well, then, let us now set to work regularly. I am very anxious to
begin.
MRS. B.
The object of chemistry is to obtain a knowledge of the intimate nature
of bodies, and of their mutual action on each other. You find therefore,
Caroline, that this is no narrow or confined science, which comprehends
every thing material within our sphere.
CAROLINE.
On the contrary, it must be inexhaustible; and I am a loss to conceive
how any proficiency can be made in a science whose objects are so
numerous.
MRS. B.
If every individual substance were formed of different materials, the
study of chemistry would, indeed, be endless; but you must observe that
the various bodies in nature are composed of certain elementary
principles, which are not very numerous.
CAROLINE.
Yes; I know that all bodies are composed of fire, air, earth, and water;
I learnt that many years ago.
MRS. B.
But you must now endeavour to forget it. I have already informed you
what a great change chemistry has undergone since it has become a
regular science. Within these thirty years especially, it has
experienced an entire revolution, and it is now proved, that neither
fire, air, earth, nor water, can be called elementary bodies. For an
elementary body is one that has never been decomposed, that is to say,
separated into other substances; and fire, air, earth, and water, are
all of them susceptible of decomposition.
EMILY.
I thought that decomposing a body was dividing it into its minutest
parts. And if so, I do not understand why an elementary substance is not
capable of being decomposed, as well as any other.
MRS. B.
You have misconceived the idea of _decomposition_; it is very different
from mere _division_. The latter simply reduces a body into parts, but
the former separates it into the various ingredients, or materials, of
which it is composed. If we were to take a loaf of bread, and separate
the several ingredients of which it is made, the flour, the yeast, the
salt, and the water, it would be very different from cutting or
crumbling the loaf into pieces.
EMILY.
I understand you now very well. To decompose a body is to separate from
each other the various elementary substances of which it consists.
CAROLINE.
But flour, water, and other materials of bread, according to our
definition, are not elementary substances?
MRS. B.
No, my dear; I mentioned bread rather as a familiar comparison, to
illustrate the idea, than as an example.
The elementary substances of which a body is composed are called the
_constituent_ parts of that body; in decomposing it, therefore, we
separate its constituent parts. If, on the contrary, we divide a body by
chopping it to pieces, or even by grinding or pounding it to the finest
powder, each of these small particles will still consist of a portion of
the several constituent parts of the whole body: these are called the
_integrant_ parts; do you understand the difference?
EMILY.
Yes, I think, perfectly. We _decompose_ a body into its _constituent_
parts; and _divide_ it into its _integrant_ parts.
MRS. B.
Exactly so. If therefore a body consists of only one kind of substance,
though it may be divided into its integrant parts, it is not possible to
decompose it. Such bodies are therefore called _simple_ or _elementary_,
as they are the elements of which all other bodies are composed.
_Compound bodies_ are such as consist of more than one of these
elementary principles.
CAROLINE.
But do not fire, air, earth, and water, consist, each of them, but of
one kind of substance?
MRS. B.
No, my dear; they are every one of them susceptible of being separated
into various simple bodies. Instead of four, chemists now reckon upwards
of forty elementary substances. The existence of most of these is
established by the clearest experiments; but, in regard to a few of
them, particularly the most subtle agents of nature, _heat_, _light_,
and _electricity_, there is yet much uncertainty, and I can only give
you the opinion which seems most probably deduced from the latest
discoveries. After I have given you a list of the elementary bodies,
classed according to their properties, we shall proceed to examine each
of them separately, and then consider them in their combinations with
each other.
Excepting the more general agents of nature, heat, light, and
electricity, it would seem that the simple form of bodies is that of a
metal.
CAROLINE.
You astonish me! I thought the metals were only one class of minerals,
and that there were besides, earths, stones, rocks, acids, alkalies,
vapours, fluids, and the whole of the animal and vegetable kingdoms.
MRS. B.
You have made a tolerably good enumeration, though I fear not arranged
in the most scientific order. All these bodies, however, it is now
strongly believed, may be ultimately resolved into metallic substances.
Your surprise at this circumstance is not singular, as the decomposition
of some of them, which has been but lately accomplished, has excited the
wonder of the whole philosophical world.
But to return to the list of simple bodies--these being usually found in
combination with oxygen, I shall class them according to their
properties when so combined. This will, I think, facilitate their future
investigation.
EMILY.
Pray what is oxygen?
MRS. B.
A simple body; at least one that is supposed to be so, as it has never
been decomposed. It is always found united with the negative
electricity. It will be one of the first of the elementary bodies whose
properties I shall explain to you, and, as you will soon perceive, it is
one of the most important in nature; but it would be irrelevant to enter
upon this subject at present. We must now confine our attention to the
enumeration and classification of the simple bodies in general. They may
be arranged as follows:
CLASS I.
_Comprehending the imponderable agents, viz._
HEAT or CALORIC,
LIGHT,
ELECTRICITY.
CLASS II.
