THE LIBRARY
OF
THE UNIVERSITY
OF CALIFORNIA
PRESENTED BY
PROF. CHARLES A. KOFOID AND
MRS. PRUDENCE W. KOFOID
RURAL CHEMISTRY.
Digitized by tine Internet Arcinive
in 2008 with funding from
IVIicrosoft Corporation
http://www.arcliive.org/details/cliemistryruralOOsollricli
RUEAL CHEMISTRY:
(Khmntartt Sntrnitrrtinn
TO
THE STUDY OF THE SCIENCE IN ITS RELATION TO
AGRICULTURE AND THE ARTS OF LIFE.
BY
EDWAED SOLLY, F.R.S., F.L.S., F.G.S.,
HON. MEMB. ROY. AGB. SOC. ENG.
Fellow of the Chemical Society, the Society for the Encouragement of Arts and
Manufactures, and the Society of Antiquaries ;
Hon. Memb. of the Royal Polytechnic Society of Cornwall, the Ipswich
Museum, and the Poole Scientific Institution ;
Professor of Chemistry to the Horticultural Society of London, Lecturer on
Chemistry in the lion. E. I. Co.'s Military Seminary
at Addiscomhe, &c. &c.
FROM THE THIRD ENGLISH EDITION, REVISED AND ENLARGED.
PHILADELPHIA:
HENRY CAREY BAIRD,
SUCCESSOR TO E. L. CAREY.
1852.
ka.
PHILADELPHIA:
T. K. AND P. G. COLLINS, PRINTERS.
PREFACE TO THE FIRST EDITION.
The following pages formed the substance of a
short series of articles on Chemistry, which origi-
nally appeared in the columns of the Gardeners'
Chronicle. The interest which they excited in the
readers of that journal, has led to their republica-
tion in a separate and more complete form. It
would have been easy to have greatly increased the
size of the book; and indeed it was frequently very
difficult to select from the mass of information which
exists those facts which appeared most worthy of
notice. The original object of the Author was to
give such an elementary sketch of the science as
should enable those ignorant of the subject more
readily to comprehend the works of the various
authors who have written on Agricultural Chemistry.
^^6264.1
VI PREFACE.
As a general rule, care has been taken, as much as
possible, merely to give well-esta])lished facts, or,
when doubtful theories are mentioned, to state dis-
tinctly that they are more or less problematical.
PREFACE TO THE THIRD EDITION.
In accordance with numerous suggestions, very
considerable additions have been made to this little
book, in preparing it for a new edition; several
important practical matters, not treated of in the
former editions, having been introduced. Brief
descriptions of the more important of the domestic
arts, such as wine and vinegar making, brewing,
the manufacture of spirits, baking, cheese-making,
cookery, &c., have been added; together with some
account of the scientific principles involved in those
arts. Numerous recent analyses of agricultural
crops have likewise been given, and the whole has
been carefully revised and corrected.
E. SOLLY.
Tavistock Square, London,
Nov. 1, 1850.
CONTENTS.
PAGE
Introduction 13
CHAPTER I.
Objects of chemistry — Affinity — Nature of combination
and decomposition — The elements — The air, its pro-
perties and composition — Oxygen and nitrogen — Com-
bustion, results of combustion — Carbonic acid gas —
Water, ice, and steam — Effects of frost — Latent heat
— Composition of water — Hydrogen ... 25
CHAPTER II.
Carbon, its different forms — Cohesion — Combustion and
decay — Carbonic acid gas, produced by respiration,
combustion, fermentation, &c. — Nature of acids and
salts — Carbonic oxide — Carburetted hydrogen, fire
damp, coal gas — Compounds all definite — Combining
weights — Nitrogen combined with hydrogen forms
ammonia — Carbonate, sulphate, muriate, and phosphate
of ammonia — Nitric acid — Nitrates — Sulphur, sulphu-
rous acid — Sulphuric acid, sulphates — Sulphuretted
hydrogen — Chlorine, muriatic acid — Iodine, bromine
— Phosphorus, phosphoric acid .... 58
CONTENTS.
CHAPTER III.
Metals — Bases — Alkalies — Potash-, its properties — Carbo-
nate and nitrate of potash, gunpowder — Soda, common
salt, sulphate, carbonate, and nitrate of soda — The
alkaline earths — Lime, its nature and properties — Car-
bonate, sulphate, and phosphate of, lime — Magnesia,
its carbonate, sulphate, muriate, and phosphate . 97
CHAPTER IV.
The earths — Alumina, its properties — Alum — Silica, or
silicic acid — Silicates of potash and soda — Glass — Sili-
cates in the soil, in plants — The metals, their oxides and
salts — Iron, its oxides — Rusting of iron — Pyrites — Sul-
phate of iron, or green vitriol — Gold — Silver — Mercury
— Copper — Sulphate of copper, or blue vitriol — Zinc —
Tin — Manganese — Lead Metallic alloys . . . 118
CHAPTER V.
Organic matter — Vegetable substances — Lignin, or woody
fibre — Starch, varieties of starch — Gum, soluble and in-
soluble — Sugar, cane and grape, its manufacture — Glu-
ten, albumen, legumine, fibrin, gliadine — Chemical
Transformations — Formation of gum, sugar, &c. — Fer-
mentation — Lactic acid — Manufacture of wine — Alco-
hol — Brandy and grain spirit — Brewing — Bread-mak-
ing — Vinegar or acetic acid 139
CHAPTER VI.
Vegetable principles — Vegetable acids — Citric, tartaric,
malic, and oxalic acids — Oils, fixed and volatile, manu-
facture of soap — Resins, pitch, and tar — Coloring mat-
ters, dyeing — Inorganic constituents of plants — Animal
CONTENTS. XI
PAGE
matter — Albumen — Fibrin— Caseine, milk, butter, and
cheese — Gelatine — Tanning, leather — Fat — Bone — Pro-
tein — Food of animals— Respiration — Circulation of
the blood — Digestion -^ Formation of fat — Cookery,
roasting and boiling — Action of medicines . . 199
CHAPTER VII.
The food of plants — Substances derived from the air —
Sources of oxygen, hydrogen, nitrogen, and carbon —
Substances derived from the soil — Sources of earthy
substances — Composition of soils, their formation — De-
composition of silicates — Mechanical structure of soils
— The saline constituents of soils — Organic matters in
soils, humus, humic acid ; their use in soils — Germina-
tion, malting — Moisture, air and warmth — Influence of
light — Office of the leaves — Roots — Formation of or-
ganic matter — Flowers, fruit, seeds — Organic and
organized matter — Vitality of embryo — Nature of
seeds — Earthy substances in plants — Effects of climate
— Action of plants on the air 246
CHAPTER VIII.
Deterioration of soils, its cause — Modes of maintaining
the fertility of the soil — Theory of fallowing — Rotation
of crops — Subsoil ploughing — Draining — Manure —
Organic manure — Animal manure, contains nitrogen
— Results of putrefaction — Sulphuretted hydrogen —
Loss of manure — Liquid manure — Animal excre-
ments, guano — Modes of fixing ammonia, by acids, by
gypsum, &o. — Strong manures — Wool, rags, oil —
Bones — ^^Super-phosphate of lime — Vegetable manures
— Sawdust, seaweed — Green manures — Irrigation —
Inorganic manures — Lime, chalk, marl, shell sand —
Xn CONTENTS.
PAGE
Gypsum — Phosphate of lime — Ashes — Burnt clay —
Soot, charcoal — Gas liquor — Potash — Alkaline salts —
Nitrates, common salt — Salt and lime . . . 284
CHAPTER IX.
Composition of particular crops — Composition of wheat —
Barley — Oats — Rye — Maize — Rice — Buckwheat — Lin-
seed — Hempseed — Oil-seeds — Beans — Peas — Lentils —
Vetches — Potatoes — Batatas, Jerusalem artichoke — ■
Oxalis — Cabbage — Turnips — Mangel-Wurzel — Carrot
— Parsnip — Clover — Lucern — Saintfoin — Composition
of particular manures — Cows' urine — Horse-dung —
Pigs' dung — Night-soil — Urine — Bones of oxen — Cows
— Horses — Pigs — Farmyard dung — Guano — Wood-
ashes — Lixiviated ashes — Peat ashes — Kelp . 333
Index 379
INTRODUCTION
No branch of knowledge has made more rapid pro-
gress, during the last hundred years, than chemistry.
From being merely a confused collection of marvel-
lous facts and incomprehensible phenomena, it has
become a definite and methodical science : no longer
mysterious and full of uncertainty, but based on
clear and simple laws, the knowledge of chemistry at
once gives us the key to a great number of natural
changes and phenomena, which without it, would be
quite unintelligible.
Chemistry is intimately connected with all other
sciences; for it embraces the study of the various
forms and conditions of matter, tjieir nature and pro-
perties, and the changes which, either from natural
or artificial causes, they undergo. The study of
chemistry is of the greatest importance in relation to
the arts of life, which all depend more or less on
1
XIV INTRODUCTION.
chemical principles. Hence, a knowledge of this
science enables us more readily to understand the
processes of the manufacturer, points out the best and
most economical mode of effecting his objects, and
teaches how that which was before useless and of no
value, may be converted into sources of wealth and
happiness.
It is needless to point out examples of the influence
which the progress of chemistry has had on our
manufactures ; for every one of them owes, more or
less directly, its present improved condition to the
labors of the chemist. Such being the case, it be-
comes interesting to inquire. What has chemistry
done for agriculture, the most important, because the
most necessary, and most extensively practised, of
all the arts? It is remarkable that agriculture
should have received infinitely less assistance from
the labors of chemists, than any other art ; but this
ceases to be surprising, when we consider how little
attention was paid by the ancient chemists to that
subject. — The chemistry of the earthy and metallic
substances presented to them easier and more attract-
ive objects of inquiry; they were led away by the
visionary hope of discovering a mode of making
gold ; and they consequently neglected everything, in
order to try all sorts of experiments, in the vain idea
INTRODUCTION. XV
of converting lead, iron, &c., or the base metals as
they called them, into gold. Hence, it is not to be
wondered at, that the chemistry of the metals was
studied and investigated, long before the nature and
properties of vegetable and animal substances were
examined. The labors of the alchemists brought to
light many valuable discoveries respecting the uses,
nature, and properties, of earthy and metallic sub-
stances; but it was only in the last century, when
the constitution of the air and other gaseous bodies
was discovered, that anything approaching to correct
ideas respecting the nature of animal and vegetable
substances was entertained.
The important discoveries of Dr. Priestley led the
way to a complete revolution in the science, and may
almost be said to have laid the foundation of agricul-
tural chemistry. It is true that, before his time,
there had been many careful and accurate observers,
and multitudes of laborious and valuable experiments
have been made on plants, by such men as Yan Hel-
mont — Evelyn — Boyle — Hales, and others ; but, be-
fore the time of Priestley and his contemporaries,
Bonnet, Ingenhousz, Henry, and Percival, little pro-
gress had been made in studying the chemical
changes on which the growth of plants depends. We
are indebted to Hales for much curious information
XYl INTRODUCTION.
respecting the rise and motion of the sap in plants,
the perspiration, or evaporation, which is constantly
going on to a greater or less extent, from the surface
of the leaves, and the effects of various substances
on plants; his chemical speculations, however, are
for the most part, of little value, though he was often
apparently on the point of making important disco-
veries. The discovery of carbonic acid gas, or fixed
air, by Dr. Black, and the beautiful experiments of
Priestley, opened a new field of inquiry and research :
he observed that plants possessed the property of
purifying the air; in fact, that they were able to
decompose the carbonic acid gas which it always con-
tains in small quantity; appropriating the carbon,
and restoring back to the atmosphere the oxygen, or
vital air, so necessary to the processes of respiration
and combustion. The knowledge of this great fact,
necessarily led to many minor discoveries respecting
the growth of plants, and the sources of their food.
After this period. Organic Chemistry began to attract
a large share of the attention of chemists, the com-
position of vegetable substances was carefully inves-
tigated, new modes of analysis were discovered, and
an immense mass of curious and useful facts was col-
lected. A great number of chemists occupied them-
selves with researches in Vegetable Chemistry, but
INTRODUCTION, XVll
for the most part they were employed in examining
the innumerable substances which plants produce;
whilst the great questions as to the food of plants,
their growth, and nourishment, were left very nearly
in the same state which the experiments of Priestley
and Ingenhousz had brought them to.
At the end of the last century, and in the com-
mencement of the present. Organic Chemistry made
rapid advances ; the labors of Hassenfratz, -Hum-
boldt, Berzelius, Saussure, Senebier, Einhof, and
Davy, contributed to throw light on many parts of
the subject ; whilst the investigations of Gay-Lussac,
Hatchett, Lampadius, Lavoisier, Marcet, Prout,
Thompson, Yauquelin, Thdnard, and others, in all
parts of Europe, led to a more complete and accurate
knowledge of the nature, composition, and properties
of organic matter.
The first chemist who wrote on agriculture appears
to have been J. G. Wallerius, who, in 1754, published
a book on the Cause of Fertility. Even before this
time, however, several books had been written on
agriculture, in which attempts were made to explain
the operations of farming on chemical principles;
such, for example, were The Rational Farjner,
1743, a curious book, containing numerous accounts
of rude chemical experiments, together with a num-
1*
xviii ' INTRODUCTION.
ber of sound practical facts: the author, however,
was evidently not a chemist. Wallerius was suc-
ceeded by several other authors, amongst whom
ought to be mentioned Cullen, Pearson, Gyllenborg,
De Beunie, Riickert, Einhof, and Dundonald ; but
the speculations of these authors (though ingenious)
were, for the most part, crude and incomplete. The
writings of Einhof were valuable for the numerous
accounts of careful experiments which they contain ;
the analyses, though not carried to that degree of
minuteness which subsequent discoveries led to, were
trustworthy and accurate, and, as such, will always
continue of value. Humboldt's Sheteh of the
Chemical Physiology of Vegetation, which appeared
at this time, is a book of far higher talent than those
just mentioned, and contains enlarged views and
cautious generalizations, which the subsequent pro-
gress of science has in most cases confirmed. At
the commencement of the present century, when
Organic Chemistry was rapidly advancing, Berzelius
and Davy endeavored to apply the conclusions to be
derived from chemical experiments, to agriculture.
If the deductions which they made were not always
correct, and if the plans which they proposed did
not always produce the effects which the authors
anticipated, it must be remembered that they were
INTRODUCTION. XIX
amongst the first to take the subject up, and that
though they did so under far more favorable circum-
stances than their predecessors did, yet that even
then the science of organic chemistry was in many
respects very imperfect and incomplete.
During the last forty years, many important
additions have been made to this department of
Chemistry; improved and more accurate modes of
chemical investigation have enabled more exact ana-
lyses to be made of the different varieties of organic
matter; the composition of those substances which
constitute the bodies of animals and plants has been
accurately and carefully ascertained. At the same
time, many valuable observations have been made
respecting the functions of plants, the conditions
requisite to germination, the formation of flowers
and seed, the chemical changes attendant on the
ripening of fruit, the office performed by roots and
leaves, and a variety of other important subjects
of inquiry. The names of Liebig, Schiibler, and
Sprengel, in Germany; Braconnot, Boussingault,
Chevreul, Colin, Chaptal, Dumas, Edwards, and
Payen, in France ; and of Daubeny, Fownes, John-
ston, Pepys, Turner, Christison, and "Way, in our
own country, deserve especial mention.
Even in so short a sketch of the subject as this, it
XX INTRODUCTION.
would not be right to omit altogether the name of
Grisenthwaite, whose book on the theory of Agricul-
ture (1819) is remarkable for the enlarged and ex-
tended views which it contains. It is true that the
author falls into many errors ; but, at the same time,
he was the first who entertained correct views of the
importance of nitrogen as an element of manure, and
of the necessity of supplying phosphates, as well as
substances containing nitrogen, to plants, like wheat,
chiefly cultivated for the sake of the azotized princi-
ple which renders them valuable as food.
Intimately connected with the progress of Vege-
table Chemistry, is the study of Vegetable Physio-
logy: a knowledge of the one is essential to a perfect
comprehension of the other; for it is impossible well
to understand the chemical changes going on in the
organs of plants, if we are wholly ignorant of the
forms and structure of those organs; and, on the
other hand, the most complete knowledge of the
anatomy of vegetables could never lead any one to
sound and correct conclusions respecting the nutri-
tion of plants. It is rather to be regretted that
both Chemists and Physiologists have appeared to
avoid availing themselves of the advantages which
each might have derived by studying the results that
the others had obtained ; it is only by comparing
INTRODUCTION. XXI
togetlier the observations of both, that correct con-
clusions can be formed. The observations made by
the older physiologists, like those of their chemical
contemporaries, were mostly imperfect, and the deduc-
tions they formed, were, in consequence, very fre-
quently erroneous ; the modes of examination, and the
instruments which they employed, were far less per-
fect than those which have been used in more recent
times. Nevertheless, the observations recorded by
Grew, Malpighi, and Duhamel, are of considerable
value ; they may be said, indeed, to have laid the
foundation of Vegetable Physiology. As the study
of Botany itself advanced, greater care was bestowed
in examining the structure and anatomy of plants ;
and, from the labors of many zealous and careful
observers, there has resulted a tolerably complete
system of Vegetable Physiology. In recent years,
De Candolle, Brongniart, Decaisne, Dutrochet, and
Mirbel, in France; Link, Mohl, Meyen, and Schlei-
den, in Germany; Amici, in Italy; and Brown,
Griffiths, Henslow, Knight, and Lindley, in England,
have, besides many others, made valuable additions
to Vegetable Physiology. The relations of plants to
climate, and the influence of heat, light, and moist-
ure, have also been studied ; especially by Daniell
and Royle in our own country.
XXll INTRODUCTION.
Amongst the names of those who have contributed
to the. science of Agricultural Chemistry, that of
Liebig stands pre-eminent. The thanks of all are
due to him, both for the valuable and laborious ex-
periments he has performed, and likewise for the
exertions which he has made to remove the many-
doubts and uncertainties that surrounded the very
elements of the subject. But little has been done
since the days of Priestley and Ingenhousz to prove
how plants obtained their food, what were the sources
whence they derived the elements of organic matter,
and the nature of the office performed by manures.
Chemists, and likewise physiologists, had formed
many ingenious speculations; but they had not em-
ployed the only real mode of getting at the truth,
namely, well-selected and carefully performed expe-
riments. Liebig, in his Organic Chemistry applied
to Agriculture and Physiology, has strongly drawn
attention to these important questions ; he has exposed
the fallacy of many of the theories which had been
formed to explain them, and has established, on good
evidence, the simple chemical rules which regulate
the growth of plants.
Although the experiments of Priestley and Ingen-
housz had shown that plants possess the power of
decomposing Carbonic Acid ; and, although they had
IXTKODUCTION. XXlll
advanced numerous arguments to prove that plants
derive the carbon which they contain from the de-
composition of that gas; yet this doctrine, although
admitted by many physiologists, was by no means
universally believed by chemists. M. Hassenfratz,
in particular, opposed these views, asserting that
plants did not derive their carbon from the decom-
position of carbonic acid existing in the air, bjit
absorbed it direct from the soil, in a state of suspen-
sion or solution; he gives the name of carbon to the
brown substance left on the evaporation of dung
water, and, in fact, to the various modifications of
decaying organic matter, subsequently described
under the general name of Humus. Few experi-
ments, indeed, were made to show that the explana-
tion of Priestley and Ingenhousz was improbable;
but "it was conceived that plants must derive their
carbon from the soil, and many theories were formed
to explain the mode in which they might be supposed
to obtain it. These theories have been rigidly ex-
amined by Liebig, and the results of his investigation
have shown, that the old views put forth by Priestley
and Ingenhousz were in truth correct.
It has long been known that plants consist of
Carbon, Oxygen, Hydrogen, and Nitrogen, and also
that they invariably contain a small quantity of inor-
XXIV INTRODUCTION.
ganic, or earthy and saline matters. The presence
of Nitrogen was formerly greatly overlooked, in
analyses of vegetable substances ; it is contained in
less quantity than the other three elements of
organic matter, and was very commonly regarded as
being merely accidental, and not a necessary consti-
tuent of plants. Improved modes of analysis have
proved that nitrogen always exists in the same pro-
portion, in certain constituents of plants; -and, as it
appears that these substances are also those which
form the most valuable part of food, it becomes a
question of the first importance — Whence do the
plants derive their Nitrogen? They obtain it, prin-
cipally, if not wholly, from the air; they do not
absorb it in the free and uncombined form, but they
absorb it combined with Hydrogen and with Oxygen,
in the states of Ammonia and Nitric Acid. "The
importance of the earthy substances in plants was,
likewise, greatly overlooked formerly. It has been
proved, by repeated experiments, that these sub-
stances are of the greatest importance in the growth
of plants, being quite essential to their development.
Although much has been done, and although- che-
mists have labored to remove the perplexities which
encompassed the subject, there is still a very great
deal which requires investigation; many important
INTRODUCTION. XXV
points. are as yet imperfectly, or even not at all,
explained, and many questions must be satisfactorily
settled before a complete system of Agricultural
Chemistry can be established. Till these difficulties
are removed, it is premature to expect that Chemistry
can be of more than partial assistance to Agricul-
ture; for, whilst many of the fundamental laws of
Agricultural Chemistry are still scarcely understood,
all attempts to apply them to practice must be in-
complete, and liable to error.
The composition of the principal varieties of
organic matter is well known ; the substances which,
by combining together, form the various constituents
of plants, have been ascertained. The food of
plants, the great , sources whence they derive it, and
the manner in which they absorb it, are known.
The various changes which organic matter undergoes,
the conversion of one substance into another, and
the influence which these changes have on the growth
of plants, is likewise easily understood ; nearly all
the purely chemical operations which are concerned
in their nutrition, can be explained by reference to
simple chemical laws; but there are many most im-
portant phenomena which are as yet wholly in the
dark. Thus, for example, the manner in which wood
is formed ; and, indeed, all those natural operations
XXVI INTRODUCTION.
in "vtliich cellular or organized matter is generated
under the influence of light and heat, are but very
imperfectly explained. A knowledge of the chemical
composition of soils, and the various substances em-
ployed as manures, enables us to comprehend the
mode in which the latter act ; and a knowledge of
the nature of those substances which plants require,
points out the best and most economical methods of
restoring to the soil, by manures, those substances
which plants remove from it: but our knowledge of
this part of the subject is very far from being com-
plete; for although it is certain that, in addition to
the great elements of organic matter, which plants
derive from both air and soil, they likewise absorb
small quantities of inorganic or mineral substances
from the soil exclusively, the office performed by the
latter in the vegetable economy is not yet well under-
stood. Many theories, indeed, have been formed
respecting their use, but very little is positively
known on the subject.
Although Agricultural Chemistry is in this imper-
fect state, and though much still remains to be done
in that branch of science, yet it is so far advanced as
to be able to render substantial assistance to the
practical agriculturist. It can teach him the princi-
ples which govern the growth of plants, and, conse-
INTRODUCTION. XXVll
quentlj, guide him in the application of artificial
means to produce the most beneficial results. He
must, however, not expect too much from the aid of
Chemistry, nor give himself blindly up to specula-
tions or theories. Whilst he gives due credit and
belief to well-authenticated facts, he must always
receive theories with caution and doubt.
Perhaps the most important advantage which a
practical man may at present derive from a know-
ledge of Agricultural Chemistry, is connected with
the use of manure. If he knows what it is that
gives the fertilizing powers to manure, and is aware
of the nature of those substances, he will soon learn
the best method of preserving and using them; he
will then understand how to make the most of the
various sources of manure at his disposal, and he
will be enabled readily to save much, that, for the
want of such knowledge, would otherwise be lost.
RUEAL CHEMISTRY
CHAPTER I.
COMBINATION — DECOMPOSITION — AIR— WATER.
1. The object of Chemistry is to determine accu-
rately the properties ' of all natural substances, to
study the changes which are going on in Nature, to
find out the rules which govern them, and the manner
in which these natural operations are influenced by
circumstances.
2. In pursuing these inquiries, the chemist is obliged
to proceed slowly and with great caution ; it is quite
impossible for him to predict beforehand the result
of a new experiment; he must try it, and then, if it
has been properly conducted, it always furnishes him
with a new fact, for he is sure that, on repeating it in
the same manner, he will obtain the same result.
Hence Chemistry is purely an experimental science ;
every fact is the result of careful experiment, and
every theory is deduced from the study of such facts.
The greatest care must be taken to distinguish facts
from theories; the former are well-established and
3
26 COMBINATION.
unquestionable truths, the latter are plausible con-
jectures, to which we are led by the attentive study
of facts. When a chemist has made a number of
experiments, or has observed many phenomena, he
endeavors to ascertain the causes of the effects he
has been studying. lie selects the most probable
explanation, and adopting it as a theory or view, to
be confirmed or disproved by future experiments,
proceeds to try in all possible ways the truth of his
conclusion. By thus forming a theory he is enabled
to arrive at the truth more easily than if he were
merely to continue making experiments at random.
It is by reasoning on the results of thousands of ex-
periments that chemists have been enabled to reduce
the science into a useful form, as they have thus been
led to discover certain great leading laws, which
govern all chemical changes or operations.
3. Nearly all the changes which are going on in
Nature may be classed under two heads. The one
kind of change is that which takes place when two
substances come together which have, as it were, an
attraction or afiinity for each other. As a familiar
example of what then happens, we may take the com-
mon process of soap-boiling. When an alkaline or
caustic lye is boiled with tallow or fat, soap is formed.
The alkali which is contained in the lye has an attrac-
tion for the fat; the two become thoroughly mixed,
and combine or unite together, and form a new sub-
stance, quite different from either the fat or the alkali^
which new substance is called soap.
CHEMICAL AFFINITY. 2T
4. This kind of action is quite distinct from simple
mixture. When we mix together two substances —
such as, for example, brown sugar and sand, no change
takes place, however long they are kept together, or
in whatever way they are treated, for they have no
affinity or attraction for each other; and, therefore,
if boiling water is poured upon the mixture, it will
soon dissolve out all the sugar and leave the sand,
and neither the sugar nor the sand will be at all
altered by having been mixed.
5. When we mix two substances which have an
attraction for each other, they are both changed, and
the new substance formed by their union is quite dif-
ferent from either ; and when two substances are thus
united or combined together, they are not so easily
separated as when merely mixed, because they require
the exertion of some attraction more powerful than
that which made them combine, to cause their sepa-
ration. In the case of the soap just mentioned, the
compound of fat and alkali does not resemble either
of its components ; it is different from the ley in not
being caustic, and differs from the fat in being easily
soluble in water.
6. It is a rule which holds good in all cases, that
whenever two substances combine or unite together,
and form a new substance, the properties of the new
substance are quite different from those of either of
its components; but when two substances are only
mixed, the properties of the mixture are intermediate,
or half-way, between those of its two components :
28 DECOMPOSITION.
thus, in the mixture of sand and sugar, we may easily
recognize both substances, for the characters of
neither are altered by being brought together.
7. Another common case of affinity is observed
•when we slake quicklime. Quicklime has a strong
affinity for water, and when it is wetted, it becomes
very hot; the lime combines with a quantity of water,
and when is has cooled, we find that the lime is much
altered, having to a great extent lost its strong
caustic properties, and become slaked, as it is termed.
Here again we observe that the properties of the com-
pound differ remarkably from its components. Dry
caustic lime, in combining with water, forms a dry
compound of lime and water, the water becomes solid,
'entering into the composition of a dry solid powder,
whilst the lime no longer possesses the power of heat-
ing when water is poured over it, and has become less
caustic (235).
8. It may perhaps seem as if these two examples
of the change produced by attraction or affinity were
processes of Art, and not of Nature. They will, how-
ever, serve as examples of what is going on in a great
many natural operations ; and as we proceed with the
subject, it will be evident that this kind of change,
by which two or more difi'erent substances unite and
form one new substance, is exceedingly common
throughout Nature.
9. The second kind of change which we shall have
to consider, is that which goes on whenever anything
decays. This change is quite opposite in its nature
DECOMPOSITION. 29
to that which we have just been describing. It takes
place whenever any substance is separated or divided
into its component parts. Thus, to return again to
the quicklime, which is made by burning chalk or
limestone, we say that the chalk or limestone is decom-
posed, when, by burning or heating it in a very hot
fire, whatever it contains which can be roasted out
by fire, is driven off, and the lime only remains
(118).
10. The decomposition of a substance is also effect-
ed when it is mixed with anything which has a very
strong attraction for one of its components. Soap is
made by the attraction which the alkali has for fat
(3) ; but if we add to a solution of soap in w^ater, any-
thing which has a stronger attraction for the alkali
than the latter has for the fat, we shall decompose
the soap : there are many substances which have
the power of doing this, but it is sufficient now to
mention one. If vinegar is poured into a solution of
soap, the soap is decomposed ; the fat is separated
and floats on the surface, and the vinegar combines
with the alkali of the soap.
11. This kind of change is always going on when
anything decays or putrefies, and therefore is of con-
siderable interest in connection with manures ; but in
fact, combination and decomposition are almost always
going on at the same time in most natural changes,
for when a compound consisting of several different
substances is decomposed, it is generally found that
3*
30 ' DECOMPOSITION.
these substances again combine together, one with
another, to form various other compounds (105, 145).
12. Combination takes place whenever substances
are brought together which have an affinity for each
other, under suitable circumstances ; chemical action
then takes place, and a compound is formed. De-
composition of a compound is caused either by the
influence of some external power, the presence of
some substance capable of acting on one of the ele-
ments of the compound, or some influence able to
weaken the chemical affinity which binds these ele-
ments together. -
13. Combination is often modified and controlled
in a very remarkable manner by circumstances, ac-
cordingly as they are favorable or unfavorable to
the union of the substances brought together. Fine
division, or any other method whereby the particles
are enabled readily to mix or come in contact, gener-
ally assist combination. When two solid lumps are
placed in contact with each other, they are only able
to touch by a very few points, and hence in many
cases do not combine even though they have an
affinity for each other. If they are finely powdered
and well mixed they are much more able to combine ;
and for the same reason if they are fusible, heat, by
rendering them fluid, and thus enabling the particles
more easily to mix, assists their combination,
14. A similar eff*ect is produced by solution in
water. In a common Seidlitz powder or saline
THE ELEMENTS. 31
draught, wc have two solutions mixed together, which
are able to act on each other, but cannot do so in the
dry state ; when water is added they are brought
thoroughly in contact, and chemical action at once
takes place. In many cases combination is greatly
assisted by heat, which exalts the chemical affinity that
the substances have for each other (35).
15. Precisely in the same way decomposition is
often curiously affected by various circumstances.
Some compounds decompose spontaneously ; they
cannot be kept any time, and without any external
influence they undergo decomposition ; this is espe-
cially the case with many animal and vegetable
substances (354). Decomposition is frequently caused
by the influence of light (187, 295, 699), or heat (9,
119, 233). The decomposition of many compounds,
likewise, is caused by the presence of particular sub-
stances. A great number of different organic sub-
stances are decomposed when a small, quantity of
some other substance in an active state of decom-
position is mixed with them ; this may be called
decomposition by example ; it is a very singular form
of decomposition, and is termed fermentation (365).
A similar change is sometimes caused by the mere
presence of a particular substance, even though it is
not itself undergoing any change whatever at the
time (361).
16. It is a common saying that there are only four
elements ; air, earth, fire, and water ; and many
82 THE ELEMENTS.
people believe that all things are composed or made
up of these four elements. This is very incorrect,
because there are many substances which do not con-
tain any of these so-called elements ; and they are,
besides, themselves compounded of many different
substances. The term elements, in the sense in which
it is used by chemists, means a certain set of simple
substances, which, by combining or uniting together,
form all the various matters that occur in Nature.
17. To return once more to the example of soap,
we may say that the elements of soap are alkali and
tallow ; but then the question will arise, what are
the elements of tallow and alkali ? which can only
be ascertained by chemical experiments. In this way,
then, we may analyze, or as it were pull to pieces,
different substances, till at last we find that we are
unable to separate or decompose them any further,
and the substances which then remain are called ele-
ments, or simple substances. It is possible that
chemists may hereafter discover that some of the
substances now called elements are really compounds,
and of course it is impossible to prove that they are
not so; all therefore that is meant by the term ele-
ment, or elementary substance, is that chemists have
not yet been able to prove them to be compounds.
18. There are upwards of sixty of these elements,
but it will not be necessary to study the nature and
properties of the whole series, because many of them
are of very rare occurrence, and found only in small
quantities.
ELEMENTARY SUBSTANCES.
33
19. The following is a list of all the substances
which are at present considered as being simple, or
elementary : —
1. Aluminum
2. Antimony
3. Arsenic
4. Barium
5. Bismuth
*6. Boron
7. Bromine
8. Cadmium
9. Calcicum
10. Carbon
11. Cerium
12. Chlorine
13. Chromium
14. Cobalt
15. Columbium
16. Copper
17. Didymium
18. Erbium
19. Fluorine
20. Glucinum
21. Gold
22. Hydrogen
23. Iodine
24. Iridium
25. Iron
26. Lantanum
27. Lead
28. Lithium
29. Magnesium
30. Manganese
31. Mercury
32. Molybdenum
33. Nickel
34. Niobium
35. Nitrogen
36. Osmium
37. Oxygen
38. Palladium
39. Pelopium
40. Phosphorus
41. Platinum
42. Potassium
43. Rhodium
44. Ruthenium
45. Selenium
46. Silicon
47. Silver
48. Sodium
49. Strontium
50. Sulphur
51. Tellurium
52. Terbium
53. Thorium
54. Tin
55. Titanium
56. Tungsten
57. Uranium
58. Vanadium
59. Yttrium
60. Zinc
61. Zirconium.
20. We will commence with those substances which
are of the greatest importance, whether simple or com-
pound, and gradually go through them, before enter-
ing upon the Chemistry of Vegetation. Foremost in
importance, of the substances whose properties we are
about to study, stands the Air.
21. We are too apt to think of the Air as being
merely empty space; we move about through it with-
34 AIR — COMBUSTION.
out feeling any resistance, and, from its being invisible
and totally unlike anything else we know, many for-
get its existence altogether. The fact is, that every
part of the surface of the globe is surrounded by air,
which floats on its surface almost like water.
22. It is easy to prove that the air is really a sub-
stance. When we try to squeeze together the sides
of an inflated bladder, the mouth of which is tightly
tied up, we feel that the bladder is full of something
which resists the pressure ; this something is the air
which it contains, and which, though so easily dis-
placed, or pushed aside, by anything moving through
it, resists strongly any force applied to it when thus
confined in a limited space ; and if whilst we are press-
ing the bladder we prick a hole in it, the air then
rushes out, we feel that the resistance is gone, and
the sides of the bladder are easily squeezed together.
23. And again, when working a pair of bellows, it
is the resistance of the air which we have to overcome
by the force of the arms, which constitutes the labor
of working the bellows ; and if the nozzle of the bel-
lows is stopped up, we presently find that it is impos-
sible to go on working the bellows any longer, because
having forced in as much air as it can hold, the natu-
ral tendency of the air to resist compression prevents
any more from entering.
24. Although we are so forgetful of the very exist-
ence of the air, it is of the greatest importance to all
our daily occupations, and even to life itself. With-
out air nothing could burn; we could have neither
COMBUSTION. 35
fires nor lights ; and, indeed, without air neither ani-
mals nor plants could live, for it is just as essential
to the life of animals as it is to the growth of plants
and the burning of coals and candles.
25. If a lighted candle is put into a large glass bot-
tle, and the mouth of the bottle is then stopped up,
the candle soon gets dim, and in a short time goes
out : the air is no longer able to keep it alight. If
we put a second lighted candle into the bottle it will
go out immediately. Were a living animal substitut-
ed for the lighted candle, after living for a certain
time in a confined portion of air, it would die, and
a second animal placed in the air would immediately
expire.
26. The question now will naturally arise : Is the
whole of the air, then, spoiled or used up ; and if it is,
why does not fresh air enter the bottle and supply its
place? The truth is, only a small portion, about one-
fifth of the bulk of the air, is able to feed the flame
of a candle; the remainder, which cannot feed flame
nor the life of an animal, is of a different kind from
the air which can ; and we find that the common air
which we breathe is a mixture of two kinds of air, or
GAS, as it is called by chemists ; — the one kind, which
we might call good air, which supports the life of
animals, and is essential to the burning of fires and
candles: and the other, or bad air, in which animals
cannot live, and which immediately puts out fire
and lights.
^7. Chemists call the good air Oxygen, and the
36 OXYGEN — NITROGEN.
bad air Nitrogen, or Azote: but we must not suppose
that, because the nitrogen appears thus useless, it is
really so ; for it is, in fact, of very great importance,
as we shall hereafter see. In the experiment just
mentioned, of burning the candle in a large bottle,
the oxygen is all combined with the elements of the
tallow, for which they have a strong affinity, whilst
the nitrogen is left unchanged because it cannot com-
bine with them ; for the same reason, also, it puts out
a fresh-lighted candle plunged into it.
28. Oxygen, when obtained pure, and separate
from any other substance, is a gas like common air
in its ordinary characters, but remarkable for the
very brilliant manner in which all kinds of combus-
tible matter burn in it. Oxygen may be breathed
with safety, but it causes all the functions of the ani-
mal system to be carried on with great vigor and
rapidity, so much so, that an animal breathing pure
oxygen would be soon destroyed, from the very power-
ful effect which the gas would have on its organs.
Oxygen has a strong affinity for most of the other
elements, and combines with them to form a numerous
and important series of compounds.
29. Nitrogen, though it resembles oxygen in ap-
pearance, yet differs from it very remarkably in
chemical characters; it extinguishes flame, and can-
not support the combustion of any substance ; it is
irrespirable, suffocating animals if they attempt to
breathe it pure, and seeming to have very little affi-
nity for other elements ; at least under ordinary mv-
COMBUSTION. 37
cumstances, it shows very little tendency to combine
with them ; under particular circumstances, however,
it does form compounds (147, 163), and some of them
are very curious and important. Common air consists
of one part of oxygen to four parts of nitrogen : it is
a mixture, not a compound.
30. When a candle burns, it gradually disappears ;
it grows shorter and shorter, and at last, when all
the tallow is burnt, the candle goes out ; but we must
not therefore suppose that it is utterly destroyed. A
change has taken place ; the tallow, or rather its ele-
ments, have combined with the oxygen of a portion
of air, and two new compounds, one of which is a gas
or kind of air, are produced. If we put a piece of
salt into water, it will get less and less, and at last
will disappear altogether, having wholly dissolved ; but
the salt is not destroyed, it is only dissolved in the
water.
31. Now we may compare the burning of a candle
to dissolving a piece of salt ; for all the solid matter
of the candle remains diffused throughout the air,
after it is burnt, just as the salt remains dissolved in
the water; but with this difference, the salt is dissolved
in the water, but not combined with it. The elements
of the tallow are dissolved in the air, but they have
combined with a quantity of oxygen, because they have
a strong affinity or attraction for it. If the solution
of salt is left for some time in a warm place, the
water evaporates, and we get the salt again vtn-
chunged ; but in the case of the candle its elements
4
38 KESULTS OF COMBUSTION.
have combined with oxygen, and they cannot be sep-
arated again from it except by the action of something
which, having a more powerful attraction for the oxy-
gen than it has for the elements of the candle, causes
it to relinquish them.
32. There are substances which have suflficient
attraction for the oxygen to effect this : we cannot
get back the tallow, it is true, but we may obtain its
elements, or the simple substances of which it was
composed. What has been said with regard to the
burning of a candle is equally applicable to the burn-
ing of wood, coal, or in fact any combustible matter.
In all ordinary cases they burn in consequence of their
affinity for the oxygen of the air, and they are never
destroyed when burnt, for their elements may always
afterwards be found combined with oxygen, in the air
in which they have been burnt.
33. It must also be remembered that when the
candle goes out for want of air, it does not do so
because all the oxygen is burnt, but because the
elements of the candle having combined with all the
oxygen of the air, or, as it were, saturated it, there
is no more free oxygen left to keep up the combustion
of the candle.
34. The changes occasioned by chemical action fre-
quently proceed slowly and quietly, but in many cases,
and especially when substances combine together
which have a strong affinity for each other, a great
deal of heat is given out. Sometimes, as soon as two
substances are brought together, they combine di-
CARBONIC ACID GAS IN AIR. 39
rectly, and become very hot ; this is the case in the
slaking of lime ; but it most usually happens that
the mere bringing together of two substances, even
though they have an affinity for each other, is not
sufficient to cause them to combine.
35. In these cases combination cannot take place
until the substances are heated up to a certain point.
Thus, charcoal has a strong affinity for the oxygen of
the air, yet it cannot combine with it whilst both are
cold ; but as soon as a part of the charcoal is heated
redhot, combination commences, and this very act
evolves so much heat that the surrounding parts of
the charcoal soon begin to burn, and thus the com-
bustion, or combination of the charcoal with oxygen,
continues and increases, until either the charcoal is
all burnt, or the oxygen in the surrounding air is
saturated with carbon, and therefore unable to cause
the combustion any more.
36. The common operation of lighting a fire is a
daily illustration of this. The fuel contains carbon,
or charcoal, ready to combine with the oxygen of the
air, but unable to do so, until, by applying a light to
it, we heat a portion up to the point required to com-
mence combination : after which the heat given out
by the chemical action going on, keeps it alight, and
causes the combustion to spread to the surrounding
fuel.
37. The atmosphere is composed chiefly of two
different gases, called oxygen and nitrogen : but
besides this, it also contains a small quantity of a
40 CARBONIC ACID GAS IN AIR.
third gas or kind of air, which is not simple, like
oxygen and nitrogen, but a compound of charcoal
(bj chemists named carbon) with oxygen, and called
CARBONIC ACID GAS (108).
38. It is known that all things containing carbon
will produce a quantity of this gas whilst burning ;
and hence we can have no difficulty in accounting for
its presence in the air. Indeed, we might at first sup-
pose that it must be always increasing in quantity ;
this, however, is not the case, for we always find ex-
actly the same quantity in any portion of air that we
analyze. The cause of this is, that all plants con-
tain substances which have a very strong affinity for
carbon, but which cannot combine with it in its solid
forms, because they are unable to come in contact
with it ; but which, when the carbon has combined
with oxygen and become a part of the air, are able,
in consequence of their having a more powerful at-
traction for it, to seize upon the carbon of the car-
bonic acid gas thus difi'used throughout the air and
cause it to relinquish the oxygen, with which it was
previously combined (697, 708).
39. These facts show us a new use of plants, for
we learn that the objects which we have only admired
for their beauty, or valued for their utility as pro-
ducing articles of food ; that even weeds themselves,
and things we usually consider as wholly useless, are
all constantly, by the agency of attraction or chemi-
cal affinity, decomposing carbonic acid gas, and thus
keeping the air in an uniform and healthy state (745).
VAPOR IN THE AIR. 41
40. The air then always contains a regular propor-
tion of carhonic acid gas, which is constantly pro-
duced by the burning of combustibles, and in many
other ways, and as constantly decomposed by the
action of plants. As we are now only considering
the properties and nature of the air, we will, for the
present, pass over further consideration of carbonic
acid gas, to which we shall shortly return (108) when
studying the nature of carbon, and merely mention
now that it is of the greatest importance to the life
of plants, being the principal source from whence
they derive the carbon necessary for their growth.
41. The air always contains dissolved in it some
water, or rather vapor, which varies in quantity ac-
cording as the air is hotter or colder. When it is
hot, a larger quantity of water is evaporated or con-
verted into vapor, and dissolved in the air, which in
consequence becomes more damp; whilst, on the other
hand, when the air becomes cold, the vapor in the air
is condensed, returning to the state of water, and the
air becomes drier.
42. This, of course, is modijSed according to cir-
cumstances; thus, in dry barren countries, where the
ground contains but little moisture, the air, when it
becomes hot, remains comparatively dry; whilst in
moist or swampy countries, under similar circum-
stances, the air becomes damp from the abundance
of vapor given off; and thus some of the principal
differences of climate depend mainly upon the quan-
tity of water dissolved in the air.
4*
42 WATER.
43. The solution of water in the air may easily be
seen, by observing the steam issuing from the spout
of a teakettle. "When the water boils strongly, and
there is a large volume of steam coming out of the
spout, we observe that just where it comes out, the
steam is almost invisible ; at a little distance it be-
comes white and cloudy, and when it gets further out
into the air it soon disappears and is again invisible.
The reason of this is, that hot steam is quite colorless
and invisible^ like air ; and it only becomes apparent
to us when it is partly cooled by rushing out into the
cold air, and therefore is beginning to condense, and
it would fall to the ground in a shower of little drops
like rain, if it were not dissolved and carried away
by the air, as fast as it issues from the teakettle.
When a large quantity of steam is quickly cooled, as
in escaping from the funnel of a steam-boat, it is con-
densed, and falls in the form of water.
44. The quantity of moisture in the air is also ren-
dered apparent to us, whenever a cold substance is
exposed to it; this cools the vapor in the air so
much, that it is condensed and appears again as water,
in little drops on the cold surface: thus a bottle of
cold water brought into warm damp air, speedily be-
comes covered on the outside with dew, or water thus
condensed from the air.
45/ The substance next in importance to air is
WATER, which exists naturally in three different
states: namely, in the solid state as ice; in the fluid
state in its ordinary condition; and lastly, as vapor
LATENT HEAT. 43
or steam. These three states of water are familiar
to every one, but few are aware what causes the great
difference between them.
46. When ice is placed before the fire, or exposed
to the sunshine, or in any other way warmed, it ab-
sorbs heat, it melts and becomes water; and when
water is heated, it assumes the form of steam or
vapor. The difference between these three forms of
water is entirely caused by the quantity of heat they
contain ; and we may truly say that water is a com-
pound of ice and heat, and that steam is a compound
of water and heat.
47. Although this seems very like chemical action,
it is really quite different, and must not be confounded
with it. Chemical action can only take place between
material substances, or those that have weight; now
heat is not a substance — it is not a thing we are able
to weigh, like all the chemical elements, and conse-
quently when it combines with any substance it only
alters the appearance and outward characters of that
substance, but does not at all change its chemical
properties or nature.
48. When heat is thus combined with a substance,
it is said to be latent (hidden), which means that it is
not sensible to the feel. This will be easily under-
stood from a very simple experiment. If we put some
water in a kettle on the fire, we find that it will soon
begin to feel warm to the hand if immersed in it; the
warmth which we then feel is called free or sensible
heat: but if we put some ice into the kettle in place
44 LATENT HEAT — STEAM.
of water, it will not become warm so soon ; the ice
melts, but the water thus formed will remain ice-cold
until the whole of the ice is melted, because all the
heat supplied to it by the fire is absorbed or combined
with the ice in melting; and therefore as the heat so
absorbed does not make the melting ice any warmer,
it is called latent. When all the ice is melted, the
water will begin to get warm.
49. In the same way heat is absorbed, or rendered
latent, when water is converted into steam. If a
kettle full of cold water is placed on the fire it rapidly
beomes hot until it begins to boil ; but as soon as that
is the case it remains constant at the same tempera-
ture. The fire of course continues to give out as
much heat as it did before, but the water does not
become any hotter ; the only change is that a small
portion of it is converted into steam, and this steam
is not apparently any hotter than the boiling water
itself was. All the heat of the fire, therefore, be-
comes latent, and is combined withr the water in thus
changing it into steam.
50. When steam is condensed, all that heat which
became latent during its formation, is given out again
in the free and sensible form. This fact is well shown
in all stills, in which we see how large a quantity of
cold water is necessary to cool and condense a com-
paratively small quantity of any steam or vapor. If
a gallon of water is converted into steam, the steam
formed will not be sensibly any hotter than boiling
water, yet it contains so much latent heat that, if it is
EFFECTS OF HEAT. 45
condensed into the liquid form again, we shall obtain
a gallon of boiling hot water, and heat enough will
be given out during its condensation to raise seven
gallons more of cold water to the boiling point.
51. The very large proportion of heat which steam
therefore contains in this latent state, shows why
steam is such an excellent means of conveying heat
about from place to place, as in the arrangements
for warming buildings, heating coppers, &c. It is
quite as hot as so much boiling water, and, in addi-
tion, has nearly seven times as much heat thus stored
up in the latent form, which becomes sensible, how-
ever, as soon as it is condensed.
52. The general effect of heat upon substances,
whether solid, liquid, or gaseous, is to expand or make
them larger ; thus whenever we heat a portion of water
or any other fluid, it increases in size : upon this fact
the construction of the common thermometer depends,
which consists of a bulb and tube containing a certain
bulk of mercury, or quicksilver ; when this is heated
it becomes larger, and when cooled, the mercury
shrinks, or occupies less space than it did before.
53. When a substance expands, or becomes larger,
it of course becomes lighter. If ten measures are
expanded by heat to eleven, it follows that ten mea-
sures of the heated substance must weigh one eleventh
less than ten measures of it when cold. For example,
air, when heated, becomes lighter, and consequently
rises, because, becoming larger, it weighs compara-
tively, bulk for bulk, less than the cool air around.
46 WEIGHT OF THE ATMOSPHERE.
54. Air, like water and solid substances, has weight
or gravity ; it presses downwards towards the centre
of the earth ; and, as the bulk of the air is very great,
the whole weight of it pressing on the surface of the
globe must be enormous. It is important to dis-
tinguish between the weight of air, and the weight
of the atmosphere. By means of a light glass globe,
an air-pump, and a good pair of scales, we can
readily ascertain the weight of a cubic foot of air,
and we find that, under ordinary circumstances, it
weighs thirty-one grains.