_Comprehending agents capable of uniting with inflammable bodies, and in
most instances of effecting their combustion._
OXYGEN,
CHLORINE,
IODINE.*
[Footnote *: It has been questioned by some eminent chemists,
whether these two last agents should not be classed among the
inflammable bodies, as they are capable of combining with oxygen,
as well as with inflammable bodies. But they seem to be more
distinctly characterised by their property of supporting
combustion than by any other quality.]
CLASS III.
_Comprehending bodies capable of uniting with oxygen, and, forming with
it various compounds. This class may be divided as follows:_
DIVISION 1.
HYDROGEN, _forming_ water.
DIVISION 2.
_Bodies forming acids._
NITROGEN, _forming_ nitric acid.
SULPHUR, _forming_ sulphuric acid.
PHOSPHORUS, _forming_ phosphoric acid.
CARBON, _forming_ carbonic acid.
BORACIUM, _forming_ boracic acid.
FLUORIUM, _forming_ fluoric acid.
MURIATIUM, _forming_ muriatic acid.
DIVISION 3.
_Metallic bodies forming alkalies._
POTASSIUM, _forming_ potash.
SODIUM, _forming_ soda.
AMMONIUM, _forming_ ammonia.
DIVISION 4.
_Metallic bodies forming earths._
CALCIUM, _or metal forming_ lime.
MAGNIUM, _forming_ magnesia.
BARIUM, _forming_ barytes.
STRONTIUM, _forming_ strontites.
SILICIUM, _forming_ silex.
ALUMIUM, _forming_ alumine.
YTTRIUM, _forming_ yttria.
GLUCIUM, _forming_ glucina.
ZIRCONIUM, _forming_ zirconi.*
[Footnote *: Of all these earths, three or four only have as yet
been distinctly decomposed.]
DIVISION 5.
_Metals, either naturally metallic, or yielding their oxygen to carbon
or to heat alone._
_Subdivision 1._
_Malleable Metals._
GOLD,
PLATINA,
PALLADIUM,
SILVER*
MERCURY†
TIN,
COPPER,
IRON,
LEAD,
NICKEL,
ZINC.
[Footnote *: These first four metals have commonly been
distinguished by the appellation of perfect or noble metals, on
account of their possessing the characteristic properties of
ductility, malleability, inalterability, and great specific
gravity, in an eminent degree.]
[Footnote †: Mercury, in its liquid state, cannot, of course,
be called a malleable metal. But when frozen, it possesses a
considerable degree of malleability.]
_Subdiv. 2._
_Brittle Metals._
ARSENIC,
BISMUTH,
ANTIMONY,
MANGANESE,
TELLURIUM,
COBALT,
TUNGSTEN,
MOLYBDENUM,
TITANIUM,
CHROME,
URANIUM,
COLUMBIUM _or_ TANTALIUM,
IRIDIUM,
OSMIUM,
RHODIUM.*
[Footnote *: These last four or five metallic bodies are placed
under this class for the sake of arrangement, though some of their
properties have not been yet fully investigated.]
CAROLINE.
Oh, what a formidable list! You will have much to do to explain it,
Mrs. B.; for I assure you it is perfectly unintelligible to me, and I
think rather perplexes than assists me.
MRS. B.
Do not let that alarm you, my dear; I hope that hereafter this
classification will appear quite clear, and, so far from perplexing you,
will assist you in arranging your ideas. It would be in vain to attempt
forming a division that would appear perfectly clear to a beginner: for
you may easily conceive that a chemical division being necessarily
founded on properties with which you are almost wholly unacquainted, it
is impossible that you should at once be able to understand its meaning
or appreciate its utility.
But, before we proceed further, it will be necessary to give you some
idea of chemical attraction, a power on which the whole science depends.
_Chemical Attraction_, or the _Attraction of Composition_, consists in
the peculiar tendency which bodies of a different nature have to unite
with each other. It is by this force that all the compositions, and
decompositions, are effected.
EMILY.
What is the difference between chemical attraction, and the attraction
of cohesion, or of aggregation, which you often mentioned to us, in
former conversations?
MRS. B.
The attraction of cohesion exists only between particles of the _same_
nature, whether simple or compound; thus it unites the particles of a
piece of metal which is a simple substance, and likewise the particles
of a loaf of bread which is a compound. The attraction of composition,
on the contrary, unites and maintains, in a state of combination,
particles of a _dissimilar_ nature; it is this power that forms each of
the compound particles of which bread consists; and it is by the
attraction of cohesion that all these particles are connected into a
single mass.
EMILY.
The attraction of cohesion, then, is the power which unites the
integrant particles of a body: the attraction of composition that which
combines the constituent particles. Is it not so?
MRS. B.
Precisely: and observe that the attraction of cohesion unites particles
of a similar nature, without changing their original properties; the
result of such an union, therefore, is a body of the same kind as the
particles of which it is formed; whilst the attraction of composition,
by combining particles of a dissimilar nature, produces compound bodies,
quite different from any of their constituents. If, for instance, I pour
on the piece of copper, contained in this glass, some of this liquid
(which is called nitric acid), for which it has a strong attraction,
every particle of the copper will combine with a particle of acid, and
together they will form a new body, totally different from either the
copper or the acid.
Do you observe the internal commotion that already begins to take place?