55. The weight of the atmosphere is, however, the
accumulated weight of many thousand cubic feet of
air, for the air surrounds the earth to a height of
many miles, floating upon its surface, and pressing
downwards in consequence of its weight or gravity.
The weight of the column of air which rests upon
any given space or surface, may be known by the use
of the barometer : and is found to be about two
thousand pounds on the square foot.
56. The barometer consists of a glass tube nearly
a yard long, closed at one end, filled with mercury,
and inserted in a cup of the same heavy liquid. The
height which the mercury stands in the tube, is an
exact measure of the weight of a column of air of
the same size as the diameter of the tube, but as high
as the whole atmosphere. The mercury in the tube
being very heavy, presses downwards, and tends to
fall in the tube ; but the air without, which also press-
es downwards, resting on the mercury in the cup,
WEIGHT OP THE ATMOSPHERE. 47
exactly counterbalances the weight of the mercury
in the tube, and so keeps it from falling.
57. When from any circumstance the weight of the
atmosphere is for a time diminished, it counterbalances
a less weight of mercury, and the column of mercury
in the tube of the barometer falls ; on the other
hand, when the weight of the air increases, the mer-
cury rises. These fluctuations in the weight of the
air are constantly going on with the changes of the
weather, and consequently the barometer is a most
valuable instrument, because it renders evident to us
the changes in the air, which being invisible we should
not otherwise know of.
58. The higher we ascend in the air, either by
going up a hill or by means of a balloon, the less
weight of air shall we have above us, and consequently
the shorter will be the column in the barometer.
Hence the use of that instrument in measuring
heights. The mercury falls about one inch for every
thousand feet as we ascend from the level of the sea.
59. We do not feel the weight of the air at all,
because it presses equally in all directions, and com-
pletely surrounds us. The weight of a column of
air resting on a table four feet square, is about four-
teen tons ; but this weight does not press upon the
table, it is met by a corresponding pressure upwards,
from the air below the table, due to the weight of all
the surrounding air.
60. In moving through the air, therefore, we merely
displace it, or move it aside ; but as we do not disturb
48 FREEZING OF WATER.
this equilibrium, or the equal pressure in all directions,
we do not feel its weight. On plunging the hand
into a pailful of water, we feel very little of its
weight, only in fact that of the small portion which
we displace, because it is much heavier than air is ;
but if we attempt to lift up the whole pailful, we then
feel the weight of the whole bulk of water.
61. Flame seems to ascend in the air ; this is not
because heat has any tendency to ascend, but because
it expands the surrounding air, makes it larger, and
therefore specifically lighter than the cold air is, and
the latter, therefore, displaces it and causes it to rise.
Hot air, though it rises in the air, nevertheless has
weight, though it is not so heavy as cold air. A piece
of cork falls through the air towards the surface of
the earth, it has weight ; yet the same piece of cork
rises upwards through water till it reaches the surface.
As the cork does not fall downwards in water, but
rises upwards, so heated air ascends in the atmosphere;
not because it has no weight or gravity, but merely
because, bulk for bulk, it has less weight than the sur-
rounding cold air. It is for precisely the same reason
that a balloon rises in the atmosphere.
62. It is, in fact, a general rule that, when sub-
stances are heated, they expand; when water is heated,
it becomes larger and lighter, and consequently rises
through the cooler portions above it. Just the re-
verse of this happens when substances are cooled;
they then become smaller and heavier.
63. There is one remarkable exception to this rule
FREEZING OF WATER. 49
in the case of water ; when water is cooled it con-
tracts, and this goes on till very near the freezing
point ; but then the water begins to expand, and in
place of continuing to contract, as all other liquids
do, it becomes larger; this leads to a very important
result in Nature. When the air above the surface of
a lake or pond becomes cold, as towards the end of
autumn, it gradually cools the surface of the water ;
the upper part becoming cold, shrinks, and conse-
quently becomes heavier, it therefore sinks through the
warmer "water. This circulation or gradual sinking
of the cooled water goes on, if the air continues cold,
until the whole of the water is very near freezing,
but then it stops ; because if the surface still goes on
cooling, the water begins to expand, becoming larger
again, and consequently lighter ; the surface, there-
fore, gets colder and freezes, whilst the lower part of
the water remains considerably above the freezing
point. If it were not for this curious fact, water
would continue to become colder, until the whole of
it froze together.
64. In passing from the liquid to the solid state,
some substances contract, such as melted lead, for ex-
ample, whilst others expand; thus ice-cold water, in
freezing, expands very considerably, and therefore ice
is even lighter than the water on which it is formed.
It is for this reason that ice floats on water, and if
the ice did not expand in forming, the curious fact just
mentioned would not prevent lakes and ponds from
freezing entirely, because the ice, if it contracted in
5
5^ FREEZING OF WATER.
forming, would then sink through the water to the
bottom, and thus soon cool the whole mass of water.
65. This expansion of water in the act of freezing,
takes place with immense force, giving rise to the
bursting of water-pipes and vessels full of water, in
cold weather. It is often supposed that this effect is
occasioned by the thaw, and not by the frost. This
is a mistake; the mischief is caused by expansion at
the moment of freezing, though we only discover it
on the approach of warm weather, when the ice begins
to melt. Another, and very important natural result
of this power, is the disintegration or breaking up of
rocks, stones, and soils by frost, during winter. A
few drops of water, in freezing, are able to break
asunder the hardest rocks, and this effect year after
year, gradually destroys them, causing them to crum-
ble down into powder (647).
66. It has already been stated that water is not an
elementary or simple substance; it is a compound,
and consists of two gases. This fact at first seems
incomprehensible, for we can hardly believe it possi-
ble that a hard and solid substance like ice, or a
weighty fluid like water, is composed of colorless
and invisible gas. The difficulty, however, greatly
diminishes when we remember that heat alone, with-
out adding anything to the weight of ice, converts it
into water, and that a little more heat will convert
that water into an invisible colorless vapor; for, as
has already been said (43), pure hot steam is quite
invisible, and only becomes visible to us when partly
COMPOSITION OF WATER. 51
Condensed by the contact of the colder air, which
deprives it of the heat necessary to keep it in a state
of vapor (43, 73).
67. The consideration of these facts makes the com-
position of water appear far less wonderful ; for we
have little difficulty in believing that steam is com-
posed of two gases, and we know that steam, water,
and ice, are, chemically speaking, the same.
68. One element of water is oxygen gas (28), that
part of the air which is so essential to life and com-
bustion : it constitutes eight-ninths of the weight of
ice, water, and steam. One thousand parts of water,
therefore, consist of
889 parts of Oxygen
111 *' Hydrogen
1000 " Water.
69. The other element, or the remaining one-ninth,
is called hydrogen gas, or inflammable air, because
it is very combustible, being the basis of the common
coal gas used for lighting the streets, and entering
into the composition of the inflammable air or fire-
damp of mines, and many other combustible sub-
stances (82).
70. Water is not, like common air, a mere mixture
of two gases: it is a compound, and therefore is quite
different in its properties from either of its two ele-
ments. The very inflammable gas, hydrogen, having
combined with a certain quantity of oxygen, which
62
SEA-WATER.
is the great promoter of combustion, forms water, a
compound which we always regard as the greatest
enemy to fire or combustion.
71. The purest kind of water which occurs naturally
is rain-water, for all others, such as spring, river, or
sea-water, are more or less contaminated or rendered
impure by substances dissolved in them. Thus sea-
water contains, along with other matters, a large
quantity of common salt, which in some places is pro-
cured from it by exposing it in shallow pits to the heat
of the sun : this causes the water to evaporate, and
leaves the salt behind.
72. The composition of sea-water from different
parts of the world is found to vary slightly. The
following table shows the composition of 100,000 parts
of sea-water from the English Channel. (Schweit-
zer.)
Water
96,474
Common Salt
2,706
Chloride of Potassium .
76
Choloride of Magnesium
366
Bromide of Magnesium
3
Sulphate of Magnesia .
229
Sulphate of Lime .
140
Carbonate of Lime
3
Iodine ....
traces
Ammonia
traces
100,000
73. Water may be artificially purified by distil-
lation; when heated and raised into vapor, all the
SPRING-WATER. 53
impurities are left behind, and accordingly condensed
steam is perfectly pure water; there are numerous
contrivances for thus purifying water. The common
still, which consists of a vessel to generate steam in,
and a pipe, passing through a tub of cold water, to
condense the steam, is a familiar example.
74. This explains why rain-water is much purer
than other sorts of water, because when the heat of
the sun evaporates water from the surface of the
earth, all the impurities which it contains are left
behind; and of course when this vapor is cooled and
falls down in the form of rain, it must be very nearly
pure.
75. Springs, which rise from the ground, always
contain earthy matters dissolved in them, which vary
in nature and quantity, with the soil through which
the springs rise. The presence of these impurities
in water in any quantity gives to it that peculiar*
character which is termed hardness. Sometimes
springs contain a small quantity of iron or sulphur,
and other substances, which constitute the many
varieties of mineral waters. These matters, like the
more common earthy impurities, are all derived
from the beds of stone, sand, or clay, through which
the springs rise; because the source of all springs is
rain-water, which, falling pure from the clouds,
becomes contaminated by filtering through the earth,
and collects in holes and cavities, or porous beds
of sand, constituting springs and wells.
5
54 PHOSPHORIC ACID IN WATER.
76. The quantity of saline and earthy matter in
spring-water varies from about 20 grains to 1800
grains in the gallon ; when above 100 grains per gal-
lon, it constitutes a mineral water. The average
quantity in ordinary spring-water is from 20 to 80
grains. The most common salts are Sulphate and
Carbonate of Lime (230), Sulphate, Muriate, and
Carbonate of Potash and Soda.
77. Thames-water contains usually from seventeen
to twenty-four grains of earthy and saline matter per
gallon, and of this at least fifteen grains consist of
carbonate of lime. The same quantity of New River
water contains about nineteen grains of solid matter,
and that of the River Lea nearly twenty-four grains.
The chief constitutent in both these waters is also
carbonate of lime.
78. The proportion of solid matter is almost al-
ways greater in well-water than in that of rivers.
A great number of other substances besides those just
mentioned are occasionally found in mineral springs;
amongst these are silica, alumina, oxides of iron, and
manganese, salts of baryta, strontia, magnesia, am-
monia, &c.
79. The presence of phosphoric acid in some Vaters
has recently been discovered (194). The following
analysis of the deep well-water from below the Lon-
don clay, shows the presence of a considerable quan-
tity of phosphoric acid. Ten gallons of the water
contained five hundred and sixty-four grains of saline
matter, consisting of
HYDROGEN.
Carbonate of Soda
. 116
Sulphate of Soda .
242
Choloride of Sodium
127
Carbonate of Lime
62
Carbonate of Magnesia .
10
Phosphate of Lime
1
Phosphate of Iron .
2
Silica
. . 4
In ten gallons
564^
55
80. Besides these saline and earthy substances,
water always contains atmospheric air dissolved in it.
This is essential to the life of fishes, and to the growth
of water-plants, which could not exist if they were
not thus supplied with common air.
81. Water is essential to the existence of all plants
and animals : it constitutes a large proportion of all
animal and vegetable substances, it is the principal
component of -the blood of animals, and the sap of
plants, and is of the greatest importance, as being
the means of introducing into their systems many
soluble matters, necessary for their healthy growth.
82. Hydrogen, the inflammable element of water,
is a substance of considerable interest ; it is true, it is
never found in Nature in a pure and separate state,
but its compounds are abundant, and some of them
very important ; when pure, hydrogen is an invisible
transparent gas, like the air; very combustible, burn-
ing readily when once inflamed, and remarkable for
being so much lighter than common air, that a thin
bladder, filled with this gas, would rise through the
56 HYDROGEN.
air in the same manner that a bubble of common air
rises through water. Balloons are sometimes filled
with pure hydrogen gas, but more commonly carbu-
retted hydrogen is employed, which, as it consists in
great part of hydrogen, is much lighter than common
air.
83. The most important of its compounds are
water, which is formed by its union with oxygen;
ammonia, a gas which it forms by combining with
nitrogen; and carburetted hydrogen or coal-gas, an
inflammable gas consisting of hydrogen and carbon.
The two latter will shortly come under notice (131,
148).
84. As hydrogen is the lightest gas known, it is
often employed by chemists as a standard of com-
parison in expressing the relative weight of all other
gases. By weighing a thin glass glpbe filled with
hydrogen, and then having pumped that gas out of
it by means of an air-pump, and filled the globe again
with any other sort of gas, a second weighing gives
us the comparative weight or specific gravity of the
gas as compared with hydrogen. Suppose, for ex-
ample, that the globe held exactly ten grains of hy-
drogen and twenty-five grains of the second gas, then
it is plain that the latter is twice and a half as heavy
as hydrogen is; or, that taking equal volumes of both,
that of the gas would weigh twice and a half as much
as the hydrogen would. We should say, then, that
the specific gravity of that gas was 2J or 2.5, taking
hydrogen as the standard of unity.
HYDROGEN. 57
85. The following table shows the weight in grains
of several gases which a bottle containing one hundred
cubic inches, or about three pints, would hold; and
also the specific gravity or relative weight of the same
gases compared to hydrogen, and also to common air,
as a standard : —
Weight in
Specific gravity
Specific gravity
grains of 100
compared to
compared to air,
cubic inches.
hydrogen, taken
as 1000.
taken as 1000.
Hydrogen . . .
2
1,000
69
Common Air . .
31
15,200
1.000
Oxygen ....
34
16,000
1,109
Nitrogen . . .
30
14,000
971
Carbonic Acid Gas
47
22,000
1,520
Ammonia . . .
18
8,500
589
Chlorine . . .
76
36,000
2,470
58
CHAPTER II,
CARBON — NITROGEN — SULPHUR — CHLORINE —
PHOSPHORUS.
86. We now come to the consideration of an ele-
mentary or simple substance, -which has been already
more than once alluded to, namely, carbon or charcoal.
Carbon is the name applied to the pure element, but
common charcoal is so nearly pure, that we may con-
sider the two words as meaning the same thing ; it is
an essential part of all kinds of fuel or combustible
substances, during the burning of which it combines
with oxygen, and forms carbonic acid gas, the sub-
stance before adverted to as always existing in the
atmosphere (37).
87. The forms of carbon which we are accustomed
to see, are almost all black, like common charcoal;
but this is not the case with all the varieties of car-
bon, for we know that the brilliant transparent gem
called the diamond, is really pure carbon, there being
no chemical difference between that gem and common
charcoal.
88. There are many substances in Nature which
exist in two or more different states, presenting very
dissimilar appearances, but being really chemically
COHESION. 59
the same. Thus, chalk and marble are very different
looking substances, but they are composed of precisely
the same elements ; the difference between them is
not caused by heat, like the difference between the
three states of water, but is wholly of a mechanical
nature. The particles composing a piece of chalk are
much smaller than those composing a piece of marble,
which are in fact compound particles, consisting of
many joined together, and hence a piece of marble
appears made of many little grains, whilst chalk is
composed of particles so small that we are unable to
distinguish them, and therefore appears to be a uni-
form substance.
89. The power which holds together the little par-
ticles composing the piece of marble or chalk, or any
other substance, is called cohesion, and this power
varies in strength in different substances ; thus it is
far stronger in marble than in chalk, and hence a
piece of marble requires a much harder blow to break
it, than a piece of chalk. In the same way, we say
that the particles composing the diamond are held
together more firmly by cohesion than the particles
composing a piece of charcoal. Cohesion is, of course,
quite independent of chemical attraction, for it holds
the different particles of a substance together, con-
stituting its mechanical strength ; whilst chemical
affinity binds together particles of two different sub-
stances, forming a compound substance, but does not
in any way affect the strength of the compound to
resist mechanical force applied to it.
60 CARBON IN PLANTS.
90. Under common circumstances, carbon is one of
the most unchangeable things we know ; neither air,
water, nor any of the substances commonly found in
nature, have any action upon it ; and hence the prac-
tice of charring the lower parts of wooden posts, which
are intended to be driven into the ground ; the coat
of charcoal thus formed, protects the wood from decay
for a much longer period than if not charred (882).
When, however, carbon is heated, its chemical affi-
nity for oxygen is greatly increased, and it no longer
appears to be the unchangeable substance which it is
whilst cold.
91. Carbon has been already stated to be a neces-
sary element of plants, which, though so various in
form and color, are nevertheless composed of very
few elements. They consist almost wholly of oxygen,
hydrogen, nitrogen, and carbon, which, by combining
in different proportions, form all the principal parts
of both plants and animals.
92. The greater number of vegetable substances
consist whoUyof oxygen, hydrogen, and carbon; whilst
animal matters mostly contain, in addition to these
three elements, a quantity of nitrogen: some of the
compounds of plants, however, resemble animal mat-
ter in containing nitrogen. When wood is charred,
or decomposed by heat, its elements are separated
from each other; the hydrogen and oxygen combine
together and form water, whilst the carbon is left
behind. When wood is burnt in the open air both
its hydrogen and carbon combine with oxygen, caus-
COMBUSTION. 61
ing flame; the combination of carbon with oxygen
proceeds slowly and steadily, the carbon continuing
to glow until all is consumed ; hydrogen, on the other
hand, being a gas, mixes and combines with oxygen
more rapidly, burning at once, with a flame.
93. All organic substances burn with a flame, and
this alone is a proof that they contain hydrogen,
because under ordinary circumstances the other ele-
ments of vegetable matter could not cause flame ; and
whenever the flame is bright, we are sure that it con-
tains a good deal of carbon, for the flame of pure
hydrogen is very pale indeed, and the brightness of
a flame, such as that of a candle, is entirely due to
the carbon contained in the tallow, which is burned
at the same time with the hydrogen, both combining
with oxygen.
94. As the products of the combustion of a candle
are carbonic acid gas and water, it would be natural
to expect that a cold substance held over the flame of
a candle would take from the vapor of water thus
formed, the heat necessary to its existence in the
state of vapor, and consequently condense it into
the fluid form. This is an experiment which may
very easily be made, for we have only to hold a cold
glass at a little distance above the flame of the candle,
and we shall soon find it lined with a fine dew of
water condensed in this manner.
95. There are several important facts to be ob-
served connected with the combustion of a lamp or
candle. The wax, tallow, or other combustible sub-
6
62 FLAME.
stance, is undergoing decomposition; and its elements,
the combustible substances of which they are com-
posed, are combining with the oxygen of the surround-
ing air to form new compounds; heat is necessary to
both of these two changes, and this heat is evolved
by the very changes themselves.
96. When a candle is lighted a portion of the fuel
is melted, drawn up by capillary action through the
wick, and decomposed and converted into combustible
vapor; this vapor burns as its elements combine
with the surrounding oxygen, and the heat which re-
sults from this chemical action renders the process
continuous, by causing the decomposition of fresh
portions of the tallow, &c., and the consequent pro-
duction of more combustible vapor.
97. In ordinary flame, therefore, several things are
necessary: air and heat are of course quite essential.
The heat evolved by the flame itself, causes a circu-
lation of air (61), provides a sort of natural ventila-
tion, and insures a constant supply of fresh air to
the burning vapors; on the other hand, this circula-
tion of air, by bringing fresh oxygen to the burning
combustible vapors, causes the evolution of heat
enough to insure the combustion of the fresh vapors,
which are about to be given out.
98. Every one knows well how necessary fresh air
is to perfect combustion ; the importance of heat is
not so evident, though it is really quite as essential.
The flame of a candle may be extinguished by a
coil of wire, or by bringing a piece of cold metal in
• FLAME. 63
contact with its outer edge, and is frequently
"snuiFed out" merely in consequence of its being
cooled. A candle, moved quickly through the air,
flares and smokes, and its combustion becomes im-
perfect, because it is cooled.
99. It is a necessary consequence of this fact,
that flame cannot pass through a piece of wire-gauze,
and the miner's safety-lamp merely consists of a lamp
surrounded with a cylinder of wire-gauze. A lamp
thus protected, may safely be taken into an explosive
mixture of air and carburetted hydrogen, the flame
may be put out, the explosive gas may burn within
the cylinder, but the flame cannot pass through the
wire gauze to set fire to the explosive atmosphere
without, because it is too much cooled by contact
with the wire gauze.
100. It is evident that the combustion of a flame
can only take place on its outside, or at that part at
which it is in contact with the air, and, as a necessary
consequence of this, it follows that flame is hollow.
It is only the outside of the flame of a candle that
gives out light, the inside is dark, because no com-
bustion is there going on. In a large flame this is
easily shown, because, as no combustion is going on,
no heat is given out, and consequently the inner
part of such a flame is comparatively cool; a small
piece of wood or paper may be held in the centre of
such a flame, and it will hardly be singed, or a small
spoon containing a portion of gunpowder may be
64 SMOKE.
placed in the centre of the flame, and the powder
■will not be fired.
101. The wick of a common candle requires con-
stant snuflSng, because, being in the very centre of
the flame, it is in fact deprived of two necessary
conditions to combustion, namely, heat and fresh
air ; composition candles with twisted wicks, on the
other hand, do not require snuffing, because, as the
candle burns, the wick constantly twists outwards
towards the edge of the flame; it is thus brought
into the hottest part of it, and at the same time is
supplied with fresh air, which causes it to burn.
102. Smoke is merely combustible matter which
is unable to burn, because it cannot come in contact
with free oxygen, or does not reach it till it is too
cold to burn. The production of smoke from a fire-
place or furnace, may always be prevented, and in
so doing a loss of heat is obviated. A great deal is
often said about the burning of smoke ; this is a very
difficult thing ; it is far more easy to prevent its
formation than to burn it when once formed. It
requires, however, constant care and attention to
prevent the production of smoke ; there is no reason
to doubt that at least nine-tenths of the dense black
smoke which contaminates the air of large towns
might be altogether prevented.
103. Carbon is unable to combine with oxygen at
common temperatures; it requires to be heated before
it can enter into combination with that substance;
but when a compound substance containing carbon is
CARBONIC ACID GAS. 65
exposed to the air, it usually happens that, if the
other elements which it contains combine with oxy-
gen, the carbon also is then able to combine with
oxygen, and forms carbonic acid gas.
104. Thus when a plant dies and decays, its ele-
ments separate and form new compounds ; but the
carbon is not set free in the form of black charcoal
— it is slowly combined with oxygen to form carbonic
acid gas (767).
105. Hence we see that decay is very like burning,
similar effects being produced by both; only that the
change which is effected by combustion in a short
time, and accompanied with a great deal of heat, is
very slowly and gradually effected by decay, very
little heat being at the same time evolved. In both
cases carbonic acid gas is produced.
106. This explains one great use of decaying vege-
table substances in manures ; they, of course, con-
tain carbon, which is slowly combining with oxygen,
and therefore always supplying the growing plants
with carbonic acid gas, which is essential to their
growth, as they, being able to decompose it, thus
obtain carbon (698, 708).
107. Carbonic acid gas is produced in large quan-
tity by the breathing of animals. A constant supply
of fresh air is requisite for the support of life, and
we know that if an animal is prevented from breath-
ing or inhaling fresh air, it will very soon be suffo-
cated. The chemical action which goes on in the
lungs of an animal, is just the reverse of that which
6*
bb ACIDS AND BASES.
takes place in the organs of plants : in the latter
case, carbonic acid gas in the air is decomposed, and
the carbon which it contained is appropriated by the
plant; whilst in the lungs of an animal, carbonic
acid is formed ; for the oxygen of the air is found,
on being expelled from the lungs, to have combined
with carbon, and become converted into carbonic
acid gas. In fact, the process of breathing is very
similar to that of combustion, the same results being
produced in either case (605).
108. Carbonic acid gas is invisible and transparent
like common air, slightly soluble in water, and re-
moj-kable for being much heavier than air, and for
extinguishing flame and destroying animal life ; it is
called an acid, although it certainly is not acid or
sour to the taste, like vinegar and the other common
acids we are acquainted with; it will, therefore, be
proper, before proceeding any further, to explain
why it is called an acid, and in fact what is meant
by that term.
109. There exists in Nature a numerous class of
substances which are called bases; amongst which are
potash, soda, and lime, &c. Now an acid is a sub-
stance that has a strong affinity for these bases, and
which in combining with one of them forms a neutral
compound, possessing none of the properties of either.
110. Some acids are exceedingly sour, and very
corrosive substances, like oil of vitriol, and aqua-
fortis; but when poured upon a base, such as potash
or soda, they combine with it directly, and both the
NATURE OF SALTS. 67
acid and the base lose their caustic and corrosive
qualities.
111. These compounds of acids and bases are
usually called Salts, or saline compounds, and are
very numerous ; for there are many acids, and many
bases. Most of the acids combine with bases in two
or three different proportions, forming sub-salts, neu-
tral salts, and acid, or super-salts. In the sub-salts,
the proportion of acid is not enough to more than
half neutralize the base; in the super-salts it is twice
as much as is required to neutralize the base; and in
the neutral salts, as the name indicates, the acid and
base are combined in single proportionals, or per-
fectly equal quantities (139, 141).
112. There is also a great number of salts called
double salts: these are compounds of two similar
salts; thus there are double sulphates, like alum, the
sulphate of alumina and potash (267) ; and double
phosphates, like the phosphate of ammonia and mag-
nesia (253). These double salts are distinct com-
pounds of the salts of which they consist, and possess
perfectly different properties from either of their
constituents; they may generally be made by merely
mixing together solutions of their two components.
The number of double salts is very considerable, but
there is also an immense number of salts which do
not thus combine together.
113. Acids have a curious property of changing
certain vegetable colors. The greater number of
vegetable blue colors are by acids changed to red,
68 TEST PAPERS.
and this property is therefore made use of by the
chemist, to detect the presence of a free acid ; for this
power of acid ceases immediately, when they are
combined with bases : because their powers are then
neutralized (110).
114. A very common illustration of this change of
color may be seen in the pickling of red cabbage.
Every one knows that red cabbages, as they are called,
are really dark purple or blue, whilst growing, and
they only become red by the action of the acid vin-
egar employed in pickling them; the same effect
would be produced if any other acid was employed.
115. If now we add to some cabbage thus reddened
by acid, a little alkali, either potash, soda, or ammo-
nia, or indeed a portion of any base, the color will
soon be restored to its original blue ; because the
acid is neutralized by the base. And if the base
employed be one of the three alkalies, or their car-
bonates, such as common pearlash, which is the car-
bonate of potash, the solution of cabbage will become
green, because free alkalies, and likewise their car-
bonates, have the power of turning vegetable blues
green.
116. Alkaline solutions have also the property of
turning certain vegetable yellows red, such, for ex-
ample, as common turmeric ; these tests, as they are
termed, are very easily applied, and papers stained
with blue or yellow vegetable colors, are consequently
most useful indicators of the presence either of free
acid, or free alkali, in a solution.
CARBONIC ACID GAS. 69
117. Although carbonic acid, being a gas. is not
perceptibly sour to the taste, like the strong acids
just mentioned, it nevertheless combines with bases,
and in so doing neutralizes, or at least weakens to a
considerable extent, their caustic properties ; but as
it has a far less powerful attraction for bases than
most other acids have, it is very easily expelled from
compounds containing it, by the action of another
acid, which seizes upon the base, and sets the car-
bonic acid gas at liberty.
118. "VVe have already spoken of the conversion of
chalk into lime by heat, in which process the chalk is
decomposed, certain matters being expelled or driven
off, and the lime left caustic. Chalk or limestone is
a compound of carbonic acid gas and caustic lime,
and is called a carbonate of lime (233).
119. The carbonic acid is combined with the lime
by so weak an attraction, that heat alone is sufficient to
expel the acid, together with a small quantity of water
which the chalk always contains. If a piece of chalk
is put into some vinegar, or indeed into any sour
liquid, the chalk will be decomposed, and the car-
bonic acid will bubble through the fluid, until the vine-
gar or other acid is fully combined with lime, and its
acid powers entirely neutralized. The same will
happen with any other carbonate.
120. In consequence of this gas being considerably
heavier than common air (85), it frequently collects
in caverns, cellars, and other similar situations, and
often occasions fatal accidents, suffocating those who
70 CARBONIC ACID.
unfortunately enter the places thus filled with car-
bonic acid. Its presence in such places in the air, in
any quantity, may always be easily ascertained, by
letting down a lighted candle into the well or cellar:
if the candle continues to burn, we know that there
is enough oxygen present to support the life of an
animal ; whilst if the candle is extinguished, we are
certain that the place is full of carbonic acid gas, and
therefore that it must not be entered until the heavy
gas has been dispersed by proper ventilation.
121. Carbonic acid is also evolved in large quan-
tities during the process of fermentation, and occa-
sions the pricking taste and effervescence of cider,
bottled ale, and other liquors. Common ale is allowed
to ferment in open vessels, so that nearly all the car-
bonic acid formed during that process (424) is dis-
persed ; but bottled ale being confined in close vessels
before its fermentation is completed, much of the
carbonic acid evolved subsequently is pent up in the
liquor, and escapes from it in innumerable small
bubbles, when the cork of the bottle is removed.
122. Carbonic acid, then, is constantly being form-
ed in several different ways ; it is produced during
the combustion of all substances containing carbon,
during the respiration of animals, during the decay
of almost all vegetable and animal substances, and
during the process of fermentation. It is likewise,
in many situations, naturally given out by the earth
in large quantities.
123. To counterbalance all these sources of in-
CARBONIC ACID. 71
crease, there is only the power of plants already
mentioned of decomposing it, by abstracting its
carbon and setting free the oxygen again (106, 698,
710, 745).
124. When two substances combine together and
form a compound, they unite in definite and invari-
able proportions. A given weight of carbon, in burn-
ing, always combines with a uniform quantity of
oxygen, to produce a certain weight of carbonic acid
gas ; and this rule holds good in all cases of chemi-
cal combination, for it is one of the distinctions
between mixture and combination, that we are able to
mix two substances together, in any relative propor-
tion we like ; but we are only able to make sub-
stances combine in certain fixed proportions.
125. Compounds do not always consist of equal
parts of their elements, for they can consist of one
part of one element, and one, two, three, or more parts
of another element; and, indeed, there can frequently
be formed several difi'erent compounds, by the union
of two elements in various proportions. When, how-
ever, we mix together two substances which can unite
together, they always combine in one of these fixed
proportions; and if there is more of the one element
than is requisite to form the compound, it is left un-
altered.
126. Thus we know that every six grains of car-
bon, or pure charcoal, require sixteen grains of oxy-
gen to burn them perfectly, and convert them into
carbonic acid ; and exactly the same quantity will be
72 CARBONIC OXIDE.
required whether the carbon is burnt in a few seconds,
or slowly combined with oxygen by the gradual pro-
cess of decay. If we were to try to combine six
grains of carbon with twenty grains of oxygen, we
should find that only sixteen grains of the oxygen
would combine with the charcoal, and the remaining
four grains of oxygen would be left unchanged.
127. When we try to burn charcoal so that it shall
get less oxygen than is requisite to convert it into
carbonic acid, we find that it is possible to do so, but
that the gas produced is not carbonic acid. Carbon
and oxygen are able to combine together in more
than one proportion ; and consequently, though
when carbon is burnt in the air, or where it can get
abundance of oxygen, it always forms carbonic acid,
yet when burnt so that it cannot combine with a suffi-
cient quantity of oxygen to form that gas, it forms a
different compound containing less oxygen, which is
called carbonic oxide.
128. This compound is a transparent colorless
gas, like carbonic acid, and resembles it also in being
totally unfit to support animal life; indeed, it appears
to be far more dangerous than carbonic acid when
taken into the lungs, even though considerably di-
luted with common air. It extinguishes flame, as
might be expected, but it is itself combustible, burn-
ing with a pale blue flame, and at the same time is
converted into carbonic acid, in consequence of
having acquired more oxygen from the air in which
it has burnt.
OXALIC ACID. 73
129. We frequently see on the top of charcoal or
coke fires a pale blue flame, quite different in appear-
ance from the usual bright flame of wood or coal ;
this is occasioned by carbonic oxide, which is formed
in the midst of the mass of burning fuel, where the
carbon, being unable to get enough oxygen to form
carbonic acid, produces this gas, which, when it
reaches the top of the fuel, meets with fresh air, and
combines with a further quantity of oxygen. When,
however, a charcoal fire is burning slowly, a quantity
of carbonic oxide escapes into the air without being
burnt into carbonic acid ; and its poisonous nature is
often shown, when persons have foolishly placed a
pan of burning charcoal in a close bedroom. The
charcoal is not only abstracting the oxygen of the
air, and converting it into carbonic acid, which can-
not support life, but is also forming quantities of the
highly poisonous gas, carbonic oxide, the presence of
which in a room, in any considerable quantity, is sure
to destroy life.
130. Besides these two compounds of carbon, there
is yet a third, intermediate in composition between
carbonic oxide and carbonic acid, though very differ-
ent from either in its properties ; this substance is
oxalic acid, a strong, and very poisonous acid. Oxalic
acid occurs in many plants, and may be easily form-
ed artificially (503); it is a white solid substance,
soluble in water, in which it forms a very sour solu-
tion ; and has a strong affinity for bases. It has
never been formed direct from carbon and oxygen.
7
74 CARBURETTED HYDROGEN.
131. Although when carbon burns in the air it
only combines with oxygen, it can, under some cir-
cumstances, combine with nitrogen and also hydro-
gen. Thus when vegetable matters decay under
water, we find that a gas is given off in bubbles
which consist of hydrogen and carbon, and is there-
fore called carburetted hydrogen.
132. This gas is, as may be supposed, inflamma-
ble; burning in the air with a tolerably bright flame,
and forming, by the combustion of its two elements,
water and carbonic acid. This gas is found in very
large quantity in coal mines, where it is called fire-
damp, and occasions violent explosions, when a light
is incautiously brought into a mixture of it and com-
mon air.
133. In these cases the gas is mixed with a quantity
of atmospheric air, but the affinity of the carbon and
hydrogen, of which it consists, for the oxygen of the
air, is not powerful enough to cause combination.
"When, however, a lighted candle or lamp is brought
into the mixture, that part is immediately raised to
the temperature at which combination can take place,
the mixture takes fire, the flame spreads with very
great rapidity, and in a few seconds the mixed gases
are changed from air and carburetted hydrogen, into
carbonic acid gas, steam, and nitrogen. At the mo-
ment of explosion the gases are very greatly expanded
by the heat of the flame, and subsequently they are
suddenly condensed, as the steam is cooled and con-
verted into water. Carbonic acid and nitrogen alone
CARBURETTED HYDROGEN. 75
being left, many of the dreadful accidents which
occur in coal mines are less caused by the violence of
the explosion, than by the suflfocating effects of the
after-damp, as the foul air left in the mines after the
explosion is termed.
134. There are also many other compounds of car-
bon and hydrogen, in which different proportions of
the two elements give rise to a great variety of differ-
ent substances: one of the most important of these is
the common coal gas, obtained by distilling or roast-
ing coals in close iron vessels, and which is used for
lighting the streets; it differs from the fire-damp of
mines, in containing rather more carbon. India-rub-
ber, gutta-percha, coal-tar naphtha, oil of turpentine,
&c., are also compounds of carbon and hydrogen.
135. In expressing the composition of any sub-
stance, chemists are in the habit of saying that it con-
sists of such and such proportions of its elements;
whatever quantity they may have taken for analysis,
they generally calculate the proportion which a hun-
dred or a thousand parts would consist of. Thus, for
example, 550 grains of pure carbonate of lime contain
308 grains of lime, and 222 grains of carbonic acid;
hence 1000 grains must contain 560 grains of lime,
and 440 grains of carbonic acid ; and 100 grains of
carbonate of lime contain bQ grains of lime, and 44
grains of carbonic acid.
136. This is a very sini^le example, but it con-
stantly happens that the composition of substances is
not so easily expressed. 1000 grains of dry gypsum,
or sulphate of lime, consist of 412 grains of lime, and
76 DEFINITE PROPORTIONS.
588 grains of sulphuric acid. The composition of
100 grains of such a suhstance is represented thus : —
Lime 41.2
Sulphuric Acid . . . . . 58.8
This merely means that one hundred grains contain
41 and two-tenths of a grain of lime, and 58 and eight-
tenths of a grain of sulphuric acid : hence there is no
real difference whether we put the dot or not : if it
is used, the figures behind are known to be fractions ;
if not they are whole grains.
137. Sulphate of lime may be expressed either as
Lime 0.412 4.12 41.2 412
Sulphuric Acid 0.588 5.88 58.8 588
1 grain. 10 grains. 100 grains. 1000 grains.
In all the analyses given in the following pages, no
fractions are used ; the composition of everything is
given as it would be obtained if 10,000 or 100,000
grains were analyzed.
138. Chemists are constantly in the habit of speak-
ing of atoms, proportions, combining numbers, and
similar terms ; it will be well briefly to describe what
is meant by these words. It has been already stated
that the composition of all compound substances is de-
finite (124); that a certain weight of carbon, for ex-
ample, can only combine with a fixed quantity of
oxygen, to form carbonic «-cid (126).
139. Let us observe what relation there exists be-
tween the quantity of different substances which can
COMBININa WEIGHTS. 77
combine together. It is found that one grain of hy-
drogen (for hydrogen, thaugh a gas, can be readily
weighed) will combine with eight grains of oxygen, to
form nine grains of steam, and this relative propor-
tion between the two elements of water is perfectly
invariable. One grain of hydrogen can combine with
exactly sixteen grains of sulphur, to form seventeen
grains of sulphuretted hydrogen (182), a compound
shortly to be described, or, with six grains of carbon,
to form seven grains of carburetted hydrogen (131).
140. These numbers, then, express the quantity of
each of these substances which can combine with one
another, for, of course, it is perfectly the same whether
we take a grain, an ounce, a pound, or any other
weight. But this is not all ; the number thus found
for carbon, namely six, is not merely the quantity of
that substance which could combine with one of hy-
drogen, but represents the quantity of carbon which
can combine with eight parts of oxygen, to form car-
bonic oxide (127), or twice eight, 16, parts of oxygen
to form carbonic acid ; and, again, eight parts of
oxygen is not merely the quantity which can combine
with one part of hydrogen, or with six parts of carbon,
but is exactly the quantity which is able to combine
with a definite proportion or equivalent, of any other
substance.
141. The numbers which are in this manner ob-
tained, are called combining weights, proportionals,
equivalents, &c, ; they express the relative proportions
in which substances combine together. Some com-
7*
78 COMBINING WEIGHTS. '
pounds consist of a single proportional of each of
these elements, but more commonly they contain one
of one element, and two, three, or more of the other;
of-ganic substances, for the most part, consist of
nearly ten or a dozen proportionals of each of their
elements (316, 369).
142. The following table shows the proportions or
combining weights of the most important simple sub-
stances.
Oxygen 8
Hydrogen 1
Carbon * 6
Nitrogen . . . . . . . 14
Chlorine 35
Phosphorus 31
Sulphur . . . . . . .16
Iron 27
143. When a compound is formed by the union of
two elements, the equivalent or combining proportion
of the compound is exactly the sum of the equivalent
of its elements; thus, for example, carbonic acid con-
sists of one equivalent of carbon, the number of which
is 6, and two equivalents of oxygen, weighing 16 ; the
sum of 6 and 16, is 22 ; this, then, is the equivalent
of carbonic acid, the quantity which will combine with
an equivalent weight of any base, for example, with
28 parts of lime, 47 of potash, and so on.
144. In the following table the combining weight
of some of the most important compounds is exhi-
bited : —
NITROGEN. 79
Water . . . . . . .9
Nitric Acid 54
Carbonic Oxide 14
Carbonic Acid 22
Sulphurous Acid 32
Sulphuric Acid .40
Phosphoric Acid 71
Muriatic Acid .*.... 36
Sulphuretted Hydrogen . . . ,17
Carburetted Hydrogen .... 8
Ammonia 17
Potash 47
Soda 31
Lime ^28
Magnesia 20
Silica 46
Alumina .51
Prot-oxide of Iron 35
145. When plants or vegetable substances consist-
ing of oxygen, hydrogen, and carbon, decay, their
elements form new compounds, the principal of which
are carbonic acid and water. We must now consider
what are the products resulting from the decay of
animal matters, and of those vegetable substances
which, like them, consist of oxygen, hydrogen, car-
bon, and nitrogen; these are water, carbonic acid,
and ammonia.
146. Nitrogen or azote differs from most other
substances in appearing to be remarkably inert; it
seems to have little or no affinity for any other sub-
stance. It is always mixed with oxygen in the air, but
it appears to have no inclination to combine with it ;
80 AMMONIA.
and when carbon, or substances containing it, are
burnt, they combine only with the oxygen, and never
with the nitrogen of the air : so that it would appear
as if the chief use of nitrogen in the air was to dilute
the oxygen, and prevent it from combining too ra-
pidly with carbon, and other substances.
147. Under some circumstances, however, nitrogen
does combine with other elements, and its compounds
are amongst the most curious and important sub-
stances we know. When animal or vegetable matters
containing nitrogen decay, we find that it, like the
carbon, is not set free in its simple and uncombined
form, but that during decay it combines with a por-
tion of hydrogen.
148. Therefore, in addition to water and carbonic
acid, the two principal substances arising from the
decay of ordinary vegetable matters, we find a pun-
gent, strong-smelling gas, composed of nitrogen and
hydrogen, which is called Ammonia.
149. This substance, though a transparent invisible
gas, is, like potash and soda, a base; like them it has
a strong affinity for acids, and when combined with
them neutralizes their powers; and, therefore, as it is
evolved at the same time with carbonic acid, it com-
bines with that acid and produces a solid salt, which
is called a carbonate of ammonia, just as the com-
pound of carbonic acid <ind lime is called a carbonate
of lime.
150. Ammonia is always produced when animal or
vegetable substances containing nitrogen are decom-
AMMONIA. 81
posed, whether by combustion or by decay ; in both
these cases carbonate of ammonia is formed, which is
a very volatile salt, and consequently is carried away
by the air, as fast as it is formed. Now water ab-
sorbs large quantities of ammonia, which, as well as
all its compounds, is easily soluble in that fluid ; and
consequently the ammonia and salts of ammonia,
formed during these processes of decomposition, are
never retained in the air, but are dissolved and brought
down to the surface of the earth, by rain.
151. Ammonia was formerly called the volatile
alkali, because in many properties it closely resembles
the alkalies potash and soda, which are distinguished
from all other bases, by that name. Ammonia, how-
ever, differs from the two other alkalies in being a
gas, whilst they are both solid, and almost all its
compounds are more or less volatile, or capable of
being converted into vapor by heat ; whilst the com-
pounds of potash and soda are all fixed, or quite in-
capable of being raised into vapor by any ordinary
application of heat.
152. Ammonia has also a less powerful affinity for
acids than the two other alkalies have, and conse-
quently it is easily expelled from its compounds, by
either potash or soda, as well as by lime and several
other bases, which set free the ammonia in the gas-
eous form, and unite themselves with the acid pre-
viously in combination with the ammonia.
153. Ammonia, in its pure state, is a colorless, in-
visible, and very pungent-smelling gas, readily soluble
82 CARBONATE OP AMMONIA.
in water ; like potash and soda, it has a very strong
affinity for acids, and is, therefore, hardly ever met
with in its free state, but always in combination with
carbonic, or some other acid. It is far less abundant
or common than the other alkalies, potash and soda;
for its principal source is the decay of animal and
vegetable substances, which contain nitrogen.
154. The most important of the salts of ammonia
are the carbonate, the muriate, the sulphate, and the
phosphate: the carbonate, which is the salt produced
during the decay of organic matters, was formerly
called salt of hartshorn, because it was mostly pro-
cured by burning horn; it is now, however, obtained
from the tar-water and refuse ammoniacal liquors of
the gas-works. A considerable quantity of ammonia
is formed during the distillation of coal, which always
contains a little nitrogen, and, therefore, gives off a
small quantity of ammonia ; this combines with a por-
tion of the carbonic acid formed by the burning of
the carbon of the coal, and collects in the hydraulic
main, or first condenser, of the gas-works; hence, also,'
carbonate of ammonia is always an ingredient of
soot.
155. Carbonate of ammonia is not obtained direct
from the gas liquor, as it would then be impure from
the tar, and other substances which exist in the gas-
water. The ammoniacal water is generally first con-
verted into a sulphate or muriate, and this is decom-
posed by heating it with chalk ; carbonate of ammonia,
which is volatile, rises in vapor, whilst sulphate or
MURIATE OF AMMONIA. 88
muriate of lime is left. Carbonate of ammonia pos-
sesses the peculiar pungent smell of pure ammonia,
though far less powerfully ; because, being but partial-
ly neutralized by carbonic acid, and united to it by
but a feeble affinity, it is constantly gradually escap-
ing from its compound, and evaporating into the air.
Like the carbonates of potash and soda it possesses
the property of reddening many vegetable yellows,
though less powerfully than the pure alkali.
156. The muriate of ammonia, commonly called
sal-ammoniac, which used also formerly to be obtained
by burning animal substances, is now procured from
the refuse of the gas-works, which contains carbonate
and other salts of ammonia. They are first of all
converted into a sulphate, by the action of oil of vitriol,
which expels the carbonic and other weaker acids;
and the sulphate thus obtained is decomposed by mix-
ing it with coQimon salt, and heating the mixture.
157. The nature of this operation is very simple.
Sulphate of ammonia, water, and common salt, or
chloride of sodium, are heated together, and are de-
composed, because sulphuric acid has a stronger affi-
nity for soda than it has for ammonia ; a portion of
water is decomposed at the same time with the salt,
supplying oxygen to the sodium to form soda, and
hydrogen to the chlorine to form muriatic acid ; the
former unites with the sulphuric acid, whilst the latter
combines with the ammonia.
158. Muriate of ammonia, like many other of the
salts of ammonia, is volatile at a certain heat ; that
84 MURIATE OF AMMONIA. ^
is to say, it becomes a vapor, and resumes the solid
form when cooled again : in the process for obtaining
the muriate of ammonia, therefore, it is converted into
vapor by the heat applied to the mixture, and is con-
densed in the solid form again in the upper part of
the vessel in which it is heated, which is kept cool on
purpose. The uses of sal-ammoniac in the arts are
numerous ; its principal consumers are the dyers and
workers in metals.
159. Ammonia has a strong affinity for sulphuric
acid; the sulphate may either be formed directly by
mixing together sulphuric acid and caustic ammonia,
or its carbonate, as in the process just described for
preparing the muriate from gas liquor ; or it may be
obtained by substituting for the sulphuric acid, added
to the gas liquor, a sulphate in which the acid is held
by a less powerful affinity than that which it has for
ammonia ; when this is done, the ammonia seizes the
sulphuric acid and causes it to relinquish the weaker
base with which it was previously combined, and which
thus unites with the carbonic acid, of the carbonate
of ammonia.
160. When, for example, a solution of carbonate of
ammonia is mixed with a quantity of sulphate of lime,
they are both decomposed ; the ammonia combines
with the sulphuric acid, and the lime takes the car-
bonic acid. Sulphate of ammonia has a strong saline
taste, but no smell : it is a perfectly neutral salt, and
may be kept any time without undergoing change. It
is readily soluble in water.
PHOSPHATE OF AMMONIA. 85
161. Phosphate of ammonia may be formed by
adding a solution of ammonia, or its carbonate, to
phosphoric acid (194); it is very soluble in water,
and decomposes when heated, the ammonia passing
off in the gaseous state, and leaving the phosphoric
acid pure. A rough salt may be made by mixing
the impure phosphoric acid obtained by acting on
bone, earth, by oil of vitriol, with gas liquor, and
evaporating the solution ; it is then, however, apt to
contain lime, tarry matter, and other impurities. It
is sometimes employed as a manure (793).
162. Ammonia often seems to combine with sub-
stances for which it really has no affinity : this is
merely a mechanical effect. Such substances have
the power of absorbing a large quantity of the gas,
which is condensed or packed up in the pores of the
substahce, but not combined with it, and is ready to
be given off again on the application of heat. Thus,
freshly burnt charcoal, and, indeed, most porous
substances, absorb or condense a large volume of this
gas. The value of charcoal as a disinfecting agent,
and purifier generally, chiefly depends upon this
power of absorbing gaseous matter. But it also
possesses bleaching powers.
163. Ammonia is not the only compound contain-
ing nitrogen, which is formed during the decomposi-
tion of animal substances ; for although nitrogen and
oxygen appear to have no affinity for each other, as
they exist together in a state of mixture in the air,
and do not enter into combination, yet when a com-
8
86 NITRIC ACID.
pound already containing nitrogen is decomposed, we
find that, besides the compound of nitrogen and
hydrogen just described, a compound of oxygen arid
nitrogen is also in some cases formed, which is pos-
sessed of very extraordinary powers, being a strong
acid, and commonly called aqua-fortis, or nitric
acid.
164. Nitrogen is able to combine with oxygen in
five difi^erent proportions, giving rise to as many dis-
tinct substances ; four of these are of comparatively
little importance, and may therefore here be passed
over; the fifth, or that containing the greatest quan-
tity of oxygen, is the only one at present worthy of
consideration.
165. Nitric acid is never found in its free or un-
combined state, but always in combination with some
base; being a very powerful acid, it is easy to under-
stand that, as soon as formed, it seizes upon some
base to combine with, and forms a neutral salt. The
commonest salts containing nitric acid, or nitrates, as
they are called, are the nitrates of potash, soda, and
lime, which are found native abundantly in dijfferent
places.
166. The nitrate of lime is very frequently to be
met with on old walls, near which organic substances
containing nitrogen have decayed and formed nitric
acid, which has combined with the lime of the mortar;
and in the same way nitrate of lime may be formed
artificially, by mixing lime with decaying substances
which can yield the acid, and, after having allowed
NITRIC ACID. 87
them to remain some time together, by pouring water
over the mixture : this dissolves the nitrate of lime,
and forms a solution, which leaves the salt in ques-
tion, when the water is evaporated by heat.
167. Although nitric acid is a very strong acid,
and has a very powerful affinity for bases, yet there
are even more powerful acids, which are strong enough
to expel it from its combinations, and we are thus
able to procure the pure acid: this is usually done by
what is called oil of vitriol, or sulphuric acid (179),
a substance consisting of sulphur, or brimstone, com-
bined with oxygen. When this acid is poured on a
nitrate, it expels the nitric acid in the form of a
very acrid or sour and biting vapor ; this, condensed
in cold water, constitutes the intensely sour liquid
called nitric acid, or aqua-fortis, and was before com-
bined with the base of the nitrate.
168. Nitric acid acts very strongly on all organic
bodies, decomposing them sometimes with great vio-
lence, and causing their elements to enter into new
combinations: thus when strong nitric acid is mixed
with oil of turpentine, it sets it on fire. This is
caused by the large quantity of oxygen which nitric
acid contains, which enables it to burn substances, or
at least makes them combine rapidly with oxygen,
which we know is the cause of ordinary combustion.
169. When we mix nitric acid with substances
which, having a strong affinity for oxygen, are able
to decompose the acid, we obtain some of the other
compounds of nitrogen and oxygen before alluded to,
88 SULPHUR.
and by various processes we are able to obtain com-
pounds of nitrogen, with most other elements, setting
out with this acid as a source of nitrogen ; for it
seems that nitrogen hardly ever will combine with an
element, except when in the nascent state ; that is,
when being evolved or set at liberty by the decom-
position of a substance, in which it was already com-
bined with some other element (769).
170. There are three other elements deserving
notice, which, like nitrogen, are of little interest in
themselves, but which, by combining with other sub-
stances, form important compounds; these are sul-
phur, chlorine, and phosphorus.
171. The properties of sulphur, or brimstone, are
familiar to every one; it occurs native, both pure
and also in combination with various metallic sub-
stances ; entering into the composition of many ores,
such as those of copper, lead, zinc, mercury, &c.
Sulphur is a pale-yellow, solid substance, insoluble in
water, having hardly any taste, but a faint and pecu-
liar smell, melting easily when warmed, and catching
fire very readily, burning with a pale-blue flame, and
giving out at the same time a peculiar and very dis-
agreeable smell. The compounds which sulphur
forms with oxygen, and also with hydrogen, are the
principal which demand attention.
172. Sulphur, like nitrogen, is able to combine
with oxygen in several proportions, and hence it
forms several distinct compounds. It is only neces-
sary to describe two of them — sulphurous acid, and
sulphuric acid or oil of vitriol.
SULPHUROUS ACID. 89
173. When sulphur is burnt in the air, it forms sul-
phurous acid, a transparent, invisible gas, possessing
a very strong and suffocating smell ; it is easily dis-
solved by water, and the solution then obtained has
a strongly sour taste.
174. A portion of sulphurous acid is formed when-
ever we light a common brimstone match ; and the pecu-
liar suffocating smell then perceived is occasioned by
this acid, and not by the sulphur alone, which has no
smell, but which is used to tip the matches because it
has a strong affinity for oxygen, and requires less
heat to enable it to commence combination than the
wood itself; but when it has once fairly got alight,
it then produces heat enough to fire the wood.
175. Sulphurous acid is a transparent gas, rather
heavier than common air, readily soluble in water,
very poisonous when breathed, and extinguishing the
flame of combustible matters ; it does not form any
important compounds when combined with bases, and
its principal interest consists in its bleaching powers.
It has long been used to destroy color in things
desired to be bleached, which are merely hung up
over some burning sulphur, and exposed to the fumes
of sulphurous acid thus formed. Articles thus bleached,
however, frequently retain an unpleasant smell of
sulphurous acid.
176. It is likewise used in fumigation, being con-
sidered destructive of contagion ; and, therefore, sul-
phur is burnt in houses where persons have died of
an infectious disorder, and in other circumstances
8*
90 SULPHURIC ACID.
"where evil effects are feared from the communication
of disease. In all these cases sulphurous acid has
really a useful influence, as it seems able to destroy
a minute quantity of poisonous matter diffused through-
out the air ; but it must be remembered, that it can
have no power of improving air which is unwholesome,
in consequence of the presence of a large quantity of
carbonic oxide or carbonic acid, for in these circum-
stances, burning sulphur would only tend to make
the air worse, both by removing oxygen, and also by
adding sulphurous acid.
177. The bleaching power of this acid may be very
well shown, by holding a lighted brimstone match
near a dark purple or blue flower, the color of which
will be immediately more or less destroyed, and we
may easily thus, either in part or wholly, render the
flower white.
178. Sulphurous acid contains less oxygen than the
sulphuric acid; in fact, it stands in the same relation to
that acid, which carbonic oxide does to carbonic acid.
Sulphurous acid is formed whenever sulphur is burnt
in the air, because, under those circumstances, it is
not able to combine with enough oxygen to form the
more powerful acid.
179. Sulphuric Acid is made by burning sulphur
mixed with nitrate of potash, which supplies it with
more oxygen than it could get by merely burning in the
air ; because the nitric acid in the nitre, when decom-
posed by the burning sulphur, gives rise to the forma-
tion of another compound of nitrogen and oxygen co»-
SULPHURIC ACID. 91
taining less oxygen, called nitrous acid, a substance
which is decomposed by sulphurous acid, when water
is present ; giving up a portion of its oxygen to the
sulphurous acid, and converting it into the sulphuric.
In fact, when sulphur is thus burnt, and the fumes
produced by its combustion are condensed in cold
water, a very acid liquid is formed, which is called
oil of vitriol, or sulphuric acid.
180. It is a heavy, very corrosive, poisonous fluid,
although its elements are only oxygen and sulphur,
the one being that part of the air necessary to sup-
port life, and the other a tasteless, yellow, solid sub-
stance. Sulphuric acid in its free state is chiefly re-
markable as being one of the strongest acids we know,
destroying vegetable and animal substances: that is
to say, abstracting and combining with some of their
elements, and causing the others to enter into new
combinations ; and having a strong afiinity for bases,
with which it forms a class of compounds called sul-
phates : some of these are of very great importance,
and must be considered hereafter (159, 213, 224, 237.)
181. Sulphuric acid is a most valuable substance
to the chemist ; being one of the strongest known
acids, it enables him to expel or drive out most other
acids from their combinations, and thus through its
agency many other acids are obtained pure and sepa-
rate, from their compounds with bases (167, 188, 195).
182. Under certain conditions sulphur combines
with hydrogen to form sulphuretted hydrogen — a
transparent colorless gas, remarkable for the exceed-
92 SULPHURETTED HYDROGEN.
ingly disagreeable smell which it possesses. It is to
the presence of this gas the nauseous, disgusting smell
of putrefying animal matter is due. Sulphuretted
hydrogen is very poisonous, and it would probably
cause many fatal accidents, were it not that its of-
fensive odor warns us of its presence, and induces
us to take measures to disperse it by ventilation and
other means.
183. Sulphuretted hydrogen is soluble in water to
a considerable extent, and the solution possesses the
strong and nauseous smell of the gas itself. The gas
is inflammable, and in burning produces water, and
sulphurous acid gas. Sulphuretted hydrogen has
sometimes been called an acid, for it possesses feeble
acid powers, combining with some bases and to a
certain extent neutralizing them.
184. Sulphur has a strong affinity for most metallic
substances forming a numerous series of compounds,
which are called sulphurets : many metallic ores
are sulphurets, and in the process by which the
metals are obtained, the first operation consists in
roasting the ores, or exposing them to a dull red heat,
when the sulphur, being a volatile substance, is grad-
ually driven off.
185. Chlorine is an element which is never found
free, but only in combination with some other element;
it is a very poisonous gas, causing very great irritation
when breathed, even though it is largely mixed with
air ; it is transparent, has a bright-yellow color, and
is remarkable for possessing in a very great degree
CHLORINE. »3
the power which sulphurous acid has, of bleaching or
destroying colors, and also contagious matters. Chlo-
rine is, therefore, now largely used in all cases where
it is wished to destroy or remove color: it is however,
a very powerful agent, and therefore must be used
with great care, as otherwise if linen, for example,
be bleached carelessly by means of it, the texture is
destroyed, and the linen becomes rotten and useless.
Common writing-paper is often found to be quite
decayed aad useless, the rags from which it was
made having been too strongly bleached with chlorine.
186. Small quantities of this gas are used with very
beneficial effects in removing foul smells, and other-
wise rendering sweet and wholesome the air of large
buildings, such as hospitals. Chlorine readily com-
bines with the metals, and most other of the elements,
to form a series of compounds called chlorides ; thus
corrosive sublimate is a chloride of mercury, &c. It
is unnecessary for us further to occupy ourselves with
this element than to know that when combined with
hydrogen it loses all these peculiar powers, and forms
a strong acid, the muriatic, which, by combining with
bases, forms a series of salts called muriates.
187. When chlorine and hydrogen are mixed to-
gether in equal volumes, an explosive mixture is form-
ed, which, on the application of a flame, detonates
loudly, and is converted into muriatic acid gas. An
explosion is also caused if the mixture is exposed in
a glass vessel to sunshine, but if kept in the dark, no
combination takes place; if merely exposed to day-
94 MURIATIC ACID.
light, but not to the direct rays of the sun, the gases
do not explode, but combine slowly and quietly.
188. The process by which muriatic acid is procured
is very simple: a quantity of oil of vitriol or sulphuric
acid is poured on some common salt, acid fumes arise,
they are made to pass through cold water, which ab-
sorbs them, and in time a very sour corrosive liquid
is obtained, which is the muriatic acid, or the spirit
of salt of the shops. In order to explain the action
which takes place in this process, it is necessary to
say a few words respecting the nature of common
salt.
189. Common salt is a compound substance, con-
sisting of two elements; the one is chlorine, the cor-
rosive yellow-colored gas just described, and the other
is a white silvery-looking metal called sodium, a sub-
stance having a very strong aflSnity for oxygen, eager-
ly combining with it and forming the alkali soda
(216).
190. The substances, then, concerned in the process
for making muriatic acid, are common salt, or, to
speak scientifically, chloride of sodium, sulphuric acid,
and of course a portion of water, as oil of vitriol is a
solution of dry sulphuric acid in water. Both the
chloride of sodium and the water are decomposed, the
oxygen of the water combines with the sodium of the
salt, whilst the hydrogen of the water combines with
the chlorine of the salt, and thus soda and muriatic
acid are formed ; the latter is given off or expelled in
the form of gas or vapor, whilst the soda combines
IODINE. 95
■with the sulphuric acid to form a neutral salt — the sul-
phate of soda. This is a very good example of com-
bination and decomposition. In consequence of the
powerful affinity which sulphuric acid has for soda,
both the salt and water are decomposed; and the
chlorine and hydrogen being free from their combi-
nations, unite together to form muriatic acid (216).
191. Chlorine is procured from muriatic acid by
the action of some substance capable of abstracting
its hydrogen; the most convenient for this purpose
are those which contain much oxygen. The usual
process is to heat together a mixture of muriatic acid
and oxide of manganese, a substance which is rich in
oxygen ; the oxygen which is thus given off, takes the
hydrogen of the muriatic acid, with which it forms
water, and sets free the chlorine.
192. Another and yet cheaper process is to heat a
mixture of common salt, oxide of manganese, and sul-
phuric acid ; in this case the sulphuric acid decom-
poses the salt, and the muriatic acid formed, is decom-
posed as fast as it is set free, by the oxygen of the
oxide of manganese.
193. Iodine, bromine, and fluorine, are substances
hitherto undecomposed, and therefore called elements,
which in many respects resemble chlorine ; like it,
they form acids by combining with hydrogen, and
unite to the metals to form a numerous series of com-
pounds resembling chlorides, which are called iodides,
bromides, and fluorides. None of these substances are
of much importance ; those most deserving of notice
are the iodide of sodium, which exists with the chlo-
96 PHOSPHORUS — PHOSPHORIC ACID.
ride in sea-water, and the fluoride of calcium, which
exists in small quantity in the bones of animals.
194. Phosphorus in several respects resembles sul-
phur ; like it, it is a readily fusible and very combus-
tible solid. It is of a white color, about as hard as
wax, and has so strong an affinity for oxygen that it
takes fire in the air with the greatest facility as soon
as it is a little warmed. Like the preceding element,
chlorine, it is never met with in a separate state, but
always in combination. Its most important compound
is phosphoric acid, the substance which is formed when
phosphorus burns in the air or in oxygen ; it is a white
solid substance, very soluble in water, and eagerly
combining with bases to form a class of salts called
phosphates (161, 242).
195. Phosphoric acid is generally obtained by de-
composing one of its compounds by sulphuric acid.
The most abundant compound of phosphoric acid is
that in which it is united to lime, called the phosphate
of lime (242) : this substance is an ingredient of the
bones of animals, and of most organic substances.
When sulphuric acid is mixed with phosphate of lime,
the latter is decomposed, and its phosphoric acid is
set at liberty. The acid may be artificially made by
burning phosphorus in the air, from which it abstracts
the oxygen, and leaves the nitrogen unaltered ; just
in the same way that carbon when burnt in air, forms
carbonic acid: only that in this case the product of
combustion is a gas, like the air ; whilst the result
of the combustion of phosphorus, is a white solid
acid.
97
CHAPTER III.
METALLIC ELEMENTS — THE ALKALIES — THE ALKALINE
EARTHS, AND THEIR SALTS.
196. In classifying the elementary substances, the
first and most obvious arrangement seems to be that
of dividing them into non-metallic and metallic ; the
former including oxygen, chlorine, &c., or the sup-
porters of combustion as they are sometimes called,
together with the non-metallic simple combustibles,
such as carbon and sulphur, &c. ; whilst the latter
includes iron, gold, lead, tin, and all the ordinary
metals, as well as a number of very scarce metals ;
some of which, however, are very abundant in a state
of combination, though they are hardly ever met with
in a pure and separate form.
197. In the pure state, the metals are chiefly im-
portant for their strength, hardness, malleability, and
other mechanical properties; their interest to the
chemist is for the most part confined to their combi-
nations, and the difi'erent compounds which they
form by combining in. various ways, with the non-
metallic elements. The oxides, or the substances
which the metals form by uniting with oxygen, are
9
98 POTASH.
perhaps the most important of all their compounds,
a very great number of them are bases (109).
198. The class of substances called bases, or those
with which acids can combine, is very numerous.
The commonest, and therefore the most important,
are the three alkalies — potash, soda, and ammonia,
together with a few substances called earths, because
they are the principal ingredients which enter into
the composition of the earth or soil. The nature and
properties of ammonia have already been considered
(148).
199. Potash never occurs pure in a free state; its
most abundant source is the vegetable kingdom, and
the simplest method of procuring it is by burning
wood. When this is done, after all the combustible
matter is burned, there remains a quantity of a white
or gray substance called ashes, which when put into
water forms a caustic solution. This is caused by the
presence of potash, which, not being altered by the
heat occasioned by the burning of the wood, is left
in the ashes.
200. In this way, however, we do not obtain the
potash pure, because, being a powerful base, and
having a strong affinity for acids, it combines with
some of the carbonic acid formed by the burning of
the carbon contained in the w^ood, and therefore the
caustic substance found in the ashes of the wood is
an impure carbonate of potash. It is obtained tole-
rably pure by pouring water on wood ashes, straining
off the clear liquor, and evaporating it ; a white salt
SALTS OF POTASH. »»
is left, whicli is the carbonate of potash separated
from most of the other matters which were contained
in the ashes, and when thus purified it is called pearl-
ash.
201. Pure potash is readily obtained from its car-
bonate, by means of quicklime ; that substance has a
stronger affinity for carbonic acid than potash has,
and accordingly it decomposes the alkaline carbonate
and leaves the alkali in its pure state: when free
from any acid, it is found to be a very caustic solid
substance, which has a strong affinity for acids, and
is difficult to keep perfectly pure, as when exposed
to the air it rapidly acquires carbonic acid from it,
and becomes converted into the carbonate.
202. Potash is not a simple substance ; like soda,
it is a compound of a metal and oxygen (190). By
the action of charcoal at a very high temperature it
may be decomposed, for at a white heat the affinity
of charcoal for oxygen is so great that it is even able
to take it from potassium, as the metal of potash is
termed. Potassium is of course never found in a
native state, for its affinity for oxygen is so great
that when exposed to the air it instantly absorbs a
quantity of that gas, and is soon converted into
potash. It may readily be proved that potash, soda,
and the earths are all compound bodies, and that they
consist of peculiar metals combined with oxygen ; but
as the affinity which they have for that element is
very great, and as they are never decomposed under
ordinary circumstances, it is quite unnecessary to
100 CARBONATE OF POTASH.
study the nature of potassium, sodium, &c., further
than to know that they are "white silvery-looking
metals, which by combining with oxygen form potash
and soda. For all practical purposes we may think
of potash, soda, and the earths as elementary sub-
stances.
203. Potash has a strong attraction for water ; so
that, when dry, pure potash is exposed to the air, it
very soon becomes moist, and in a short time has
attracted so much water from the air as to appear
changed into a liquid. This power of attracting
water from the air is common to most of the salts of
potash, as well as to many other saline compounds ;
it is termed deliquescence, and such salts are said to
be deliquescent. Pearlash, if left exposed to the air,
rapidly becomes moist, and finally runs into a liquid,
which is a very strong solution of that salt in water;
pearlash, therefore, must always be kept in a dry
place, and in well-closed vessels.
204. In the same way, we often find that common
salt, when kept in a damp place, becomes very moist:
this is not occasioned by any attraction which the
salt itself has for the moisture in the air, but by
certain saline impurities usually contained in the
salt, which have this power in a high degree (252).
205. Chloride of potassium may be formed by
heating the metal potassium in chlorine, or by acting
upon potash by muriatic acid (190) ; it is not a salt
of much interest; it has been occasionally recom-
mended as a manure (891).
NITRATE OF POTASH. 101
206. One of the most important of the salts of
potash, is the nitrate, or, as it is commonly called,
saltpetre, or petre, which is found native in many
places as a white powdery matter on the surface of
the ground, and is procured pure by washing the
earth, and evaporating the solution of nitre thus
obtained.
207. Nitre is a perfectly neutral salt, and is in
that respect very different from the carbonate of
potash, which, although far less caustic than pure
potash, has still very considerable caustic powers, in
consequence of which it is so commonly used in
washing, and for other household purposes. Car-
bonic acid, in combining with the alkalies, does not
seem able to neutralize them, or destroy their alka-
line powers so completely as most other acids can ;
and therefore it must be remembered that the carbon-
ates of the alkalies still possess some of the powers
of the alkalies themselves. The other compounds
formed by the alkalies with the more powerful acids
are quite neutral, and in them no traces of the alka-
line nature of the bases can be found.
208. One of the principal uses of nitre is in the
manufacture of gunpowder, which consists of nitre,
charcoal, and sulphur, finely powdered, and very care-
fully mixed together. The chemical action which
takes place during the burning or explosion of gun-
powder is very simple. The nitre consists of potash
and nitric acid, the latter substance contains a large
quantity of oxygen, combined by a comparatively
9*
102 ■ GUNPOWDER.
y^eaik attraction with a portion of nitrogen. The finely-
powdered charcoal has a very strong attraction for
oxygen, and when sufficiently heated is able to decom-
pose the nitre, seizing upon the oxygen of the nitric
acid, and forming carbonic acid, a small portion of
which combines with the potash of the nitrate, and
forms carbonate of potash.
209. The use of the sulphur in gunpowder is simi-
lar to its use in the lighting of a common sulphur
match ; it very easily catches fire, and the flame thus
produced instantly heats the charcoal so much that it
is able to decompose the nitre.
210. The mechanical force of gunpowder when
fired, is occasioned by the instantaneous production
of a large quantity of gas from a small bulk of solid
matter: as the whole of the nitrogen, and the greater
part of the carbonic and sulphurous acids formed, are
given off in the gaseous state, and comparatively little
is absorbed by the potash.
211. During the burning of gunpowder, a small
portion of sulphuretted hydrogen is commonly formed,
which occasions the bad smell (182) commonly per-
ceived: the hydrogen necessary for the formation of
this gas is derived from a little moisture which gun-
powder generally contains; pure and perfectly dry
gunpowder contains no hydrogen, and hence, in its
firing, no sulphuretted hydrogen can be found.
212. Nitre is one of the few compounds of nitric
acid which are found native, and, indeed, it was till
lately almost the only source of that acid. It is also
SODA— COMMON SALT. 103
used as a manure, and will therefore come before us
again on a future occasion (898).
213. Sulphate of potash is a soluble salt, readily
formed by acting on any of the ordinary salts of the
alkali, such as the carbonate or nitrate, by sulphuric
acid; it is chiefly used by the manufacturers of alum
(257).
214. Salts of potash are met with in a great many
plants in small quantities; they are likewise almost
always to be found in the soil, and potash is by no
means uncommon in stones; indeed, it is evident that
the salts of potash found in the soil must have been
derived from the gradual breaking down and decom-
position of stones and rocks containing compounds of
potash.
215. The second alkali, soda, is in its general cha-
racters similar to potash; it is a very caustic, solid,
white substance, has a powerful attraction for acids,
and is consequently never found in a pure and sepa-
rate condition, but always in combination with an
acid, or some other substance. The most abundant
source of soda is common salt, which exists in very
large quantities in sea-water, and is likewise found
native in the earth, when it is called rock-salt, to
distinguish it from the salt obtained by the evapora-
tion of sea-water, and called sea or bay salt.
216. Common salt has already been stated to be a
chloride of sodium (189), a compound of chlorine with
a white brilliant metal called sodium. It used for-
merly to be called a muriate of soda, because it was
104 NITRATE OF SODA.
known that sulphuric acid poured on salt expels mu-
riatic acid, whilst, on the other hand, there are sub-
stances which can take away the acid and leave caus-
tic soda. It is now known that dry salt contains
nothing but chlorine and sodium ; and when it is de-
composed by sulphuric acid, or in any other way, the
muriatic acid and soda evolved were not contained
in the salt, but are formed by the decomposition of
a portion of water, the oxygen of which unites with
the sodium to form soda, whilst the hydrogen com-
bines with the chlorine to form muriatic acid. Hence,
though strictly speaking common salt is a chloride
of sodium, yet for practical purposes it may be con-
sidered as a muriate of soda; because whatever
change it undergoes, or in whatever manner it is de-
composed, soda and muriatic acid are given out just
as if they were really the components of salt. Soda
is an oxide of sodium.
217. The only other compound of soda, which
occurs native in any quantity, is the nitrate or cubic
nitre, as it is commonly called. It is found native
in large quantities in certain parts of South America,
and is used to a considerable extent as a manure.
When it was first brought over to this country, some
few years ago, it was proposed to substitute it for the
nitrate of potash in the manufacture of gunpowder,
and in the preparation of nitric acid. It was, how-
ever, found that it possessed the property of attract-
ing moisture from the air ; and hence, being always
more or less damp, it could not be used by the gun-
CARBONATE OF SODA. 105
powder-makers. When first imported its price was
low, and it was accordingly advantageously substi-
tuted for the more expensive nitrate of potash in the
manufacture of nitric acid ; but as the price of nitrate
of soda soon rose, it was no longer found profitable
to use it for this manufacture, and now almost the
only purpose for which it is employed is as a manure.
It appears to resemble the nitrate of potash in its
effects on growing plants, and like it to exert con-
siderable influence on the fertility of certain kinds of
land (901).
218. The "soda" of commerce is, as will be
readily supposed, not the pure alkali soda, but is a
carbonate, and, like the carbonate of potash, pos-
sessed of considerable caustic properties. It was
formerly for the most part procured by burning sea-
weed, the ashes of which contain a large quantity of
carbonate of soda, and immense quantities of sea-
weed were annually collected and burnt, for the pur-
pose of obtaining weed-ash, kelp, or barilla, as the
crude salt was called.
219. Of late years, however, means have been
discovered of obtaining the carbonate of soda by de-
composing common salt ; from which it is now manu-
factured so cheaply that it has not only superseded
the use of kelp or barilla for all purposes where car-
bonate of soda is required, but has also from its low
cost been substituted to a great extent for potash
and pearlash ; and hence the carbonate of soda, or
"soda/' as it is commonly called, is very largely used
106 SALTS OF SODA.
in the arts of glass and soap-making, and other pro-
cesses where an alkali is employed.
220. In order to obtain carbonate of soda by the
decomposition of common salt, it is first of all neces-
sary to convert the salt into a sulphate ; this is done
by mixing it in certain proportions with oil of vitriol
or sulphuric acid, and heating the mixture in a
furnace. Muriatic acid is expelled, and the sul-
phuric acid, which has a powerful attraction for the
soda, combines with it and forms sulphate of soda
(190).
221. The second process is to mix the sulphate of
soda thus formed with chalk and pounded coal, and
to strongly heat the mixture in a furnace ; the sul-
phate is decomposed at a high heat by the charcoal
or carbon of the coal, which takes oxygen both from
the sulphuric acid and from the soda, forming a sul-
phuret of sodium. This in turn is decomposed by the
chalk, and a carbonate of soda is produced, which is
of course impure, containing charcoal, and an in-
soluble compound of lime ; so that, by pouring water
on the crude salt after it is taken out of the furnace,
a clear colorless solution is procured, yielding on
evaporation a clean and nearly pure carbonate of
soda.
222. This "soda "contains a large quantity of
water, although apparently dry ; and when left ex-
posed to the air, it does not, like the carbonate of
potash, attract water from the air, but, on the con-
trary, parts with it and becomes drier, at the same
SALTS OF SODA — THE EARTHS. 107
time crumbling down to a fine powder, which is found
to be less caustic than it was before it underwent
this change. The reason of this is, that when the
carbonate of soda, by exposure to the air, parts with
a quantity of water, and consequently becomes much
lighter, it at the same time gradually combines with
a second dose of carbonic acid, which it obtains from
the air, and its caustic qualities become more fully
neutralized than they are in the common carbonate.
223. The salts of soda are for the most part white,
and easily soluble in water ; and, like the compounds
of potash, are widely diffused throughout nature.
They are found, besides the sources already men-
tioned, in many rocks and soils : a great many plants,
more especially those which grow near the sea or in
salt marshes, contain large quantities of salts of
soda ; and a good many of the compounds which
this alkali forms with different acids are found native,
though in far smaller quantities than the nitrate.
224. The sulphate of soda is also found native in
Spain and other countries, and is frequently met with
in mineral waters ; it is also called Glauber's salts,
and Cheltenham salts, as it is the principal ingredient
in the mineral springs of Cheltenham. Sulphate of
soda is left after the process for obtaining muriatic
acid (190): it is occasionally employed as a manure.
225. The earth, or soil, consists of a mixture of
various ingredients ; but the greater part of it is com-
posed of certain substances which are called earths.
Some of these are bases, and resemble the alkalies ;
108 LIME.
■whilst the remainder are not bases : that is to say,
they seem to have no affinity for acids, and cannot
combine with them to form salts. The most import-
ant of the earths -which are bases, are called lime,
magnesia, and alumine ; the two former are called
alkaline earths, to distinguish them from the last, as
they possess the property of reddening vegetable
colors, though in a far less powerful manner than
the alkalies, whilst alumine does not. Silica is not a
base.
226. Lime, in its pure condition, is a highly caustic
■whitish-gray solid substance, slightly soluble in -water,
but far less so than the alkalies are. It has a very
strong attraction for acids, being even able to decom-
pose the salts of the alkalies, in consequence of the
superior attraction which it has for the acids contained
in them ; and it is for this reason that it is customary
to mix quicklime with wood-ash, which contains com-
paratively little free potash, as the greater part is
combined with carbonic acid (200), when it is desired
to make a very strong caustic ley : the quicklime de-
composes the carbonate of potash, combines with the
carbonic acid, and becomes converted into carbonate
of lime ; whilst the potash, being no longer com-
bined with an acid, is able to exert its caustic powers.
Lime is the oxide of a metal called Calcium (202).
227. In consequence of its strong affinity for acids,
lime never occurs native in a pure and simple state,
but always in combination with some acid ; the most
common compounds of lime are the carbonate, and
CARBONATE OP LIME. 109
the sulphate ; the former of these, especially, is a very
abundant substance, existing naturally in immense
quantities in the different forms of chalk and lime-
stone ; it is also very commonly an ingredient of the
soil, and constitutes a considerable part of the bones
of animals, and shells.
228. As has already been stated (119), lime has a
less powerful attraction for carbonic acid, than it has
fof any other acid ; and therefore when we pour a
quantity of any acid over carbonate of lime, great
bubbling, or frothing is occasioned by the escape of
the carbonic acid, which is set at liberty, when the
lime combines with the new acid (117).
229. This bubbling, or effervescence, as it is called,
enables us very easily to ascertain whether a stone be
limestone or not, and likewise whether any particular
soil contains carbonate of lime ; for if any acid, such
as vinegar, does not occasion any effervescence, it is
certain that no carbonate of lime is present ; and if,
on the other hand, it does expel bubbles of gas, we
may be quite sure that a portion of some carbonate
is present, and by far the most common of these is
the carbonate of lime.
230. All the forms of this substance are tasteless,
and quite insoluble in pure water ; but rain-water,
which commonly contains dissolved in it a very small
quantity of carbonic acid, has the power of dissolving
carbonate of lime : hence we commonly see the surface
of chalk or limestone appearing to be gradually cor-
roded, or worn away by the rain ; and for the same
10
110 CARBONATE OF LIME.
reason, buildings of freestone or limestone are much
less durable than those which are built of granite, a
stone which does not contain carbonate of lime, and
is, therefore, not thus acted on by rain-water.
231. In this kind of action, no chemical change is
effected : the carbonate of lime is merely dissolved by
water holding in solution carbonic acid; hence when,
either from heat or any other cause, the carbonic acid
is expelled from the water, it is no longer able to hold
the carbonate of lime in solution, which is therefore
deposited again unaltered.
232. Spring-water, for example, which often holds
carbonate of lime thus dissolved, becomes milky or
turbid when boiled, and not unfrequently deposits fur
in the inside of boilers and kettles ; such water is of
course not fit for domestic uses, cooking, &c.; but by
simple boiling it is at once rendered far better, the
chalk being then separated.
233. The uses of carbonate of lime are very nume-
rous : one of the most important is for burning into
lime. This is a very curious process, for heat gene-
rally increases the attraction which two different sub-
stances have for each other ; yet in this and some
other cases it rather diminishes it, and the strongest
heat is unable to drive off carbonic acid from its com-
bination with potash or soda, though lime, which
parts with it so readily when heated, is able when cold
to take it from either of the alkalies.
234. When quicklime is mixed with vegetable or
animal substances, it renders the process of putrefac-
SULPHATE OF LIME. ' 111
tion far less noisome than it is under ordinary cir-
cumstances ; because the lime absorbs sulphuretted
hydrogen, carbonic acid, and many of the products
of decay.
235. When quicklime is slaked with water, it crum-
bles down to a powder, and is found to have combined
with a quantity of water ; although it appears quite
dry, for the water is chemically combined with the
lime : if this lime thus slaked is left exposed to the
air, it combines with carbonic acid, and becomes
changed into carbonate of lime, and at the same time
parts with the water with which it had previously com-
bined. Slaked lime is less strongly caustic than quick-
lime, because part of the action of lime on organic
matter is caused by its strong affinity for water ;
nevertheless, even slaked lime possesses strong caustic
properties.
236. Common mortar, which consists of slaked
lime mixed with sand, chopped hair, &c., is a hydrate of
lime ; its setting depends chiefly on the absorption
of carbonic acid from the air, which forms again with
it a kind of chalk or limestone. Hence mortar gradu-
ally improves, becoming harder after a time, when it
has absorbed a sufficient quantity of carbonic acid
from the air to be wholly converted into carbonate.
237. Sulphate of lime is less common and abund-
ant than the carbonate ; it is, however, a frequent in-
gredient in the soil, in spring and mineral waters, and
is found sometimes in large beds, constituting what
is called plaster-stone, gypsum, and alabaster ; these
112 NITRATE OF LIME.
are all compounds of lime and sulphuric acid, and pre-
cisely similar in composition. Common plaster of
Paris is dry sulphate of lime, or gypsum, deprived by
heat of the water which it naturally always contains,
and, when mixed with a small quantity of water, it re-
combines with it, and becomes a hard, dry, solid sub-
stance.
238. The burning of gypsum to make plaster of
Paris, is quite different from the burning of chalk to
make quicklime : in the former case the native sul-
phate of lime, which contains water, is heated and the
water thus expelled ; whilst in the burning of lime not
only is the water expelled which the chalk usually con-
tains, but also the acid itself, with which the lime was
combined.
239. Sulphate of lime is dissolved in small quantity
by water, and accordingly we find it almost always
present in spring-water, which derives it from the soil
through which it rises ; it is the presence of this sub-
stance in spring-water which gives it that hardness
which distinguishes it from common river-water, and
renders it less pleasant to use than soft water ; in fact,
one of the great distinctions found between hard and
soft water is the presence or absence of sulphate, or
carbonate of lime, which, though contained in but
small quantity, greatly influences its usefulness for
domestic purposes (232).
240. Nitrate of lime is a white salt, easily soluble
in water, and readily formed by acting on lime or its
carbonate by nitric acid. It is also formed whenever
PHOSPHATE OP LIME. 113
organic matters containing nitrogen are suffered to
putrefy in contact with lime; when animal manure and
lime are left together, nitrate of lime is formed ; the
same salt is frequently found in the mortar of old
walls, particularly those of stables and similar out-
houses. When mixed with a solution of carbonate
of potash, both salts are decomposed ; nitrate of pot-
ash and carbonate of lime being formed. By this
process, nitre has often been made in what are called
nitre-beds.
241. Muriate of lime, or, more properly speaking,
chloride of calcium, is a very soluble salt, easily formed
directly from lime and muriatic acid, and remarkable
for its great attraction for water (203). It exists in
sea-water, and consequently is often found in common
salt. Mixed with a solution of carbonate of ammonia,
both salts are decomposed, chalk and muriate of am-
monia being formed ; this is remarkable, because those
two salts, when mixed together dry, and heated, form
muriate of lime and carbonate of ammonia (155).
242. There is only one other compound of lime of
much importance, and which has already been men-
tioned ; this is the phosphate. It is found in small
quantity in most plants, and forms a great part of the
solid matter of the bones of animals (594, 836, 876).
243. Phosphate of lime is by no means abundant
in nature, but it exists in small quantity in a great
many substances. Traces of phosphoric acid are
found in a great number of rocks and stones, in the
10*
114 PHOSPHATE OF LIME.
soil, in almost all plants, and in animal matters. It
never occurs free, or uncombined, but always in com-
bination with a base, and this is very commonly lime.
Thus we always find phosphate of lime in wheat, and
all these vegetable substances which constitute part
of the food of man and animals ; and we find it in a
very considerable quantity associated with carbonate
of lime, in the bones of all animals, who obtain from
it all the substances on which they feed. Phosphate
of lime is insoluble in water, but readily dissolves in
solutions containing a little free acid.
244. Phosphate of lime is easily decomposed by
the more powerful acids, such as sulphuric acid and
muriatic acid ; in the former case an insoluble sul-
phate will be formed, and phosphoric acid left in
solution ; and in the latter, a clear solution will be
obtained containing phosphoric acid (195) and muriate
of lime, a salt which is also very easily soluble in
water.
245. Sulphuric acid does not wholly decompose
phosphate of lime, though it takes from it the greater
part of the lime which it contains; the phosphoric acid
is still combined with a small quantity of lime, con-
stituting a bi-phosphate of lime (840); the results of
the action of sulphuric acid, therefore, are sulphate
of lime, a super or bi-phosphate of lime, and free
phosphoric acid; the two latter may be readily sepa-
rated from the gypsum by the addition of water, they
being very soluble, whilst the latter is very little so-
luble in that fluid. A mixture of phosphate of lime
MAGNESIA. 115
and sulphuric acid is frequently called super-phos-
phate of lime, and is much used as a manure.
246. Magnesia is an earth somewhat similar to
lime, but far less common and abundant ; like lime,
it is the oxide of a very combustible metal, which,
exposed to the air, soon takes oxygen and forms the
earth. The base of magnesia is called magnesium
(202). Magnesia occurs usually in connection with
lime, forming what is called magnesian limestone,
which is a mixture of carbonate of lime and carbonate
of magnesia.
247. The commonest forms in which magnesia is
found are the carbonate, the sulphate, the muriate,
and the phosphate. The carbonate is sometimes found
native, pure, but by far more frequently it is mixed
with carbonate of lime or limestone, the properties of
which it considerably modifies. When carbonate of
magnesia is strongly heated, it parts with its car-
bonic acid, and the pure earth magnesia is obtained.
248. This earth is almost insoluble in water, and
far less strongly caustic than lime; it also has less
affinity for carbonic acid, so that when left exposed
to the air, it does not, like lime, rapidly become con-
verted into carbonate, by absorbing carbonic acid
from the air, but remains for a long time caustic;
and hence, when a magnesian limestone is burnt in a
limekiln, the quicklime obtained of course contains
caustic magnesia, which, if exposed to the air, will
remain caustic long after the lime has become recon-
verted into carbonate; it is for this reason that lime-
116 SALTS OF MAGNESIA.
stone containing magnesia cannot be used for some
purposes, where the caustic powers thus retained are
objectionable (873).
249. The carbonate of magnesia, like the carbonate
of lime, and indeed all other compounds of that acid,
is easily decomposed by any more powerful acid (117).
250. When magnesia or its carbonate is acted on
by sulphuric acid, sulphate of magnesia is formed,
which is a salt easily dissolved by water, and distin-
guished by a peculiar sweet-bitter taste. It is found
in many mineral waters, and exists in unusually large
quantity in some springs near Epsom, in consequence
of which it is commonly called Epsom salts. A solu-
tion of sulphate of magnesia is readily decomposed
by the alkaline carbonates ; carbonate of potash,
soda, or ammonia, throwing down carbonate of mag-
nesia.
251. The compound of muriatic acid and magnesia,
or chloride of magnesium, is also frequently found in
mineral waters, and exists in some quantity in sea-
water ; it is very soluble in water, and therefore, when
sea-water is evaporated in order to procure the com-
mon salt which it contains, it is never wholly evapo-
rated; but when the greater part has been driven off
by heat, and a large quantity of common salt is depo-
sited, the remaining liquor, commonly called bittern,
which contains a little common salt, and nearly all
the muriate of magnesia, and other easily soluble
salts, is drawn off.
252. The muriate of magnesia, like the muriate of
SALTS OP MAGNESIA. 117
lime, is a very deliquescent salt; that is to say, it
has a very strong attraction for water, and hence,
when exposed to damp air, it soon becomes moist,
and at last we find, instead of the solid salt, a very
strong solution of it in water. It is to the presence
of a small quantity of these two salts in common sea-
salt that its deliquescent properties before alluded to
are due (204).
253. The phosphate of magnesia, like the carbon-
ate, is seldom found alone, but usually mixed with
the phosphate of lime : thus we find it associated
with that substance in small quantity in many animal
and vegetable matters, and likewise in the soil ; like
the phosphate of lime, it is insoluble in water, but
readily soluble in dilute acids. Phosphate of mag-
nesia has a considerable tendency to form double
salts (112) ; thus a double phosphate of magnesia and
ammonia is very frequently found in plants and
animals; it is readily formed artificially by adding
phosphate of ammonia to a solution of sulphate of
magnesia; it is slightly soluble in water, and has
been strongly recommended as a manure. The uses
of magnesia are limited, and the most important pur-
poses to which its compounds are applied are as
medicines.
118
CHAPTER IV.
METALLIC ELEMENTS — THE EARTHS METALS — METAL-
254. Alumina, or pure clay, is a very abundant
and widely-diffused substance. It occurs native both
pure and in combination, but it is most usually met
with mixed with another earth, called silex, and com-
bined with a quantity of water. It is sometimes
found pure and free from water or any acid, ^nd con-
stitutes the hard gems called ruby and sapphire ; but
these are very rare, and seldom met with. Alumina
is the oxide of a metal called aluminum (202, 225).
255. The properties of alumina, in the ordinary
state in which it occurs in the soil, are very different
from those of the bases described in the last chapter ;
it combines with acids to form salts, but is quite in-
soluble in water, has no caustic powers, and does not
absorb carbonic acid from the air. It has a strong
attraction for water, and when thoroughly wet, it
appears in the form of a very tenacious paste, re-
markable for its great plasticity, and the ease with
which it may be moulded into any form. All the
varieties of clay derive their tenacious property
SILICA. 119
from the large quantity of this earth which they con-
tain; and the whole of the art of making pottery,
bricks, tiles, &c., is in great part dependent on this
property of alumina.
256. This earth is able to combine with acids, but
the salts which it forms are mostly of very little im-
portance, and we need not inquire into their charac-
ters. The only one which is found native is the phos-
phate, but this is by no means of common occurrence;
it is only found in certain districts, and in very
limited quantity.
257. The sulphate of alumina is largely manufac-
tured from certain kinds of slate or shale, which con-
tain alumina and sulphur. When sulphate of alumina
is mixed with sulphate of potash, the two salts com-
bine and form a double salt, the sulphate of alumina
and potash, or common alum. If a little potash is
added to a solution of alum, the sulphate of alumina
will be decomposed, pure alumina will be separated,
and sulphate of potash alone remain in solution (112).
258. Silica, or silex, is the only other earth of
much importance besides the three already men-
tioned ; it is found abundantly, both pure and mixed
or combined with alumina and other substances, con-
stituting, in a nearly pure condition, quartz, sand,
flint, &C'., and, when associated with alumina, form-
ing clay and a numerous series of stones ; being, in
fact, an essential ingredient of the greater number of
the hard stones with which we are acquainted.
259. Silica differs from the preceding earth, alu-
120 SILICA.
mina, in not being a base — in being unable to com-
bine with acids ; indeed, it has rather the character of
an acid, for it is able to combine with the alkalies so
much in the manner of acids, that it is very frequently
termed silicic acid. Silica is the oxide of a peculiar
substance having many of the properties of metal,
and to which the name of Silicon has been given
(202).
260. Silica, in its common forms, is quite insoluble
in water, unacted on by the air, and, under ordinary
circumstances, a very unchangeable substance : when,
however, combined with the alkalies, it is easily dis-
solved in water, and the compound thus formed is
sometimes present in very small quantity in mineral
waters.
261. When silica is obtained by the decomposition
of any of its soluble compounds, it appears in the
form of a transparent jelly, which dries into a very
fine white powder, like flour ; when freshly precipi-
tated from a solution, this jelly is slightly soluble in
water and in dilute acids, a property, however, which
it loses by being thoroughly dried.
262. The ordinary forms of silica or silicic acid,
such as sand or flint, are very little acted on by
potash ; but when finely powdered silica is mixed with
potash or soda, and strongly heated, they melt and
form a clear transparent substance, which is in fact
glass. Indeed, so strong is the affinity which silica
has for potash and soda, that, if fine sand or pounded
flints are mixed with the carbonate of either of those
SILICA. 121
bases, and strongly heated, the carbonic acid is ex-
pelled, and the silica and alkali unite to form a glass.
Such a compound is called a silicate.
263. Common glass always contains other sub-
stances, but the basis of all good glass is this com-
pound of silica and alkali — either silicate of potash
or soda. The proportions taken of the two ingredi-
ents are always such that the glass obtained shall be
perfectly unacted on by water; but if more alkali be
employed than is requisite to form a good glass, a
silicate will be obtained which is readily soluble in
water. A solution thus made is easily decomposed
by any acid, as the potash has comparatively but
a weak attraction for the silica, and hence that
substance is separated from its solution on the addi-
tion of almost any acid.
264. Though potash is scarcely able to combine
with silica at a common temperature in its usual
states, yet when the silica is in an exceedingly iBne
powder, the alkali is able to dissolve a small quantity ;
but this action is far slower and less perfect than
when the two are strongly heated together.
265. Silica is almost always an ingredient of the
soil, and exists there not only in its solid and insolu-
ble form of sand, but also in the soluble condition of
silicate of potash or soda ; it will easily be seen that
as many stones contain silica, they will, whilst gra-
dually decomposing and crumbling down by exposure
to the air, constantly add to the soil silica in a very
finely divided state, and therefore well adapted to
11
122 SALTS OF THE METALS.
combine with either potash or soda ; and besides, as
many stones contain silica in combination with potash
or soda, so these stones, in crumbling awaj, present
a constant source of soluble silica.
266. Silica is found in many plants, such as, for
example, corn and grasses, the stalks of which mainly
derive the strength requisite to enable them to grow
erect from the silica which they contain. Plants de-
rive this earth from the soil, and are only able to ab-
sorb by their roots the silica, which, by having com-
bined with alkali, has become soluble in water, and is
consequently able to enter into the structure of the
plant.
267. Silica, or silicic acid, combines with lime,
magnesia, and alumina, to form silicates, as well as
with the alkalies, potash and soda ; these silicates are
for the most part insoluble in water, and constitute,
either pure, mixed, or combined together, an immense
variety of different stones ; the action of the atmo-
sphere and other natural circumstances combine to
effect the gradual decomposition of such compounds.
268. Besides the three earthy bases already spoken
of, and a few others of far less importance, as they
are very rare, and only to be found in particular
places, there are a numerous series of bases called
metallic oxides, several of which are of great import-
ance in the arts, and two of which are almost always
present in small quantity in the soil.
269. Most of the common metals, such as iron,
lead, and zinc, gradually tarnish, and become rusty
SALTS OF THH METALS. 123
when exposed to the air : the reason of this is that
they have a strong aflBnity for oxygen, and under
these circumstances they gradually become covered
with a film of an oxide, or compound of the metal with
oxygen. Many of these metallic oxides are bases,
and form with acids a very numerous series of salts.
270. Modern discoveries have shown that both the
earths and alkalies, are, in fact, the oxides of peculiar
and very oxidizable metals (202). Hence the earths,
alkalies, and ordinary metallic oxides, are all classed
together under the general term, base : they combine
with acids to form salts ; thus gypsum, or sulphate of
lime, is a compound of lime, which is the oxide of a
peculiar metal, and sulphuric acid. Green vitriol, or
sulphate of iron, is a compound of oxide of iron and
sulphuric acid ; and Cheltenham salts, or sulphate of
soda, consists of soda (the oxide of sodium) and sul-
phuric acid.
271. To speak correctly, green vitriol should be
called sulphate of oxide of iron, but such a system
would be very inconvenient ; it is therefore customary,
when speaking of the salts formed by the oxide of a
metal, merely to call them by the name of the metal.
Hence, when chemists speak of sulphate of iron, and
carbonate of lead, they always mean salts of the
oxides of those metals ; the metals themselves, not
being bases, could not combine with the acids to form
salts.
272. The salts formed by the combination of the
different metallic oxides are called just as if they were
124 IRON.
salts of the metals themselves, because the oxides of
the ordinary metals have no special names, like pot-
ash, and soda, &c. ; thus the sulphate of the oxide of
lead, for example, is simply called sulphate of lead.
When there are two separate oxides of a metal, both
of "which form salts with acids, that which contains
least oxygen is called a protoxide, and that which
contains most, a peroxide; the addition of proto or
per to the name of a salt, shows whether it is a salt
of the protoxide, or of the peroxide ; thus the proto-
sulphate or per-sulphate, means a sulphate of the
protoxide, or peroxide.
273. The most widely diffused an^ abundant of all
the metallic oxides, as well as that which is the most
important and valuable in the arts, is the oxide of
iron, which exists in different quantities in a great
variety of stones, is. very common in soils, and is con-
stantly present, though only in small quantity, in
the blood of animals, and in the juices of plants.
274. Iron is very rarely indeed found native in
its pure metallic state, but is usually met with in the
form of an oxide, either pure or combined with car-
bonic acid, and mixed with alumina and silica. Thus
the rich black and red iron ores of Cumberland and
other places are nearly pure oxide of iron, whilst the
common clay iron-stones, as they are called, of Staf-
fordshire and Wales, are either carbonate or oxide of
iron, mixed with various proportions of alumina and
silica.
275. The important art of smelting iron is entirely
OXIDES OF IRON. 125
a chemical operation, and depends mainly, upon the
fact th«,t, at a high temperature, carbon has a
stronger affinity for oxygen than iron has ; and hence,
■when the native oxide of iron is heated with coal or
charcoal, it is decomposed, and carbonic acid gas and
metallic iron are the results of the process.
276. When those ores are smelted which consist
principally of oxide of iron, they are at once heated
with carbon ; but when the clay iron-stones are used
— and they are the ores most commonly employed —
they are first submitted to a preparatory process,
something like the burning of lime, in order to ex-
pel the carbonic acid gas which they contain ; and
when thus converted into oxide of iron, they are
mixed with carbon and lime, the use of the latter be-
ing to combine with the silica or silicic acid and alu-
mina, and form with them fusible silicates called the
slag, which greatly assists in the melting and running
together of the newly-reduced iron ; and, besides, by
covering the metallic iron with a glassy coat, they
protect it from further oxidation from the oxygen of
the air.
277. Iron is able to form two distinct compounds
with oxygen, according to the quantity of that ele-
ment with which it combines : when it is combined
with two-sevenths of its weight of oxygen, it consti-
tutes a black substance, which is called the protoxide,
and when combined with three-sevenths, forms a
brownish-red substance, called the peroxide. These
oxides are both bases, and each forms a distinct series
11*
126 RUSTING OF IRON.
of salts by combining with acids ; but the salts formed
by the protoxide have always a tendency to absorb
oxygen from the air, and thus become converted into
the salts of the peroxide.
278. The color of a great many stones and soils is
principally caused by the presence of a small quan-
tity of either the peroxide of iron, or of a mixture
of both its oxides.