It is produced by the combination of these two substances; and yet the
acid has in this case to overcome not only the resistance which the
strong cohesion of the particles of copper opposes to their combination
with it, but also to overcome the weight of the copper, which makes it
sink to the bottom of the glass, and prevents the acid from having such
free access to it as it would if the metal were suspended in the liquid.
EMILY.
The acid seems, however, to overcome both these obstacles without
difficulty, and appears to be very rapidly dissolving the copper.
MRS. B.
By this means it reduces the copper into more minute parts than could
possibly be done by any mechanical power. But as the acid can act only
on the surface of the metal, it will be some time before the union of
these two bodies will be completed.
You may, however, already see how totally different this compound is
from either of its ingredients. It is neither colourless, like the acid,
nor hard, heavy, and yellow like the copper. If you tasted it, you would
no longer perceive the sourness of the acid. It has at present the
appearance of a blue liquid; but when the union is completed, and the
water with which the acid is diluted is evaporated, the compound will
assume the form of regular crystals, of a fine blue colour, and
perfectly transparent*. Of these I can shew you a specimen, as I have
prepared some for that purpose.
[Footnote *: These crystals are more easily obtained from a
mixture of sulphuric with a little nitric acid.]
CAROLINE.
How very beautiful they are, in colour, form, and transparency!
EMILY.
Nothing can be more striking than this example of chemical attraction.
MRS. B.
The term _attraction_ has been lately introduced into chemistry as a
substitute for the word _affinity_, to which some chemists have
objected, because it originated in the vague notion that chemical
combinations depended upon a certain resemblance, or relationship,
between particles that are disposed to unite; and this idea is not only
imperfect, but erroneous, as it is generally particles of the most
dissimilar nature, that have the greatest tendency to combine.
CAROLINE.
Besides, there seems to be no advantage in using a variety of terms to
express the same meaning; on the contrary it creates confusion; and as
we are well acquainted with the term Attraction in natural philosophy,
we had better adopt it in chemistry likewise.
MRS. B.
If you have a clear idea of the meaning, I shall leave you at liberty to
express it in the terms you prefer. For myself, I confess that I think
the word Attraction best suited to the general law that unites the
integrant particles of bodies; and Affinity better adapted to that which
combines the constituent particles, as it may convey an idea of the
preference which some bodies have for others, which the term _attraction
of composition_ does not so well express.
EMILY.
So I think; for though that preference may not result from any
relationship, or similitude, between the particles (as you say was once
supposed), yet, as it really exists, it ought to be expressed.
MRS. B.
Well, let it be agreed that you may use the terms _affinity_, _chemical
attraction_ and _attraction of composition_, indifferently, provided you
recollect that they have all the same meaning.
EMILY.
I do not conceive how bodies can be decomposed by chemical attraction.
That this power should be the means of composing them, is very obvious;
but that it should, at the same time, produce exactly the contrary
effect, appears to me very singular.
MRS. B.
To decompose a body is, you know, to separate its constituent parts,
which, as we have just observed, cannot be done by mechanical means.
EMILY.
No: because mechanical means separate only the integrant particles; they
act merely against the attraction of cohesion, and only divide a
compound into smaller parts.
MRS. B.
The decomposition of a body is performed by chemical powers. If you
present to a body composed of two principles, a third, which has a
greater affinity for one of them than the two first have for each other,
it will be decomposed, that is, its two principles will be separated by
means of the third body. Let us call two ingredients, of which the body
is composed, A and B. If we present to it another ingredient C, which
has a greater affinity for B than that which unites A and B, it
necessarily follows that B will quit A to combine with C. The new
ingredient, therefore, has effected a decomposition of the original body
A B; A has been left alone, and a new compound, B C, has been formed.
EMILY.
We might, I think, use the comparison of two friends, who were very
happy in each other’s society, till a third disunited them by the
preference which one of them gave to the new-comer.
MRS. B.
Very well. I shall now show you how this takes place in chemistry.
Let us suppose that we wish to decompose the compound we have just
formed by the combination of the two ingredients, copper and nitric
acid; we may do this by presenting to it a piece of iron, for which the
acid has a stronger attraction than for copper; the acid will,
consequently, quit the copper to combine with the iron, and the copper
will be what the chemists call _precipitated_, that is to say, it will
be thrown down in its separate state, and reappear in its simple form.
In order to produce this effect, I shall dip the blade of this knife
into the fluid, and, when I take it out, you will observe, that, instead
of being wetted with a bluish liquid, like that contained in the glass,
it will be covered with a thin coat of copper.
CAROLINE.
So it is really! but then is it not the copper, instead of the acid,
that has combined with the iron blade?
MRS. B.
No; you are deceived by appearances: it is the acid which combines with
the iron, and, in so doing, deposits or precipitates the copper on the
surface of the blade.
EMILY.
But, cannot three or more substances combine together, without any of
them being precipitated?
MRS. B.
That is sometimes the case; but, in general, the stronger affinity
destroys the weaker; and it seldom happens that the attraction of
several substances for each other is so equally balanced as to produce
such complicated compounds.
CAROLINE.