279. The rusting of iron, which proceeds so rap-
idly when iron is exposed to damp air, is caused by
the attraction which the metal has for oxygen. It
is very remarkable that iron is unable to combine
with the free oxygen always in the air, but is able to
take it from water, its compound with hydrogen ; for
we find that in dry air, iron remains clean and bright
for a long time, but very rapidly rusts when exposed
to the joint action of air, carbonic acid gas, and
moisture, under which circumstances water is de-
composed, and oxide of iron formed.
280. The rust of iron is not a pure oxide, but
commonly a mixture of both oxides with a portion of
carbonate, or compound of the protoxide with car-
bonic acid. Rust generally contains a considerable
quantity of ammonia, for which substance oxide of
iron has a strong attraction ; when oxide of iron is
thrown down from a solution which contains it, by
ammonia, it is very difiBcult to expel the whole of
the ammonia from the precipitated oxide even by
strongly heating it.
281. Although iron cannot combine with the free
BURNING OF IRON. 127
Oxygen of the air at ordinary temperatures, yet when
strongly heated it rapidly absorbs oxygen, and then
becomes converted into a black scaly oxide ; when-
ever a piece of iron is heated in the fire, a quantity
of a brittle, black oxide is formed on its surface,
which easily rubs off the iron — and hence this metal
is gradually worn away by exposure to fire ; it is
from this reason that the iron pokers, fire-bars, and
other things much exposed to the fire, gradually get
thinner and thinner, from the constant oxidation of
the surface whilst hot, and the removal by rubbing
of the brittle coat of oxide thus formed.
282. When a piece of iron is very strongly heated,
it at last begins to hum ; that is to say, the combi-
nation of the external part with oxygen goes on so
rapidly, and evolves so much heat, that the whole
mass of iron is kept sufficiently hot to continue this
process of combination, and in consequence the iron
glows brightly, gives off abundance of sparks, and
runs down in drops of the melted oxide, for some
time after it has been removed from the fire in which
it was heated. In fact, iron, when thus strongly
heated, would catch fire and continue to burn like
charcoal, if it were not rthat the crust of oxide
formed protects the metal from further oxidation,
and soon stops its combustion.
283. One of the most common and abundant of
the ores of iron is called pyrites, which is a com-
pound of iron and sulphur ; it is not used in the
manufacture of iron, because it is very difficult to
128 PYRITES, OR SULPHURET OF IRON.
separate the sulphur completely from the iron, and
the native oxides and carbonate are far more con-
venient sources of the metal.
284. Pyrites, or sulphuret of iron, is, however,
a substance of considerable importance in the arts,
being one of the sources of sulphur, which is ob-
tained by heating pyrites in an oven, so constructed
that the sulphur, which is expelled in the state of
vapor from the pyrites, is cooled and condensed
into the solid form in a different part of the oven.
285. Pyrites, when exposed to the air, soon crum-
bles down, and undergoes a very curious change, in
consequence of absorbing and combining with oxygen.
Both the iron and the sulphur combine with oxygen,
and form oxide of iron and sulphuric acid ; and hence
the result of this action is sulphate of iron, or com-
mon green vitriol, a salt much used in the arts for a
variety of purposes.
286. Pyrites is most abundantly found in the form
of variously-shaped balls imbedded in chalk; to
which the common name of "thunderbolt" is very
improperly applied. As the chalk-hills on the sea-
side gradujilly wear away, from the action of the sea
and weather, these balls of pyrites get exposed to
the air, and fall down on the beach, whence they are
collected for the use of manufacturers. Many springs
of water contain a small quantity of iron, in conse-
quence of which they have a peculiar inky taste;
this is usually derived from the gradual oxidation of
SULPHATE OF IRON. 129
sulphuret of iron ; and from the same reason soils
also sometimes contain traces of this salt.
287. Sulphuret of iron is likewise very commonly
found in coal, being sometimes dispersed throughout
it in the form of little yellow shining particles, and
sometimes as layers or lumps of the solid sulphuret;
its presence in coal is for some purposes highly objec-
tionable ; because, whether the coal is burnt in its
crude state, or after being converted into coke, a
quantity of sulphurous acid gas is always formed by
the imperfect combustion of the sulphur; and that
nauseous-smelling gas causes serious mischief in
several operations in the arts, and consequently in
such cases, coal free from sulphuret of iron can only
be employed. It is the presence of this substance
in coal that causes the strong suffocating smell of
sulphurous acid sometimes given out by coal and coke
fires (173).
288. The oxides of iron are quite insoluble in
water, but many of the salts of iron, like the sulphate,
are readily soluble in it ; the solutions of these salts
are all decomposed w^hen alkali is added to them ;
this combines with the acid, and the oxide of iron is
separated as an insoluble powder.
289. The most important of the salts of iron is
the sulphate, or common green vitriol : it may be
formed by acting upon iron by dilute sulphuric acid ;
when this is done, a large quantity of hydrogen gas
is given off, in consequence of the decomposition of
a portion of water; the oxygen combines with the
130 . GOLD.
iron to form oxide of iron, which unites with the acid
to form proto-sulphate of iron, whilst the hydrogen
escapes. Green vitriol is, however, made on a large
scale, principally from pyrites, in the manner just
described (285).
290. Sulphate of iron, when pure, is a green trans-
parent salt, wholly soluble in water ; exposed to the
air it becomes brown and earthy-looking, being par-
tially decomposed, owing to the absorption of oxygen
and formation of peroxide; when strongly heated, it
is wholly decomposed, water and sulphuric acid being
given off, and oxide of iron left. When pure proto-
sulphate of iron is decomposed by an alkali, a gray
or black precipitate is formed of the protoxide; after
a short time this precipitate becomes red, having
absorbed oxygen, and become peroxide.
291. The number of different metals known to
chemists is very considerable, amounting in all to
forty-six; but of these the greater number are com-
paratively rare, and of little importance, not being
used for any practical purpose, and consequently
chiefly interesting in a scientific point of view. It
will, therefore, be sufficient to consider briefly the
leading characters of eight of the most important of
them (19).
292. Gold is found native in a pure and separate
state ; it has very little affinity for oxygen, never
tarnishing or showing any tendency to oxidize in the
air either at common temperature or when strongly
heated. It is insoluble in acids, except in a mixture
SILVER. 131
of nitric and muriatic acid, which dissolves it; such
an acid contains free chlorine, for the oxygen of the
nitric acid takes the hydrogen of the muriatic acid,
and sets free the chlorine; hence, we learn that the
only solvent of gold is, in fact, a solution of chlorine.
293. When a solution of chloride of gold, thus
obtained, is mixed with a solution of potash or soda,
a dark-colored precipitate falls: this is an oxide of
gold; when heated, it parts with the oxygen which
it contains, and pure gold is left. The soluble com-
pounds of the metal gold are all very easily decom-
posed, because the metal has but a very feeble affinity
for oxygen, chlorine, &c.
294. Silver, like gold, occurs native in its pure
metallic state, but it more commonly is found com-
bined with sulphur, as a sulphuret. It resembles gold
in having a feeble affinity, for oxygen, so that it does
not oxidize either at common temperatures, or when
heated, and most of its compounds are easily decom-
posed, the silver reassuming the metallic state. Sil-
ver readily dissolves in nitric or sulphuric acid, and
the solutions obtained yield oxide of silver, when
decomposed by an alkali; the oxide of silver is a
salifiable base, and combines with acids to form salts.
295. The compounds of silver are nearly all de-
composed by mere exposure to light. So feeble is
the affinity which it has for most other substances,
that the greater number of its compounds are decom-
posed or reduced by mere exposure to sunshine. This
fact is interesting as an illustration of the chemical
132 MERCURY.
powers of liglit, and, further, as giving us the found-
ation of that very beautiful art of producing pic-
tures by means of light — the Daguerreotype. The
salts of gold, also, and some of the compounds of
mercury are very easily decomposed, v*'hen exposed
to the action of light.
296. Silver has a very strong aiSnity for chlorine,
and the chloride of silver is quite insoluble in water;
hence silver cannot be dissolved in muriatic acid; and
if muriatic acid, or any solution containing chlorine,
either free or in combination, be added to a solution
of silver, the whole of the metal will be thrown down
as insoluble white chloride. A solution of nitrate of
silver is, therefore, a very useful test to ascertain the
presence of chlorine in any solution.
297. Silver has also a strong affinity for sulphur,
combining eagerly with it and forming a shining gray
brittle substance. The tarnish which we see on old
silver is a thin coat of sulphuret, formed by the sul-
phuretted hydrogen which generally exists in the air
of towns. Gold and silver are frequently called no-
ble metals, from their having no tendency to oxidize
when exposed to the air.
298. Mercury, or quicksilver, likewise, is some-
times found native in the metallic state, but by far
most commonly as a sulphuret ; it is obtained from
its ore by heating it with a mixture of iron filings
and lime; these substances combine with the sulphur;
and the mercury, being a volatile metal, is obtained
by a process of distillation.
COPPER. 133
299. Mercury is fluid at all ordinary temperatures,
but, by exposure to very intense cold, it may be
frozen into a brilliant hard solid, looking like silver;
when heated nearly to redness it boils, rises in vapor,
and may be distilled, just like water. When mercury
is kept for some time at a heat very near its boiling
point, it slowly absorbs oxygen, and becomes con-
verted into a red earthy-looking oxide. Mercury is
easily oxidized and dissolved by the strong acids ; it
forms two oxides, and both of them are salifiable
bases — the protoxide is black, the peroxide red; when
strongly heated, these oxides are decomposed into
metallic mercury and oxygen gas.
300. Chlorine acts strongly on mercury, and forms
two chlorides, corresponding in composition to the
two oxides ; the protochloride, or calomel, is a power-
ful and valuable medicine — the perchloride, or corro-
sive sublimate, a violent poison. The former is in-
soluble in water — the latter soluble ; they are both
easily decomposed by alkaline solutions — calomel
yielding the black protoxide, and corrosive sublimate
the red peroxide of mercury.
301. Corrosive sublimate has been a good deal
used to prevent the dry-rot of wood, cordage, &c. ; it
combines with some forms of organic matter, and
renders them less prone to change. Sulphur and
mercury easily combine, and form a beautiful red
compound, vermilion, or sulphuret of mercury ; it
occurs native as cinnabar, the chief ore of the metal.
302. Copper exists naturally in the pure metallic
12
134 ZINC.
state, but chiefly as a sulphuret, constituting copper
pyrites ; it is obtained from this ore by roasting, when
the sulphur is gradually driven off and an impure
oxide of copper left, which is subsequently strongly
heated with charcoal, to reduce it to the metallic
state. Copper has a considerable affinity for oxygen,
which it absorbs from the air at common tempera-
tures. Oxide of copper is a black substance, readily
obtained by heating copper in the air, or by decom-
posing any of its salts, such as the sulphate, by an
alkali.
303. The salts of copper are mostly of a blue or
bluish-green color ; they are all decomposed by alka-
line solutions, a blue hydrated oxide of copper being
precipitated; if ammonia be employed, no precipitate
is obtained, or, if formed, easily dissolves, because the
oxide of copper is soluble in solution of caustic am-
monia, forming a very beautiful deep-blue liquid : this
property is useful in testing for the presence of
copper.
304. Sulphate of copper, blue or Roman vitriol,
may be formed directly. It is manufactured on a
large scale, like the sulphate of iron (285); by ex-
posing the roasted sulphuret to the air, it absorbs
oxygen, and is converted into the sulphate. It is a
bright-blue salt, easily soluble in water, and used for
several purposes in the arts. It is frequently em-
ployed as a steep for seed-corn.
305. Zinc is never found in the metallic state; its
ores are calamine, which is a carbonate, and blende.
TIN. 135
a sulphuret ; it is obtained by roasting the ores, which
in the one case drives off the carbonic acid, and in
the other dissipates the sulphur ; the roasted ore is
then mixed with charcoal and distilled ; the metal is
volatile at a very high temperature.
306. When zinc is strongly heated in the air, it
burns with a bright flame, and is converted into a
white oxide, which may also be obtained by acting
on the metal by an acid ; the metal easily oxidizes
and dissolves, forming a salt from which the oxide
may be obtained, on the addition of an alkali. Sul-
phate of zinc, or white vitriol, is a white salt, very
easily soluble in water, and made either from the
metal and sulphuric acid, or from the native sul-
phuret.
307. Zinc has a strong affinity for chlorine ; by
dissolving the metal in muriatic acid, a solution of
the chloride is obtained. It is very soluble in water,
and has been much employed to preserve wood and
canvas from decay.
308. Tin occurs native almost entirely as an oxide,
from which the metal is obtained pure by merely
heating with charcoal. Heated in the air it easily
oxidizes, and by the action of acids a protoxide and
peroxide may be procured. Peroxide of tin, the same
substance which occurs native as tin-stone, is arti-
ficially made, as a polishing powder, being called
"putty powder." Oxide* of tin has a remarkable
affinity for coloring matter, and hence is much used
by dyers in fixing colors. The bisulphuret of tin is
136 MANGANESE — LEAD.
of a beautiful golden yellow color, and is employed
for various ornamental purposes in the arts, under
the name of mosaic gold.
309. Manganese, like tin, is found only as an
oxide ; it is a metal in many respects considerably
resembling iron, but having a much stronger attrac-
tion for oxygen, and consequently obtained in the
metallic state with very great difficulty ; it forms
several oxides, only one of which, however, is a base;
some of its salts are employed in dyeing ; and the
peroxide is much used in the process for obtaining
chlorine (191). Manganese is very often found asso-
ciated with iron in rocks and stones, and not unfre-
quently exists in minute quantity in soils; it is com-
paratively speaking, however, a rare metal.
310. Lead is obtained almost exclusively from the
native sulphuret; it never is found in the pure me-
tallic state. The sulphuret is roasted, by which the
sulphur is gradually driven off, and an impure oxide
formed, which remains mixed with a large quantity
of sulphuret; this is then smelted with small coal or
other carbonaceous matter. Lead has a strong affinity
for oxygen, in consequence of which it tarnishes
slowly at common temperatures, and quickly when
melted. At a red heat, lead is gradually converted
into a yellow substance called litharge — this is an
impure protoxide ; if still longer exposed to the air
and heat, it absorbs more -oxygen and becomes red
lead or minium ; besides these two, there is yet a
third oxide of lead, which, however, cannot be formed
LEAD IN WATER. 137
by further heating red lead under the influence of air,
but which is easily made by acting on red lead by
nitric acid ; the lead then acquires a third portion of
oxygen and becomes a dark brown peroxide.
311. Of these three oxides, only one, the protoxide,
is a base ; the other two oxides, when acted on by
acids, part with a portion of their oxygen, and pass
into the state of protoxide before they can combine
with the acid. The most important of the salts of
lead is the carbonate, or white lead, a substance
better suited than any other which is known for the
manufacture of white paint; it is made either by
decomposing a soluble salt of lead by an alkaline
carbonate, or by exposing lead to the action of the
vapor of vinegar and carbonic acid gas. The acetate
of lead, likewise, is manufactured on a large scale,
and used for various purposes in the arts.
312. Lead has a strong affinity for sulphur, and
in consequence of this most of the salts of lead are
decomposed by sulphuretted hydrogen ; the blacken-
ing of white paint is due to this cause. As the sul-
phuret of lead is decomposed by chlorine, white paint
thus blackened maybe cleaned by muriatic acid; this
converts the black sulphuret into a white chloride,
though it never looks so white as the carbonate did
before.
313. Lead is acted on by pure water in a very re-
markable way, being oxidized and dissolved with great
facility; this is not the case with common water con-
taining salts of lime, &c. (75). Rain-water, or very
12*
138 - METALLIC ALLOYS.
pure water, kept in leaden cisterns, or passing
through leaden pipes, often dissolves so much lead
as to become unwholesome, or even poisonous ; and
for the same reason leaden covers to cisterns are
equally objectionable, because the water which con-
denses on the cover, being of course pure (73), cor-
rodes and dissolves the lead, and dripping down again
into the cistern, contaminates the water, which other-
wise might have remained pure and wholesome : a
great deal of disease is probably caused by want of
attention to these facts.
314. Many of the metals, when melted together,
combine to form what are called alloys, or mixed
metals ; some of these appear to be regular definite
compounds, though others are obviously mere mix-
tures. The most important of the alloys are gold
and copper, and silver and copper, which are harder
than gold or silver alone ; these alloys are used for
plate, coin, &c. Zinc and copper, or brass ; tin and
copper, or bell-metal; tin and iron, or common tin
plate, which is often supposed to be merely tin,
though it really consists of thin plates of iron, alloyed
on the surface with tin, so as to have the strength
and stifi"ness of the iron, together with the free-
dom from rusting of the tin. Zinc and iron, or "gal-
vanized iron," as it is frequently called, is iron
alloyed or covered on the surface with a film of zinc,
which greatly protects it from corrosion ; and, lastly,
lead and tin, or pewter, and common solder.
139
CHAPTER y.
ORGANIC MATTER — THE NATURE AND COMPOSITION OF
VEGETABLE SUBSTANCES.
315. We have now very briefly described most of
those substances which are of importance in studying
vegetable chemistry. Before explaining the action
which they have on the growth of plants, it will be
proper to go a little more into detail respecting the
nature of organic matter ; that is to say, the various
compound substances which constitute the bodies of
animals and plants.
316. Most of the substances hitherto described,
such as water, ammonia, carbonic acid, common salt,
&c., consist wholly of two elements, and are therefore
sometimes called hinary compounds. On the contrary,
all animal and vegetable substances consist of three
or four elements, and are consequently termed ter-
nary or quaternary compounds. It has been already
stated that plants and animals are composed of carbon,
oxygen, hydrogen, and nitrogen (92). It is very
important to understand clearly the nature of the
compounds formed by these elements.
317. When we endeavor to analyze a plant, that
140 LIGNIN.
is to say, to ascertain of what it is composed, we find
that the greater part of it consists of carbon, oxygen,
hydrogen, and a small portion of nitrogen, combined
together. When we burn it, or in any other way
weaken the affinity which the elements have for each
other, they separate, and, by combining together,
generally form water, carbonic acid gas, and ammonia.
318. When a plant is boiled in water, it is found
that part of the plant dissolves in the water, whilst
part remains insoluble, and we are unable by long-
continued boiling to make the whole of it dissolve in
the water. These, then, are two great divisions of
vegetable matter — that which is soluble in water, and
that which is not. By very simple operations of this
kind it is easy to discover that plants are composed
of a variety of different compound substances, readily
distinguished from each other by the different pro-
perties which they possess. Of those which are
usually found in all plants, the most abundant are
called lignin, starch, gum, sugar, gluten, and albumen.
The four former consist of carbon, oxygen, and hy-
drogen alone, whilst the two latter contain, in addi-
tion to these elements, a portion of nitrogen.
319. Lignin, or pure woody fibre, exists in almost
all plants; it constitutes the greater part of the stem,
wood, bark, and branches of trees; and is present,
though in smaller quantity, in the leaves and flowers
of trees, shrubs, and succulent plants. It is the most
solid constituent of plants, giving strength to those
parts in which any quantity of it exists. It may
WOODY FIBRE. 141
readily be separated from the other matters with
which it is associated, bj bruising and long-continued
boiling in water and spirit; by these means the softer
or more soluble substances may be separated, and
pure lignin is left. In the process for preparing flax,
the stems of the flax plant are allowed to remain in
water for some time; the green soft parts decay,
and at last nothing but the lignin or woody fibre is
left.
320. Pure lignin is a white, tough, fibrous substance,
composed of an infinite number of very fine threads
or fibres, perfectly insoluble in water, and not at all
altered by keeping in dry air. When heated in the
air it soon turns brown, being partly decomposed: if
it be still further heated, it takes fire and burns with
a bright flame, the results of its combustion being
water and carbonic acid gas. Its composition is —
Carbon 4980
Oxygen 4462
Hydrogen . . , . , . 558
10,000
321. The woody fibre of plants is not pure b'gnin.
It consists of cells and tubes more or less incrusted
and filled up with resinous and other matter, which
renders them stiff and hard. The fibre of fine linen
or cotton may be taken as an example of tolerably
pure lignin ; because the foreign matters originally
associated with it have been almost entirely removed,
142 GUN-COTTON.
by various processes which the fibre has undergone,
in the diflferent operations of the manufacturer.
322. Pure lignin, or cellulose, as it is sometimes
termed, is scarcely at all acted on by acid or alkaline
solutions, either hot or cold, unless they are very
concentrated. Strong sulphuric acid converts it into
gum (359). Strong nitric acid produces a very re-
markable effect on lignin, and changes it into gun-
cotton, or xyloidine. In this action the lignin is
partially decomposed, and a portion of its oxygen
and hydrogen, in those proportions which would form
water, is replaced by some of the oxygen and nitro-
gen of the nitric acid.
323. Gun-cotton is best formed by steeping pure
clean cotton wool, quite free from all oily matters,
either in very strong nitric acid, or in a mixture of
nitric and sulphuric acids ; the addition of the latter
is merely made for the purpose of rendering the nitric
acid stronger by extracting the water which it con-
tains. The cotton increases considerably in weight,
and when well washed and dried is found to be highly
explosive. It detonates at a heat a very little above
that of boiling water, with a bright flash, and is wholly
converted into carbonic acid, nitrogen, steam, &c.
324. Woody fibre has a strong affinity for various
coloring matters, and also for some particular metallic
oxides, especially alumina, and the oxides of iron and
tin ; solutions of these substances are consequently
much used by dyers. The cotton to be dyed is first
impregnated with the mordant, as these substances
STARCH. 143
are called, and subsequently dyed by being immersed
in the colored solution (542).
325. When wood is distilled, or roasted in close
vessels, various substances are formed; amongst these
are vinegar or pyroligneous acid (488), and wood or
pyroxylic spirit. The latter is a volatile, pungent-
smelling liquid, which burns easily, with a pale flame
like spirit of wine. It is much used by hatters, var-
nish-makers, and others, as a solvent for resins.
326. Starch is almost always found in considerable
quantity in all parts of plants. When pure it is a
white powder, insoluble in cold water, but readily
dissolving in that fluid when boiling hot. There are
many difl'erent varieties of starch, distinguished from
one another by some peculiar property, and which
have received various names, according to the plant
from which they are obtained. Common wheat
starch, which exists in large quantities in the seed of
wheat, is a good example of the general character of
this substance.
327. When starch is dissolved in hot water, it
forms a thick, viscid, semi-transparent liquid, which if
evaporated leaves a yellowish, transparent, horn-like
substance, which readily swells and softens in cold
water. Hot water, though it greatly changes the
appearance and properties of starch, does not in any
way alter its chemical composition.
328. Starch is obtained from wheat by steeping it
in water, and subsequently squeezing and washing
the softened grain, and then allowing the milky
144 STARCH.
liquid thus obtained to stand for some time. The
cells and membranes which inclose the starch are
thus broken and destroyed, and as the starch is inso-
luble in cold water, it is then easily washed out, and
separated from the husk and other insoluble parts of
the grain ; the water is then allowed to settle, the
starch falls to the bottom, and is collected and dried.
329. This softening and destruction of the mem-
branes of the seed is greatly assisted by the presence
of a small quantity of certain acids in the water,
which dissolves the gluten ; a small quantity of lactic
acid is always produced when grain is thus steeped
in water, and this is essential to the manufacture of
starch. A similar effect may be produced by a weak
alkaline solution, and accordingly a dilute solution
of caustic soda is employed by starch-makers to
soften particular sorts of grain, such as rice, Indian
corn, &c. (377).
830. When grated potatoes are placed on a sieve,
under a stream of water, a very large quantity of
starch may be washed out. The starch will soon
settle to the bottom of the water, the soluble matters
of the potato, will be dissolved, and at last.there will
remain on the sieve little else beside the lignin or
fibre which the potatoes contained, together with a
quantity of starch which cannot be separated from
the fibre by mere washing.
331. Potato-flour, arrowroot, tapioca, and sago,
are all varieties of starch ; similar substances are
likewise obtained from Iceland moss, the seed of the
STARCH. 145
chestnut, and many other plants. They all agree in
general chemical characters with wheat-starch, and,
like it, consist of carbon, oxygen, and hydrogen,
rather less than one-half of their weight consisting of
oxygen. Starch consists of —
Carbon 4425
Oxygen , 4908
Hydrogen 667
10,000
332. When starch is examined by the help of a
magnifying glass, it is found to consist of variously
shaped transparent little grains, marked in a very
peculiar manner. These grains vary in shape and
size according to the plant from which they are ob-
tained; this fact renders it possible to ascertain
whether any particular sample of starch is arrow-
root, potato starch, wheat starch, or a mixture of
several kinds.
333. The quantity of starch obtained from differ-
ent plants varies very much. Good wheat generally
yields from 70 to 75 per cent. ; barley contains nearly
80; oats and rye, 60 to 65; beans 40 to 45; peas
about 50; potatoes 15 to 20; arrowroot, 20 to 25.
Almost all the seeds and grain used as articles of
food, such as wheat, barley, oats, rye, maize, rice,
millet, &c., contain a large quantity of starch. Semo-
lina is prepared from hard Italian wheat; it is the
hard granular particles which escape the action of
the mill-stones. Macaroni is the dried paste of hard
13
146 GUM.
•wheat, which is pressed out from a box through aper-
tures, which gives it its hollow form. The polenta
of the Italians is prepared by roasting maize when
the seed is only half ripe.
334. There is a peculiar modification of starch
which exists in the tubers of the Jerusalem artichoke,
dahlia, and many similar plants, and is called inulin;
it contains a rather smaller proportion of carbon than
common starch does.
335. Under the name of Gum are included several
substances, which differ considerably in their nature
and properties. They all agree in being tasteless, or
nearly so; but some dissolve readily in water, and
form a clear, transparent solution ; whilst others do
not dissolve, but merely soften and swell up in water,
forming a gelatinous mass. Gum Arabic is a good
example of the first kind, whilst common cherry-tree
gum belongs to the insoluble variety of gum.
336. Gum is a natural exudation from many
plants, appearing on their surface in the form of
transparent drops or tears, which dry and harden in
the air. Most fruits contain a considerable quantity
of gum, and exudations of gum are frequently found
on many fruits, particularly the plum. There is a
peculiar substance resembling gum, to which the
name of pectine is given, and which exists in most
fruits ; it gelatinizes with water, and gives to fruits
the property which they have of forming imperfect
jellies. Black currant and apple jelly consists chiefly
GUM. 147
of pectine. The same form of gum is found in the
carrot, parsnip, and many similar roots.
337. A solution of gum in water is called mu-
cilage ; comparatively a small quantity of gum ren-
ders water thick and slimy : such a solution feels
sticky to the fingers ; it dries slowly, and leaves a
small quantity of gum on the surface of any sub-
stance over which it has been spread. Gum is inso-
luble in spirit of wine ; hence mucilage is precipi-
tated, and the gum it contains thrown down as an
insoluble curd when mixed with spirit. The juices
of many plants are sticky from the quantity of gum
which they contain.
338. Gum consists of the same elements as starch,
namely, oxygen, hydrogen, and carbon; but it cod-
tains a rather larger proportion of oxygen than
starch does. Gum consists of —
Carbon 4268
Oxygen 5059
Hydrogen 637
10,000
339. Associated with gum in many plants, there
is found a substance which dissolves easily in water,
and like gum, forms a sticky thick solution; it is
distinguished readily from gum, however, by possess-
ing a sweet taste, whilst gum is insipid or tasteless ;
it is called sugar or saccharine matter, under which
names a considerable variety of different substances
are included.
148 SUGAK.
340. Sugars are divided into two classes: those
which are crystallizable, and those which are uncrys-
tallizable : that is to say, those which, when their
solution in water is evaporated, are obtained in the
form of regular-shaped little grains, like common
cane' sugar, and those which under these circum-
stances do not form regular grains, but remain thick
viscid liquids, like treacle. The crystallizable sugars
are divided into two classes — cane sugar, and grape
sugar; these two varieties differ slightly in composi-
tion, the latter containing rather more hydrogen and
oxygen in proportion to its carbon than cane sugar ;
they differ very considerably in chemical properties,
grape sugar only being capable of undergoing fer-
mentation (365).
341. Sugar exists in a great many vegetables, but
it very frequently happens that there are so many
other substances present, that the sweet taste of the
sugar is quite hidden. It is only in those plants which
contain a very large proportion of sugar, or which
do not contain any strong-tasted substances, that
we are able to recognize sugar by its sweet taste.
Most ripe fruits contain a large quantity of sugar ;
it is likewise found abundantly in the sap of a good
many trees, from some of which, like the sugar maple,
it is procured in such quantities as to be extracted as
an article of commerce.
342. The composition of sugar is similar to that of
starch : the proportions in which its three elements,
oxygen, hydrogen, and carbon, are united together
SUGAR. 149
are very nearly the same as in starch. The varieties
of sugar contain slightly different proportions of these
elements ; thus the composition of cane sugar is not
precisely the same as that of sugar obtained from
grapes, beet-root, or other plants. Cane sugar con-
sists of —
Carbon 4499
Oxygen 4860
Hydrogen 641
10,000
The composition of grape sugar is —
Carbon 3671
Oxygen 5651
Hydrogen ...... 678
10,000
343. The manufacture of sugar from the sugar-cane
is chiefly carried on in tropical countries. The canes
are cut in pieces, and crushed in a rolling mill, so as
to squeeze out the juice. The juice thus obtained is
mixed with a small quantity of lime, and rapidly
heated to the boiling point. The scum which sepa-
rates is collected and removed, and when the juice is
sufficiently evaporated, it is allowed to cool that the
sugar may separate. The uncrystallizable syrup, or
molasses, is drained off from tjie crude sugar thus
obtained, and which is termed raw or Muscovado
sugar.
344. Sugar is refined by dissolving the raw sugar
13*
150 SUGAR.
in a proper quantity of water; a portion of albumen
is added, either blood or white of egg ; the solution
is then heated, and the albumen, as it coagulates and
separates, entangles and removes all the solid im-
purities which the sugar contained. The solution is
purified and bleached by filtration through charcoal
(162), carefully evaporated, and then allowed to
crystallize. The evaporation of the cane juice musji
be carried on as rapidly as possible, but at the same
time, exposure to a high temperature is very objec-
tionable, because the higher the heat, and the longer
the juice is exposed to it, the greater will be the
quantity of molasses formed ; a number of ingenious
arrangements have consequently been devised to
facilitate the evaporation of the solution of sugar at
the lowest possible temperature.
345. Sugar is readily soluble in water, and also
dissolves, though less easily in alcohol. When a
strong hot syrup is sufi'ered to cool slowly sugar is
deposited in large and regular crystals. In the
manufacture of sugar-candy, as these crystals are
termed, the syrup is left quiet, and strings are sus-
pended across it, which assist in the deposition and
formation of large and clear crystals. In ordinary
sugar-refining, the formation of crystals is not desired,
and therefore the solution is continually stirred
whilst it is cooling. When sugar is melted, it loses
its crystalline character, and becomes barley-sugar :
if a very high heat is employed to melt the sugar, it
becomes converted into caramel, or burnt sugar; this
ALBUMEN. ' 151
has a dark brown color, and is used to give color to
brandy and other similar spirits.
346. Albumen and gluten in many respects are
very similar ; they exist in plants in smaller quantities
than the three substances already described ; but they
are nevertheless most important, and of especial in-
terest, as their presence in vegetables is essential to
their value as food (597).
347. When the clear juice of any plant is boiled,
there usually collects on the surface a thick green
scum, which may easily be separated by straining
the liquor through linen. This scum consists almost
entirely of albumen and gluten, the former being a
distinct proximate vegetable principle, the latter a
mixture of two separate principles, fibrin and glia-
dine, with oil ; they are associated together, and
exist in greater or less quantity in almost all plants.
In general, the seeds of plants contain even a larger
relative proportion of these substances than the plants
themselves. A modification of these substances, which
is found in many plants, is called legumine or vege-
table caseine, because it is almost identical with the
peculiar principle of milk, called caseine (568).
348. The flour of wheat contains a considerable
proportion of gluten; it may be readily separated
from flour by tying a portion of thick paste in a
piece of linen, and then kneading the paste thus in-
closed in linen under a stream of cold water ; by this
process all the starch will gradually be washed out,
152 FIBRIN.
and at last there will remain in the linen nothing
but gluten.
349. Gluten, when thus obtained, is a grayish
white, soft, solid substance, elastic and tough, and
almost resembling a piece of animal skin in appear-
ance ; it may be dried by carefully warming it, till
all the water which it contains is evaporated; and
when dry may be preserved for a long time without
its undergoing any change. By boiling gluten in
alcohol it is separated into three substances — pure
vegetable fibrin, an oil, and a tough glue-like sub-
stance called gliadine. Vegetable fibrin is insoluble
in water, soluble in dilute alkaline liquids, very prone
to decompose, and apparently identical with animal
fibrin in nature and composition.
350. Albumen, fibrin, caseine, and gliadine, con-
tain nitrogen ; and all organic substances containing
nitrogen have a great tendency to putrefy. Albu-
men consists of —
Carbon . . . . . . 5501
Hydrogen 723
Nitrogen 1592
Oxygen with Phosphorus and Sulphur 2184
10,000
351. Vegetable fibrin consists of—
Carbon . . . . . . . 5460
Hydrogen 730
Nitrogen 1581
Oxygen with Phosphorus and Sulphur 2229
10,000
ORGANIC CHANGES. 153
352. It is certainly a very surprising fact that so
many different substances should be formed by the
combination of the same elements in different pro-
portions. Nothing can well be more dissimilar than
oil and sugar, flax and starch; yet it is easily proved
that they all consist of the same elements — carbon,
oxygen, and hydrogen.
353. The knowledge of this might naturally lead
one to suppose, that if the whole difference between
such substances consists in the relative proportions of
carbon, oxygen, and hydrogen which they contain, it
might be possible, by some chemical operation, to
take away a small portion of carbon or hydrogen,
and thus, by altering the relative proportions of the
elements, to convert starch into gum, or flax into
starch. Now this can really be done ; and strange
as it may appear, it is nevertheless true, that, by
ver}^ simple means, it is easy to change gum, starch,
and lignin, &c., into each other.
354. The various vegetable substances, though so
different in properties, are very similar in chemical
composition, and may for the most part be readily
converted or changed into each other, by simple
means. They may, when pure, be preserved un-
changed for an unlimited time, if quite dry ; but
when exposed to air and moisture they sooner or
later begin to decompose. Those which consist of
carbon, hydrogen, and oxygen alone, are far less
prone to decompose than those which contain in addi-
tion nitrogen ; and these latter, when decaying, pos-
154 ORGANIC CHANGES.
sess the singular property of causing substances
which do not contain nitrogen to decompose or change
likewise.
355. When vegetable substances, such as lignin or
sugar, are burnt in the air, water and carbonic acid
are produced ; precisely the same substances are
formed by decay, as by combustion. When gluten
and albumen are burnt, water, carbonic acid, and
ammonia are formed.
356. The transformation of one organic substance
into another, is a very interesting and remarkable
operation. It is plain that such changes must be
constantly going on in the organs of plants, and
hence everything which throws light on the nature
of these transformations is of interest.
357. When the chemical affinity which unites the
elements of any compound substance is feeble, and
especially when the compound consists of several ele-
ments, there is always a considerable tendency to
decompose, and the elements are very prone to ar-
range themselves in simpler, and more permanent
combinations. Very slight circumstances therefore
are able to determine the decomposition of such
compounds, and the change may be brought about
in various ways.
358. Some of these transformations are spontane-
ous, some require the presence of a particular sub-
stance, which however has no direct chemical action
on the compound itself, or on any of its elements ;
and many are induced, or caused by the example of
FORMATION OF GUM. 155
some other compound, which is itself in an active
state of decomposition.
359. When strong sulphuric acid is poured over
lignin, it rapidly changes it into gum ; after a few
minutes the fibrous character of the lignin disappears,
and a thick slimy substance is formed ; if the acid is
then diluted with water, and chalk be then added to
neutralize the acid, sulphate of lime will be thrown
down, arid a solution of gum is obtained. If the acid
is left in contact with the gum it soon begins to char
it, and finally completely decomposes it.
360. Starch may also be converted into gum by a
very simple process ; when starch is heated consider-
ably above the boiling point of water, it is changed
into a kind of gum ; large quantities of starch are thus
made into gum by roasting, and used by the calico-
printers under the name of British gum; by chemists
it is called dextrine. The same change may be ef-
fected by boiling gelatinous starch with dilute sul-
phuric acid ; it soon loses its gelatinous character,
"becomes sticky, and is converted into gum. Starch
also undergoes this change when acted on by diastase
(685); a small quantity of this substance, added to a
considerable quantity of gelatinous starch, rapidly
converts it into gum.
361. If, having converted a portion of lignin into
gum by the action of strong sulphuric acid, we add a
quantity of water '•so as to dilute the acid, and then
boil the whole together for some hours, the gum will
gradually be changed into sugar; by this process, then,
156 FORMATION OP SUGAR.
we may convert flax, hemp, or woody fibre of any
kind, even old rags, for they consist chiefly of lignin,
into sugar. When the change is complete, the sul-
phuric acid may be neutralized by the addition of a
quantity of chalk; sugar, and a little sulphate of lime,
will then be left in solution. By continuing to boil
starch with dilute sulphuric acid, in the manner just
described, after it has all been converted into gum,
sugar is also obtained.
362. In these very curious transformations, the
sulphuric acid employed does not undergo any altera-
tion whatever: none of it is decomposed, it retains all
its powers unimpaired, and it is easy to recover, at
the end of the operation, the whole of the acid origin-
ally employed. It does not abstract anything from
the substances with which it is boiled, nor does any
part of the acid unite or combine with them.
363. All the eff"ect which the acid produces is, that
its presence under these circumstances causes a change
in the chemical nature of the substances with which
it is boiled. In the case of starch, it is thus enabled'
to take up and combine with about one-sixth of its
weight of water, or rather of oxygen and hydrogen,
in those proportions which would form water, and in
so doing the starch is converted into sugar. The
same effects may be produced with many other acids
besides the sulphuric (373).
364. Sugar, spirit of wine, and vinegar consist of
the same elements : they contain oxygen, carbon, and
hydrogen ; but the elements are united in different
FERMENTATION. 157
proportions: the properties of these three substances
are as opposite as they well can be, and yet, the
whole difference is in the proportions of their ele-
ments. It is well known that, when a solution of
sugar ferments, it is changed into spirit ; it parts
with a portion of carbon and oxygen, and the ele-
ments left constitute spirit ; hence, during ferment-
ation, carbonic acid is given off. Again, when
spirit and water is exposed to the air and moderate
warmth, it soon changes into vinegar : this change is
wholly effected by the absorption of a little oxygen
from the air.
365. Fermentation is a very singular process, and
a knowledge of the effects which it produces, enables
us to understand many changes which would other-
wise appear incomprehensible. Under ordinary cir-
cumstances, pure sugar, dry or dissolved in water,
may be kept for a long time without its undergoing
any change ; when, however, it is mixed with a small
quantity of certain decomposing matters containing
nitrogen, it ferments, and is changed into spirit.
The substance added, does not combine with the
sugar or its elements, but, whilst itself decomposing,
it causes the sugar also to change.
366. Fermentation, then, is the spontaneous de-
composition of a substance, occasioned by the presence
of a small quantity of decomposing matter. The
yeast, or ferment of beer, possesses the power of in-
ducing the decomposition of sugar and similar sub-
stances when mixed with them. Common yeast, and
14
158 FERMENTATION.
all substances which possess the power of causing
fermentation, contain nitrogen ; they are compounds
of carbon, oxygen, hydrogen, and nitrogen, and are
accordingly very liable to decompose. During the
fermentation of any liquid, the azotized matters
present, which constitute the ferment, and are in an
active state of decomposition, gradually separate,
either rising to the surface or falling to the bottom.
This ferment, yeast, or barm, may then be removed
and added to any other solution, the fermentation of
which it is desired to excite. In most cases, there is
more azotized matter present than is require^ to in-
duce the fermentation of all the sugar, and hence
there is generally a quantity of ferment left over,
when the operation is finished.
367. Most varieties of sugar are capable of under-
going fermentation, but it appears that, in all cases,
they previously pass into a state of grape sugar.
When a solution containing sugar and ferment is
kept for some time at a moderate temperature, the
sweet taste of the sugar gradually disappears, much
gas is given off, the mixture froths up from the escape
of carbonic acid, and, when the fermentation is com-
plete, spirit is found in place of sugar. When such
a fermented liquor is distilled, the spirit passes over
before the water, being more volatile; at least, the
first portions of the liquid which pass over contain
the greater part of the spirit.
368. Common spirit of wine is a mixture of alcohol
and water ; by repeated distillation with substances
FERMENTATION. 159
•which have a strong affinity for water, pure alcohol
may be obtained ; it is much lighter than water, and
boils at a lower temperature than that liquid. Alco-
hol consists of carbon, oxygen, and hydrogen ; but
contains in proportion less carbon, and much less
oxygen, than starch or sugar do.
369. In expressing the composition of starch,
sugar, and the other principles of plants, the propor-
tion of the different elements, per cent., has been
given ; for some reasons, however, it is more conveni-
ent to calculate the number of equivalents of each
constituent ; and this is not difficult to do when the
composition of the substance is once known.
370. For example : ten thousand parts of sugar is
found to consist of carbon 4198, hydrogen 643, and
oxygen 5159 : now, the equivalents or combining
weights of these three elements are respectively 6, 1,
and 8. If, then, we divide the numbers just given
by these combining weights, we shall obtain 699
equivalents of carbon, 643 of hydrogen, and 644 of
oxygen ; and on equally reducing these, so as to ob-
tain the lowest number of equivalents, preserving this
ratio, we shall at last find that sugar consists of 12
equivalents of carbon, 11 of hydrogen, and 11 of
oxygen.
371. This mode of stating the composition of a
substance, is very convenient in explaining the various
transformations which organic matter undergoes.
When a solution of sugar begins to ferment, the first
thing is, that the cane sugar passes into the state of
160 FERMENTATION OF SUGAR.
grape sugar ; each equivalent of cane sugar takes up
and combines with three additional equivalents of
water. This change may be thus expressed: 1 equiv.
cane sugar contains 12 equiv. carbon, 11 equiv.
oxygen, 11 equiv. hydrogen. In passing into grape
sugar it takes up 3 equiv. of water, or 3 equiv. oxy-
gen, and 3 equiv. hydrogen, and so becomes 1 equiv.
of grape sugar, containing 12 equiv. carbon, 14 equiv.
oxygen, 14 equiv. hydrogen.
Carbon. Oxygen. Hydrogen.
1 equiv. Cane Sugar, containing 12 11 11
and 3 equiv. Water *' 0.3 3
forms — — —
1 equiv. Grape Sugar " 12 14 14
372. In the second stage of fermentation, this
grape sugar is decomposed and separated into alco-
hol, carbonic acid, and water : 1 equiv. of grape sugar
containing 12 equiv. carbon, 14 equiv. oxygen, 14
equiv. hydrogen, during fermentation is resolved as
follows : —
Carbon. Oxygen. Hydrogen.
1 equiv. Grape Sugar, containing
12
14
14
forms
—
—
—
2 equiv. Alcohol "
8
4
12
2 equiv. Water *'
2
2
4 equiv. Carbonic Acid "
4
8
373. In the same way, the changes which occur
during the transformation of starch into grape sugar,
may be similarly explained : when this happens,
each equivalent of starch takes up four equivalent^
FERMENTATION OF VINEGAR. 161
of water, and forms one equivalent of sugar: it
follows from this fact, that the quantity of sugar
formed always weighs considerably more than the
starch from which it is obtained.
374. One equivalent of starch contains 12 equiv.
carbon, 10 equiv. oxygen, 10 equiv. hydrogen ; when
acted on by diastase, or boiled with a dilute acid,
it takes' up in addition the elements of 4 equiv. of
water, or 4 equiv. of oxygen, and 4 equiv. hydrogen,
and is converted into 1 equiv. of grape sugar, con-
sisting of 12 equiv. carbon, 14 equiv. oxygen, 14
equiv. hydrogen.
Carbon. Oxygen. Hydrogen.
1 equiv. Starch, containing 12 10 10
and 4 equiv. Water "0 4 4
forms — — —
1 equiv. Grape Sugar " 12 14 14
375. A liquid which has already undergone the
vinous or alcoholic fermentation, is still able to
undergo another change, namely, the acetic ferment-
ation ; which occurs where weak spirit of wine, in
contact with some ferment, is exposed to the air.
Alcohol and water together, whether exposed to the
air or not, undergoes no change whatever ; when a
small quantity of decomposing azotized matter is
added, then the acetic fermentation commences, and
vinegar is formed (476).
376. In the formation of vinegar from spirit, the
presence of air or oxygen is necessary. One equiv-
alent of alcohol consists of 4 equiv. carbon, 2 equiv.
14*
162 LACTIC ACID.
oxygen, 6 equiv. hydrogen (372) ; in passing into
vinegar, it takes up 4 equivalents of oxygen, and
forms 1 equivalent of acetic acid.
Carbon. Oxygen. Hydrogen.
1 equiv. Alcohol, containing 4 2 6
and 4 equiv. Oxygen "04
forms — — —
1 equiv. Acetic Acid " 4 3 . 3 •
and 3 equiv. Water "03 3
377. When azotized matters are beginning to
decompose, they are at first not able to excite the
true alcoholic fermentation in solutions of sugar ; it
is necessary for this that their decomposition should
be tolerably active and advanced. But even in this
early stage they are able to effect a very important
change in the nature of sugar, and cause it to undergo
a peculiar acid fermentation, the result of which is
the formation of lactic acid. The relation of this
substance to sugar may be learnt from the fact that
it contains 6 equiv. carbon, 5 equiv. hydrogen, and
6 equiv. oxygen (445, 570).
378. It sometimes happens also that, in place of
lactic acid, another acid substance, called the butyric,
is produced. This is especially the case when a
solution of sugar is left in contact with caseine, in
the first stage of decomposition. Butyric acid is
a colorless, sour, pungent-smelling liquid, readily
soluble in water and alcohol, and consisting of 8
equiv. carbon, 7 equiv. hydrogen, 8 equiv. oxygen.
379. There are several other forms of fermentation
PUTRID FERMENTATION. 163
besides these, though the alcoholic and the acetous
are by far the most important. It is evident, how-
ever, from the great facility with which starch, gum,
sugar, &c., are converted into each other, that all of
these forms of organic matter may be readily made
to undergo any of these kinds of fermentation, and
likewise that the nature of the change thus brought
about will depend entirely on circumstances.
380. Organic matter, placed under proper circum-
stances, may be made to pass through several suc-
cessive stages of fermentation ; the last of these is
usually the putrefactive fermentation, the results of
which are chiefly carbonic acid, ammonia, and water.
When it is desired to excite any particular kind of
fermentation, care and attention are always requisite
to prevent it from proceeding too rapidly, or too far,
as, when this is the case, it very commonly changes
into the putrefactive fermentation, and, when this has
once commenced, it is hardly possible to stop its
progress.
381. A number of important arts are wholly based
upon these facts ; and many of the arts of life are
more or less dependent in principle upon the effects
just described. The manufactures of wine, spirit,
beer, vinegar, bread, cheese, starch, leather, &c., may
be mentioned as examples.
382. Grapes contain sugar, and a small quantity
of azotized matter, capable of acting on the sugar as
a ferment; but no fermentation can take place, so
long as air is altogether excluded. The azotized
164 GRAPES.
matter present will not enter into an active state of
decomposition, unless free oxygen has access to it.
Consequently whole grapes, or those in which the
skin remains perfect and entire, may be dried and
converted into raisins; but if the skin is once injured,
a little air gets in, and fermentation soon commences.
The fermentation of grape juice will not take place
if the grapes are pressed in a jar containing carbonic
acid gas, or nitrogen.
383. When grapes are pressed, which is the first
process of the wine-maker, they are generally bruised,
and then allowed to remain some little time in the
pressing-vat, before the operation is completed. This
allows fermentation to commence, for it begins as
soon as the juice comes in contact with the air; and
this fermentation, besides softening the skins and
cellular tissues of the grapes, also dissolves a portion
of the coloring and astringent matter which the skins,
seeds, and stalks contain. The pressing is then com-
pleted, and the juice separated from the residue,
which is termed the murk, or the mark.
384. A certain degree of warmth is always neces-
sary to fermentation. The fermenting liquid must
not be lower than 51° or higher than 85°. A tem-
perature of 70° is that most favorable to rapid fer-
mentation. When the liquid is cooled, its ferment-
ation suffers a proportionate check, and if cooled too
much, it ceases altogether. When this is the case,
it can only be brought on again by the careful appli-
cation of heat.
FERMENTATION OF WINE. 165
385. The must, as the expressed juice of the grape
is called, being left undisturbed in the fermenting
tun, soon passes into a state of active fermentation;
the azotized matter decomposes, causing at the same
time the decomposition of the sugar; the liquid be-
comes turbid and froths up from the escape of carbo-
nic acid. After a time these appearances cease, the
liquid clears, and fermentation becomes very feeble.
386. The fermentation of the wine, however, is
not yet completed; the half- formed wine is racked
off into casks, and allowed to continue slowly ferment-
ing for some time, the casks being kept quite full, so
that the froth and ferment which rises to the open
bunghole, easily escapes as fast as it rises. When
it is judged that this second fermentation has con-
tinued long enough, the casks are closed and left for
some time.
387. As the quantity of alcohol which is thus pro-
duced depends wholly on the proportion of sugar
which existed in the must, so, when the grapes are not
sweet, and the quantity of sugar is small, the wine
formed will be very weak. In such cases, therefore,
either the must is concentrated by evaporation, or a
portion of sugar is added to augment the proportion
of fermentable matter in the must. Much better
wine is formed by thus increasing the sugar in the
must previous to its being fermented, than by the
addition of spirit to the wine when its fermentation
is complete.
L It is generally better to add sugar than to
166 FERMENTATION OF WINE.
concentrate the must by boiling, because, in the latter
case, a portion of the azotized matter necessary to its
subsequent fermentation, is rendered insoluble and
useless. Care must, however, be taken not to add too
much sugar, as, when this is done, fermentation pro-
ceeds very slowly ; the proportion of sugar should in
no case be greater than one-eleventh of the weight of
the must.
389. During the two stages of fermentation through
which the must passes, the greater part of the azo-
tized matter undergoes decomposition, becomes inso-
luble, and falls down, constituting, together with the
other insoluble matters, the lees of the wine. The
sugar disappears, carbonic acid gas is given off, and
alcohol formed. A small quantity of certain peculiar
volatile oils is also formed, to the formation of which
the wine owes its flavor, or bouquet. A considerable
quantity of tartar or bitartrate of potassa likewise is
thrown down during the fermentation of the wine.
This salt, which is soluble in water, but almost inso-
luble in a mixture of water with spirit of wine, exists
naturally in the juice of the grape; as the ferment-
ation proceeds, and alcohol is formed, the tartar
being consequently no longer soluble in the liquid, is
deposited in the form of crystals on the side and
bottom of the cask (498).
390. The fermentation and ripening of wine con-
tinues for a long time in the wood ; a small quantity
of undecomposed azotized matter remains in the wine;
this acts as a very slow ferment, and hence the wine
FERMENTATION OF WINE. 167
continues to improve, more spirit being formed, and
consequently more tartar thrown down. Wine also
becomes stronger when kept in the wood, because,
under these circumstances, a greater proportion of
water passes oiF by evaporation, than of alcohol.
This is always found to be the case when a mixture
of spirit and water is kept in a slightly porous vessel,
the water evaporates faster than the spirit.
391. Finally, the wine is either racked off into a
clean cask, the lees being left behind, or it is clarified,
or fined, with albumen or isinglass, and then bottled.
Wines which are intended to be sparkling or efi'er-
vescing are bottled before the fermentation is quite
finished, so that the carbonic acid subsequently
evolved, remains stored up in the liquid.
392. In making what are termed home or domestic
wines, the juice of various fruits, &c., is mixed with
sugar and fermented. A good deal of skill is required
in this operation, and care must be taken so to pro-
portion the difi^erent ingredients, as to insure a proper
fermentation. It is a very common error to use too
much sugar, and not add enough ferment to cause its
due fermentation ; for this purpose the yeast or fer-
ment of wine is best ; that obtained from the ferment-
ation of beer injures the flavor of the wine.
393. When the vinous fermentation of must is quite
complete, it should not be suffered to remain longer
in contact with the lees, because when this is the case,
especially with weak wines, many circumstances may
tend to commence the acetous fermentation, giving
168 CIDER — PERRY.
the wine an acid flavor. When this has once com-
menced, and the wine is what is technically termed
pricked, it is very difficult to render the wine whole-
some again ; wines are subject to many diseases, as
they are called, and some of them may be prevented
or remedied. The chief cause of them is, the pre-
sence of a minute quantity of ferment, of some kind
or other. When wine is not perfectly clear, it is
evident that it contains "ferment," and is, conse-
quently, peculiarly liable to ferment and turn sour.
394. There are many other fermented liquids
which are prepared in the same way as wine, and,
like it, contain alcohol, derived from the fermentation
of sugar. Thus cider obtained from apples, perry
from pears, and mead from honey, derive the alcohol
which they contain from the sugar of fruit or honey,
and owe their flavor chiefly to the volatile oils formed
during its fermentation.
395. In the preparation of these liquids, especially
cider, it is often necessary to put a stop to the fer-
mentation when it is arrived at a certain point ; this
is usually eff'ected by the fumes of burning sulphur ;
a small quantity of sulphuric acid gas arrests the
fermentation of a large quantity of fermenting liquid.
Fermentation is arrested or altogether prevented in
a very remarkable manner by the presence of various
substances, such as some of the strong acids, certain
salts, and some of the volatile oils, even in very
minute quantity. No substance possesses this power
to a greater degree than sulphuric acid gas (173).
BRANDY. 169
396. When wine is distilled, the liquid which passes
over is brandy, and not a pure spirit of wine ; a small
portion of the volatile flavoring matter of the wine
passes over with the alcohol and water. By repeated
rectifications this flavor may be removed, and a pure
spirit of wine, or alcohol, obtained.
397. Good wine brandy, such as Cognac, when
obtained by distilling wine, is always colorless like
water ; but old brandy, or that which is kept some
time in the wood, acquires more or less of a brownish
color, in consequence of its dissolving a portion of the
coloring matter of the cask. The manufacturers of
brandy, who prepare a spirit sold under the name of
brandy, but really derived from some other source
than the juice of the grape, color their spirit with
oak-wood, burnt sugar, treacle, or even more objec-
tionable substances.
398. Spirit is obtained in a great number of ways,
and varies in flavor according to the mode in which
it is prepared. Sometimes, as in the manufacture of
liqueurs, which are, in fact, flavored brandies, some
substance is purposely added to alter the flavor.
Maraschino and Kirschwasser are brandies distilled
from the fermented juice of crushed cherries, and
derive their agreeable flavor from the volatile oil
and prussic acid which exist in the kernels of the
cherry ; but maraschino is likewise frequently fla-
vored by the addition of cloves, orange, or cinnamon.
Noyeau is flavored with the kernels of bitter almonds..
15
170 SWEET WORT.
399. The more common kinds of spirit, though all,
in fact, obtained from the fermentation of sugar, are
yet in the first instance obtained from starch; this
substance, however, in all cases, is first converted
into grape sugar, and then undergoes the vinous fer-
mentation.
400. Distillers either employ malted grain, or a
mixture of malt with raw grain. In the first case, a
very large portion of the starch which the grain con-
tains is already converted into sugar ; and when raw
grain is used, its starch is gradually changed into
sugar in the process of mashing (413).
401. The malt, or mixture of malt and grain, is
ground, and then stirred or mashed into warm water,
in the mash-tub ; in this operation, the soluble mat-
ter of the grain is extracted, and the starch converted
into sugar. The wort, as this infusion of grain is
called, is then cooled, drawn oif, and transferred to
the fermenting tuns ; a quantity of good yeast or
ferment is added, and the mixture is left to ferment
for several days.
402. The fermentation of the sweet wort is allowed
to go on as long as it can be safely left, without fear
of the acetous fermentation being brought on ; for it
is the object of the distiller to convert the whole of
the saccharine matter which it contains into spirit.
When this is done, the fermented wort, whioh is then
termed wash, is transferred to the still, and heated.
The product is a dilute, weak spirit, and requires to
be rectified or distilled again.
WHISKEY. 171
403. During the fermentation of the wort, as in all
similar operations, a quantity of a peculiar volatile
oil is produced, some of which passes over with the
spirit when it is distilled ; that which is obtained
towards the end of the distillation is generally most
contaminated with this oil, and is termed faints.
The wash usually yields rather more than one-tenth
of its volume of pure alcohol, or one-fifth of strong
spirit, half of which is pure alcohol ; — for the strong-
est spirit which can be thus obtained, always con-
tains a considerable quantity of water (368).
404. As there is an excise duty on the manufac-
ture of spirit, it is necessary to estimate the strength
and quantity of spirit which the distiller obtains. In
doing this the spirit is stated to be over or under
proof. Proof spirit consists of equal parts of water
and alcohol. It was formerly the custom to pour a
small quantity of the spirit to be tested, over gun-
powder, and then set fire to it ; if the spirit was
strong, the gunpowder fired, and then the spirit was
called proof spirit; but if it contained too much
water, the gunpowder was not fired.
405. This method of testing the strength of spirit
is highly inaccurate. As alcohol is much lighter
than water, the strength of spirit is easily ascertained
by weighing a portion of it in a bottle, the capacity
of which is known ; this gives its specific gravity, or
weight, compared with an equal bulk of water, and
from that it is easy to calculate its strength.
406. The flavor of the grain spirit, or whiskey,
thus obtained, depends a good deal on the ferment
172 GIN.
used in its manufacture. The whiskey obtained by
means of beer or porter yea^ Iras always an inferior
flavor to that prepared in the Highlands and in Ire-
land, where no brewer's yeast can be obtained.
Whiskey is sometimes artificially flavored ; thus, in
the old Usquebaugh, nutmegs, cloves, cinnamon, and
other similar substances were added; and Geneva, or
gin, was originally prepared by bruising juniper
berries in the mash-tun, along with the grains and
malt.
407. In the manufacture of common gin, a small
quantity of oil of turpentine is frequently substituted
for the juniper berries ; as the flavor thus communi-
cated to the spirit greatly resembles that derived
from juniper. The best Dutch gin, Hollands or
Schiedam, is chiefly obtained from rye, mixed with
about one-third its weight of malted barley, and fer-
mented ; the weak spirit first obtained by the distilla-
tion of this liquid is then rectified once or twice off
juniper berries, by which means it loses the crude
flavor which it originally had, and acquires the agree-
able one of the junipers.
408. Other spirits are similarly prepared from
various substances — in fact, almost all vegetable sub-
stances, containing either starch or sugar, may be
made to yield spirit by fermentation. Very large
quantities of spirit are manufactured from potatoes,
which are grated, and the pulp mashed in water with
a small quantity of ground malt, in an active state of
fermentation. Great care is required in the manage-
BREWING. 173
ment of potato wash, as the wort is very liable to
pass into the acetous fermentation. The spirit
obtained possesses a peculiar, and by no means
pleasant flavor, which, however, may be removed by
rectification.
409. Rum is obtained chiefly in the West Indies,-
from the fermentation of molasses, or uncrystalliza-
ble sugar, mixed with a portion of sugar-cane juice,
and a few crushed fragments of the cane itself; if
these are not added, the spirit has very little flavor.
The fermentation of the liquor is assisted by the ad-
dition of skimmings from the sugar-boilers, and some
of the refuse from a previous distillation, called dun-
der, and which is a tolerably active ferment. When
first distilled, rum has often a harsh and disagreeable
flavor ; it loses this after being kept some time in
410. In India, a great variety of spirits, which
are described under the general name of arrack, are
prepared. The chief sources are rice, sugar-canes,
and the sweet juice of various palm and other trees,
abounding in sugar. This juice, which is called
toddy, ferments very easily ; and if care be taken
that it does not pass into the acetous fermentation,
yields a pure and well-flavored spirit.
411. In the manufacture of beer, the object of
the brewer is, to obtain a solution containing the nu-
tritive matters of the grain in a soluble and partly
fermented state; part of the sugar being already
converted into spirit, whilst the fermentation of the
15*
174 MASHING.
rest has been prevented, and its tendency to ferment
altogether destroyed.
412. The first operation is to convert the inso-
luble starch in the grain into soluble gum and sugar ;
this is effected by malting. The grain is moistened
•and allowed to germinate, and, in so doing, it be-
comes sweet, starch disappears, and sugar is formed ;
if germination were allowed to go on, the sugar thus
formed would be absorbed by the young embryo
plant, and the labor of the maltster consequently
lost ; as soon, therefore, as the required chemical
change is effected, he dries the malt, destroys the vi-
tality of the seed, and prevents further loss (690).
413. Barley generally contains about 8 or 9 per
cent, of sugar and gum ; after being converted into
malt it contains 30 per. cent, of those substances,
and of this at least half is sugar. In the process of
malting, some of the azotized matter originally con-
tained in the seed is lost (685).
414. Although barley is generally used in the
ttianufacture of malt, yet most other grains may be
rendered swefit by a similar process. In various
countries, rye, wheat, oats, maize, rice, and millet,
are malted.
415. In the manufacture of beer, as in the prepa-
ration of distillers' wash, the malt is first ground, or
rather crushed, and then mashed or infused in warm
water, at a temperature of about 160° ; so as to ex-
tract all the soluble matters which it contains. The
malt is kept constantly stirred in the mash-tun for
MASHING. 175
about three quarters of an hour, the tun is then cov-
ered, and the whole is left quiet for about the same
time, or rather longer.
416. Two objects are attained in the process of
mashing ; the soluble matters in the malt are ex-
tracted, and a further portion of the starch is con-
verted into sugar and gum, by the influence of the
diastase which the malt contains (685) ; and hence, if
a quantity of raw grain is mixed with the malt, the
starch which it contains will be found to be converted
into sugar and gum in the mash-tun.
417. It is of the first importance to use water of a
proper temperature in the mash, tun ; a good deal of
heat is given out in the process of mashing, and this
must be allowed for. If the water is too hot it con-
verts the starch into a jelly, which interferes with its
conversion into sugar; this is called setting the mash.
If on the other hand the mash is too cool, the con-
version of the starch into sugar will likewise be very
slow and imperfect, and the wort will have a great
tendency to turn sour.
418. When the mash is complete, and the wort has
become clear, it is run off from the spent grains ;
which are then mashed a second time with fresh warm
water, to dissolve the soluble matters still left in the
grains after the first mashing. The product of the
first mash alone is used for ale, while that of the sub-
sequent operations is employed for common or small
beer. Sometimes the grains are subjected even to a
third mashing.
176 BOILING THE WORT.
419. The sweet wort is then run into the copper,
and boiled, and the sooner this is done after it has
been drawn off, the better. Sweet wort contains a
much larger quantity of vegetable albumen than is
necessary to insure the requisite degree of fermenta-
tion, and this, if left in it, would be almost sure to
cause it to pass into the acetous fermentation. By
boiling the wort, a considerable quantity of this albu-
men is rendered insoluble, and precipitates in flakes.
The wort must, however, not be boiled too long, or
the whole of the albumen will be thrown down.
420. When the wort has been boiled a certain time,
a quantity of hops is added ; the hops are not allowed
to boil with the wort the whole time, or too much of
their rank flavor would be thus extracted, and the
long-continued action of heat would drive off some of
the fragrant volatile oil which they contain, and the
presence of which is essential to the flavor and good-
ness of the beer (431).
421. This part of the operation, as indeed are all
which in any way depend on the regulation and
management of fermentation, is very delicate, and
requires much care ; the boiled wort is very prone to
pass into the acetous fermentation ; it must be rapidly
cooled, and brought down to the temperature best
suited for alcoholic fermentation.
422. The wort must be cooled to about 60° or
thereabouts, and if this is not quickly done the wort
begins to decompose ; it acquires a rank and disagree-
able flavor, and becomes slightly mouldy; this, which
FORMATION OF YEAST. 177
is termed foxiness. can never be completely remedied
if it has once commenced. It is peculiarly common
in moist, close, warm weather.
423. The cooled wort is then run into the ferment-
ing vat or gyle-tun ; if left to itself, fermentation
would soon commence ; but it is far better to add at
once some good yeast from the last brewing, stir the
whole up well together, and then, having covered the
vat, leave it quiet ; in a few hours the whole will be
in an active state of fermentation.
424. In three or four hours, bubbles of gas will be
seen rising from all parts of the liquid, a ring of froth
forming at first round its edge, and gradually increas-
ing and spreading till it meets in the centre, and the
whole surface becomes covered with a white creamy
foam. The bubbles of gas then rise and break in
such numbers, that they emit a low hissing sound,
and the white foam of yeast continues to increase in
thickness, breaking into little pointed heaps, which
become brownish on the surface and edges.
425. The yeast gradually thickens, and at last
forms a tough, viscid crust, which, when the ferment-
ation begins to slacken, would break and fall back
again into the vat, if it was not removed. The
brewer skims it off and removes it as soon as he
judges that the fermentation is complete; but if he
thinks that the fermentation has ceased too soon, he
stirs the whole up again so as to mix the yeast with
the wort. This, which is called rousing the vat, pro-
178 FERMENTING THE WORT.
longs the fermentation, or rather causes it to recom-
mence.
426. Whilst the fermentation of the wort is pro-
ceeding, it gradually becomes clearer ; the ferment
added, as well as that which is generated in the wort
(for all the azotized matter present is soon brought
into the same condition of active fermentation), is
gradually separated; meanwhile the sugar is decom-
posed, spirit is formed, carbonic acid given off, and a
considerable amount of heat is generated. Where
the quantity of wort is large, this rise in temperature
amounts to ten or fifteen degrees.
427. In making ale and beer, it is the object of
the brewer to leave a portion of the sugar in the liquid,
he therefore removes the yeast so as to put a stop to
further fermentation; but in brewing porter he does
not remove the ferment so soon, but allows the fer-
mentation of the wort to continue for a longer time.
It is sometimes found convenient to add a small
quantity of sugar to the wort.
428. After the first fermentation is finished and
the yeast removed, the liquor is racked or drawn off
into casks, when it undergoes a second fermentation
far more slow and protracted than the first. This is
termed cleansing, and, whilst it goes on, a consider-
able quantity of mucilage, spent ferment, and other
impurities subsides, constituting the lees or dregs.
Wl^en this second fermentation is complete, the liquor
is drawn off into casks, the bungholes of which are
then well closed.
-USE OF HOPS. 179
429. The proportion of alcohol in different kinds
of ale, &c., varies greatly; small beer usually con-
tains from one to two per cent. ; ale from four to
nine; and porter from four to six per cent, of alcohol.
It is commonly calculated that a bushel of good malt
should make about twelve gallons of ale, or twenty-
four gallons of beer; but if the ale is intended to be
kept, a greater proportion of malt must be taken.
430. The quantity of hops taken varies according
to the strength of the liquor, and many other circum-
stances. Strong ale, which is intended for keeping,
must have more hops than that which is intended to
be used at once. From three-quarters of a pound to
a pound and a quarter is the quantity used to each
bushel of malt. Occasionally, other bitters are used
together with hops ; there are several which may be
very well used for this purpose, such as the bitter of
the chamomile flower; but there are others occasion-
ally employed which are highly objectionable, like
quassia. The bitter principle of this wood does not
answer the same objects as that of the hop, and is
besides very unwholesome.
431. Hops are used in brewing, for several pur-
poses. The aromatic bitter which they contain great-
ly improves the flavor of the drink ; their volatile
oil prevents further fermentation, and renders it less
likely to turn sour ; and the tannin and astringent
matter of the hops help in precipitating the mucila-
ginous and albuminous substances which the wort
180 MALT LIQUORS.
contains, and which, if left in the beer, woukl be very
apt to cause its fermentation.
432. The goodness of ale and porter depends a
great deal on the water with which it is brewed ; it
is sometimes supposed that the water must be soft,
but this does not appear to be really the case, because
the water employed in many of the largest and best
breweries is decidedly hard, and contains a very con-
siderable quantity of sulphate of lime (239).
433. Porter is essentially ale brewed with a por-
tion of scorched or high-dried malt, and the ferment-
ation of which has been allowed to proceed so far
that nearly the whole of its sugar has disappeared.
It was formerly brewed entirely from high-dried malt,
but as in that case a large quantity of the sugar
was needlessly destroyed, it was found better to use
common malt, mixed with a small proportion of high-
dried malt ; this gives the desired color and peculiar
flavor of porter or brown stout. Sometimes other
coloring matters are used for the same purposes;
these for the most part must be regarded as adulte-
rations.
434. The slow, continued fermentation which malt
liquors undergo whilst kept ripening in the casks, is
essential to their preservation ; because the carbonic
acid thus generated protects them from the influence
of the air ; hence, too, the casks must be kept closely
bunged up to prevent the escape of this gas. As
soon as this fermentation ceases, and air gets access
BAVARIAN BEER. 181
to the liquor, oxidation commences, and it begins to
pass into the acetous fermentation(476).
435. For the same reason, also, when a cask has
once been tapped, it should be used at once ; the
liquor is brisk at first, being charged with carbonic
acid, which renders it pleasant to the taste, and pre-
serves it from further change ; ere long the carbonic
acid escapes, the liquor becomes flat, then the oxygen
of the air begins to act upon it, and it soon turns
sour.
436. Malt liquor, which has once become clear and
fit for use, must never be shaken ; as ferment is
always formed and deposited, even during the very
slow fermentation which takes place in the cask :
agitation not only renders the liquor thick and
turbid by diftusing the spent ferment throughout it^
but is very likely to induce a fresh fermentation,
which would probably pass into the acetous one.
437. In the Bavarian mode of brewing, the fer-
mentation of the wort is allowed to proceed very
slowly, exposed to a low temperature in large open
vessels. Though slow, this fermentation is very
complete, the whole of the ferment is deposited at
the bottom of the vat, whilst very little rises to its
surface, and there is hardly any frothing of the wort.
Beer thus made has very little tendency to enter
into a new state of fermentation, even by the action
of the air.
438. BREAD-making depends in great part on fer-
mentation ; a small quantity of sugar which exists in
16
182 BREAD-MAKING.
dough is converted into carbonic acid and spirit, by
the action of the yeast or ferment mixed with it ; the
carbonic acid thus evolved by dividing the dough,
and forming little holes and cavities throughout its
mass, renders the bread light and porous.
439. There are two distinct objects to be attained
in the manufacture of bread, the one is the chemical
union and transformation of the starch and other
components of the grain, the other the formation of
a uniformly light, spongy, and easily digestible mass ;
the latter is merely a mechanical effect, but both
objects are effected by chemical means.
440. The flour of wheat and other grains used in
bread-making, consists chiefly of starch, together
with a much smaller proportion of sugar, gum, and
azotized matters. These substances may be made to
undergo various changes, and these changes may be
brought about in many different ways; the most com-
mon and convenient, is to excite in them a state of
vinous or alcoholical fermentation.
441. There are two distinct modes by which this is
effected, namely, the use of leaven and of yeast or
barm. Leaven is dough which has been kept till it
has turned sour; when this is mixed with a quantity
of fresh dough, it has the power of communicating to
the whole of the latter its own state of fermentation.
442. A quantity of flour is kneaded up into dough
with a suitable quantity of water, and then left in a
warm place; it will soon become sour, and a greater
or less degree of fermentation will be established in
USE OF LEAVEN. 183
it, but it will be irregular and very uncertain. If,
however, a small piece of this sour dough is taken and
thoroughly kneaded up with a large lump of fresh
dough, the whole of the latter will very soon enter
into a uniform state of fermentation; and if a
small piece of this is set aside for the next baking,
it will be in a fit state for use by the time that it is
required.
443. The leaven may be formed either of the same
kind of flour as the bread is intended to be made with,
or any other sort; it is most commonly the custom to
employ bean, pea, or some similar flour, which passes
very easily into fermentation, or at least to mix a
portion of it with the flour used in forming the leaven.
When well made, leaven may be kept fit for use for
weeks and months, and by adding a portion of dough
to the leaven as large as that removed for the use of
the bread-maker, the stock of leaven is always kept
up.
444. In this country, however, the use of leaven is
almost wholly superseded in favor of yeast. This
substance can usually be obtained from a neighbor-
ing brewery, and a small quantity of it mixed up with
the dough, brings it rapidly into the required state
of fermentation, without communicating to it the sour
taste which leaven always gives to bread. In many
parts of Europe, however, and when yeast cannot be
had, all the bread is made with leaven.
445. Leaven added to dough excites in it a true
alcoholic fermentation, but it also produces a portion
184 USE OF YEAST.
of lactic acid (377), and frequently vinegar likewise;
the latter is for the most part driven oiF in the sub-
sequent process of baking, but the former remains in
the bread.
446. The baker usually commences by mixing
together in a suitable vessel a proper proportion of
yeast, warm water, common salt, and flour. The
salt is first of all dissolved in warm water, which is
then allowed to cool down to about 80° or 90°, after
which the yeast and then the flour is added. The
quantities taken vary slightly. The third part of a
sack of flour, a pailful of warm water, four or five
pounds of salt, and three or four pints of yeast, are
about the usual proportions.
447. This mixture, which is called the sponge, is
worked up to the consistence of stiff batter, and then
left in a small trough for an hour or two, covered
over with a cloth. During this time a tolerably
active fermentation is commenced, and as the mix-
ture is tenacious and viscid, the carbonic acid gene-
rated does not escape in bubbles, but is retained in
the dough, causing it to swell up to about twice its
original size.
448. If the sponge is made too thin, the gas thus
generated will escape as fast as it is evolved ; if of the
right consistence, the whole of it will be retained.
If the fermentation is allowed to continue too long,
the sponge will become sour, and pass into the state
of leaven; the baker, however, does not permit this,
but when he judges that the fermentation has pro-
BAKING. 185
ceeded far enough, he adds about twice as much
more flour as he originally took.
449. The sponge and flour are then very fully and
carefully kneaded together, so as to insure the com-
plete mixture of the half-fermented sponge with the
fresh flour ; this is a very laborious part of the opera-
tion, but it is quite essential to the success of the
process, for if it is not very thoroughly attended to,
the ferment will not be equally and uniformly dif-
fused throughout the whole of the dough.
450. The dough is then left for about an hour and
a half; it is then kneaded a second time, divided into
pieces of proper size and weight to form loaves, and
then set aside in a warm place for a short time.
Lastly, the loaves are put into the oven and baked,
during which operation they are still more expanded
and enlarged. In baking, the loaves generally rise
or swell up to about twice the size which they pre-
viously had.
451. The object of all these difi*erent processes is
to decompose the sugar which the flour contains, for
the purpose of generating carbonic acid, and thus
rendering the dough light and porous. The sugar,
therefore, which the flour contains is essential to
bread-making : but though the whole, or the greater
part, of this sugar is of necessity thus decomposed,
by the action of the yeast, yet when bread is analyzed
it is found to contain very nearly as much sugar as
flour does.
452. When the yeast is mixed with the flour, it
16*
186 BAKING.
immediately begins to act on the sugar, causing its
decomposition into alcohol and carbonic acid ; but at
the same time it also acts upon the starch, and pro-
duces in it a change analogous to that which diastase
effects in the germination of a seed. It consequently
happens, that though the sugar which originally ex-
isted in the flour is almost entirely decomposed, yet
a quantity of sugar, nearly equal in amount, is pro-
duced or generated from the starch (360).
453. In baking the bread a further portion of the
starch is decomposed; more gum and sugar are formed,
the azotized matters uniting with them and the modi-
fied starch, make a uniform substance, which is far
more digestible than flour or unbaked bread. At the
same time that these chemical changes are effected,
the fermentation is altogether stopped, a considerable
quantity of water and the alcohol formed during the
rising of the bread are driven off, and the bread is at
the same time expanded and rendered still lighter,
by the action of the heat of the oven on the gas con-
tained in its cavities (62).
454. The necessity of attending to the proportions
in which the several ingredients of bread are mixed,
as well as the need of mixing them very thoroughly,
is evident. If the dough is badly mixed, the car-
bonic acid, in place of being regularly diffused
throughout the substance of the dough, will be col-
lected into large irregular bubbles, and then the bread
will be full of large holes and cavities, in place of
being uniformly light and spongy ; and the loaf,
ADULTERATION OF BREAD. 187
though perhaps as large as it would have been if well
made, will be close and heavy.
455. The goodness of bread depends a good deal
on the proportion of water which it contains. The
usual quantity in well-made bread is about 44 per
cent., but it varies somewhat according to the fineness
and goodness of the flour. The percentage of water
is also modified in a remarkable manner by the pre-
sence of various saline substances. The use of com-
mon salt improves bread in several ways ; it not
merely improves its mechanical texture, and renders
it more wholesome and digestible, but it also increases
its retentive power from moisture.
456. When inferior or damaged flour is used, it is
generally found that the bread rises slowly and im-
perfectly, and when baked is close, and has a bad
color. Saline matters are found to correct this to a
considerable extent, and some salts far more power-
fully than others ; alum is sometimes employed for
this purpose. No object is gained by adding it to
good flour, but in the case of inferior flour its use
decidedly improves the bread; and though it is un-
questionably an injurious adulteration, yet it is harm-
less compared with some of the other salts which
have been employed for the same purpose.
457. A very small quantity of alum greatly im-
proves the color of the bread, and also causes it to
rise better, thus making inferior bread equal to the
best. As far as the mere alteration of color is con-
cerned, its use only serves to please the eyes of the
188 EFFECTS OF BAD YEAST.
customer, or rather to deceive him into the belief that
he is buying better bread than is really the case.
The increased lightness which it causes is, however,
really an improvement.
458. Some bakers have even added sulphate of
copper to the dough. This salt produces, in very
minute quantity, the same eft'ects on bread as alum
does. Being a highly poisonous salt, its use is most
objectionable ; fortunately, it is an adulteration very
easily detected.
459. Carbonate of ammonia, which is sometimes
mixed with slightly damaged flour, is a harmless ad-
dition. It does not improve the color of the bread,
but renders it lighter, and removes any sour flavor
which the bread might otherwise acquire, either from
the inferior quality of the flour, or the nature of the
ferment employed (462).
460. When bread is made with leaven, it always
has a distinctly sour taste ; this is partly caused by
the leaven itself, and partly by an acid fermenta-
tion which it induces in the flour or dough. It
sometimes happens also that bread which is made
with barm or yeast has a similar sour taste ; this is
usually caused by want of skill or care in the prepa-
ration. It is occasionally caused by the use of sour
yeast, when the latter has been kept too long or is
spoilt, and then of course the bread will have a sour
taste, the same as if it were made with leaven.
461. In places where a fresh supply of new yeast
cannot always be had, sour yeast must sometimes be
EFFECTS OF BAD YEAST. 189
used, but there is no need for the bread to be bad in
consequence; because it is quite possible to remove
the sour taste of the yeast before using it. The ad-
dition of a small quantity of carbonate of lime, soda,
or magnesia, will effect this ; but, of course, care must
be taken not to use more of either of these salts than
is necessary to neutralize the acid matter present.
462. The sour taste which bread acquires when it
is badly made, or when damaged flour is used, is less
easily corrected. Nevertheless, it may be greatly
diminished, if not altogether prevented, by the ad-
dition of a small quantity of carbonate of soda or
ammonia. The latter salt may often be employed
with great advantage, and, being a volatile salt, it is
raised in vapor by the heat of the oven. Any excess
of it, therefore, is driven off by the heat, and in es-
caping, assists in making the bread lighter.
463. Yeast is not unfrequently bitter, and then
communicates a very unpleasant flavor to the bread
made with it. This may be derived from hops, espe-
cially when the yeast is collected from beer which is
strongly hopped. But yeast sometimes also acquires
a bitter taste from keeping, which is quite independ-
ent of that derived from the hops ; this also may be
remedied to some extent in various ways. One way,
which is said to be very effectual, consists in throwing
into the yeast a few clean cinders freshly taken from
the fire, but allowed to cool a little on the surface.
When cold, the cinders fall to the bottom, and the
yeast is poured off. This operation appears to de-
190 ARTIFICIAL YEAST.
pend in principle upon the singular property ■which
freshly-burnt charcoal has of absorbing gases, and
removing coloring and odorous matter generally from
substances to which it is added (162).
464. When, however, there is any great difficulty
in procuring fresh and good yeast, it is generally
better to use artificial yeast, or to prepare a ferment
on purpose ; this is by no means difficult, and then
the inconveniences just mentioned are wholly avoided.
There are a great number of different ways of making
artificial yeast. The object usually is to obtain a
quantity of paste or dough in an active state of fer-
mentation, and then, by removing the water, to check
further change until the ferment is wanted. By
carefully washing and pressing beer yeast, so as to
separate the moisture as much as possible, it becomes
far less liable to spoil than it is in its fresh state.
465. A tolerably good kind of dry yeast may be
made by mixing together a decoction of wheat and
bean flour with a small quantity of brewer's yeast ;
w^hen the whole is in a state of active fermentation,
enough wheat or barley flour is added to form a thick
dough, which is then thoroughly kneaded, formed into
small cakes, and carefully dried. A very good fer-
ment may at any time be obtained from one of these
cakes, by crumbling it into warm water, and leaving
the mixture a few hours quiet in a warm place.
466. Yeast may also at any time be prepared
direct from malt. When a thick paste or dough of
wheat flour is left in a warm place, it soon begins to
UNFERMENTED BREAD. 191
ferment and emits a sour smell ; at the end of a week,
however, it loses this sour smell and acquires a
vinous one, and is then able to act powerfully on
sugar as a ferment.
467. If a small quantity of dough in this state is
diffused in some warm water, and added to a strong
decoction of malt and hops, such as brewers make,
or even of malt alone, it soon brings the whole into
active fermentation, and in a few hours a quantity of
good fresh yeast will be deposited. When the alco-
holic fermentation is complete, the clear liquor may
be poured off, and the yeast is fit for bread-baking.
468. The object to be attained by the use of fer-
ment or leaven in the manufacture of bread being a
purely mechanical one, and as the process of ferment-
ation is always uncertain and troublesome, a great
number of attempts at different times have been made,
to make bread without its undergoing any ferment-
ation whatever, though hitherto with but partial suc-
cess. With care and attention, however, excellent
unfermented bread may be made.
469. It is sometimes stated by those who recom-
mend the use of unfermented bread, that, in the ordi-
nary mode of bread-making, a large portion of the
most valuable part of the flour is destroyed by fer-
mentation ; this is not really the case. Very little,
indeed, of the azotized matter of the flour is lost dur-
ing the fermentation of the dough; the chief effect
produced is the loss of a portion of sugar, but, as a
nearly equal quantity of sugar is at the same time
192 UNFERMENTED BREAD.
formed from the starch (462), the real effect of the
fermentation may be said to be principally the loss of
about five per cent, of starch. The weight of the
baked bread is always much greater than that of the
flour from which it is made, owing to the large
quantity of water which is incorporated with it.
Two parts of flour make about three parts of bread.
470. The best of the various chemical modes of
making bread, is that in which dry carbonate of soda
and muriatic acid are employed. A small, but
definite quantity of dry carbonate of soda is thor-
oughly mixed with the flour ; enough pure muriatic
acid to neutralize it perfectly is dissolved in the
proper quantity of water, and the flour then added ;
whilst the water and flour^are being mixed, the acid
acts on the carbonate of soda, decomposes it, expels
its carbonic acid, and forms chloride of sodium, or
common salt, with its base.
471. Hence, in this process the same efl'ect in the
end is produced as in the ordinary mode of bread-
making, but with this difference, that it has not un-
dergone any sort of fermentation, and that nothing
has been lost. A light and spongy dough is produced,
containing abundance of bubbles of carbonic acid ;
and the only residue of the process, the common salt
formed, so far from being objectionable, is, in fact,
necessary to the formation of good bread.
472. Another point in favor of this process is,
that it takes much less time than the old methods do,
because there is no need to leave the dough to rise by
UNFERMEKTED BREAD. 193
fermentation ; in fact, the less time the dough is left
to itself, and the more rapidly the operation is car-
ried on, provided the dough is thoroughly mixed, the
better will the bread be.
473. The most serious objection to this mode of
bread-making is, that, unless great care be taken,
there is considerable risk of introducing poisonous
substances into the bread if the acid is not perfectly
pure, even when all reasonable precautions are taken
to avoid adulterations. It is, of course, necessary to
take care that the carbonate of soda is most thor-
oughly mixed with the flour, and great attention
must be paid to the proportions of the several ingre-'
dients.
474. In toasting bread, two very different effects
are produced — the modified starch in combination
with gluten, which the bread contains, is rendered
still more soluble, and a fresh portion of gum is
formed, whilst, at the same time, a part of the bread
is more or less charred or carbonized.
475. In making toast and water, it is sometimes
recommended to burn the toast well, so as to make it
quite black ; this is often very good advice, for the
porous charcoal thus formed is a powerful purifying
agent, and when water has a bad flavor, the addition
of a piece of blackened toast does not merely cover
the flavor, but removes it, and renders the water more
wholesome. The soluble matters, and also the finely
powdered charcoal held in suspension, both contribute
to render toast a very useful addition to water.
17
194 ACETIC ACID.
476. Acetic acid, or vinegar, is formed when a
mixture of spirit and water, together with some fer-
ment, is exposed to the air ; a portion of oxygen is
absorbed, and acetic acid is formed. This change
takes place when any liquid containing a portion of
spirit and some organic substance, like gluten, is
exposed to the air and kept moderately warm ; the
acetous fermentation, as it is called, then commences,
and vinegar is formed.
477. When a liquid containing spirit, water, and
some decomposable organic matter is exposed to the
air, unless the temperature is too low, it soon begins
to turn sour, and forms vinegar. When a solution
which has fully undergone the alcoholic fermentation
is thus kept at a temperature of 70° to 85°, it slowly
and -gradually undergoes this change ; but unless
care is taken it is very apt to become mouldy and
putrefy (380).
478. The acetous fermentation is facilitated by the
addition of a little ferment; hence in the manufacture
of vinegar from wine or beer, yeast or ferment of
some sort is usually added. W^hen a small quantity
of wine which has turned sour during its fermentation,
is added to a much larger quantity of properly fer-
mented wine, it induces the whole to pass into the
acetous fermentation, and good vinegar is formed.
For this reason also, better vinegar can be made in
an old cask or vat which has been often used, than
in a new one.
479. Wine-vinegar, however, is commonly made in
ACETIC FERMENTATION. 195
vats provided with false bottoms pierced full of holes,
a layer of vine-stalks and mark is first placed in the
vat, covering the false bottom, and the vats are then
nearly filled with wine. The vine-stalks and mark act
as a ferment, and soon bring the wine into a state of
active fermentation: air is absorbed, heat given out,
and vinegar is formed (383).
480. Care is always taken to check the rapidity
of this fermentation, or to prevent the liquor from
becoming too warm ; if this were permitted, the spirit
of the wine, as well as the vinegar formed, being both
volatile, would be driven off, or at least a consider-
able portion of them would be lost.
481. Any liquid containing spirit may be fermented
into vinegar; and, consequently, as starch and sugar
may be converted into spirit, so, solutions containing
those substances may readily be turned into vinegar,
by being fermented : when this is the case, the pro-
cess is not stopped when the alcoholic fermentation
is complete, but is allowed to proceed as long as
possible.
482. In countries where wine is made, vinegar is
chiefly made from the grape ; in other places malt is
usually employed. A similar form of vat is used for
that purpose as in the manufacture of wine-vinegar,
the only difference being, that a sweet-wort is substi-
tuted for the wine. Grape-mark, which is commonly
called rape by the vinegar-makers, is generally used
as a ferment.
483. As soon as the wort has acquired a certain
196 VINEGAR.
degree of sourness, and, in fact, before the acetous
fermentation is quite complete, it is racked off; this
is necessary to prevent it from passing into a state of
putrefaction, which would be sure to happen if it
were left too long in contact with the ferment (380).
484. Vinegar, whether prepared from wine or
malt, has a great tendency to spoil by keeping, in
fact to putrefy ; this is merely caused by the impuri-
ties which it contains. As made from malt, it always
contains spirit, sugar, gum, and ferment, in greater
or less quantity. It is thick and turbid, and must
be clarified before it is fit for use Or can be kept ;
this is done by the use of isinglass or some sitnilar
fining. Sometimes also it is purified by filtration
through powdered charcoal.
485. When vinegar putrefies, the change is not
confined to the impurities alone which it contains,
the acetic acid also is decomposed, and hence, as
soon as the putrefactive fermentation commences, the
liquid begins to lose sourness and becomes flat and
insipid. The impurities of the vinegar may of course
be wholly separated by distillation. Distilled vinegar
has no tendency to spoil by keeping ; it is quite as
strong and sour, or even stronger than it was before,
but its flavor is not quite so agreeable.
486. Vinegar is sometimes conveniently strength-
ened by the addition of sugar. In this case the im-
purities which it contains, carry on the slow ferment-
ation of the sugar, and cause its conversion into
vinegar. The sugar must be added from time to
PYROLIGNEOUS ACID. 197
time, and the liquid should be kept at a temperature
of from 70° to nearly 90°.
487. Very pure vinegar is sometimes made from a
mixture of spirit of wine, and water, exposed to the
air at a proper temperature. A large cask is filled
with wood shavings which have been steeped in vine-
gar, and the mixture of alcohol and water is allowed
to trickle through it at the same time that a current
of air passes through the cask. The large surface
which is thus exposed to the air, and the influence of
the vinegar contained in the shavings greatly assist
the action ; oxygen is absorbed, the mixture becomes
warm, and after passing once or twice through the
cask is wholly converted into vinegar.
488. Another source of acetic acid is the destruc-
tive distillation of wood. When wood is burnt, only
water and carbonic acid are formed ; but when wood
is distilled or roasted in close vessels out of the con-
tact of air, it is decomposed, and several new sub-
stances are formed by the recombination of its ele-
ments ; the most important of these substances is
vinegar, or, as it is called when thus procured,
pyroligneous acid (325).
489. Acetic acid cannot be obtained perfectly dry.
The substance obtained by the above-mentioned pro-
cesses, is a solution of acetic acid in water ; this may
be concentrated, but if we attempt to obtain the acid
free from any water, it is decomposed. Acetic acid
forms numerous salts, some of which are important
in the arts, such as sugar of lead, which is an acetate
17*
198 ACETIC ACID.
of lead, and pyrolignite of iron, "which is an impure
acetate of iron ; the salts made with the crude wood-
vinegar, or pyroligneous acid, are commonly called
pyrolignites.
490. The strongest acetic acid is usually obtained
by neutralizing vinegar with carbonate of soda or
lime. By evaporating the liquid, a dry acetate of
soda or of lime is procured, and these salts, when
acted on by strong sulphuric acid, give off acetic
acid in the form of a very pungent acid vapor, which
may be easily condensed by cold. A small portion
of water distils over with the acetic acid, and is con-
densed with it, forming a very strong solution.
199
CHAPTER VI.
VEGETABLE PRINCIPLES — NATURE AND COMPOSITION
OF ANIMAL SUBSTANCES.
491. It is well known that plants possess very
various properties : some are noted for their fragrant
smell, others for the brilliant colors they produce ;
some yield oils, others resins, and a great many are
valued for their peculiar medicinal qualities : all
these various properties are caused by the presence
of a certain quantity of some organic substance, some
peculiar compound of oxygen, hydrogen, carbon,
and nitrogen, which is formed by the plant.
492. The number of these organic substances
which have been discovered in plants is very great :
it is quite unnecessary to describe or even enumerate
them all ; it will be sufficient to mention very briefly
the most important of them, arranged under three or
four heads.
493. Amongst the substances formed by plants, is
a numerous series of organic acids : substances com-
posed of oxygen, hydrogen, and carbon, which pos-
sess acid powers, and combine eagerly with bases to
form neutral salts. In general, they do not exist in
200 VEGETABLE ACIDS.
plants in the free state, but are combined with
various bases derived from the soil ; sometimes they
are found in the state of perfectly neutral salts, but
more frequently they form acid salts (111); that is to
say, there is more acid than the base is able to neu-
tralize ; such plants have a sour taste.
494. When the salts of organic acids are burned
or strongly heated, the acids are decomposed ; in
these cases, the base, which was previously combined
with the organic acid, is found, after its destruction,
combined with carbonic acid, in the state of a car-
bonate (546).
495. The most important of the organic acids, are
the acetic, citric, tartaric, malic, and oxalic. There
are few plants which do not contain a small portion
of one or other of these acids, either in the free
state, or else combined with a base. Unripe fruit
contains a considerable quantity of malic and tar-
taric acids ; and the leaves and stems of many plants,
such as sorrel and rhubarb, have a strong, sour taste,
from the presence of oxalic and malic acids. The
nature and properties of acetic acid have already
been described (476).
496. Citric acid exists in a free state, abundantly
in the juice of limes and lemons, and in unripe goose-
berries, currants, and other similar fruits ; it is easily
procured from these sources, in white crystals, having
an agreeable, sour taste, and readily dissolving in
water. Citric acid is used in considerable quantity
by dyers : none of its salts are of much importance.
TARTARIC ACID. 201
497. Pure citric acid is obtained from the juice of
limes or lemons, by a process resembling that used in
the preparation of pure acetic acid (490). The sour
juice is saturated with powdered chalk, which forms
with its acid an insoluble citrate of lime ; this is
well washed with pure water, to remove the mucilage
and other foreign matters present in the juice of the
fruit. The pure citrate of lime is subsequently de-
composed by dilute sulphuric acid, sulphate of lime
is formed, and, as the clear solution cools, the citric
acid is deposited in crystals.
498. Tartaric acid is obtained from the juice of
grapes, pine-apples, and several other fruits; its
principal source is wine, from which it is deposited as
a super-salt of potash. The hi- or super-tartrate of
potash is slightly soluble in water, but almost insolu-
ble in a mixture of spirit and water ; hence, after
the fermentation of grape juice and consequent form-
ation of spirit, the bitartrate of potash previously
dissolved, is thrown down as a crystalline precipitate,
constituting argol, or cream of tartar (309).
499. Tartaric acid is manufactured from tartar, by
the use of lime and sulphuric acid. When tartar is
boiled with chalk, the excess of wine in the tartar
combines with lime, and forms an insoluble tartrate
of lime. This salt, decomposed by sulphuric acid,
yields pure tartaric acid.
500. The tartar deposited by red wine, has always
a pink or red color, and contains some of the coloring
matter of the grape. By boiling it with a portion
202 OXALIC ACID.
of powdered animal charcoal, the color may be re-
moved. By merely exposing the crystals of tartar
to the sun and air, they become bleached to a consi-
derable extent ; for this purpose they are spread out
upon laj-ge sheets of canvas, and left some time thus
exposed, after which, they are dissolved and recrys-
tallized.
501. Tartaric a'cid is a white crystalline solid, like
citric acid, easily soluble in water, and uniting to bases
to form salts called tartrates. It is chiefly used in
dyeing, and calico-printing; it is also used in medi-
cine, and in the manufacture of saline and effervescing
drinks.
502. Malic acid occurs associated with citric acid
in apples, pears, and in the stems of common rhubarb.
It forms salts called malates, but neither the acid nor
any of its salts are of much importance; they are
not used for any practical purpose.
503. Oxalic acid exists in considerable quantity
in rhubarb, sorrel, and a great many other plants ;
it is, however, generally made artificially from sugar.
When sugar, starch, lignin, &c., are heated with strong
nitric acid, violent action takes place, and the organic
substances are decomposed, the whole of their hydro-
gen being abstracted, and the carbon and oxygen
left in those proportions which form oxalic acid (180).
504. The commonest salts of oxalic acid in plants
are oxalate of lime and super-oxalate of potash. The
former is a white insoluble salt, readily obtained by
adding oxalic acid to a solution of lime. In conse-
OILS. 203
quence of the strong affinity which lime has for oxalic
acid, and the fact that the compound which they
form is insoluble in water, oxalic acid is a very valua-
ble test for the presence of lime and all its soluble
compounds.
505. The super-oxalate of potash is a soluble
crystalline salt; it is found in sorrel, rhubarb, and
many similar plants, giving them a sour flavor; it
occurs in many fruits associated with malic and tar-
taric acid. This salt, which is termed salts of sorrel,
and sometimes also (though most improperly) salt of
Jemons, is used in taking out iron-moulds, or stains
in linen caused by oxide of iron. This use depends
upon the fact, that the oxalic acid has a strong affinity
for oxide of iron, and forms with it a readily-soluble
salt, whilst the acid used has not corrosive powers,
and therefore does not in any way injure the texture
of the linen.
506. The oily substances formed by plants are like-
wise very numerous; they are of two kinds, fixed and
volatile; those which when exposed to the air remain
without diminishing their bulk, and those which when
so exposed evaporate. Olive oil, castor-oil, and
cocoa-nut oil, belong to the former class, whilst oil
of lavender, oil of cloves, and oil of lemons, are vola-
tile oils.
507. All vegetable oils, whether fixed or volatile,
contain carbon and hydrogen; in addition to which
the greater number contain a portion of oxygen.
They are all combustible, and when burning form
204 OILS.
water and carbonic acid gas. Oils are found in all
parts of plants, but rather more abundantly in the
seeds and fruits than in other parts. The seeds of
some plants, such as the poppy, linseed, rape, and
mustard, contain frequently nearly half their weight
of oil.
508. Fixed oils are divided into fat oils, and dry-
ing oils: the former remain fluid when exposed to
the air, like olive oil ; the latter gradually harden,
and dry up into a kind of varnish, like linseed oil.
Fat oils are used for soap-making, in wool-spinning,
to burn in lamps, and in diminishing friction ; those
like cocoa-nut and palm oil, which remain solid at
common temperature, are used for the manufacture
of candles. Drying oils are employed in preparing
paints and varnishes; for this purpose they are usually
boiled, which causes them to dry and harden even
more rapidly than in the fresh state.
609. The odors of plants are for the most part oc-
casioned by the presence of volatile oil, in greater or
less quantity. The volatile oils are obtained by dis-
tilling the plants which contain them with water ;
fixed oils are procured by pressing the seeds in
which they are found, either cold or after a slight
roasting ; the former process gives the purest oil.
610. The most important of the non-drying fat
oils, are those of the olive, cole-seed, rape, poppy,
almond, mustard, and till, or sesamum. The chief
drying oils are, linseed, hemp, nut, and castor. These
COMPOSITION OF OILS. 205
oils are all lighter than water, fluid at common
temperature, and very combustible.
511. Amongst the solid oils maj be mentioned the.
oils of palms and cocoa-nuts, and the various vege-
table butters. The different waxes, too, of which
there are a great number, are closely connected in
nature with these solid vegetable oils. These sub-
stances all consist of carbon, oxygen, and hydrogen.
512. The volatile oils, such as those of turpen-
tine, lemons, orange-peel, bergamot, sabine, and pep-
per, (Stc, are pure hydrocarbons. They contain no
oxygen ; while those of cloves, peppermint, caraway,
and lavender, &c., contain oxygen. Camphor may be
said to be an oxidized volatile oil; its composition is
the same as oil of turpentine, with the addition of
one equivalent of oxygen.
513. When the fixed oils are acted on by bases,
they are decomposed, and resolved into certain fatty
acids, and a peculiar sweet, uncrystallizable substance
called glycerine. Most of these oils are mixtures of
three distinct, fatty substances, distinguished by dif-
ferent properties ; these are termed stearine, marga-
rine, and elaine or oleine, and, when acted on by a
base, they are respectively decomposed into glycerine,
and stearic, margaric, or oleic acid.
514. Stearine is a white, friable, crystalline solid,
which exists in many of the solid oils ; it melts at a
temperature of 130° ; when saponified or heated
with a base, such as potash, it is decomposed, and
yields a soap, or salt of stearic acid and potash.
18
206 STEARIC ACID.
This soap is readily decomposed by a stronger acid,
and then yields pure stearic acid, which resembles
stearine in appearance and properties. It is, how-
ever, a distinct acid, and melts at 158°.
515. Margarine closely resembles' stearine, but it
is more fusible, melting at 116°. When saponified,
it yields margaric acid, a substance very similar to
stearic acid, but more fusible, melting at a tempera-
ture of about 140°.
516. Elaine, or oleine, qonstitutes the fluid part of
oils ; it remains liquid at all common temperatures,
and, treated with alkalies, yields a fatty substance,
oleic acid, which greatly resembles oleine in proper-
ties.
517. These substances may to some extent be se-
parated by mechanical means alone. When semifluid
oils, those which consist of stearine and oleine, are
cooled, and then strongly pressed, the whole of the
fluid oil or elaine may be squeezed out, and nearly
pure stearine is obtained. The stearine, or mixture
of stearine and margarine thus procured, is an ex-
cellent material for candles, whilst the fluid oil which
is pressed out may be used for various other pur-
poses not requiring solidity.
518. Stearic acid, however, being harder and still
less fusible, makes even better candles than stearine ;
hence it has become a considerable manufacture.
The stearine is boiled with alkali or lime, and the
salt formed, then decomposed by a stronger acid.
519. Candles made of stearic acid are hard, bril-
SOAP-MAKING. 207
liant, and nearly equal to wax : tlie acid, however,
has a great tendency to crystallize, ,which interferes
with its use for the manufacture of candles. At one
time a small quantity of arsenic was added to the
stearic acid, as it was found to counteract this tend-
ency. It has since then been found that other sub-
stances will produce the same effect, and thus the
addition of this very objectionable substance is ob-
viated. A great number of different mixtures of
stearine, stearic acid, wax, spermaceti, and other
solid fatty substances, in various proportions, are
used in the manufacture of candles.
520. Soap may be stated to be a salt, or rather a
mixture of several different salts ; namely, the mar-
garate, stearate, and oleate of potash and soda. Soap
is either hard or soft ; the former is made with soda
alone, or a mixture of soda and potash, whilst the
latter is made exclusively with potash.
521. In making soap, all that is necessary is to
boil together caustic alkali with the oil or fat to be
saponified ; carbonated alkali will not combine with
the fat acids. The first thing, therefore, is to prepare
a strong caustic alkaline lye ; for this purpose the
kelp, barilla, or other crude alkali, is mixed with
lime, which decomposes the alkaline carbonates, and
sets free the caustic alkali ; the mixture is then lix-
iviated with water, and a strong alkaline lye is ob-
tained.
522. The oil, fat, or tallow, is next heated in a
suitable boiler, and the alkaline lye is then gradually
208 SOAP-MAKING.
added, the mixture being kept constantly heated and
well stirred. A cream-like liquid is thus formed, and
when the proper quantity of alkali has been added,
and the mixture has been boiled long enough, a quan-
tity of common salt is stirred in, and the whole is
allowed to cool, the fire being withdrawn.
523. Soap is easily soluble in pure soft water, but
it is insoluble, or nearly so, in a strong solution of
common salt ; consequently, when salt is added to
the newly-formed soap in the boiler, it causes the
separation of the soap from the lye. The cream-like
liquid quickly separates into two parts, the lower one
being clear and transparent, and containing common
salt, glycerine, and the impurities of the lye (513),
whilst the upper part is thick and opaque. As it
cools it solidifies, and forms hard soap.
524. The addition of common salt to a thick hot
solution of soda soap has no other eifect than that just
described ; but when it is added to a potash soap, there
is produced in addition another effect which is purely
chemical. The salts which the fatty acids form with
potash are decomposed by the chloride of sodium ; a
mutual exchange of acids takes place ; and hence,
when a potash soap is mixed with a solution of com-
mon salt, both the soap and the chloride of sodium are
decomposed, and soda soap and chloride of potassium
are the results.
525. When the spent lye has been separated from
the soap, the latter is heated a second time so as to
melt it, well stirred up, and then poured into wooden
SOAP-MAKING. 209
frames or moulds, to cool and harden. Good soap
contains generally about one-third of its weight of
water; the exact proportion depends upon the mode
in which it is made. It is possible to prepare a solid
soap containing as much as two-thirds of its weight
of water.
626. Such soap looks very well whilst fresh, but it
soon begins to shrink and shrivel up when kept. The
retailers of soap generally store up their soap in a
damp place, where it shall lose as little' weight as
possible by evaporation ; sometimes they keep it in
strong brine, and many devices are adopted to in-
crease the weight of soap, by causing it to take up a
larger proportion of water.
527. Common yellow soap is made in the same
way as white or curd soap ; but it contains, in addition,
a quantity of resin. This is a useful addition ; and
such soap is both good and cheap. The yellow soap
is softer and more soluble than hard white soap ; there
is consequently more of it wasted in washing.
528. Black, or soft soap, is made entirely with
potash, and is generally manufactured from the com-
monest and cheapest oils ; it is semi-transparent, and
has usually a dark greenish color, speckled through-
out with little white spots. These spots are caused
by the addition of tallow, which, though it does not
really in any way add to the goodness of the soap, is
generally mixed up with it, because many persons
imagine that the soap is not good, unless it exhibits
this peculiar appearance.
IS*
21t) USE OF SOAP.
529. Soap forms a clear solution in pure water; it
■will not dissolve in saline solutions, and is decomposed
by a great many salts of lime, and, indeed, nearly-
all earthy and metallic salts decompose soap, and
throw down insoluble compounds of the fatty acids
with the bases of these salts. It is for this reason that
hard water is not fit for washing ; the soap is decom-
posed by it, and rendered insoluble. The slimy scum
which is formed by soap in such water, is a compound
of the fatty acids of the soap, with lime.
530. Water which is hard in consequence of its
containing carbonate of lime (230), deposits earthy
matter, and becomes softer by mere exposure to the
air ; the same effect is at once produced by boiling
the water for a few minutes, so as to drive off the
carbonic acid. Water which is hard from the pre-
sence of other salts of lime, may be improved by the
addition of a little carbonate of soda ; this will throw
down some of the lime ; and, rendering the water softer,
will make it much fitter for washing, and prevent a
great waste of soap.
531. Soap is easily soluble in spirit of wine; such
a solution afi'ords a very good test of the relative
hardness of waters ; the white precipitate it forms,
is a measure of the quantity of earthy matter present
in the water. When such a solution of soap is eva-
porated, the spirit is driven off, and the soap is ob-
tained in a transparent state; various perfumed soaps
are thus made. A solution of soap in spirit, to which
RESINS. 211
a portion of camphor has been added, constitutes
opodeldoc.
. 532. The resins, which are not less numerous than
the oils, resemble them in chemical composition and
combustibility; they are formed in large quantity by
many plants, and are very frequently seen adhering
in large transparent drops to the bark of trees which
produce them. Kesins frequently look very much
like gum, but they may readily be distinguished from
gum by the fact that they are quite insoluble in water,
whilst- gum easily dissolves or softens in that fluid
(335).
533. Most of the resins as they are obtained from
the trees which yield them are fluid, or at least soft,
and contain a portion of volatile oil; this is separated
by heat, and then the pure resin is left. Common
turpentine, which is a natural exudation, consists of
resin and oil of turpentine ; it is distilled, and the
oil of turpentine is thus procured, whilst the resin
called colophony is left. A healthy pine-tree yields
from six to twelve pounds of turpentine annually.
534. When resinous woods are distilled or burnt,
they yield tar. The trees are commonly cut down
and burnt, so that the heat given out melts the resin
in the wood ; and that which escapes burning, runs
down and is collected below.
535. In the manufacture of tar, the billets to be
burnt are piled into a stack, and then covered over
with turf ; the combustion of the wood is thus smoth-
ered and kept down, and the loss of tar is prevented.
21:2 TAR.
In France, the wood is generally distilled in large
brick ovens. Tar differs from common turpentine in
consequence of the mode in which it is obtained ; it
is darker colored, and contains less volatile oil, as a
good deal of the volatile oil is injured and decom-
posed, during the extraction of the tar, by the heat
of the fire.
53G. When tar is heated strongly and boiled, the
volatile oil which it contains is gradually driven off;
there then remains a brittle, black, shining, fusible
solid, called pitch.
537. There is another variety of tar, which is ob-
tained during the manufacture of coal gas, and
formed by the destructive distillation of bituminous
coal. This substance resembles vegetable tar in na-
ture and properties. It contains a volatile oil called
naphtha, or coal-tar oil ; and when this substance is
driven off by distillation, there remains a kind of pitch.
Coal naphtha resembles the native rock oil, or mineral
naphtha ; it is very combustible, and forms a valuable
solvent for caoutchouc and some of the resins. It
consists of hydrogen and carbon — the same elements,
therefore, as oil of turpentine.
538. Most of the simple resins, like common rosin
or colophony, the residue of the distillation of tur-
pentine, are brittle, fusible, and very combustible
solids, which easily dissolve in alcohol, or pyrox-
ylic spirit ; but are quite insoluble in water. They
are found to consist of mixtures of several distinct
acid substances. When resin is boiled in an alkaline
RESINS. 213
solution, it readily combines with the base, and forms
a soluble salt — a compound of the acids of the
resin with the alkali.
539. This property of resins of -dissolving in alka-
lies is practically employed by the paper-makers,
who prep are a size for the commoner sorts of paper
by dissolving resin in a solution of carbonate of
soda. Such a solution is immediately decomposed by
any of 'the strong acids, which combine with the
soda, and separate the resinous acid in an insoluble
state. For the same reason, too, resin is used as a
constituent of common yellow soap. .
540. There are likewise found a number of gum-
resins, as they are called, which have some of the
propertres of gum, and yet resembles resins ; these
are mixtures of gum and resin. They dissolve, though
but imperfectly, in both water and spirit of wine.
541. Plants contain an immense variety of dif-
ferent coloring matters, all of which, however, when
analyzed, are found to consist of nothing but oxygen,
hydrogen, and carbon, or these three with the addi-
tion of nitrogen. The nature and properties of these
sutstances are as various as their colors. They are
all destroyed by heat, which burns them, like all the
other varieties of organic matter. When burnt, the
results are water, carbonic acid, and frequently am-
monia.
542. Some vegetable colors are tolerably perma-
nent, whilst others are very fugitive, fading in a short
time when exposed to air and light, &c. Most vege-
214 VEGETABLE COLORS.
table colors are soon bleached by sulphurous acid,
and rapidly destroyed by chlorine. The art of the
dyer consists in staining wool, linen, and cotton of
various colors ; some of the colors he employs are
metallic, but the greater number are of vegetable or
animal origin. Dyes are divided into those which at
once permanently stain the fabric to be dyed, such
as indigo ; and those which require the use of some
mordant or substance to fix them. The most import-
ant mordants are alumina, oxide of iron, and oxide
of tin. These substances have a remarkable attrac-
tion for coloring matters, and also for the fibres of
cotton, wool, and silk ; they consequently assist in
dyeing those materials of various colors.
543. Lastly, there are a number of peculiar veget-
able substances, to the presence of which in plants
their medicinal properties are in many cases due.
Chemists have obtained from various plants a great
number of substances called " active principles,"
some of which are highly poisonous, whilst others in
small quantities are valuable medicines. Amongst
this class of substances are the vegetable alkalies, as
they are called ; these are compounds of oxygen,
hydrogen, carbon, and nitrogen, which possess the
power of combining with acids and forming neutral
salts. They are, of course, destroyed by heat, and,
whilst burning, give off the usual results of the com-
bustion of organic matter — water, carbonic acid, and
ammonia.
514:. All plants contain a small quantity of inor-
ASHES OF PLANTS. 215
ganic matter. Besides the lignin, gum, sugar, starch,
gluten, and other similar substances which consist
of carbon, hydrogen, oxygen, and nitrogen, and
which burn in the air when heated, there are always
found substances which cannot burn, but which are
of an earthy nature; these substances remain as
ashes, when plants are burnt.
645. The inorganic substances found in plants are
by no means numerous ; the most common are salts
of lime, potash, soda, magnesia, oxide of iron, and
silica. These substances are found in the ashes of
plants, combined with carbonic, sulphuric, phosphoric,
and some other acids.
546. The ashes of plants very frequently contain
a considerable quantity of carbonate of potash (494);
this salt does not exist in the growing plants, but is
formed during their combustion. Potash is found in
a very great number of plants, sometimes in combina-
tion with sulphuric acid, or silica, but more commonly
united to tartaric, oxalic, or some other organic acid,
constituting a tartrate, oxalate, or other salt of potash.
When plants are burned, all the organic acids are
burned, as well as the lignin and similar substances
which th^y contain ; consequently, although in living
plants the potash is combined with organic acids to
form neutral or even acid salts, yet, as these acids
are destroyed when plants are burned, caustic potash
is left (199), which, of course, combines with carbonic
acid to form carbonate of potash.
547. In the same way, carbonate of soda is fre-
216 SILEX IN PLANTS.
quently formed by burning plants which contain salts
of soda united to various organic acids. Before the
mode of obtaining carbonate of soda from common
salt (220) was discovered, the chief source of that
salt was the ashes of sea-weed, and other marine
plants.
548. The ashes of many plants contain silica (266),
generally in combination with either potash or soda.
Canes, and almost all plants allied to the grasses, are
completely coated over with a thin film or varnish of
silica. Sometimes even, as in the case of the bamboo,
solid lumps or concretions of silica, called tabasheer,
are found in the joints of the plant.
549. When a stack of hay or straw has been burnt,
so that all the volatile or combustible matters have
been dissipated, there is found a large quantity of a
dark-colored glassy-looking substance, which consists
principally of silicate of potash previously existing in
the plants, and which, being unaltered by the heat
given out during their burning, is merely melted, to-
gether with other substances contained in the plants,
into a glass. This may also very easily be observed,
by burning a piece of straw in the flame of a candle :
abundant white ashes w^ill be left, which continue to
retain nearly the form of the straw, and which, if
kept in the flame of a candle, melt into an imper-
fect sort of glass; this is principally silicate of potash.
550. The quantity of this substance which exists
in the stems of different plants, varies much ; some,
such as the plants used for polishing, commonly called
LIME IN PLANTS. 217
Dutcli rushes, contain even more than haj or straw ;
and cane contains so much silica, that it appears
completely coated with flint.
551. Lime is almost invariably found in the ashes
of all plants, and frequently constitutes a large pro-
portion of the earthy substances present in them. It
sometimes exists in combination with sulphuric acid,
as sulphate of lime (237), but far more commonly
united to phosphoric acid, or in the state of phosphate
of lime (242). It is likewise very frequently found
in considerable quantity in plants, combined with
organic acids, particularly as oxalate of lime ; hence
the ashes of plants commonly contain a portion of
carbonate of lime, which is formed in a similar man-
ner to the carbonate of potash already described
(494). The quantity of oxalate of lime in some
plants is so large, that, upon cutting them througli
with a knife, multitudes of little crystals of this salt
may be seen by means of a common pocket lens.
552. Magnesia is very often found associated with
lime, more especially in the state of phosphate of
magnesia (253), and as a double phosphate of mag^)
nesia and ammonia ; but as this salt is decomposed
by heat, the ammonia being volatile, only phosphate
of magnesia is found in the ashes.
553. The ashes of almost all plants contain a trace
of oxide of iron; and occasionally of the oxide of
manganese also ; and in one or two rare instances a
minute quantity of copper has been found, especially
in certain fungi.
19
218 ANIMAL MATTER.
654. Animals, like plants, consist almost entirely
of four elements, but these are grouped or combined
together to form various different compounds. The
bodies of all living animals contain a considerable
quantity of water : when this is evaporated by heat,
there remain certain substances, which may be readily
separated from each other in consequence of the
different properties which they possess, just in the
same way that we can separate the various substances
which compose plants (318).
555. The constituents of the bodies of animals may
be naturally divided into the organic substances of
which the softer parts of animals are composed, and
the earthy or inorganic matters, such as the bones.
556. Animal substances, for the most part, are ra-
ther more complicated in their nature than vegetable
substances; they almost all consist of oxygen, hy-
drogen, carbon, and nitrogen ; in consequence of the
presence of this latter element, they are more liable
to decompose than those vegetable substances which
do not contain it.
557. The principal substances which compose the
bodies of animals, and which are, therefore, called
proximate animal principles, are : albumen, fibrin,
caseine, gelatine, and fat, or oil ; besides these,
chemists have detected a multitude of other sub-
stances ; but these five are the most important, or
those which constitute the greater bulk of animal
matter.
558. There are many varieties of albumen and
ALBUMEN. 219
fibrin, which, in consequence of peculiar properties, or
slight differences in composition, have received differ-
ent names ; it is unnecessary to study the nature of
all these substances ; we may include them under the
general terms, albumen and fibrin. Albumen con-
sists of —
Carbon . 5484
Hydrogen 709
Nitrogen 1583
Oxygen with i
Phosphorus and I . . . . 2224
Sulphur J^
10,000
559. Albumen is a white, solid substance, which
swells up, and slowly dissolves in water, forming a
clear, transparent solution. Albumen is separated
from its solution in water by the addition of certain
acids, and also by the action of heat ; w^hen a
clear solution of albumen is boiled, the albumen sep-
arates in the form of a white curd or scum ; if the
solution contain much albumen, the whole becomes
solid.
560. This substance exists in many parts of the
animal system. The white of the egg consists of
hardly anything else ; when a fresh egg is boiled,
the albumen separates as a white curd ; it coagulates,
or becomes insoluble in water. Albumen occurs in a
state of solution, in blood, and many of the liquids
and softer parts of animal bodies. It is also found
in a dry or solid form. Hair consists of albumen,
together with a small portion of gelatine.
220 ALBUMEN.
561. Dry albumen may be kept for a long time
without undergoing decomposition ; but in solution,
or when moist, it is very liable to change. When
heated, it burns ; and the results of its decay, as
well as of its combustion, are water, carbonic acid,
and ammonia ; it leaves a small quantity of white
ash, which consists principally of phosphate of lime.
562. When perfectly pure, albumen appears to be
nearly insoluble in pure water ; but it readily dis-
solves in a weak alkaline solution, a very small quan-
tity of which, gives water the power of dissolving
albumen. Albumen is also soluble in acetic and
phosphoric acid ; these substances, therefore, do not
throw it down from its alkaline solutions, but it is
precipitated by sulphuric, muriatic, and most other
acids, and the albumen thus thrown down is found to
have combined with a portion of the acid used to
precipitate it.
563. Most metallic salts also precipitate solutions
of albumen, forming with it insoluble compounds ;
it is for this reason, that white of egg is recommended
in certain cases of poisoning, as, for example, with
corrosive sublimate. Albumen is used in many cases
as a fining material; when mixed with any solution
which it is desired to purify, and then precipitated, it
separates in a curdy form, and, in so doing, entangles
and separates the solid impurities previously suspend-
ed in the solution. When there is a large quantity
of free alkali, or of acetic acid present, a solution of
albumen cannot be coagulated by heat alone.
FIBRIN. 221
564. Fibrin, when pure, is a white elastic sub-
stance, insoluble in water, whether hot or cold ; but
soluble in acid and alkaline solutions. The muscle
or flesh of animals consists principally of fibrin,
associated with albumen and gelatine ; when dry,
fibrin may be easily preserved ; but when moist, like
albumen and gelatine, it soon begins to decompose.
The composition of fibrin is almost identical with that
of the albumen ; they consist of the same elements,
united together in nearly the same proportions. Fi-
brin, contains —
Carbon 5456
Hydrogen 690
Nitrogen . . . • . . . . 1572
Oxygen, with '\
Phosphorus and V .... 2282
Sulphur J
10,000
565. Fibrin exists in the bodies of animals in two
states ; solid, and in solution : in the former state, it
occurs in muscle or flesh ; in the latter state, in the
blood ; the soluble fibrin of the blood, however, soon
becomes insoluble after it has been taken from the
body, and separates as a clot or coagulum. Blood
consists of water holding in solution albumen, fibrin,
a peculiar red coloring matter, fat, and various inor-
ganic substances, including chlorides of sodium and
potassium, carbonates, sulphates, and phosphates of
potash, soda, lime, and magnesia, and also a portion
of oxide of iron.
19*
222 CASEINE.
566. The blood which is sent out from the heart
through the arteries all over the body, differs slightly
in chemical nature, from the blood which returns
through the veins to the heart, undergoing an im-
portant change in the course of its circulation : when
blood leaves the heart, it is of a bright red color, and
contains oxygen, which has been absorbed in the
lungs ; when it returns to the heart, it is black, and
contains carbonic acid in place of oxygen (606). A
pound of blood contains nearly two ounces of solid
matter ; of this about ninety grains is inorganic, the
rest organic.
567. The fibrin, which exists in the arteries, is
slightly different in chemical properties from that
which is obtained from the veins. The latter ap-
proaches very nearly in character to albumen, it
liquefies under the influence of a warm solution of
nitrate of potash, and forms a solution which is co-
agulated by heat and metallic solutions. This kind
of fibrin is almost identical with the fibrin of flesh.
When fibrin is burnt, it leaves a light-colored ash, vary-
ing in amount from one to two and a half per cent. ; it
consists chiefly of phosphates of lime and magnesia.
668. Caseine is a substance which very closely re-
sembles albumen, in its properties and composition ;
it is insoluble in pure water, but dissolves in dilute
acid or alkaline liquids, in the latter far more per-
fectly than in the former : it exists in milk, in which
it is dissolved by a small quantity of alkali ; the ad-
dition of acid to milk, by neutralizing the alkali,
causes the separation of the caseine as a curd.
MILK.
223
569. Cascine differs from albumen in not being
separated from its solutions by boiling ; in chemical
composition they are almost identical, the only dif-
ference being that caseine contains no phosphorus.
Caseine consists of —
Carbon
5496
Hydrogen
715
Nitrogen
1580
Oxygen
2173
Sulphur
36
10,000
Caseine contains about one quarter per cent, of inor-
ganic matter.
670. Milk, like blood, consists principally of water
holding organic matter in solution or suspension ;
milk contains caseine, fatty matter, a peculiar kind
of sugar, and small quantities of saline substances,
particularly phosphate of lime and various alkaline
salts. When milk is kept at a certain temperature,
it soon begins to change, a portion of the caseine turn-
ing into a kind of ferment, commences putrefaction ;
this induces an imperfect fermentation of the sugar,
and converts it into lactic acid, and this acid by com-
bining with the alkali present in the milk, causes the
coagulation or separation of the rest of the caseine.
Perfectly fresh milk is always feebly alkaline; but it
frequently happens that a small quantity of lactic
acid is formed almost as soon as it is exposed to the
air, which combines with and neutralizes the alkali
originaily present in the milk.
224 BUTTER.
671. The sugar of milk, when pure, cannot under-
go the alcoholic fermentation ; but bj certain means
it may be modified and converted into grape sugar,
which can ferment. The Tartars, by causing milk
to undergo the alcoholic fermentation, prepare an
intoxicating drink which contains alcohol.
572. An imperial gallon of fresh cow's milk, con-
tains about one pound seven ounces of solid matter.
Of this five ounces are fat, nearly eight ounces case-
ine, and about seven ounces sugar. The saline mat-
ters present in the milk include about eighteen grains
of common salt, and one hundred and sixty grains
of phosphate of lime.
573. Milk derives its opaque white appearance
from the presence of innumerable minute globules of
fatty matter, which are suspended throughout it ; it is,
in fact, a natural emulsion, or a solution holding par-
ticles of oil in suspension.
574. Cream, or the lighter part of milk, consists
principally of these minute globules, or drops of oil,
separated from each other by the solution of caseine,
&c., in which they float ; being lighter than water,
they rise to the surface, when fresh milk is allowed
to stand. The operation of churning consists merely
in agitating the cream, under the influence of a mode-
rate degree of warmth; the particles of oil then
unite and collect together in masses, forming butter.
575. It is diflBcult to remove the whole of the
caseine from butter, and its presence is highly objec-
tionable from its great proneness to putrefy ; by care-
BUTTER. 225
ful and complete washing the greater part may be
removed. Salt is generally added, as its presence
greatly checks the tendency of the caseine to change,
and consequently helps to keep the butter sweet.
576. In making butter there are two distinct meth-
ods employed. The one consists in churning the
entire milk, the other in churning the cream alone ;
the latter is said to give the richest and finest butter,
though]^ the former is considered to give a larger
yield. In either case a certain amount of incipient
fermentation appears to be essential to the process of
churning, and a moderate degree of warmth, as well
as the contact of atmospheric air, are necessary.
577. The milk or cream intended to make into
butter, is not used perfectly fresh, but is always
allowed to stand some little time, in order that it may
pass into this state of incipient fermentation, and a
small quantity of lactic acid may be formed. The
same state may be immediately brought on by the
addition of a little sour cream, which acts on the
rest as a ferment. There is some danger in doing
this, however, that the whole may pass into the pu-
trid fermentation (380).
578. In consequence of the extreme facility with
which caseine undergoes decomposition, and the rapi-
dity with which it passes into the state of putrid fer-
mentation, the utmost care and attention must always
be paid to insure complete cleanliness in the dairy.
The least taint of impurity in the vessels employed,
220 BUTTER.
is sufficient to bring on this sort of fermentation, and
of course render the products useless.
579. However well butter is made, and however
thoroughly it has been washed, it always retains a
small portion of water and caseine ; and in conse-
quence of this it is apt to turn rancid and acquire a
bad flavor. If butter be carefully melted, these im-
purities will fall to the bottom, and may be sepa-
rated ; but though butter so treated keeps better, yet
it is always found that its flavor is slightly injured.
Clarified butter may be kept sweet for weeks, and
even months, without the addition of salt.
580. The yellow color of butter made in summer,
is derived from the grass and plants on w^hich cows
feed. Winter butter is pale, or nearly colorless,
and often has a tallowy appearance. Such butter is
very frequently colored yellow by the addition of
annotto, carrot-juice, or some other yellow coloring
matter. These substances, though not unwholesome,
can only be regarded as adulterations, and are de-
cidedly objectionable.
581. The tendency of butter to turn rancid is
much diminished by the use of a small quantity of
common salt. It must however, be remembered that,
though the bad flavor of butter which is very slightly
turned, may to some extent be covered or concealed
by the addition of salt, yet that its rancidity is not
thereby at all corrected or remedied.
582. Cheese varies considerably in composition,
according to the mode in which it is prepared. When
CHEESE. 227
made from fresh milk, cheese consists of caseine and
fatty matter; when made from skimmed milk, it con-
tains little or no fat: in either case, during the press-
ing and curing of the cheese, it undergoes a peculiar
kind of fermentation, which gives rise to several
complicated chemical changes in its composition.
Cheese is generally made from milk, by the action of
rennet, the lining membrane of the stomach of the
calf, which has the property of causing the coagula-
tion of the caseine. Cheese which contains butter,
becomes soft and viscid when toasted ; whilst that
which contains none, becomes hard and shrivels up
almost like horn.
583. The curd of milk may be separated in a
great variety of ways ; any substance capable of
entering into fermentation, and the greater number
of acids, organic as well as inorganic, cause its
coagulation. As the caseine of milk is held in solu-
tion by a small quantity of alkali, which causes fresh
milk always to give a slightly alkaline reaction to
colored vegetable test-papers; so the addition of an
acid, or of any substance which by inducing fer-
mentation can generate lactic acid, neutralizes this
alkali, and consequently precipitates the caseine.
584. The most powerful of all the ferments which
are thus able to cause this separation of the caseine,
is rennet, which is in fact a membrane in a state of
slow putrefaction. When a piece of this substance
is put into milk, the temperature of which is then
slowly raised to 120°, or thereabouts, a slight degree
228 CHEESE.
of fermentation will be caused, and the caseine -will
be separated as a curd.
585. The whej, as the residue of the milk is called,
after the separation of the curd, contains nearly all
of the sugar ; nearly the whole of the fatty matter
which it contained is entangled and separated by the
coagulation of the caseine.
586. The variety of cheeses is very great, depend-
ing upon a number of circumstances. One important
distinction is caused by the state in which the fatty
matter is associated with the caseine. In double
Gloucester, for example, the oil and caseine are inti-
mately mixed together ; whilst in Cheddar, the oil is
not so thoroughly mixed with the caseine, but is
chiefly collected into little drops or globules, many
of the little cavities in the cheese being, in fact, filled
with oil.
587. Stilton cheese is made from entire milk, to
which an additional quantity of cream has been
added; Parmesan is made from skimmed milk; and
Cheshire cheese is made from fresh milk without any
alteration whatever. The diflference between single
and double Gloucester is caused by the fact, that the
milk for the former is partially skimmed so as to
remove about half the cream, whilst that for the
latter is left entire. Cream cheese, properly speak-
ing, is not really a cheese; it is rather cream, from
which the watery parts have been allowed to drain.
588. A very strong and high-flavored cheese is
sometimes made, by allowing milk to become sour
GELATINE. 229
spontaneously, and then collecting and pressing the
curd thus formed. The color of cheese is very com-
monly heightened by the use of annotto, or some
other yellow dyestufF. In using these substances,
care should always be taken to use only pure mate-
rials.
589. Gelatine, the fourth great principle of ani-
mal matter, is a tough, colorless substance ; in cold
water, it very slowly softens and dissolves ; in boil-
ing water, it dissolves more readily, and forms a so-
lution, which becomes a jelly as it cools. The skin,
horns, and hoofs of animals, consist principally of
hard, dry gelatine ; and it likewise occurs in many of
the softer parts of the body, associated with albumen.
690. Common glue and isinglass consist almost
wholly of gelatine ; the former is prepared by boil-
ing the clippings of skin, refuse horns, hoofs, and
similar matters, in water ; a strong solution of gela-
tine is thus obtained, which, as it cools, becomes a
jelly, and is then termed, size ; this, when cut in
slices, and dried in the air, is the glue of the shops.
591. Isinglass is the lining membrane of the swim-
ming bladder of the sturgeon ; but inferior sorts of
isinglass are obtained from other fishes. Gelatine
is insoluble in spirit. In the dry state, it may be
preserved unchanged, for any length of time ; but
when moist, or dissolved in water, it very soon begins
to change ; it becomes mouldy, and putrefies. Gela-
tine consists of —
20
230 ' GELATINE.
Carbon 5077
Hydrogen 715
Nitrogen 1832
Oxygen with ^
Sulphur and I . .... 2376
Phosphorus J
10,000
592. One of the most remarkable properties of
this substance, is its strong affinity for tannin ; when
any astringent solution, which contains tannin, is
added to a solution of gelatine, they combine together,
and form an insoluble, elastic compound, which is re-
markably stable, and does not putrefy or ferment.
The skins of animals, which consist chiefly of gela-
tine, are converted into leather, by tanning, or steep-
ing them in solutions of tan.
593. Gelatine is used as an article of food, as in
the preparation of soups and jellies ; by whitewashers
and paper-makers in the form of size ; in the man-
ufacture of glue ; and, as a fining material for clar-
ifying wine, beer, &c., when they are turbid. This
latter use is a purely mechanical one ; a jelly, com-
monly called finings, is prepared by the action of
very weak vinegar on isinglass, and a quantity of
this is difi'used through the liquid to be clarified ; it
of course precipitates any tannin which may be
present, and as it subsides carries with it all the solid
impurities which were previously suspended through-
out the liquid, rendering it turbid.
594. The fat of animals is perfectly similar in
FAT — BONE. 231
nature to vegetable oil : some kinds of fat are solid,
others fluid, at common temperature ; but they all
become fluid when made sufficiently hot ; animal oils,
like those of vegetable origin, contain no nitrogen —
they consist of carbon, oxygen, and hydrogen, and
when burnt form carbonic acid and water ; like ve-
getable oils, also, they consist of margarine, stearine,
and oleine, united to a peculiar base (513), and con-
sequently they form soap when boiled with alkalies.
595. The bones of animals contain a very large
proportion of earthy matters ; and, indeed, derive
their strength and solidity principally from the quan-
tity of those substances which they contain. When
bones are burnt, there remains, after the combustion
of all the organic matter which they contain, about
three quarters of their weight of earthy substances ;
this is phosphate of lime, together with a small por-
tion of carbonate of lime ; bones consist of phosphate
and carbonate of lime, cemented together as it were
with gelatine and a little albumen ; they also contain
a small quantity of oil. Ivory and the teeth of ani-
mals are composed of the same substances as bone.
Hoofs and horn likewise contain phosphate and car-
bonate of lime, but in far less quantity ; they consist
principally of gelatine (589).
596. The same remarkable similarity of chemical
composition which is found amongst vegetable sub-
stances, is likewise observed amongst those of animal
origin ; the various proximate elements which consti-
tute the bodies of animals, are, for the most part,
232 PROTEIN.
almost Identical in composition, and, like vegetable
substances, they appear more or less convertible into
each other. A very slight alteration in the relative
proportion of the elements of which they consist,
causes very great differences in their nature and pro-
perties. As in consequence of the very peculiar
nature of nitrogen, all substances which contain it
are exceedingly liable to change, therefore all those
forms of animal matter which contain any nitrogen,
very soon pass into a state of decomposition.
597. On comparing together the various substances
which constitute animal and vegetable matter, it is
observed that lignin, gum, sugar, and starch, are all
perfectly distinct in nature and properties from any
of the substances usually found in the bodies of ani-
mals : a remarkable similarity, however, exists be-
tween the fibrin, albumen, legumine, and oily sub-
stances of plants, and certain forms of animal matters.
598. The albumen, fibrin, and legumine of plants
closely resemble the albumen and fibrin of animals ;
indeed, some of the varieties of these substances may
be said to be absolutely identical ; they consist of
the same elements, and possess the same properties:
thus, for example, there is no chemical difference be-
tween that variety of albumen which exists in peas,
beans, and other leguminous seeds, which is called
legumine, and that form of albumen which is found in
milk, cheese, &c., and called caseine (347, 569).
599. When albumen, fibrin, or caseine, are acted
on by a solution of potash or soda, they soon dissolve,
PROTEIN. 233
forming a clear solution ; and if an acid is added to
this, so as to neutralize the alkali, a precipitate falls,
which is precisely the same from whichever of these
three substances it is obtained ; to this precipitate the
name of protein is given. Protein consists of oxygen,
hydrogen, carbon, and nitrogen, like the substances
from which it is obtained ; but it contains no sulphur
or phosphorus, whilst they always contain a small
quantity.
600. The knowledge of this fact, that the fibrin
and albumen, &c., of plants, are identical in compo-
sition with some of the most common forms of animal
matter, throws great light on the nutrition of animals.
It shows that the gluten and albumen of plants used
as food, may immediately enter into the system of
the animal ; whilst gum, starch, sugar, &c., must
undergo a change, before they can constitute a part
of the body of an animal.
601. It has already been stated that vegetable
and animal oils consist of the same three elements ;
many of these oils contain precisely the same pro-
portions of carbon, oxygen, and hydrogen : hence
by some chemists it has been supposed, that the oil
which exists in those vegetables used as food, might
contribute directly to the formation of fat, without
undergoing any change ; though, on the other hand,
many facts might be quoted to show that this view
is improbable; and that the fat of animals is formed
from starch, gum, and sugar, by a kind of fermenta-
20*
234 RESPIRATION.
tion in the animal system ; and that the fatty matters
of the food are not directly appropriated by the ani-
mals which feed on them.
602. Bearing in mind, then, that the strength of
man and animals depends mainly on muscle, and
that the formation of muscle is greatly dependent on
the amount of organic subject containing nitrogen in
their food, it becomes a matter of the first importance
to study the mode of increasing the quantity of these
matters in food.
603. Some animals feed entirely on vegetable
food ; others feed entirely, or in part, on flesh : in
either case they derive their nitrogen, or the sub-
stances containing it, from plants. Animals do not
appear to have any power of absorbing nitrogen from
the air; all the albumen, fibrin, &c., which they con-
tain, is therefore either directly or indirectly obtained
from plants.
604. The most important of the chemical functions
of animal life may be classed under the two great
heads of nutrition and respiration ; and, consequently,
food also may be divided into those kinds which con-
tribute to the one or other of these two objects.
The changes which ordinary food undergoes in pass-
ing through the stomach of an animal, are briefly
these : mechanical division, efi*ected by chewing, &c.;
chemical division or digestion, eff*ected in the stomach ;
chemical transformation, conversion of starch, &c.,
into animal matters ; absorption of azotized matters
identical in composition with animal matters, and
CIRCULATION OF THE BLOOD. 235
wliich are passed directly into the blood ; and lastly,
separation of useless matters as excrementitious.
60'"). The chemical office of food is, to supply to
the body albumen and fibrin, the elements of blood ;
in order to counterbalance the waste continually going
on in the system, by the constant addition of all
those matters which enter into its composition ; and
secondly, to contribute to the formation of animal
matter, by the transformation of starch and other
substances of vegetable origin.
606. Respiration has already been described (107)
as being, chemically speaking, a mere process of com-
bustion, in which carbon and hydrogen are burned at
the expense of the oxygen of the air ; this process
of combustion is carried on through the medium of
the blood, and goes on in all parts of the body. In
the lungs, the blood is exposed to the contact of a
quantity of atmospheric air ; oxygen is absorbed,
and carbonic acid given off; the blood thus charged
with free oxygen is sent, by the action of the heart,
to all parts of the body, in the innumerable minute
bloodvessels which terminate the arteries ; carbon and
a portion of hydrogen are taken up, and the oxygen,
which leaves the heart free, returns to it through
the veins, converted into carbonic acid and water ; the
former is at last given off from the blood, and expired
from the lungs, previous to the absorption of a new
quantity of fresh oxygen from the air.
607. Two great objects are effected by the circula-
tion of the blood : the one is the removal of carbon
236 DIGESTION.
and hydrogen, by means of free oxygen, which, by
combining with those elements, produces heat, and
keeps the body at a uniform temperature ; the other
is the addition of new matter, to replace that which
is removed. The digested food, or chyme, as it is
called, on passing from the stomach into the smaller
intestines, becomes mingled with a portion of bile, a
secretion of the liver, consisting of soda and a pecu-
liar fatty acid. In passing through the smaller in-
testines, the chyme is separated into two portions —
one containing the elements of blood, called chyle,
which is absorbed and carried into the blood, the
other containing rejected matters, which are passed
from the system as excrementitious.
608. The true nature of the change produced in
food, by the action of the gastric juice in the stomach
of an animal, is by no means satisfactorily under-
stood. This remarkable secretion contains a notable
quantity of free muriatic acid, and possesses great
powers of reducing organic matters to a state of so-
lution ; especially, when aided by the temperature of
the body.
609. The excess of fluid taken into the system
with the food, is conveyed away from the body
through the medium of the kidneys, as urine ; a
secretion which also contains the rejected azotized
matters of the blood, in the form of two peculiar sub-
stances, to which the names of urea and uric acid
have been given ; these substances consist of carbon,
oxygen, hydrogen, and nitrogen, and are very prone
FOOD OF ANIMALS. 237
to decompose, especially when mixed with other forms
of organic matter.
610. Urea has been made artificially, by chemical
means, but uric acid has not yet been so obtained :
its only source is the animal system. When urine is
kept in a moderately warm temperature, it soon be-
gins to decompose ; when fresh, it is generally slight-
ly acid, but after a short time, it becomes alkaline
from the decomposition of urea, and formation of
ammonia. The half solid urine of birds and serpents
contains a large quantity of uric acid, in combination
with ammonia. Guano, the decomposed excrement
of sea-fowl, likewise contains a considerable portion
of this salt.
611. It is evident that food of all kinds may be
classed under two great divisions ; according as it
yields the elements of flesh, or contains substances
capable of being at once transferred to the blood,
and so carried to all parts of the body ; or as it
merely contains substances capable of undergoing
transformations, or of supplying the waste caused by
respiration.
612. The quantity of food required by an animal
for either of these objects, varies greatly, and de-
pends entirely on circumstances : when the waste
going on in the system is great, a large supply of
blood-making food, that which is rich in the elements
of nutrition, will be required. When, however, the
body is exposed to cold, or to violent exercise, the
loss must be met by a proportionate increase in food
238 FORMATION OF FAT.
rich in the elements of respiration. It happens,
however, that the food of animals, for the most part,
is rich in both forms of nutriment.
613. A large accumulation of fat in an animal can
never be considered as healthy ; but, on the other
hand, leanness or the absence of fat is also unhealthy,
because, if at any time exposed to cold, hunger, or
violent exercise, the tissues of the body itself will be
consumed and converted into elements of respiration,
whilst in an animal supplied with a reasonable pro-
portion of fat, the latter will be consumed first, before
the tissues of the body will be thus acted on.
614. Some animals fatten far more easily than
others do ; this depends partly on their general con-
struction, and partly on the circumstances to which
they are exposed — such as temperature, abundance
and kind of food, exercise, &c. In man, too, the
greater or less activity of the mind exerts a very
remarkable influence on all the functions of the body;
and, therefore, amongst others, on the formation of
fat.
615. Setting aside individual peculiarities of con-
struction, the size of the lungs, &c., the circumstances
most favorable to the formation and secretion of fat,
are warmth, little exercise, abundance of food, and
the absence of all worry and irritation. Under these
circumstances, an animal is supplied with as much of
the elements of flesh as suffices to keep up the healthy
state of all the tissues of the body ; having an excess
of the elements of respiration, there is a natural
COOKERY. 239
tendency to store up fat, -which is that form of mat-
ter which accumulates in animals, as a provision
against future demands, just as plants form and store
up starch. Hence the effect of stall-feeding, upon
cattle.
616. In cold climates a larger quantity of the ele-
ments of respiration are required, or the tissues of
the body will begin to suffer. In carnivorous animals
there is always more or less of this waste of the body
going on, and hence the demand for azotized food.
In the case of herbivorous animals, or those which
feed wholly on vegetables, there is very little of this
waste. In cold countries a larger quantity of food is
required, and can be digested, than in hot ones. A
greater quantity of the elements of respiration is
needed to generate the proper amount of heat ; and
at the same time, as the air is much colder, and
therefore more condensed, a larger quantity of
oxygen is taken in at the lungs by each inspiration
(52, 107).
617. The art of cookery, or the preparation of
food, is a very important one, and has been yet
only partially brought into a systematic and intel-
ligible form. A great many of the processes of the
cook can be explained and regulated on known che-
mical principles ; but, at the same time, there are
also many which appear to depend on facts not hith-
erto recognized or explained.
618. The object of cookery is to render digestible
and palatable the various substances used as food ;
240 BOILING MEAT.
many of "which, without such preparation, would he
wholly indigestible and useless. The chief agents
employed are heat and moisture. The real object of
the cook should be to render wholesome food digest-
ible and palatable, and not, as is too often the
case, to render unwholesome things agreeable to the
619. In boiling meat two things are effected. It
is exposed to a heat of 212°, and, as far as it is in
contact with the water, the soluble substances which
it contains are extracted. These are, in fact, very
different operations, though they are commonly con-
founded together.
620. The albumen of flesh, which is to a consider-
able extent in a fluid state, is coagulated and brought
into the solid form by exposure to a heat of boiling
water; albumen begins to coagulate at a temperature
of 168°. Now, when meat is plunged into boiling
water, the albumen in the outer parts is immediately
rendered hard and insoluble, and the passage of heat
to the inner parts of the meat proceeds very slowly.
If, therefore, the joint is of any size, the inside will
not be thoroughly boiled, until the whole has been
boiled so long that the outside is quite overdone.
621. In order to boil meat well, it should be put
into cold water, and then gradually heated up to the
boiling point; a slow and gradual application of heat
is that best fitted to render meat tender and digest-
ible. The time of boiling must, however, of course
depend on the size of the joint to be cooked. Meat
BOILING MEAT. 241
should never be boiled rapidly, not only for the reason
just given, but also because, when the water boils
strongly, the steam carries off a large portion of the
volatile matters of the meat, and so renders it less
savory and palatable. The best effect is produced by
only allowing the water to simmer or boil very gently.
In a large kitchen, boiling by steam is better, more
manageable, and more economical, than with an open
fire.
622. The gelatine of flesh, on the other hand, is
softened by the action of the hot water; it is chiefly
in a solid form, and softens and gradually dissolves
in the heated water. In steaming, by the long-con-
tinued action of a gentle heat, the whole of the
gelatine is softened and brought into an easily
digestible condition.
623. When meat is made into soup, if simply sim-
mered in water, the gelatine only will be dissolved.
The fat either remains entangled in the fibre of the
meat, or melts and rises to the surface of the water.
By adding vegetables, or any substance containing
starch, which acts as a thickener, a sort of emulsion
is formed, and a large quantity of the oil remains
divided and suspended throughout the soup, much in
the same way that the oil or butter is naturally dif-
fused in milk (573).
624. Generally speaking, gelatine is more easily
digested than albumen, though the latter is the more
nutritious. It is a mistake to suppose that the jelly
of meat is the most nutritious part of it ; the value
21
242 BOILING VEGETABLES— ROASTING MEAT.
of gelatine as a part of food is commonly overrated.
Its value consists chiefly in its being easily soluble,
and therefore more readily digestible, than albumen
or fibre.
625. In boiling vegetables, very similar results are
produced ; the solid parts are softened and rendered
more soluble, whilst the albumen is coagulated. It
should always be borne in mind, that there is nothing
gained by heating the water very strongly so as to
make it boil rapidly ; but, on the contrary, it is
highly objectionable. Water which simmers, is very
nearly quite as hot as that which boils rapidly, and
does not carry off so much of the volatile principles
of the food.
626. When it is desired to soften and dissolve food
as much as possible, pure soft water is best ; but
when it is designed only to soften, but not dissolve
it, hard water is preferable. In general, the solvent
powers of hard water are much less than those of
soft water. For this reason, pure soft water is best
for making soup, whilst hard water is best for boiling
joints of meat. Salt is constantly added to the
water used for cooking ; this diminishes its solvent
powers, rendering it harder, and therefore better
fitted for those operations which are intended to
soften the food, but not dissolve it.
627. In roasting meat, the chemical changes pro-
duced are not very dissimilar from those effected by
boiling. A good deal depends on the management
of the fire ; if it is too hot at first, the outside of the
FAT — OIL. 243
meat will be scorched and burnt before tbe inside is
properly warmed. By the use of the spit, or by
otherwise causing the turning of the joint, the action
of the fire is rendered more slow and gradual ; and
by basting, or continually pouring the gravy which
drips from the roasting meat, over it ugain and
again, the evil effects of too much heat on the out-
side are guarded against.
628. The effect of roasting meat, is to harden the
albumen; whilst the gelatine is liquefied, and the
fibre becomes softened and rendered easily digestible.
If meat is over-roasted, so that it becomes dried up,
more harm than good is done ; because, when the
heat has driven off the natural juices of the meat,
its continued action, instead of softening it more,
renders it hard and less soluble, and therefore less
digestible.
629. Fat, taken in conjunction with other sub-
stances, is a valuable part of food, provided it enters
the stomach in a proper state. Fat should always
be divided and mixed up with other substances, so
that the mere application of heat may not at once
cause its separation. The oil in seeds is so divided
by the starch and other matters with which it is
associated, that it is wholly digestible ; ground up
with water, oil seeds furnish an emulsion resembling
milk.
630. The oil used in cookery should, as far as
possible, be brought into this state ; if it is permitted
to come into the greasy state, it is not only far less
244 USE OF SALT — DIGESTION.
digestible itself, but likewise produces a similar effect
on the substances with which it is mixed. These
two conditions may be well observed, on comparing
together good melted butter, with that which has
been allowed to '' oil."
631. Common salt is a necessary ingredient of all
good food. Its use in the preparation of food is evi-
dent from the preceding remarks ; it is also valuable
in its preservation, acting as an antiseptic, and pre-
venting it from undergoing fermentation or change.
Salt is further important as aiding digestion, to which
both the soda and muriatic acid it contains are ne-
cessary (608).
6'62. The effects of various condiments and spices
on the appetite are very remarkable; stimulating it,
and sometimes in a very beneficial manner. The prin-
ciples upon which these substances act is very ill un-
derstood, and cannot be satisfactorily explained by
reference to ordinary chemical facts ; indeed, it can
hardly be otherwise till the chemistry of digestion is
more fully understood.
633. The phenomena of digestion in some respects
resemble those of fermentation. The substances used
as food, are for the most part all very liable to
undergo fermentation ; and the nature of the change
thus brought about depends wholly upon circum-
stances. Any derangement in the process of diges-
tion, may permit some other change to commence,
and the system must then be immediately thrown
out of order. A very great number of diseases may,
ACTION OF MEDICINES. 245
either directly or indirectly, be traced to some dis-
turbance in the functions of digestion.
634. Very little is known respecting the mode in
which medicines act, or the effects which they pro-
duce when taken into the stomach. The influence of
some substances may, to a certain extent at least, be
explained, such, for example, as dilute sulphuric acid,
which it is evident must react upon any common
salt it meets with, generating muriatic acid and sul-
phate of soda. Again, the manner in which one form
of indigestion, arising from the incipient fermentation
of food, is arrested by certain volatile oils, or by
saline draughts charged with carbonic acid, may be
explained ; but the mode in which bark, opium,
and indeed nearly all other drugs act, is quite
unknown.
635. It is true that chemists have ascertained that
these substances derive their active powers from the
presence of minute quantities of various peculiar prin-
ciples which they contain. These substances have
been separated, analyzed, examined, and named; but
the knowledge thus obtained has not thrown much
light upon the real mode in which they act. It has
merely shown the nature of the active agent, but
neither the way in which it acts, nor the principle
,upon which its activity depends (513).
21*
246
CHAPTER VII.
THE FOOD OF PLANTS — ITS NATURE AND SOURCES.
636. Having shortly described the elements of
vegetable matter, and enumerated the principal com-
pounds of those elements which are found in plants,
we may at once proceed to consider the sources of
the food of plants ; that is to say, the means natu-
rally provided to insure them a due supply of the
various substances necessary to their growth; namely,
oxygen, hydrogen, carbon, nitrogen, and the various
earthy and saline substances which are always found
in plants.
637. There are only two sources whence it is pos-
sible for plants to derive these matters; namely, the
air and the soil ; let us inquire what substances they
can obtain in this manner, and how they avail them-
selves of the food thus offered to them.
638. It has been already stated, that the air at
all times contains a small quantity of carbonic acid
gas (37) ; it likewise always contains a still more
minute proportion of ammonia, which is constantly
being formed by decay. Here, then, we see that the
air contains the four elements of organic matter; and
THE AIR. 247
when, in addition to these facts, we remember that
the air is always more or less damp, it is easy to
understand that plants can derive from the air, alone,
the greater part of the substances which they require
(41, 150).
639. Although the air contains so large a propor-
tion of oxygen, and although that substance is in a
free state, that is to say, not combined with any
element, but ready to combine with any substance
for which it has an affinity, yet it does not seem that
plants derive the oxygen which they contain directly
from the air.
640. In the same way, there is no evidence to show
that they are able to absorb nitrogen from the air.
It might have been supposed that plants would obtain
the nitrogen which they require, directly from the
air, which contains nearly four-fifths of that gas ; but
there is very good reason to believe that this is not
the case, and that plants can only obtain nitrogen,
or assimilate it, as chemists say, by absorbing it in
combination with some other substance.
641. What has just been said with regard to oxy-
gen and nitrogen, is equally applicable to carbon and
hydrogen : the former is a solid substance, and there-
fore, as one might rightly conclude, plants cannot
absorb it in the separate state ; when combined with
oxygen in the form of carbonic acid gas, and possibly
also when in the form of carburetted hydrogen (131),
it can be absorbed by plants. Hydrogen has never
been found in the air, except in a state of combina-
248 THE SOIL.
tion ; the commonest compounds of hydrogen, and
indeed almost the only ones from which plants could
obtain that element, are water and ammonia. It
may be laid down as a rule, that plants can only
absorb oxygen, hydrogen, carbon, and nitrogen, in a
state of combination, and moreover that those com-
pounds, to be absorbed, must be either fluid or gas-
eous.
642. The soil consists of silica, alumina, lime, mag-
nesia, oxide of iron, small quantities of various
alkaline and earthy salts, and a portion of decaying
organic matter. It likewise contains water, and the
small quantity of ammonia and carbonic acid which
the rain has brought down from the air. Plants
cannot derive the elements of organic matter from
the earthy constituents of the soil, or from the or-
ganic matter which it may contain, unless there is
air present ; by the action of air these substances
decay, and are gradually changed into gases, which
plants can absorb.
643. It is commonly supposed that plants derive
the whole of their food from the soil ; but this is an
error: it is a fact well ascertained by chemical ex-
periments, that plants derive the greater part of their
nourishment from the air, although the soil is equally
essential to their growth.
644. The earthy substances contained in plants are
principally obtained from the soil: it is true that the
air contains exceedingly minute traces of various
earthy and saline substances, which are suspended in
THE SOIL. 249
it in the form of dust, and carried about by the
winds ; but the quantity which plants can derive from
this source is comparatively small. The air near the
sea-shore, and even to a great distance inland, is
frequently loaded with saline particles derived from
the sea : after a storm at sea a quantity of salts thus
suspended in the air is very considerable.
645. The fact that some solid substances can be
thus carried along in the air in a state of very fine
powder is important, and well worthy of being re-
membered, as it explains many apparently mysteri-
ous phenomena. It is exceedingly diflScult to detect
the very minute quantity of solid matter contained
in the air, but there is no doubt that it often does
exist, although we are not aware of its presence.
646. Setting aside the small quantity of earthy
matters which plants may derive from the air, it is
evident that the great source of the lime, potash, and
other similar substances contained in plants can only
be the soil : hence, the chemical composition of the
soil must exert great influence on the plants which
are cultivated in it.
647. The soil or earth is essential to the growth
of plants in several distinct ways. It enables them
to fix themselves firmly, as, from its open porous na-
ture, it allows the roots to extend in various directions,
and obtain a secure hold, so that the plant can grow
erect into the air, without danger of being blown
away by the winds. The soil likewise supplies them
with substances essential to their growth ; such as
250 SILICATES.
carbonic acid and ammonia, either generated by the
decay of substances which the soil naturally con-
tains or absorbed from the air, and also yields them
the earthy and alkaline salts which they require.
648. As may be supposed, the soil is very variable
in composition ; its nature is generally a good deal
dependent on the subsoil and stony matters which
are buried beneath the surface, many of which are
slowly decomposing or crumbling away, and adding
to the soil the substances of which they consisted.
649. The origin of all soils appears to be the dis-
integration or gradual crumbling down of rocks,
from the action of frost, and various chemical and
mechanical agents ; and, therefore, all soils contain
innumerable little fragments of different rocks,
which are slowly but constantly becoming smaller,
as the chemical combinations of which they consist
are broken up and destroyed.
650. This gradual decomposition of stony particles
in the soil is caused by the action of the air. Many
of the common rocks are compounds of several dif-
ferent earthy and alkaline substances, in which silica,
united to lime, alumina, potash, and soda, forms sili-
cates of those or similar bases (267).
651. Silicates of this kind, or natural compounds
containing silica in combination with several earthy
and alkaline bases, are quite insoluble in water, and
are scarcely acted on, even by the strongest acids ;
nevertheless, they gradually decompose when ex-
posed to the air. Under the joint action of the moist-
SOILS. 251
ure and carbonic acid in the air, these compounds
are disintegrated, carbonate of potash or soda is
formed, and in part washed away bj the rain, whilst
the insoluble earthy bases are left, in the form of a
very fine powder.
652. The most abundant constituent of soil is com-
monly silica, which frequently forms nearly nine-
tenths of the whole of its weight ; but this is by no
means always the case, for in calcareous or limestone
countries, we frequently find soils containing a very
large quantity of lime ; whilst others, again, contain
a large proportion of alumina. These differences in
the proportion of the earthy components of the soil,
give rise to the varieties of light or free, and stiff or
clayey soils, which are also modified by the presence
of a greater or less quantity of organic substances.
653. Silica and alumina, which are generally the
two principal constituents of soils, differ very greatly
in their respective uses. The former is of import-
ance, both chemically and mechanically. Chemically,
as forming a soluble compound with alkali, and thus
being absorbed by the roots of plants, and confer-
ring strength and stability to their structures; and
mechanically, by diminishing the extreme closeness
and tenacity of alumina, and thus, by making the
soil more porous and open, allowing the passage of
air and water through it, and enabling the roots of
plants more easily to penetrate it than they could
were it wholly composed of alumina.
654. On the other hand, the use of alumina is
252 SOILS.
principally mechanical, tending to keep the soil
moist, from its attraction for water, and likewise
being highly useful in absorbing ammonia, both from
the air and from all decaying substances evolving it
in the vicinity, by virtue of that property which
many porous substances, and more especially char-
coal, possess, of absorbing or condensing that gas
(162) ; which, as we shall shortly show, is of great
importance in the growth of plants.
665. Soils differ greatly in their mechanical as
well as in their chemical nature. The same sub-
stances constitute a soil possessing very different pro-
perties, according as they are in the form of little
grains like sand, or in very fine powder. This state
of mechanical division is of great importance for
several reasons, and most particularly in relation
to w^ater. A soil containing a large quantity of
alumina is generally known by its stiff, tenacious
character, and is remarkable for its great retentive
power for water ; whilst those consisting principally
of silica, and more especially those in which it exists
in the form of sand, are generally light and porous
soils, and far less retentive of water.
656. Again, a soil containing alkaline silicates in
the form of little grains, always contains free alkaline
matter in a soluble state, set free by the decomposi-
tion of those silicates, and this separation of alkaline
matter continues so long as there is any of the solid
silicates left ; this effect would cease in a short time
if all the silicates were very finely powdered ; they
SOILS. 253
-would soon undergo decomposition, and the whole of
the alkaline salts would then be washed out by the
rain (651).
657. The best soils are those in which the earthy
constituents are so proportioned that the light,
porous qualities of the one are balanced by the close,
retentive properties of the others ; for they are then
most uniformly suitable to vegetation.
658. The silica and alumina in soils are of course
almost wholly free and uncombined with any acid, as
the former is not a base, and the latter has hardly
any affinity for the weaker acids, such as the carbonic.
Small quantities of silica are almost always found in
soils, combined with either soda or potash, forming
those curious compounds before alluded to, in which
the silica seems to play the part of an acid (259) ;
soils never contain more than a very small quantity
of these substances; but it is evident that plants,
such as grasses, which contain silica, must obtain it
from the soil in a soluble form, by gradually absorb-
ins: it in combination with alkali, dissolved in water.
659. Silica also exists in soils in combination with
several bases together, such as lime, potash, soda,
magnesia, and alumina, constituting the natural
rocky silicates just spoken of ; the nature and com-
position of these compounds, as well as their tend-
ency to decompose, varies considerably in different
soils.
660. Lime and magnesia, both of which have a
powerful affinity for acids, are never present in the
22
254 SOILS.
soil except in combination with some acid, and this
is most commonly the carbonic; the former substance
is also not unfrequentlj found combined with sul-
phuric acid, constituting gypsum, or sulphate of lime
(237).
661. The oxides of iron in the soil are usually
nncombined, as they have not sufficient attraction for
carbonic acid to combine with that gas, which is
always present in the air. They in great measure
occasion the variations of color observed among
soils; for according as the iron is in a state of prot-
oxide or peroxide, it gives to the soil a black or
brownish-red color.
662. It must not be supposed, however, that the
color of soils is wholly dependent on the iron which
they contain, or that the blackness of any particular
soil is indicative of the presence of oxide of iron.
The decomposing vegetable substances, which all
soils contain in greater or less quantity, are usually
of a brown or black color, and therefore not unfre-
quently give a very dark color to a soil which only
contains a very small portion of oxide of iron.
663. Sulphate of iron is also sometimes present in
soils in very small quantity, being formed by the
gradual oxidation of sulphuret of iron in the manner
previously mentioned (286). A very minute quantity
of this salt of iron confers upon the soil peculiar
properties, which render it appropriate for particular
plants; but a slight increase of its amount is at-
tended with bad results, for, unless in very minute
SOILS. 255
quantity, it is poisonous to plants ; and hence such
soils as contain much sulphate of iron are invariably
barren, or incapable of supporting healthy vegeta-
tion.
664. The saline matters in the soil are principally
the sulphates, muriates, nitrates, and phosphates of
the alkaline and earthy bases. The nature and
quantity of these substances vary considerably, but
they never constitute more than a very small portion
of the soil; their influence upon vegetation is, how-
ever, considerable, for certain plants seem to require
particular saline substances, and do not grow well in
soils not containing them.
665. Thus all kinds of grass and corn contain silica
and phosphoric acid ; the former substance requires
the presence of an alkali, either potash or soda, to
render it soluble, and to enable it to enter the roots
when it is dissolved in water ; whilst the latter is also
always associated with a base, which is usually either
lime or magnesia. In the same way, all plants are
found to contain small quantities of similar saline and
earthy matters.
666. The relative proportion of the different ingre-
dients of soils vary very greatly. The chief consti-
tuent of nearly all soils is generally silica, in the
form of sand ; and in fact there are comparatively
but few good fertile soils in which this is not the
case. The sandy matter of most silicious soils con-
sists of nearly pure silica, but in some cases it con-
tains alumina, lime, &c. (625). The following ana-
256
COMPOSITION OF SOILS.
lyses, taken from SprengeVs book on the composition
of soils, will serve as examples of the general nature
of ordinary soils ; they are examples taken from
lands in the north of Germany.
Silica and fine Sand .
94,998
92,980
96,721
Alumina
610
820
370
Oxides of Iron . . . .
1,080
1,666
480
Oxide of Manganese .
268
188
trace
Lime, chiefly combined with Silica
L 141
748
5
Magnesia ....
208
168
80
Potash
56
65
trace
Soda .....
44
130
36
Phosphoric Acid .
80
246
trace
Sulphuric Acid
41
trace
trace
Chlorine (in common Salt) .
4
trace
58
Humic Acid ....
400
764
800
Humus, containing Nitrogen
. 2,070
2,225
1,450
100,000 100,000 100,000
667. The nature and quantity of the organic sub-
stances in the soil have great influence upon its
character and fertility. They act in several ways.
By slowly decaying, they present a constant source
of carbonic acid, and likewise of ammonia, if they
contain nitrogen ; whilst, by rendering the soil open
and porous, and at the same time augmenting its ab-
sorbent powers, they assist in keeping it uniformly
moist. They also increase the means which the soil
possesses of absorbing and condensing ammonia and
carbonic acid from the air.
668. It is a remarkable fact, that a mixture of two
or three earths, such as lime, silica, and alumina, is
ORGANIC SUBSTANCES IN SOILS. 257
better fitted to absorb moisture and gaseous matter,
than either of the earths taken singly ; and in the
same way, the addition of organic matters to the soil
has the effect of increasing this power still further ;
and, therefore, as was before said, the best soils are
those containing a quantity of each of the three
earths, mixed with a moderate proportion of decaying
organic matters.
669. Some soils contain a very large quantity of
organic substances, and indeed not unfrequently con-
sist almost wholly of the remains of vegetables : the
different varieties of peat are of this character. In
such soils we observe the bad effects of the presence
of too much organic matter in a soil. It is thus
rendered tough, porous, and spongy, so that it is
soon saturated with water, or completely dried, by
changes of weather. Besides all this, it frequently
contains a peculiar acid, produced during the decay
of vegetable matter, which is hurtful to the growth
of plants.
670. Another use of the organic constituents of
the soil is, that they furnish to the plants growing on
it the saline substances which they naturally con-
tain ; and which not being subject to decay are gradu-
ally washed out by the rains during the decomposition
of the organic substances, and are ready to be ab-
sorbed by the roots of growing plants.
671. The decay of the vegetable remains in the
soil, never proceeds so far that the whole of the ele-
ments which they contain are converted into carbonic
99*
258 HUMUS.
acid and water. The first change which they under-
go, when exposed to air and moisture in circum-
stances favorable to decay, is a diminution of the
quantity of oxygen and hydrogen, and likewise,
though in a smaller relative proportion, of the carbon
which they contain.
672. The result of this is a change of color some-
what similar to that produced by slightly burning or
singing them by heat: they become more or less
brown, according to the degree to which this change
has proceeded. Whilst in this state, they constitute
what is called HUMUS, the name by which chemists
distinguish all kinds of vegetable matter when in a
state of decay, and more especially woody fibre, which
indeed usually constitutes a very large proportion of
the bulk of plants.
673. This process of decomposition proceeds slowly
for a considerable time, the relative proportion, of
the oxygen and hydrogen to the carbon gradually
decreasing, carbonic acid and water being all the
time formed, until, at last, the humus, consisting of
carbon with only a small proportion of oxygen and
hydrogen, ceases to undergo any further change ; it
then is termed mould by chemists.
674. In order to understand this process, which is
one of great importance in connection with the growth
of plants, it must be remembered that woody fibre
and most vegetable substances consist of carbon, oxy-
gen, and hydrogen. Though the elements of these
substances are united together in nearly the proper-
DECAY OF HUMUS. 259
tions to form carbon and water, we must nevertheless
clearly understand that they are not composed of car-
bon and water, but that they are distinct compounds
of the three elements; and therefore, of course, that
the water produced during their decay is not merely
set at liberty by a process of decomposition, but is
formed by the hydrogen which is given off during
decay, entering into combination with oxygen.
675. When woody fibre and similar vegetable sub-
stances are exposed to air and moisture, they decay;
the chemical affinity which binds their elements to-
gether seems to be weakened, and the elements
acquire a tendency to form new and more simple
combinations. The oxygen and a portion of the
carbon unite and constitute carbonic acid ; whilst a
portion of the hydrogen combining with oxygen from
the air, gives rise to the formation of water.
676. This explains the use of air in facilitating the
decay of these substances ; for it is evident that if
free oxygen be required to combine with the hydro-
gen, this process cannot go on without a constant
supply of fresh air. The rapidity of the decay of
vegetable matters in the soil, therefore, depends
greatly on the porosity or closeness of the soil, per-
mitting a more or less perfect action of air.
677. In soils containing a large proportion of clay
or alumina, the decay of vegetable matter or humus
proceeds very slowly, because the close, dense nature
of the soil greatly retards the free access of air ;
though in other respects, such soils are decidedly
260 HUMIC ACID.
favorable to decay, inasmuch as they remain long
moist, and a certain degree of moisture is essential to
decay.
678. It is necessary to acquire a clear conception
of the nature of what is called humus, and the office
"which it performs in the nutrition of plants. It was
formerly supposed that plants derived their carbon
from the organic matter of the soil, that the brown
decaying substances called humus were directly ab-
sorbed by plants, and their carbon appropriated : it
is now known that this is not the case. The real use
of humus is, that it constantly generates carbonic
acid.
679. When water is poured on humus or decaying
vegetable matter, very little of it is dissolved, and the
water acquires a pale yellow color: if, however, the
water contains potash or soda, either caustic or in
the state of carbonate, it dissolves far more humus,
and acquires a deep brown color ; the cause of this
is, that the alkalies facilitate the decay of that sub-
stance. Under the influence of the alkalies, a pecu-
liar acid is formed, which has accordingly been
termed the humic. The brown solution obtained
under these circumstances contains humic acid in
combination with potash or soda.
680. It has been supposed that this acid might be
formed by the action of alkalies on the humus or de-
caying matters which the soil contains, and that the
humates, or compounds of humic acid, thus formed,
being absorbed by plants, might supply them with
GERMINATION. 261
carbon. There is, however, no proof whatever that
this really is the case ; on the contrary, as has al-
ready been stated, there is every reason to believe
that decaying vegetable matters merely yield carbon
to growing plants, by generating carbonic acid gas.
681. The food of plants, then, is carbonic acid
gas, water, and ammonia, partly derived from the
air, and partly from the soil; and certain earthy and
saline substances, derived almost wholly from the
soil. Let us consider the circumstances under which
plants are able to absorb and assimilate these sub-
stances, and what other conditions are requisite to
their growth.
682. The important influence which water has on
the changes which vegetable substances are liable to
undergo, has already been alluded to, when speaking
of albumen, fibrin, and the other similar substances
which enter into the composition of seeds. All these
substances, which under the joint action of air and
moisture, are so liable to undergo various changes,
become comparatively fixed and unchangeable, when
well dried and protected from the action of water.
During the germination of seeds, a great change
takes place in the nature of the substances composing
them. Carbonic acid is formed by the combination
of a portion of the carbon which they contain, with
the oxygen of the air. The conditions requisite to
the germination of seeds are, therefore, moisture, a
certain degree of heat, and the presence of air.
683. Light appears to be prejudicial, and, there-
262 GERMINATION.
fore, darkness may be said to be also necessary to
the perfect germination of seeds; and these condi-
tions are all secured by a good soil. The office per-
formed by moisture is, in the first place, principally
mechanical, serving to soften and swell up the dry
matters composing the seed, and by assisting in the
introduction of air to facilitate the changes requisite
to germination ; it likewise acts chemically, its pre-
sence being essential to the conversion of starch into
gum and sugar. It is also possible that water may
sometimes be decomposed during germination, its
oxygen combining with carbon to form carbonic
acid.
684. When seeds germinate in a confined portion
of air, we find that the air does not increase in bulk
at all ; the nitrogen is not at all affected, but the
oxygen is found to have combined with a quantity of
carbon, and to be converted into carbonic acid, and,
in consequence, the insipid and comparatively inso-
luble starch contained in the seeds, has changed into
more easily soluble, sweet, and mucilaginous, or
gummy substances, fit for the nourishment of the
embryo plant, before its roots and leaves are suffi-
ciently developed to enable it to derive support from
the different sources of food presented to it.
685. When the access of air is prevented, whilst
at the same time seeds are exposed to moisture, they
are unable to undergo this change ; germination, or
the growth of the embryo, cannot take place, and the
seeds decay; a portion of the water is decomposed,
GERMINATION. * 263
and the oxygen and hydrogen which it contained
unite with the elements of the vegetable matter, and
form carbonic acid, ammonia, carburetted hydrogen,
and other substances.
686. The first chemical change which takes place
in a germinating seed, is the change of a portion of
its azotized constituents into diastase (360), a sub-
stance which does not exist previously in seeds, but
is formed by the process of germination : it appears
to be a peculiar modification of vegetable albumen.
This change cannot be eff'ected without the pre-
sence of free oxygen, which removes the excess of
carbon. The azotised matter converted into diastase
immediately begins to act as a kind of ferment,
causing the starch and gum of the seed to pass into
the state of sugar. During the earliest stage of
germination, a small portion of vinegar or acetic acid
is formed. Alkalies tend to assist germination, be-
cause they combine with and neutralize this acid.
687. The chemical changes attendant on the pro-
cess of germination, are very different from those
which go on during the growth of a complete plant.
Before the formation of leaves, and in the very ear-
liest stages of its growth, a plant requires only
warmth, moisture, and the presence of air ; but sub-
sequehtly, it requires, in addition to these, carbonic
acid and light.
688. It is the oxygen of the air alone which is
essential to the germination of seeds, for the nitro-
gen being unable to combine with carbon, under or-
264 PROCESS OF MALTING.
dinary circumstances, is quite useless in diminishing
the quantity of that substance contained in the
seeds : its presence in the air is, however, very use-
ful, serving to dilute the oxygen and to prevent
its acting too rapidly. Seeds are found to germinate
very quickly in pure oxygen gas, but the plants pro-
duced are weak and unhealthy.
689. The germination of seeds may be readily
effected in water, although they are for the most part
unable to grow and vegetate under that fluid. The
change which, under ordinary conditions, is effected
in seeds by the oxygen of the atmosphere, is, under
these circumstances, caused by the oxygen of the
small quantity of common air always dissolved or
held in solution by water. In no case can a seed
germinate unless free oxygen is present, or some
other means exist by which a portion of the carbon
in the seed can be removed, so as to cause the change
in the constituents of the seed before described.
690. In the process of malting, or converting raw
grain into malt, the object to be attained is to change
a large portion of the starch which the barley con-
tains into gum and sugar. This is effected by steep-
ing the grain in cold water, and then heaping it up
together on the floor of the malt-house ; it is thus
placed in the most favorable conditions for germ-
ination, and consequently the chemical changes
attendant on that process immediately commence.
The seeds lose carbon, and at the same time convert
the oxygen of the air into carbonic acid ; the embryo
PROCESS OF MALTING. 265
or young plant begins to increase in size, and the
grain becomes warm from the heat evolved by the
chemical action. In malting barley about 20 per
cent, of starch is changed into sugar and gum (412).
691. If this were suffered to continue, the sugar
and gum formed would be consumed by the growing
young plant, and the malt would then become use-
less. When, therefore, the process has proceeded to
a certain extent, it is stopped by the gradual appli-
cation of heat, which, by driving off the water and
drying the grain, destroys the conditions requisite
for the further growth of the young plant, and pre-
serves the grain in the state most proper for the uses
of the brewer and distiller.
692. Malting essentially consists of four distinct
processes, which are respectively called steeping,
couching, flooring, and kiln-drying. The barley is
first of all steeped in stone vats or tanks filled with
water ; it swells, and at the same time gives out a
small quantity of carbonic acid, together with some
coloring matter. The grain is allowed to remain in
the steeping tanks for from forty to forty-five hours ;
sometimes the water is renewed ; during this time it
has expanded considerably, and increased in weight
from fifteen to twenty per cent. The malster judges
that it has been steeped long enough, when it is so
soft that the two ends of the grain can be easily
squeezed together, between the thumb and finger.
693. The water is then drained off, and the steeped
grain is spread over the floor in square heaps, about
23
266 SEED STEEPING.
thirty inches deep, in which state it is allowed to
remain about twenty-six hours. After this, the grain
begins to heat, and, if left to itself, would ere long
become so hot that it would be injured. This is pre-
vented, however, by the malster ; who takes care to
turn over and gradually diminish the thickness of the
heaps of malt about twice a day. When the steeped
grain is first couched, the surface grains soon dry up
a little ; but as soon as the heap begins to heat a
little, these grains again become moist ; this is termed
the sweating of the grain, and shows that germi-
nation is commencing.
694. The time required for malting varies ac-
cording to the temperature and the kind of malt it
is desired to make ; about fourteen days is the
average time. Winter is far better suited to malting
than summer, because in the former it is much easier
to regulate and keep down the temperature than it
is in summer. The malster judges of the progress
of his operation entirely by the growth of the young
roots, which the seed puts forth.
695. In drying malt, the great object is to drive
off water and destroy all further growth, without ex-
posing the malt to so high a temperature as would
risk its injury or decomposition ; as, in that case, the
sugar which had been formed would be destroyed
and lost. The application of heat, therefore, must
be very gentle and gradual ; in fact, the less heat
the malt is exposed to, the better will it be. When
thoroughly dried it is screened, so as to remove the
EFFECTS OP LIGHT. 267
dried rootlets, which are of course brittle, and hence
easily detached from the grain. After this, the
malt is once more spread out and exposed to the air,
in order that it may mellow and become soft and
mealy.
696. There are several chemical means by which
germination may be accelerated, but in general very
little benefit is derived from such processes. Thus,
for example, substances which have a strong affinity
for hydrogen assist germination, because they tend
to decompose water, and set free oxygen. For this
reason, solutions containing free chlorine are found
to cause seeds to germinate more rapidly than they
would otherwise do.
697; When seeds are sown in the earth, they are
placed in a situation where they are protected from
the action of light, and exposed to the influence of
air and moisture ; and provided they are not too
cold, that is, above the freezing point of water, they
will germinate and produce plants. Below that tem-
perature seeds cannot germinate, because, as has
been already said, the action of water is in the first
instance to soften the seed, and this it cannot effect
when so cold as to assume the solid form itself. If
buried too deep in the soil, the free access of air to
the seeds will be retarded, or even perhaps wholly
prevented, and under these circumstances of course
they cannot grow.
698. The faature of the soil, too, is of considerable
importance: very clayey soils allow a less perfect
268 EFFECTS OF LIGHT.
action of air than those which are of a more porous
and open structure, and in the former, therefore, the
process of germination proceeds more slowly.
699. In the next stage of the growth of plants, or
when they have leaves, they begin to absorb carbon
from the air instead of parting with it; and this they
do by decomposing the carbonic acid always present
in the air, a power which they possess when exposed
to the influence of light.
700. The effects of light in increasing and dimin-
ishing chemical affinity are highly curious, and but
very imperfectly understood : there are a good many
substances which, although they have an affinity for
each other, cannot combine in the dark. In the
same way, that peculiar chemical change which goes
on when plants grow, cannot proceed well in the
dark ; the decomposition of carbonic acid and water,
and the combination of their elements in order to
form lignin or starch, &c., goes on very imperfectly
without light.
701. The effect of Light, in causing chemical com-
bination and decomposition, is quite independent of
its brightness or illuminating power. The rays of
light which reach the earth from the sun, possess
three distinct classes of properties ; those which give
light, those which give heat, and those which cause
chemical action. In passing through different sub-
stances it is found that one or other of these proper-
ties is lost; the heating rays, for example, passing
GROWTH OP PLANTS. 269
through, whilst those which give light are stopped
(18T, 295).
702. Chemical action is caused in the cells of the
leaves by the agency of these chemical rays of light,
which enable the vital power as it is called, to form
organic matter : hence it is frequently said that Light
stimulates vegetation. Chemical action is also aug-
mented by Heat, which, though it cannot alone effect
those changes usually produced by light, considerably
assists them, and is therefore classed with light as a
stimulus.
703. Electricity also, that marvellous power, in
many respects so similar to light and heat, the effects
of which we frequently see in lightning and thunder
storms, is believed to exert great influence on vege-
tation ; but though there certainly appears much
probability of the truth of this, it is as yet not proved
by direct and unexceptionable experiments.
704. When the young plants appear above the
surface of the ground, their mode of growth is
changed : they then require air and light, and being
no longer preserved by the soil from the action of
light, are immediately able to effect the decomposi-
tion of carbonic acid.
705. The roots of a plant require little more than
moisture. The water which they obtain from the
soil contains those saline and gaSeous matters which
the plants want, whilst the leaves require in addition
to these matters the influence of light, and all these
they obtain by growing up into the air.
23*
270 GROWTH OF PLANTS.
706. When plants are shaded from the light, or
covered up, either artificially or by the leaves of
surrounding plants, the action of light is impeded, and
they are unable to effect the proper decomposition of
carbonic acid. Every one knows that, under these
circumstances, plants become unhealthy and send up
long weak shoots, endeavoring to reach the light, and
to place their leaves in a situation where they will
be exposed to its influence.
707. The existence of most plants may be divided
into four periods: firstly, germination, or the deve-
lopment of the young plant from the embryo; second-
ly, the growth of the plant to maturity; thirdly,
blossoming, and the formation of seed or reproductive
parts ; and, fourthly, decay, or a cessation of vital-
ity, and consequent decomposition of the organic
structure.
708. In each of these four periods different che-
mical changes are going on, and therefore different
conditions are requisite for the perfection of those
various processes. In the commencement, water, air,
a certain degree of warmth, and the absence of light,
appear nearly all that is required for the growth of
the embryo, which obtains food from the matters
stored up in the seed, until it has so far increased in
size as to have acquired roots and young leaves, and
in other respects has become fitted to derive nourish-
ment from external sources.
709. During the growth of the perfect plant, it is
observed that, in addition to water and a certain
GROWTH OF PLANTS. 271
degree of warmth-, carbonic acid, ammonia, and cer-
tain earthy and saline substances, are required ;
whilst light, which in the first stage of its growth
appears prejudicial, is now required to assist in those
complicated chemical changes which are going on,
when the compound organic substances, such as
woody fibre, gum, starch, gluten, &c., are formed in
the organs of the plant by the combination of the
elements of water, carbonic acid, and ammonia.
710. Hence during the day, or whilst plants are
exposed to the influence of light, the carbonic acid
absorbed by them is decomposed, the carbon alone
being retained in their structure, whilst the oxygen
is given off.
711. During the night, or when light is withdrawn,
this process of decomposing carbonic acid and acquir-
ing carbon goes on very slowly, and accordingly some
of the carbonic acid then absorbed by the roots is
given off again unchanged, by other parts of the sur-
face of the plants, in place of undergoing decomposi-
tion. For plants are at all times receiving from the
soil carbonic acid, which must necessarily enter their
system with the water they absorb from the [soil
through their roots ; but they can only derive nourish-
ment from it when, in consequence of the influence
of light, they are able to efi'ect its decomposition, and
so, by retaining the carbon, to increase the quantity
of organic matter which they contain.
712. In the third stage of the existence of a plant,
or during the formation of seed, the same general
272 USE or the leaves.
conditions are required which are necessary during
the second ; for the formation of seeds and fruit is
governed by very nearly the same laws which regu-
late the production of leaves and woody fibre. Those
causes which are most influential in maintaining the
healthy growth of the leaves, such as temperature, a
due supply of food, and more especially light, are
likewise the most important in the growth and per-
fection of the seed.
713. The principal chemical use of the leaves is to
assist in the formation of the organic substances ex-
isting in plants, which they do by exposing the crude
juices to the action of light, and thus effecting those
peculiar changes dependent on the combination of
carbon, nitrogen, hydrogen, and oxygen, under the
influence of light, on which the growth and increase
of plants depend.
714. The organic substances thus formed in the
leaves are either stored up in the stem of the plant,
or in other ways appropriated to its increase and
perfection ; and in most cases but little of them re-
mains in the leaves. The office of the fruit or seed-
vessel is different ; for though, like the leaves, it is
able to assist in the production of organic matter,
the substances so formed are retained and stored up
in itself, and the fruit or seed-vessel, not only returns
nothing to the plant on which it grows, but in addi-
tion attracts to itself a large portion of the vegetable
matter formed, by the combination of carbon, oxygen,
FLOWERS AND FRUIT. 273
and hydrogen, under the influence of light in the
leaves.
715. Thus, whilst the leaves are continually adding
new matter to a plant, the fruit, on the other hand,
by absorbing that matter, checks the growth. Hence,
also, the practice of pruning fruit-trees with a view
to improve the fruit ; the young fruit thus gets an
additional supply of organic matter, which would
otherwise have gone to the formation of fresh leaves
had not the branches been removed. It must not,
however, be supposed that the formation of flowers
and seeds is similar to the formation of woody fibre,
or leaves; very difi'erent changes take place, but the
same general conditions are required by plants in
both cases.
716. Flowers do not, like leaves, possess the power
of decomposing carbonic acid under the influence of
light; on the contrary, flowers appear at all times to
give out carbonic acid. From this it is evident, that
they must consist principally of substances containing
in proportion less carbon than the ordinary proximate
principles, such as. gum and lignin. There is a com-
mon belief that plants in blossom deteriorate the air,
and, therefore, that their presence in bedrooms is
highly objectionable. It is true that flowers gene-
rate carbonic acid ; but it is probable that the evil
efi'ects occasionally produced by flowers in sleeping-
rooms, are occasioned by a minute quantity of volatile
oil, to the presence of which the smell of flowers is
to be attributed; and many of which, even in very
2T4 FLOWERS AND FRUIT.
small quantities, act powerfully on the animal sys-
tem.
717. When fruits are first formed, they act very
like leaves ; they absorb food from the air, and under
the influence of light form organic matter, whilst at
the same time they collect and appropriate much of
the organic matter generated by the surrounding
leaves. At this period of their growth fruits have
very little taste, and in composition they somewhat
resemble leaves ; when they have attained a certain
size, they undergo a new change and ripen, during
which they acquire a sweet, or slightly acid taste.
718. In the first stage of the ripening of fruit,
acid matter is generated, in consequence, apparently,
of the conversion of some of the tasteless constitu-
ents of the fruit into malic, tartaric, and other or-
ganic acids. During the second period of ripening,
the greater part of these acids is converted into
sugar, and a portion of coloring matter is at the
same time formed. The formation of sugar and
coloring matter takes place quite independent of the
plant ; for fruits may be ripened after removal from
the plant which produced them.
719. In the first period of vegetation, when a seed
has been placed in the conditions requisite to germi-
nation, the embryo plant has no power of obtaining
food for itself, either from the air or the soil ; it is
entirely dependent on the seed for a supply of those
matters which are necessary to its growth. A seed,
then, is a magazine, or store of food, prepared for
ORGANIZED MATTER. 275
the use of the young plant ; and accordingly a large
quantity of the matters secreted by a plant, are
necessarily employed in the formation of seed.
720. In the case of all plant^ which shed their
leaves annually, at the end of the season buds are
formed. • In some respects these resemble seeds ;
they consist of growing points, surrounded by small
scales, which in time would develop into branches
and leaves ; but they are closely wrapped up in sev-
eral layers of a brown scaly matter, which protect
them during the winter from the action of cold and
other injurious influences.
721. When spring comes on and the weather is
milder, the buds undergo a chemical change a good
deal resembling germination. It frequently happens
that the buds open before the winter is really over,
or that there is a return of cold weather, which kills
them, and thus gives the tree a very material check.
Buds may be formed at any time during the. year ;
but they are, generally speaking, and of course with
the exception of flower-buds, formed only at the end
of the year, and at the time when the leaves fall off".
In cold and uncertain seasons it is common, however,
to see two or even more sets of buds formed in the
same year.
722. There is a great distinction between organic
and organized matter. The former term signifies, as
has already been explained, sugar, starch, or similar
compounds ; whilst by the latter name is meant the
cellular and fibrous parts of plants. The chemist
276 NATURE OF SEEDS.
may by artificial means readily make some forms of
organic matter, and convert them into others; but
he cannot make organized matter ; the latter is a
product of vital action, and has never been formed
by artificial means.
723. The first change efi'ected by plants, is to con-
vert carbonic acid and water, under the influence of
light, into starch and similar forms of organic matter;
the second. operation is to form these substances into
the various cells and tubes which compose the struc-
ture of plants. The former is a purely chemical
operation ; the latter requires something more,
namely, the exertion of vital power.
724. As starch, though it is very easily convertible
into other substances under the influence of a fer-
ment, is nevertheless one of the most stable of all
the products which a plant forms ; so it is also that
one best fitted to serve as nutrition to a young plant,
and is the substance always prepared in plants, to
act as a store of nutriment for any future growth.
Whenever a growing point or embryo is formed, a
quantity of starch also is, at the same time, deposited.
725. Thus starch is found in all seeds and buds,
as well in those which are formed on underground
stems and tubers, as in those which are formed at
the extremities of the branches. Whenever an
embryo or point of growth begins to. develop, the
chemical action, in the first instance, is the same.
The azotized matter begins to change, diastase or
some similar substance is generated ; this acts on the
NATUEE OF SEEDS. 277
store of starch, and sugar and other soluble princi-
ples are formed. For this reason all kinds of tubers,
such as potatoes, for example, become sweet as soon
as the eyes or buds begin to grow: it is an effect
similar to the malting of grain.
726. The embryo of a seed possesses vitality, but
has no power, at first, of assimilating the elements of
organic matter directly from the air ; it is, therefore,
able to convert starch, gluten, and other proximate
principles, into organized matter, and consequently
grows and increases in size, by feeding on the store
of organic matter prepared for its use in the seed.
727. The means provided to insure the reproduc-
tion of plants, are very various. In some plants,
seed only is formed ; whilst in others we observe
tubers or collections of food, prepared and preserved
in underground receptacles, for the nourishment of
the yonng plants of the next season.
728. Many plants, such as wheat, barley, beans,
&c., form seeds which consist merely of an embryo,
or growing body, surrounded with a supply of organic
food suflBcient for the use of the young plant, until
it has grown large enough to feed itself. The seeds
of other plants are more complete, being surrounded
with an additional quantity of organic matter, which,
by decaying, insures to the roots and leaves of the
young plant, a due supply of gaseous food as soon as
it is able to feed itself by those organs.
729. The seeds of all plants which bear fruit, are
of this kind. When a peach, for example, falls from
24
278 INORGANIC MATTER.
the tree which produced it, the soft pulpy matter of
the fruit soon decomposes, and by the time that the
seed begins to germinate, the fruit is wholly converted
into humus; hence the roots of the young plant are
placed in a soil rich in carbonic acid, as soon as it is
possible for them to absorb it.
730. During the whole existence of a plant, from
the formation of its first leaves till its death, it is
constantly absorbing moisture from the soil through
the roots, and as constantly parting with it by the
leaves. The water thus collected from the soil, con-
tains carbonic acid, ammonia, and such saline matters
as are present in the soil. If the leaves of the plant
are exposed to the action of light, the carbonic acid
and ammonia are decomposed, together with a portion
of the water, and organic matter is formed.
731. During the night, or in the absence of light,
this change takes place but imperfectly ; and hence,
then, the water absorbed by the roots, which is still
given oif by the leaves, carries with it a considerable
portion of the gaseous matter collected from the
soil.
732. The exact office in the nutrition of plants,
performed by the saline substances they absorb, is as.
yet but imperfectly known. Some plants appear to
require particular substances, and it is known that
certain substances cannot be formed by plants, unless
the soil contains particular saline matters. All plants
contain more or less lime, as well as other bases, such
as potash and soda ; these, of course, are never in
INORGANIC MATTER. 279
the pure state, but combined either with organic or
inorganic acids, or else with chlorine. Albumen,
gluten, caseine, and fibrin, are always found to contain
a small quantity of certain phosphates, particularly
those of lime and magnesia; hence these substances
appear to be essential to the formation of those prin-
ciples in plants.
733. It is not known whether plants have any
power of selection by their roots ; that is to say,
whether they are able to absorb from the soil only
those substances which they require, or whether they
absorb all the soluble matters present in it. To a
certain extent, they seem to have some power of
selection, but at the same time they are very fre-
quently injured by the absorption of poisonous
matters from the soil.
734. When the roots of a healthy young plant are
plunged into a vessel containing water, in which two
different saline substances are dissolved in equal pro-
portions, the plant will not take up both salts in
similar quantity. If, after continuing this experi-
ment some days, we then evaporate the remainder of
the solution, we shall find that the plant has taken
up the two salts in very different proportions; per-
haps half of the one salt has been absorbed, but only
one-third of the other.
735. The quantity of inorganic matter found in
plants is various at difi"erent periods of their growth.
In general, young- plants contain a larger proportion
than old ones; and as seeds contain a supply of all
280 EFFECTS OF CLIMATE.
that young plants require, a quantity of these salts
is necessary for the ripening of seed ; hence plants
require a large supply of inorganic matter from the
soil, during the third period of their existence, or
during the formation of seed.
736. These are, in very general terms, the condi-
tions requisite to the growth of plants; but there are
many special conditions appropriate to particular
species, and many important circumstances, which
must not be overlooked in studying the chemistry
of vegetation. The differences of climate, and their
influence on the growth of plants, are not less
remarkable than those of the soil itself ; and, indeed,
the very same soil would possess a very different
degree of fertility in different climates.
737. In the hot moist regions of the tropics, plants
grow with far more rapidity, and vegetation is more
vigorous, than in temperate regions. In tropical
countries, decay proceeds far more rapidly than it
does in our own country ; carbonic acid and ammonia,
the food of plants, are produced in greater quantity
than here ; whilst, from the greater power of the
sun, plants are able to assimilate more of those
substances than they can in colder countries.
738. The same circumstances which are favorable
to the putrefaction of organic matters, are likewise
those which facilitate the decomposition of inorganic
compounds in the soil (651). Consequently, in warm
tropical climates, a more copious supply of the re-
quisite earthy matters is continually being set free,
DEATH OF PLANTS. 281
ready to be absorbed by the plants ; proportionate,
in fact, to the augmented vigor of the vegetation.
739. Hence, in endeavoring to introduce into one
country the plants of another, it is necessary to con-
sider the conditions under which they naturally
grow ; and care must be taken to imitate as closely
as possible those conditions, not merely as regards
soil, but likewise in respect to temperature, moisture,
and light. These, however, are practical matters,
into which it is unnecessary here to enter.
740. In the last stage of the existence of a plant,
or when, either from excessive cold, disease, or merely
old age, the vitality becomes extinct, all that curious
series of changes by which organic matters are gene-
rated under the influence of light in the cells of
plants, ceases ; decay commences, the organic com-
pounds of the plant begin to decompose, and their
elements rearrange themselves into simpler forms.
The greater part of the hydrogen combines with
oxygen, and is gradually given off in the state of
water ; the nitrogen and hydrogen combine, and form
ammonia ; whilst the carbon is slowly dissipated in
the air in the state of carbonic acid, and at last little
remains beside mould, or charcoal in combination with
a small quantity of oxygen and hydrogen (673), and
the insoluble earthy matters which the plant may
have contained.
741. A plant dies, when, at the end of the season,
it has passed through the various stages of its exist-
ence, fulfilled the office for which it was created, and
24*
282 DISEASE OF PLANTS.
formed seeds or reproductive particles, which will
insure a fresh growth of the same kind of plant next
year; after this, vitality gradually declines in energy,
the formation of fresh organic matter ceases, and
that already formed begins to decompose.
742. In following out the chemical changes which
occur during the life of a plant, we find all through-
out, that there is a constant struggle going on be-
tween vital force and the ordinary chemical aflfinities
of the elements of vegetable matter. The influence
of vital energy tends to form complex combinations,
whilst the natural affinities of the elements tend to
form simple ones. So long as the former is the more
powerful, the plant grows and flourishes ; as soon,
however, as the latter gets the upper hand, the plant
withers and fades — disease, and perhaps death, fol-
low.
743. This kind of struggle is well seen in the an-
nual fall of the leaf. During the whole of the sum-
mer, whilst the vital energy is great, lignin, starch,
sugar, and other similar compounds, are formed in
the leaves, and through their agency; towards the
close of the year, when they have fulfilled the ob-
jects for which they were formed, these efi'ects cease,
the vital power diminishes, and ordinary chemical
agency gets the ascendant. The first effect of this
is oxidation ; the leaves begin to absorb oxygen, their
green coloring matter oxidizes and becomes yellow,
the leaves wither, fade, die, and fall off*. But even
then chemical power continues to act on them ; they
ACTION OF PLANTS ON THE AIR. 283
remain subject to its influence till they are wholly
decomposed, or nothing but a little mould remains.
744. Disease is occasioned by many causes ; but
independent of numerous minor sources, such as the
attacks of insects, &c., the most important are defi-
ciency of light, deficiency of vital energy, and defi-
ciency of heat ; any of these alone, or a combination
of them, induces disease in plants, and often leads to
death, by enabling the elements of organic matter to
commence those changes which constitute decay and
decomposition.
746. As has already been observed, plants are
constantly employed in preserving the purity of the
atmosphere : they feed on the foul or vitiated air
produced by respiration, combustion, and decay ;
and their vigor and luxuriance are always in propor-
tion to the impurity of the air. It must, however,
be clearly understood, that there is a limit to the
quantity of carbonic acid plants are able to decom-
pose ; an excess would kill them ; whilst, if there
were none of it in the air, they could not live. The
vegetation of the whole globe is just enough to keep
the air in a uniform state of purity (106, 123, 710).
284
CHAPTER VIII.
ARTIFICIAL SOURCES OF THE FOOD OF PLANTS — ACTION
OF MANURES.
746. When we remember, that although plants
derive a large portion of their nourishment from the
air, yet at the same time they absorb considerable
quantities of saline matters from the soil, it is evident
that all plants must more or less impoverish the
soil, by taking away that which causes its fertility.
747. The natural vegetation of any country en-
riches rather than deteriorates the soil, because
nothing is carried away from its surface ; the plants
which grow on it return to the soil, during their
decay, all the earthy and saline substances which
they had absorbed from it during their growth, whilst
they add to it a considerable quantity of the carbon
they had collected from the air.
748. Very different, however, is the condition of
cultivated lands; on them large crops are raised year
after year, which are removed and carried away to a
distance, to form the food of men and animals.
Such land is gradually impoverished ; because with
the crops a large quantity of inorganic matter, ne-
FALLOWING. 285
cessary to the fertility of the land, is removed. It
remains for us to inquire, what are the best means
of restoring these matters to the soil ; and likewise,
in how far it is possible to increase the fertility of
the soil, by augmenting the natural quantity of any
of its constituents.
749. In practice there are three courses adopted
to maintain the fertility of the soil ; namely, fallow-
ing, a rotation of crops, and the application of
manure.
750. In order to comprehend the effect produced
by fallowing, it is necessary to remember the mode
in which soil is formed. As has already been stated,
soils consist principally of small fragments of differ-
ent rocks and stones, which, from a variety of causes,
have gradually crumbled down to powder. The sand
or fine particles of stone in the soil are constantly
decomposing (649) and adding to the soil, potash,
soda, and very finely divided earthy matters ; it is
from sources of this kind that most of the saline sub-
stances present in the soil, are derived.
751. The soluble salts formed in this manner, are
dissolved by the rains, and in great part washed
away from the surface ; a portion, however, always
remains in the soil, and is absorbed by plants. When
a crop of some plant, requiring, for example, a large
quantity of potash, is raised in such a soil, it often
happens that the crop takes away nearly all the solu-
ble potash the soil contains ; and in consequence, it
would be impossible to raise a second crop of that
286 ROTATION OF CROPS.
plant on the same soil, as there would not be potash
enough in it.
752. If, however, the soil is left for some time
fallow, if no crop at all is raised on it, the soil has
time to renew itself; by the action of the air, the
further decomposition of the silicates and other simi-
lar stony compounds in the soil, is effected, and a
fresh supply of potash is provided.
753. The same end is obtained by a system of ro-
tation. In place of sowing a second crop of the
plant which requires so much potash, some other
plant is taken, which does not require potash, but
which requires other substances that the soil con-
tains.
754. In both these cases we restore, by the slow
effects of the air, those substances which we remove
with the first crop. In manuring, we at once add to
the soil that which the plants require.
755. Generally speaking, wheat cannot be grown
on the same land year after year, and accordingly
various systems of rotation are adopted. It is
probable, however, that as soon as we know what are
the substances required by wheat and other crops, we
shall at once know how to restore to the soil those
substances which each crop removes, and thus be
enabled to obtain crops of the same plant, for any
number of years in succession, from the same soil.
The labors of chemists are, however, hardly far
enough advanced for this at present.
756. The period of time over which the rotation
SUBSOIL PLOUGHING. 287
is made to extend, varies greatly in different countries
and in different soils. The ordinary period in Eng-
land is four or five years, but it is sometimes extended
to nine, or even more. In the ordinary four or five
course system, wheat is only grown once in four or
five years, manure being given only once, at the
commencement of the course, when a crop of turnips
being grown, is fed off by sheep ; the land thus re-
ceiving a rich dressing of sheep's dung (812).
757. With respect to the natural sources of saline
matters in the soil, it must be observed that, al-
though their nature and quantity are in a great mea-
sure influenced by the composition of the subsoil, and
stony substratum ; yet it frequently happens that,
from want of mixture, the soil is deficient in some of
those very substances which the subsoil is rich in ;
and in consequence the soil becomes considerably im-
proved by mixture, or by spreading over the surface
some of the decomposing stones dug from below.
758. We are apt to think that a soil must of
necessity contain portions of those substances which
enter into the composition of the substratum ; but
this is by no means always the case. Thus the sur-
face-soil of a chalk district is not unfrequently nearly
wholly destitute of calcareous or chalky matters ;
and soils in such situations are, therefore, often im-
proved by spreading lime over the surface.
759. It is consequently of high importance to
know the nature and composition of the subsoil, as
well as the surface soil ; for by a judicious use of the
28S JUANURB.
former, the soil Itself may frequently be very much
improved, and probably some saving effected in the
quantity of manure required for the land.
760. The system of subsoil ploughing, so success-
fully practised in many parts of the country, is con-
nected with this subject, and depends mainly upon
the advantages derived from admixture of the subsoil
with the surface. In this operation, a plough is em-
ployed to break up and pulverize the soil to a
considerable depth below the surface, without bring-
ing the soil so disturbed up to the top ; by this
process the permeability of the soil to air is greatly
increased, and in consequence, the subsoil is soon
brought into a fit state to be mixed with the ordinary
soil, by the use of a suitable plough.
761. Part of the benefit derived from this opera-
tion is doubtless due to the greater openness conferred
upon the soil, which permits a more perfect access of
air and moisture, and allows the roots of the growing
plants more easily to penetrate through it ; but at the
same time, advantage is also derived from the greater
supply of saline and soluble earthy matters which
are thus made available for the use of the plants.
762. A very great variety of different substances
is included under the general name of manure.
Some of the substances added to the soil act princi-
pally in a mechanical way, improving its texture ;
others are chiefly valuable as sources of carbonic acid
and ammonia ; whilst many are useful as supplying
saline and earthy matters in which the soil may be
ORGANIC MANURE. 289
deficient. It would be easy to divide all manures
into these three classes ; but it is more convenient to
divide them simply into the organic and the inor-
ganic; because many manures act in all these three
ways at once, improving the texture of the soil and
supplying carbonic acid, ammonia, and saline matters.
763. The Chinese, who are very economical of
their manure, apply it in small quantities at several
distinct periods to their plants, when they judge it to
be wanted ; it may in fact be said that they manure
their plants, whilst in Europe it is the custom to
manure the soil ; this must of necessity be the case,
where labor costs less than manure.
764. Organic manures may in general terms be
described as consisting of any kind of organic matter
in a state of decay or putrefaction. Setting out with
the knowledge that organic matter consists of carbon,
oxygen, hydrogen, and nitrogen, it is not difiScult to
understand the changes produced by its decomposi-
tion.
765. The complicated changes which organic
matters undergo in decomposing are generally divided
into four separate classes, namely: Fermentation, or
the formation of new compound substances by the
partial decomposition of a compound, the change
being induced or commenced in consequence of the
presence of some other decomposing matter ; Putre-
faction, or the complete decomposition of organic
matter and its conversion into different inorganic
compounds, such as water, ammonia, carbonic acidy
25
290. RESULTS OF PUTREFACTION.
sulphuretted hydrogen, &c. ; Decay, a slow process
of oxidation, almost analogous to combustion, differ-
ing from putrefaction in being dependent on the pre-
sence of free oxygen or air. This change is always
accompanied by the evolution of heat; Mouldering,
a change intermediate between putrefaction and
decay, taking place in organic matters exposed to
the action of water, but not to that of air.
766. Organic manures consist of mixtures of vari-
ous organic substances in a state of putrefaction or
decay. The more changeable substances at once
enter into putrefaction, sometimes communicating
their own state to those which are less changeable,
sometimes only inducing decay in them ; thus, for
example, urine soon putrefies by itself, and, if mixed
with straw, it gradually causes the latter to heat and
decay.
767. Whilst describing the different varieties of
organic matter, attention has constantly been drawn
to the results produced by their putrefaction. It
has been repeatedly stated that the substances formed
by the putrefaction of organic matter are water, car-
bonic acid, and ammonia. The nature and rapidity
of the change is, however, greatly modified by cir-
cumstances.
768. Organic matter containing nitrogen changes
far more rapidly than that not containing this ele-
ment (350). It might have been supposed that under
such circumstances the nitrogen would be given off
in a free and uncombined state ; it is therefore re-
RESULTS OF PUTREFACTION. 291
markable to find that, at the moment of escaping
from one compound, it enters into combination with
another element. This fact is important, and de-
serves a little further consideration, for it is found
that, at the moment of separation, substances have
a peculiar tendency to enter into fresh combinations.
769. Substances in this state, or whilst being set
at liberty by the decomposition of compounds which
previously contained them, are sjiid to be in the nas-
cent state. It is always found that substances which
have an affinity for each other, but under ordinary
circumstances cannot combine, are able to do so when
in the nascent state.
7J0. All attempts have failed to cause the combi-
nation of a mixture of hydrogen and nitrogen gases ;
but when these two substances are in the nascent
state they combine readily, and ammonia is formed.
771. The rapidity with which animal substances
decay or putrefy depends on moisture, warmth, and
air. It has been stated that substances of this kind
may be preserved a long time if dry ; water is neces-
sary to their putrefaction. It is well known that
meat may be preserved fresh a long time if frozen,
or kept at a temperature below the freezing point of
water, whilst, on the other hand, if kept in a warm
place, it soon begins to change.
772. The decomposition of moist animal matter
may likewise be accelerated by the mixture of potash,
soda, or lime, &c., with it; under these circumstances
nitric acid is formed (166), though all the ammonia
292 RESULTS OF PUTREFACTION.
formed at the same time is lost (152). It appears
that the mixture of these bases assists in the formation
of the acid, in consequence of the strong affinity
which they have for it, and that therefore they in-
crease the natural tendency which nitrogen has to
separate from the carbon, oxygen, and hydrogen
with which it is united in organic matter. ,
773. Whilst animal matters are putrefying, they
commonly emit a very offensive smell: now, as neither
water, carbonic acid, ammonia, nor nitric acid can
cause this, it is evident that some other substance
must, at the same time, be formed. The fact is, that
the nauseous odor given off under these circumstances
is occasioned by the formation of sulphuretted hydro-
gen (182).
774. Sulphur and hydrogen, though hardly able
to combine with each other under common circum-
stances when brought together, unite readily when
the hydrogen is in that peculiar nascent state above
adverted to. Thus, when organic substances con-
taining small quantities of sulphates decay, a portion
of the hydrogen, whilst set at liberty, combines with
some of the sulphur contained in the sulphates, and
sulphuretted hydrogen gas is formed.
775. This gas is evolved in considerable quantity
during the decomposition of nearly all animal sub-
stances, and likewise those vegetables, such as cab-
bage, &c., which contain both nitrogen and sulphur;
though its odor is not unfrequently almost over-
ANIMAL MANURES. 293
powered by the strong pungent smell of the ammonia
evolved at the same time.
776. When such decomposing substances are ex-
posed to the air, the sulphuretted hydrogen gas formed
is dissipated, and carried away in the atmosphere ;
but at the same time a large quantity of the ammonia
also formed is lost, and this is of course highly ob-
jectionable. The value of these kinds of manure
depends in great part on the quantity of nitrogen
which they are able to supply to the plants; and
everything tending to assist in retaining that sub-
stance in the soil, and rendering it available to the
growth of plants, is advantageous; whilst, on the
other hand, everything increasing its loss, or dissi-
pation in the air, lessens the value of the manure, and
renders its application of less service. ^
777. Animal manures, to a slight degree, modify
the mechanical texture of the soil ; though from their
great proneness to decompose, the effects of this kind
which they produce are comparatively transitory.
Their principal value consists in the ammonia and
carbonic acid, or nitric acid, which they yield, and
the earthy and saline compounds which they contain.
In addition to this, they are also of value by facili-
tating the decomposition of vegetable substances
employed as manure (767).
778. As perhaps the most useful part of these kinds
of manure is the volatile substances formed during
their putrefaction, great care should be taken to suffer
25*
294 ANIMAL MANURES.
as little as possible to escape, and be lost. It is pro-
bable that the best method of preserving the greater
part of such manure, is to dissolve it in water. The
employment of liquid manure is gradually coming
more and more into use, and the prejudices against
its application are vanishing, as the beneficial results
produced by its use become known.
779. Organic manure is of comparatively little
value in a chemical point of view, until it has under-
gone decomposition; plants do not seem able to ab-
sorb and appropriate organic matter ; hence, in all
cases, whether applied fresh or decomposed, it must
undergo decay or putrefaction, before it can consti-
tute food for plants. It appears further, that plants
cannot absorb solid matter ; it is, consequently, also
requisite that these matters should be soluble in
water, or capable of entering^ into the organs of
plants in a fluid state. When water is added to
organic manure in a state of decomposition, putre-
faction is assisted, the escape of gases is diminished,
and the useful part of the manure obtained in that
form best suited to the wants of growing plants.
780. When plants are growing very vigorously,
and are abundantly supplied with manure, it appears
that they sometimes do absorb a small quantity of
organic matter together with the inorganic pro-
ducts of putrefraction. Vegetables forced with
abundance of strong animal manure, such as pig's
dung, are frequently found to have acquired a bad
taste, from the presence of a minute quantity of some
LIQUID MANURE. 295
substance, which they have absorbed undecomposed,
from the manure.
781. The greatest attention should be paid to the
modes of collecting, preserving, and economizing
animal manure. There can be no doubt that a very
large quantity of manure is constantly wasted under
the old systems of using it, and the least considera-
tion will convince any one of this.
782. The food of plants consists principally of
certain volatile- or gaseous substances, produced,
amongst other ways, by the decomposition of organic
matter; we add organic matters to the soil, to supply
plants with more food than they could otherwise
obtain. If, then, previous to using these substances
as manure, they are exposed for some time to the air,
sun, and rain, a considerable portion of the volatile
products of putrefaction must be lost ; and yet this is
constantly done.
783. Manure should be carefully collected — none
should be neglected or suffered to go to waste ; it
should be preserved in proper receptacles, sheltered
from the sun and rain, so that the volatile products
of its decay may neither be lost by the heat of the
former, nor w^ashed away by the latter; and lastly,
by the action of water it should be softened, and as
much as possible reduced to a fluid state, so that it
may be easily and uniformly applied to the land.
The formation of liquid manure-tanks deserves the
most serious attention of the farmer.
784. In the application of these kinds of manure.
296 ALL ANIMAL MATTER VALUABLE AS MANURE.
it has to be remembered that although carbonic acid
and ammonia are the principal food of plants, yet
that there are limits to the quantity of these sub-
stances they can absorb, and that too great a supply
of such food is not only useless, but objectionable,
and even highly injurious. It is useless to give a
plant abundance of carbonic acid and ammonia, if
we do not at the same time give it those earthy and
saline substances which it requires (554). Even if
both are supplied to plants, it is impossible for them
to absorb more than a limited quantity. Excess does
harm (745).
785. As animal matter is either directly or in-
directly formed from vegetable substances, it is
natural to expect that animal substances must con-
tain, in addition to the four elements of organic
matter (556), the same earthy substances which plants
contain, and this is really the fact (595). The phos-
phate and carbonate of lime of the bones is obtained
from plants, and the alkaline and other salts found
in the various parts of the animal body are derived
from a similar source.
786. The knowledge of this fact necessarily leads
to the conclusion that all animal matter must be val-
uable as manure. The flesh and softer parts of ani-
mals, as well as the bones and other solids of the
body, are composed of the same substances, both
inorganic and organic, as plants ; and during their
putrefaction yield them up again in a fit state to
be absorbed by plants.
EXCREMENTS. 297
787. The vegetable substances which constitute
the food of animals contain more earthy and saline
matters than animals require, and they are ac-
cordingly passed from the body as excrementitious.
The food of animals in great part goes to supply the
waste occasioned by respiration. In this process,
carbonic acid is formed by the oxidation of carbon
in the body, by the oxygen of the air; hence, in
the air expired from the lungs, it is found that
the oxygen is more or less combined with carbon,
and converted into carbonic acid (107, 606). The
heat evolved by the combination of this carbon with
oxygen keeps up the warmth of the body. The
waste of organic matter in the body thus occasioned,
is supplied by food, the organic part of which sup-
plies that consumed by respiration; but as the great-
er part of the inorganic substances contained in food
are not required for this purpose, the excess is void-
ed in the solid and fluid excrements.
788. There are few things of greater value as
manures than these offensive and apparently useless
substances, which consist of a mixture of organic
and inorganic matters ; the former, in consequence
of the nitrogen they always contain, ready to de-
compose, and furnish carbonic acid and ammonia ;
the latter, those very substances which we require to
add to the soil, being the very substances which are
removed with crops. In consequence of the volatile
nature of the products of their decomposition, every
means must be employed to prevent their loss.
298 LOSS OF MANURE.
789. When animal substances are left for some
time exposed to the air, they undergo decomposition,
and there at last remains nothing but the more fixed
substances which they contained, together with a
quantity of salts of ammonia, formed during the de-
composition of the easily putrefiable matters. This
residue is a valuable manure, though in forming it a
very large portion of the ammonia produced is lost
by evaporation. The guano or huano of South
America, which has of late excited so much attention,
is the remains of the excrements of sea-fowl, which
has partly undergone this change (813).
790. There are other modes besides that already
adverted to (162), whereby the loss of ammonia may
be prevented. Both ammonia and its carbonate are
volatile, and though by the addition of water it is
easy to retard their escape, it cannot be entirely pre-
vented. It has therefore been proposed to add to
liquid manure a small quantity of some acid, which
shall combine with the ammonia to form a neutral
salt, and so prevent further loss from volatility. The
trials which have hitherto been made appear per-
fectly satisfactory, and the only question is — which
is the best method of thus neutralizing or fixing it ?
791. The simplest method of fixing ammonia is to
add to the manure a small quantity of a weak solu-
tion of any acid; but we may also fix it by the addi-
tion of any salt containing an acid united to a base
by a less affinity than the acid has for ammonia ;
FIXING AMMONIA. 299
when this is done, the salt is decomposed, the base is
set free, and the acid combines with the ammonia.
792. Ammonia may be fixed by the addition of a
small quantity of sulphuric, nitric, muriatic, phos-
phoric, or any other acid. Sulphuric is, generally
speaking, the cheapest, and therefore the most con-
venient to employ; the quantity to be added of course
depends on the quantity of ammonia in the manure ;
when enough acid has been used, all smell (153, 155)
of ammonia disappears. A slight excess of acid
does no harm, as it is certain to become neutralized
by the bases always present in the soil.
793. It not unfrequently happens that, from local
circumstances, a large supply of some other acid
liquors may be obtained, more particularly in the
vicinity of manufactories ; all such substances may
be used with advantage. The comparative value of
the diiferent salts of ammonia is as yet unknown;
perhaps the best acid, if it could be procured cheap
enough, would be the phosphoric. Phosphate of
ammonia forms a most valuable manure.
794. Various salts have been proposed for the pur-
pose of fixing ammonia ; amongst these the best
appear to be gypsum, or sulphate of lime (237), and
copperas or green vitriol, the sulphate of iron (289).
When either of these salts is mixed with solutions
containing ammonia in the state of a carbonate,
both are decomposed, sulphate of ammonia is formed
(159), and carbonate of lime or oxide of iron is left,
as an insoluble powder. For several reasons, acid is
300 LIQUID MANURE.
preferable to fix ammonia ; it is more easily used,
and requires far less care and attention in "mixing
with the solution containing ammonia.
795. Animal substances must have undergone
decomposition before they can serve as the food
of plants. It has already been stated, that plants
appear only able to absorb nitrogen in a state of
combination (640) ; no form of organic matter is
suitable to the nourishment of a healthy plant. It
is the office of the leaves to convert carbonic acid,
ammonia, and water into organic matter, and hence
organic matter must be resolved by decomposition
into these substances, before it can be absorbed by
plants.
796. There are some plants, however, which seem
to be exceptions to this rule, and which appear able
to feed on organic substances. Certain fungi and
parasitical plants, or those which grow upon others,
probably feed by directly absorbing organic matter.
The small fungi which constitute the various forms
of mouldiness are of this description ; they flourish
in the dark, and grow on any kind of dead organized
matter. All plants which have leaves, and require
the influence of light, feed on gaseous matter, and
never on organic compounds, except during the first
period of their growth (719).
797. Liquid manure, consisting chiefly of urine
and other waste animal manures diluted with water,
is never so valuable in its fresh state as it becomes
after a time, when the organic matter is chiefly con-
LIQUID MANURE. 301
verted into carbonic acid, water, ammonia, &c. The
time required for this change varies from four to
eight weeks, or even more, according to the season
of the year ; putrefaction being much more rapid in
hot than in cold weather.
798. The substances containing nitrogen are those
which first begin to undergo putrefaction, and ac-
cordingly ammonia is one of the earliest products of
the putrefaction of liquid manure ; at this time much
of the ammonia is in the caustic state, and hence it
is not so fit for manure as it is subsequently, when
combined with carbonic acid in the completely putre-
fied liquid. In consequence of the great volatility
of caustic ammonia, much of it is lost by evaporation,
in the early stage of putrefaction ; it is for this rea-
son that close tanks for liquid manure are so much
recommended, and that the addition of fixers is found
advantageous.
799. Amongst the principal animal substances
employed as manures are urine, and dung of all
kinds, the flesh and blood of dead animals, fat and
oily matters, hair, wool, skin, and, lastly, horns,
hoofs, and bones. These substances are all more or
less valuable, as yielding to the soil a large quantity
of the substances which constitute the food of plants;
they putrefy, and their elements form new combina-
tions with great rapidity. Those which change most
readily, of course yield ammonia and carbonic acid
most rapidly, and these constitute the most powerful
26
302 ' STRONG MANURE.
manures : those which decompose more slowly are
less powerful, but more lasting in their effects.
800. Urine, dung, and the decomposing carcases
of all animals are excellent manure ; they are for
many 'purposes considered to be too strong, and
means are adopted to diminish their power. These
manures evolve, during their rapid decay, a very
large quantity of ammonia, carbonic acid, &c., far
more, in fact, than plants require or can absorb.
This excess is hurtful, and must be prevented.
801. There are two ways by which this may be
effected ; the one is to mix Strang manure with a
considerable quantity of some substance far less
prone to decomposition, so as to dilute it, or check
its putrefaction ; the other, and certainly infinitely
the worse way, is to expose it to the air for some
time, and not to use it until a great part of the am-
monia evolved by its decomposition is dissipated, or
combined with acids ; what remains is then sufficient-
ly mild to be used with safety.
802. In order to preserve as much as possibla the
valuable parts of these manures, they should be
mixed with a certain quantity of vegetable refuse
manures, such as sawdust, weeds, &;c. This addition
tends to check their too rapid decomposition, and
prevents the great loss which ensues when manure
putrefies too rapidly and becomes hot from the effects
of its own decomposition ; and at the same time the
vegetable matters added are gradually brought into
a state which renders them also a most valuable ad-
STRONG MANURE. 303
dition to the soil. Farmyard dung is a mixture of
this kind.
803. In mixing weeds with strong animal manures,
it must be borne in mind that their seeds are in many
cases not destroyed, although all the rest of the
plants may be completely decomposed. Rapid Mid
active putrefaction will no doubt destroy the seed
also, but this is not desirable ; because, when the
manure ferments very strongly, it heats, and a con-
siderable portion of volatile matter is sure to be lost.
Many seeds have so hard a husk that they will not
be at all injured by exposure to mere ordinary putre-
faction, and retain therefore their vitality through
the decomposition of the dung. Some seeds will
even pass uninjured through the stomach of an
animal, and not have their vital powers impaired even
by the process of digestion.
804. In most cases it is a waste of manure to burn
weeds, and whenever it is practicable it is better to
form them into dung by rotting them with other sub-
stances ; but when they are full of seeds, or it is not
possible to destroy their vitality by so doing, it is
doubtless better economy to burn them than to run
the risk of a fresh crop for the next season.
805. As the hedges, banks, and ditches round the
manure-yard or mixed heaps are always sure to be
well manured, and to get a good deal of the exhala-
tions which are lost during the fermentation of the
manure itself, so the weeds which grow in such situa-
tions are of course peculiarly luxuriant and abundant.
304 MANURE-HEAPS — HEDGES — DITCHES.
The farmer should take particular care to destroy
them, and never allow them to come to seed, in such
situations. It is unnecessary to describe the bad ef-
fects produced by the abundant crops of weeds which
too often are left to seed in the immediate vicinity of
the manure-heaps.
806. A very bad custom, too, is often followed of
leaving manure-heaps too long untouched, so that
they become in fact covered with a mass of weeds,
which are left to flower and seed. The labor saved
in not turning over and trimming the. heap, is not a
tenth part of that required to remedy the evil done
in thus rendering the land foul.
807. One of the greatest obstacles to good farm-
ing is the practice of keeping wide and foul hedges ;
they serve not merely as harbors for vermin, but as
nurseries for weeds. The preservation of game is, in
fact, the bane of the farmer ; for his farm is at least
diminished in value by one half, from the various
evils which are thus introduced.
808. Those, however, who advocate the total re-
moval of hedges certainly go too far ; for hedges are
useful as shelter, and in other ways. A small and
well-trimmed hedge, if constantly attended to, does
not, after all, require very much labor to keep it in
good order.
809. The extremely offensive odor of night-soil is
a great obstacle to its collection and use as manure.
In its fluid state the expense of conveying it to any
distance is of course great, and accordingly various
NIGHT-SOIL. 805
plans have been adopted to reduce it to the solid
form, both to diminish cost of conveyance, and also
to admit of. its being used with the drill; in these,
however, a portion of the volatile constituents is
generally lost, though what remains is undoubtedly
a valuable manure.
810. In the manufacture of some of the best of
these " disinfected night-soils," charcoal-powder,
burnt clay, and other similar porous substances, are
used to absorb the gases evolved (162).
811. The most economical mode of using night-soil
is, probably, to allow it to putrefy, diluted with water,
and mixed with a considerable quantity of vegetable
matter, and to employ it as liquid manure. Of course
this cannot be done when it is intended subsequently
to carry it to a distance.
812. The dung of different animals varies consider-
ably in its value as manure, depending, in great part,
on the substances which constitute their food ; that of
those which live on animal food being of course richer
in nitrogen than that of vegetable feeders. The
value of those kinds used as manure are in the fol-
lowing order : Pig's dung, night-soil, sheep and
rabbit's dung, horse dung, and cow dung ; the first
being that of most value.
813. In manuring land by feeding off with sheep,
not only does the land receive a large quantity of
valuable manure from the dung, urine, and perspira-
tion of the animals, but it likewise has its mechanical
26*
306 GUANO.
texture materially modified by the constant treading
of the sheep.
81i. Guano, the residue of the putrefaction of the
excrement of sea-fowl, consists chiefly of various
salts of ammonia, inorganic compounds, and unde-
composed organic matters, analogous in nature to
horn and wool (818). The salts of ammonia dissolve
easily in water, and are at once absorbed by plants,
whilst the undecomposed organic matter, gradually
undergoing decomposition, continues for some time
to yield a regular supply of ammonia. In guano,
there exists all the chemical elements of an excellent
manure ; but of course it does not produce the
same mechanical effect on the soil which yard dung
does.
815. In using guano as liquid manure, it must be
remembered that the solution formed by pouring
water over it only contains the ammonia and about
one quarter of the phosphates, the rest of the phos-
phates, and the organic matter, being almost insolu-
ble in water ; hence the residue is nearly as valuable
a manure as that which is dissolved ; and in order
to derive the whole bene^fit from the manure, the in-
soluble part must, by agitation or other means, be
kept suspended in the liquid whilst it is being spread
over the ground.
816. Analogous in nature and value to these sub-
stances are dead fish, and the refuse matters left in
curing and preserving fish; sugar-refiners' waste,
which is a mixture of charcoal, blood, and the various
REFUSE MATTERS. 307
organic matters containing nitrogen, which exist in
crude sugar ; and wool, soap, an abundant refuse
from the wool-mills, consisting of putrid urine, in
which the wool is boiled to remove the grease which
it naturally contains, and which is consequently rich
in ammonia.
817. Strong animal manures are doubly valuable;
for not only do they contain abundance of those
matters which constitute the food of plants, but they
also assist in rendering useful materials which would
without them be of far less service. Whether these
manures are employed in the liquid or in the solid
form, some means should be adopted to retain the
ammonia, either by the addition of acids or by some
other method. (7»8).
818. These remarks are far less applicable to
animal manures, such as fatty substances, horn, wool,
bones, &c., which change but slowly. These sub-
stances for the most part act slowly and gradually,
and in a very different manner from the softer parts
of animals.
819. In general, the strength of animal manures
is in proportion to the quantity of nitrogen which
they contain ; those which contain much of that ele-
ment decompose rapidly, and evolve a considerable
quantity of ammoriia, whilst those containing little or
no nitrogen change slowly, and, though valuable, and
perhaps more lasting in their effects as manures, are
far less powerful for the time.
820. Woollen rags, hair, feathers, clippings of horn
and skin, greaves, the refuse of the tallow-melters, the
308 WOOL — RAGS — OIL.
refuse of glue manufactories, and similar matters,
form valuable manures ; because, though they do not
decompose so rapidly as other animal manures, they
slowly and gradually decompose, and continue to give
out ammonia, &c., for a very long time.
821. The substances of this sort employed as
manures are very numerous; including as they do the
refuse of all those processes of the arts in which
animal matters are used, their value in all cases
chiefly depends on their slowly decomposing, and
affording a continual source of ammonia, &c.
822. Although oil or fat of all kinds contains no
nitrogen, and therefore exhibits very little tendency
to change when pure, yet when mixed with earth, the
large surface which is exposed to the air assists in its
decomposition, particularly if other animal matters
also are present; and it accordingly forms a valuable
constituent of mixed manures.
823. The dregs of oil, w^aste blubber, and refuse
oils of all sorts, are excellent manures ; soap, likewise,
in which oil or fat is combined with alkali, is used
with advantage whenever it can be obtained at a
moderate price. The waste soap of the wool factories
has already b^en mentioned as of great value (816).
824. The water which runs to waste from many
manufactories in which soap is employed might be
used with great advantage for manure ; it often holds
in solution a considerable quantity of valuable matter,
and might be well employed in the formation of
liquid manure. ^y^
BONES. 809
825. The drainage-water of towns, generally con-
taining, as it does, urine, refuse from the kitchens,
soap, &c., is an excellent manure; the most valuable
substances which it contains exist in a state of solu-
tion; the mud which falls to the bottom when it is
left to stand at rest, is comparatively speaking of
little value.
826. The last animal manure which it is necessary
to speak of is bones, though, as their chief value con-
sists in the inorganic matters which they contain,
they might almost be classed amongst the inorganic
manures.
827. Bones consist of earthy matters together with
a quantity of gelatine and fat ; the value of bones
as a manure consists in their mechanical effect on the
texture of the soil, the earthy substances which they
supply (876), the ammonia given out during the decay
of the gelatine or glue, and the carbonic acid and
hydrogen supplied by the fat (595).
828. The quantity of putrefiable matter in bones
is small in proportion to their whole weight, and its
decomposition is retarded by the large quantity of
earthy matter they contain ; hence bones form a good
and lasting manure.
829. Boiled bones form a better manure than raw
or green bones, l^his appears to be caused by the
removal of fat by boiling ; the fat which bone con-
tains retards the decomposition of the gelatine, and
probably also renders the phosphate of lime less so-
luble than it is when the oil is removed.
310 BONES.
830. In stating that boiled bones form a better
manure than raw or unboiled ones, it is of course ev-
ident that the operation of boiling cannot in any •way-
increase the absolute quantity of manure which they
can supply, but merely renders them more rapid in
their action ; as they become less lasting in their
effects, in exact proportion to the rapidity of their
action when first used.
831. As phosphate of lime is insoluble in pure
water, and but slightly soluble in water containing
carbonic acid, and as the most valuable component
of bone is phosphate of lime, we should be led to
expect that they would form a lasting manure, pro-
ducing a beneficial effect so long as any of the phos-
phate of lime remains unabsorbed. As the quantity
of this substance which plants are able to obtain from
bone in one season is comparatively small, it has been
proposed to mix with bones some substance which
shall render the phosphate of lime more soluble.
832. The cheapest and most convenient substance
for this purpose is sulphuric acid or oil of vitriol (179,
245) ; this forms with bones a compound called " su-
perphosphate of lime," one of the most valuable of
the artificial manures yet proposed.
833. Crushed bones, either burnt, or in the raw
state (the former, however, being preferable), are
mixed in a leaden vessel with sulphuric acid ; after a
short time the acid is found to have completely de-
composed the bones and reduced them to the state of
a moist solid, which, however, may be easily rubbed
BONES AND SULPHURIC ACID. 311
to powder, and used in any way as manure, either
alone, or mixed with dry soil.
834. The effect thus produced by the sulphuric
acid is very simple ; burnt bones consist of phosphate
and carbonate of lime, the latter in a far smaller pro-
portion than the former; when sulphuric acid is pour-
ed over burnt bones the carbonate of lime is wholly
decomposed, being converted into gypsum or sulphate
of lime (245) ; the phosphate of lime is partly de-
composed, the sulphuric acid takes from it the great-
er part of the lime forming gypsum, whilst the rest
of the lime being still combined with the phosphoric
acid, constitutes a very sour and easily soluble salt,
a biphosphate or superphosphate of lime.
835. As the most valuable part of this manure is
soluble in water, it may easily be used as a liquid,
being dissolved in water. "Whether used dry or in
solution, it is most advantageous to use with it some
manure containing ammonia, such as yard dung,
guano, or any of the strong animal manures.
836. It is frequently the custom to mix a consi-
derable quantity of earth or soil with putrefying
animal manure. This to some extent is a good prac-
tice; the earth added prevents too rapid putrefaction,
and retains some of the products of decomposition;
a considerable quantity of ammonia, which would
otherwise be lost, is absorbed by the soil (162). The
addition of burnt clay or charcoal is useful for a
similar reason.
837. The use of lime, on the other hand, is de-
312 VEGETABLE MANURES.
cidedly objectionable; it increases the rapidity of
decomposition, and tends to the formation of a por-
tion of nitric acid, but its use causes the loss of a
large quantity of ammonia, in consequence of its
power of decomposing all the salts of ammonia (152),
combining with the acid which they contain, and
expelling the ammonia in the state of gas. The
addition of lime renders putrefaction a far less
noisome process, as the lime absorbs the sulphuretted
hydrogen evolved (182), which would otherwise
escape into the air.
838. Wood ashes mixed with putrefying animal
matters act in a similar manner to lime ; the alkali
which they generally contain frequently accelerates
decomposition, but occasions loss of ammonia.
839. A good deal of what has been said respecting
animal manures is equally applicable to those of
vegetable origin ; but in general the decay of vege-
table manures is far less rapid than that of animal
substances, and they are more valuable for their
mechanical effects, and the carbonic acid and saline
matters which they supply ; whilst^ in addition to
these, animal manures yield ammonia, the substance
of which is indispensable to the formation of gluten,
albumen, fibrin, and caseine, the most important of
the constituents of vegetables (602).
840. The use of decaying vegetable matters has
already been described whilst speaking of the nature
of humus, and the organic constituents of the soil
VEGETABLE MANURES. 313
(667). A moderate quantity is very desirable, but
too much is decidedly hurtful.
841. A soil containing a very large quantity of
humus or vegetable matter in a state of decay is
always full of carbonic acid ; seeds do not germinate
well in such a soil ; and the excess of carbonic acid
is even hurtful to plants themselves (745).
842. The principal vegetable substances employed
as manure are straw of all kinds, leaves, sawdust,
bran, oilcake, seaweed, and green manures, or crops
which are merely sown to be ploughed in, and thus
afford food to a second crop, of some more valuable
plant.
843. All these manures when mixed with soil
slowly decay, and yield carbonic acid and small
quantities of saline and earthy matters. They are
most advantageously used when employed in combi-
nation with some kind of animal manure ; this is the
case in farm-yard manure.
844. Straw alone decays but slowly, but when
mixed with the dung and urine of cattle, it soon
begins to change, and in a short time the whole is
brought into a state of decomposition (802).
845. In this case, a sort of putrid fermentation is
caused ; the animal manure decomposes rapidly, and
causes a similar change to take place in the vegetable
substances with which it is mixed (766) ; decomposi-
tion proceeds rapidly, heat is evolved, and if the
bulk of the mixture is large, this action becomes so
27
314 SAWDUST.
energetic that the value of manure is seriously in-
jured, by the high temperature to which it is thus
exposed.
846. The decay of some vegetable manures may
be facilitated by the addition of lime ; for the objec-
tion which applies to the mixture of lime with animal
manures is not applicable to the ordinary vegetable
manures. The latter for the most part contain but
little nitrogen, their value principally depending on
their mechanical action, and on the formation of
carbonic acid.
847. Vegetable manures decay more or less rapidly
in proportion to the quantity of nitrogen which they
contain ; green manures contain a notable quantity
of gluten and , albumen, and accordingly decompose
rapidly, whilst sawdust, which consists principally
of woody fibre, and contains hardly any nitrogen,
decomposes slowly. Sawdust is, therefore, a most
excellent substance to mix with the excrement of
animals, and other strong animal manures.
848. Wood sawdust is valuable as manure in pro-
portion to the facility with which it decomposes, and
the inorganic matters which it contains; that obtained
from young trees decomposes with more facility than
the sawdust of old wood.
849. The wood of those trees which contain much
resinous matter decays less rapidly than other woods,
and is therefore not so valuable as a constituent of
mixed manures (802). Those woods which, when
burnt, yield a large quantity of ashes rich in alkaline
GREEN MANURES. 315
salts (199), are useful additions in the state of saw-
dust to manures rich in ammonia.
850. There are a few manures of vegetable origin
which contain a considerable quantity of nitrogen,
and which consequently approach very near in nature
to those formed of animal substances : such, for ex-
ample, is yeast or barm ; this consists of matter rich
in nitrogen in a state of incipient putrefaction {^QQ),
and is a very strong manure.
851. So also is oilcake, the residue left after ex-
pressing the oil from seeds like linseed, which are
rich in oil ; it contains much gluten and albumen,
and is for that reason a strong and valuable manure.
852. Green manures, as they are called, always
contain enough nitrogen to insure their own decom-
position, though it goes on far slower than does that
of animal manures; the value of green manures is
shown in the ploughing up of an old pasture ; and
even more strongly in the case of those crops which
are sown, merely to be ploughed in, when they have
formed a quantity of organic matter.
853. Some plants decompose with far more readi-
ness, than others; for the most part, water plants,
both sea and land, decay less easily than land plants;
they notwithstanding are useful manures. Seaweed,
employed alone, decays but slowly ; it is, however,
valuable for its mechanical effects, and likewise for
the alkali which it contains; it may be used with
great advantage together with strong tinimal manures
(802).
316 DRAINING.
854. Green manures, which contain but little
nitrogen, may also be used very advantageously
together with urine and similar animal substances,
which soon bring them into a state of decomposition.
A similar effect is also produced by steeping these
matters in the ammoniacal liquor of the gas-works
(154, 886) ; the whole of the vegetable matter is soon
reduced to a pasty decomposing mass, w^hich is a very
good manure.
855. The dry and less changeable kinds of vegeta-
ble matter are chiefly valuable for their mechanical
effects, the influence which they exert upon evapora-
tion, and the inorganic matters which they contain;
they likewise may, however, be brought into a state
of decomposition by the addition of animal matters
(802).
856. The number of inorganic substances employed
as manures is very great, and their use is naturally
much dependent on the nature of the soil. In many
cases, great benefit is derived from mixing soils;
either mixing a portion of the subsoil with the sur-
face-soil (761), or by adding to the soil earth brought
from a distance, and possessing a different nature and
composition.
857. The earthy matters thus added to the soil
can hardly be called manures, although in truth they
considerably resemble manures in the mode in which
they act. By draining, deep ploughing, mixing, and
by the use of mineral manures, either the mechanical
DRAINING — IRRIGATION. 31T
texture of the soil is improved, or substances are
added to it in which it was previously deficient.
858. It is almost unnecessary to say anything re-
specting the importance of draining, and the change
which it produces in too retentive soils, and in soils
which from their position are naturally wet and
swampy. The facts which have previously been
stated show that too much moisture in a soil is hurt-
ful, preventing the free circulation of air throughout
it, and in several ways interfering with the healthy
growth of plants ; this is remedied by draining.
859. By draining, and subsoil ploughing, the ac-
cess of air is facilitated, and the decomposition of
silicates and similar stony compounds in the earth is
assisted. In mixing, or by adding mineral manures,
we increase the quantity of certain inorganic compo-
nents of the soil.
860. Amongst the modes of fertilizing the soil and
augmenting the growth of crops, the subject of irri-
gation must not be omitted. The effects produced
by flooding grass-land are well known; they depend
on several distinct causes.
861. Yery dry parched land is therefore much im-
proved by irrigation, when from the heat of the climate
the greater part of the natural moisture of the soil is
evaporated; under such circumstances, the artificial
application of water is necessary for the successful
cultivation of plants, and accordingly it is a constant
practice in tropical countries, in the cultivation of
rice and similar crops.
27*
318 ROAD-DRIFT.
862. Water is of service in temperate climates
as a solvent of saline matters, as assisting the decay
of organic matters in consequence of the air which it
holds in solution, as bringing saline substances which
are useful to plants, and as affording a supply of
organic matter capable of affording ammonia, nitric
acid, &c., by its subsequent decomposition.
863. In flooding land, the saline substances con-
tained throughout the soil, and formed by the decom-
posing agency of the atmosphere (651), are dissolved,
and consequently brought into a condition fit for
absorption by growing plants ; but quite independent
of this, almost all water contains a considerable
quantity of inorganic matter (76), which in many
cases is a valuable addition.
864. In those cases where drainage- water is allowed
to mix with that employed for irrigation, of course
the organic matters and saline substances which the
former contains, produce their effect in addition to
that of the latter. The benefit is produced almost
entirely by the liquid, and the substances which it
holds in solution ; the fine mud which it leaves on the
surface of the ground is of comparatively but little-
value.
865. Road-drift and the scrapings of ditches are
often used as manures with very beneficial results :
their value of course depends in great part on their
composition, and the nature of the soil to which they
are applied ; the scrapings from roads made of stone,
MUD — INORGANIC MANURES. 319
sucli as whinstone, are more valuable than those from
grit or sandstone.
866. This difference depends entirely on the alka-
line matters, &c., which the whinstone contains ; but
besides this, road scrapings are often rich in animal
matters, derived from the dung and urine of cattle.
Road-drift is seldom used alone, but forms an excel-
lent addition to more concentrated manures, such as
alkaline salts, guano, super-phosphate of lime, &c.
867. The fine mud deposited in stagnant waters,
and on the banks of many rivers, is of value as ma-
nure, though by no means so valuable a substance as
is frequently supposed ; its composition varies con-
siderably, and sometimes, particularly in the vicinity
of large towns, it contains a considerable quantity of
animal matter, phosphoric acid, and ammonia ; but,
generally speaking, the most valuable part of the
manure is carried away by the water (826). Even
ill those cases when it is rich in animal matters, its
weight, and the heavy expense of carrying it to any
distance, very seriously interfere with its use.
868. The mode in which many inorganic matters
act is very imperfectly understood, and must of neces-
sity remain so until the office performed by saline
and earthy substances in the nutrition of plants is
explained. It is, however, certain that the addition
of an earthy substance to the soil is of no use, if the
soil already contains abundance of that particular
compound; and consequently that the applicability
320 LIME.
of any such manures, is wholly dependent on the
nature and composition of the soil.
869. When reading accounts of experiments with
various inorganic manures, it must ^always be borne
in mind that on one soil salts of potash, on another
nitrate of soda, and on a third phosphate of lime,
may be the best manure, because the soil happens to
be deficient in alkaline salts or phosphates.
870. Plants almost invariably contain salts of the
alkalies, and lime, or magnesia ; sometimes combined
with organic acids, sometimes with sulphuric, muriatic,
or phosphoric acid. Phosphates of lime and mag-
nesia, in particular, are very commonly 'met with in
plants. It will be proper to enumerate briefly the
artificial sources of these inorganic substances, and
to consider the best method of supplying them to the
soil.
871. Lime is a very common ingredient in plants,
and is also found in almost all fertile soils ; the ad-
dition of lime or calcareous matter, therefore, to soils
which are destitute of it, or contain but very little, in-
variably improves them. Lime is added to the soil
pure, in the form of quick and slaked lime ; as a car-
bonate in the various forms of chalk, limestone, marl,
shell-sand ; as a sulphate in gypsum and plaster-
stone ; and as a phosphate, in bones, native phos-
phates, and the various organic manures already
referred to.
872. When quicklime is spread over the surface
of land, other effects arc produced besides the mere
LIME. 321
addition of carbonate of lime. The quicklime soon
absorbs moisture, and crumbles to powder, it then
gradually absorbs carbonic acid from the air, and re-
turns to the state of carbonate (235). The chalk
"which is thus formed is in a state of very fine pow-
der, and becomes more thoroughly mixed with the
soil than it could be by ordinary means ; but at the
same time the quicklime has greatly assisted in pro-
moting the decomposition of inorganic and organic
matters in the soil, and probably caused the formation
of a small quantity of nitrate of lime, a salt of some
value as a manure.
873. Caustic lime possesses the power of gradually
effecting the decomposition of earthy and alkaline
silicates in the soil, combining with alumina and silica,
and setting free the potash which they contain ; con-
sequently, one of the most important of the chemical
effects produced by the action of lime upon the soil
is that of rendering useful a portion of the potash
which it previously contained in an insoluble, and
therefore useless state.
874. There is great difference in the value of dif-
ferent kinds of lime for this purpose. All limestones
which consist merely of carbonate of lime yield pure
caustic lime when burnt (119), but many limestones
contain a portion of carbonate of magnesia, and
these when burnt yield a mixture of caustic lime
and magnesia. Such lime is in general objectionable
as manure. It is probable that the tendency which
magnesia has to remain caustic for a long time, ab-
322 GYPSUM.
sorbing carbonic acid but slowly from tlie air, is the
cause of this (248). Limestones which contain much
alumina and oxide of iron do not burn into good
lime, because the lime and claj partly unite and form
a kind of slag.
875. Chalk, shell-sand, and indeed shells them-
selves, which consist of carbonate of lime and a small
quantity of animal matter, are useful additions to all
soils which contain but little lime. Quick or caustic
lime is especially useful in soils rich in humus. Soils
of this kind generally contain a small quantity of
acid, which greatly interferes with their fertility ;
this acid is neutralized by the addition of lime. Both
lime, and likewise its carbonate, are valuable addi-
tions to soils containing sulphate of iron (289, 663).
That salt which is hurtful to vegetation, is decom-
posed by lime ; gypsum is formed, whilst the iron
remains as an oxide or carbonate.
876. Sulphate of lime, or gypsum, is likewise a
very useful addition to all soils which do not natu-
rally contain it. It is partly useful as supplying lime
and sulphuric acid, and partly a^ serving to fix am-
monia from the air (794), and thus yielding plants
more of that substance than they could otherwise
obtain. Gypsum is sometimes employed after being
burnt, and sometimes unburnt ; the only use of the
burning is that it renders it very easily crushed, the
gypsum in fact falling to powder when burnt. This
operation is rather roasting, than burning, because,
PHOSPHATE OF LIME — ASHES. 323
if too strongly heated, it loses its property of again
absorbing water.
877. Phosphate of lime is found native as a min-
eral in Spain and other countries ; it certainly forms
a most valuable manure for poor soils. As phos-
phate of lime is found in nearly all plants, all sub-
stances containing it are useful as manures (732).
The native phosphate of lime has, as yet, hardly
come into use at all as a manure, in consequence of
the expense of collecting and carrying it to any dis-
tance. Phosphate of lime exists abundantly in bones
(595), and in smaller quantity in all organic ma-
nures, and in the ashes of plants. A minute quantity
of phosphate of lime is found in many rocks, and in
particular kinds of chalk and marl, which are conse-
quently valuable additions to the soil. The copro-
lites, and other forms of fossil manure which have
been so much talked of, of late, contain a considerable
quantity of phosphate of lime ; large deposits of these
substances exist in various parts of the country.
878. There are no mineral manures which contain
phosphate of magnesia ; it exists in many soils, and
in a good many organic manures. Bran contains a
considerable quantity of this salt. Magnesia, in its
pure and caustic state, appears to be hurtful to
plants, but some of its salts are useful ; thus, sul-
phate of magnesia, or Epsom salts, has been found a
valuable manure for potatoes, &c.
879. Ashes of all kinds constitute an important
class of manures. They are of value for the char-
324 ASHES.
coal, lime, phosphoric acid, and alkaline salts which
they contain. The ashes of organic substances, such
as the ashes of wood and vegetable matters, consist
principally of those substances which plants require.
Kelp, or the ashes of seaweed, consists of similar
saline compounds, generally containing more alka-
line salts than the ashes of common land plants.
Soap-maker's ash, w^hich consists of the insoluble
part of wood-ash, contains a considerable quantity of
phosphate of lime, and is consequently a valuable
manure (890).
880. The ashes of turf, peat, and weeds, consist
of pretty nearly the same substances as the ashes of
trees and other plants ; they therefore constitute
valuable manures. The good effects which have been
produced by paring and burning, are in great part
due to the charcoal and saline matters w^hich are
spread over the soil in the form of ashes. The earth
which adheres to the roots and plants burnt in this
process acquires considerable power of condensing
ammonia from the air (162). This is because burnt
clay, or clay which has been strongly heated, has its
mechanical properties very greatly altered, and ac-
quires the property of absorbing ammonia in large
quantity. When dry burnt clay, which has been
exposed to the air for some time, is moistened or
breathed upon, it gives out a very perceptible smell
of ammonia.
881. The ashes of coal are of less value as manure
than most other ashes; they do not contain alkali or
CHARCOAL — SOOT. 325
phosphoric acid, but consist of silica, alumina, oxide
of iron, and a small quantity of sulphate of lime.
Their chief value appears to consist in the charcoal
and sulphate of lime which they contain.
882. Although charcoal has been spoken of as
undergoing no change whatever under ordinary cir-
cumstances (90), and as having no tendency to oxi-
dize or form carbonic acid when exposed to the air,
yet in some conditions when exposed to moisture,
warmth, and air, the more porous kinds of charcoal
do slowly and gradually form carbonic acid; and this
action appears to go on more rapidly when charcoal
is mixed with humus (672) and other decaying organic
matters.
883. Waste charcoal of all kinds is useful as
manure, particularly in close and retentive soils ;
hence it is often the custom to burn or char sawdust,
brushwood, and dry vegetable rubbish: a mixture of
ashes and charcoal is thus obtained, which is more
valuable than that which is left when such matters
are entirely burnt to ashes. For various purposes in
the arts, such as the manufacture of gunpowder, that
charcoal is best which contains the least quantity of
inorganic matter, but for manure it is just the re-
verse (162).
884. In connection with ashes, soot, and the refuse
of gas-works may be mentioned, although very dif-
ferent in their nature. Soot consists principally of
finely-divided charcoal or carbon, but it contains a
considerable quantity of salts of ammonia; hence it
28
326 GAS LIQUOR.
is a powerful and valuable manure. If a little quick-
lime is mixed with soot, the salts of ammonia will be
decomposed, and the strong pungent smell of ammonia
becomes evident. For this reason lime and soot
should not be used together as manure : the objection
of course does not apply to the use of chalk and
soot.
885. Soot contains a good deal of the ammonia
formed during the combustion of coal, but, in con-
sequence of its volatility, a considerable portion is
lost. In the process for making gas, where coal is
roasted in close iron vessels, all the ammonia is saved
and is condensed by means of cold water. The gas
is made to bubble through a quantity of water: this
condenses the ammonia, and constitutes what is
termed gas liquor, or the ammoniacal liquor of the
gas-works. It is a solution of ammonia, partly caus-
tic, and partly combined with carbonic acid and
sulphuretted hydrogen (183).
886. Ammonaical liquor is a strong and excellent
manure, resembling in some respects the manures
formed by the decay of animal substances. As ob-
tained from the gas-works, it is almost always too
strong to be used as a manure for grass-lands or
crops, and must be diluted with four or six times its
bulk of water. Gas liquor may also be conveniently
used, mixed with green vegetable manures, the de-
composition of which it greatly facilitates (854).
• 887. In consequence of the volatility and caustic
nature ol" free ammonia, it is found advisable for
ALKALINE SALTS. 327
most purposes to fix the ammonia of gas liquor.
This may either be done with an acid, with gypsum,
or sulphate of iron (792, 794) : a cheap acid like the
sulphuric is, generally speaking, the most convenient.
Gas liquor resembles putrid urine, inasmuch as it is
very rich in ammonia; but it differs from it in not
containing the fixed alkaline and earthy salts which
that manure does.
888. As the strength of gas liquor mainly depends
on the salts of ammonia which it contains, and as the
relative quantity of these salts varies considerably, it
is difficult to state the exact quantity of any acid
necessary to neutralize the ammonia; the average
quantity of strong sulphuric acid requisite for this
purpose is from 20 to 25 lbs. for every 100 gallons
of gas liquor; a little excess of acid hardly ever does
any harm, as it immediately becomes neutralized bj
lime, &c., in the soil.
889. Potash and soda, as has been several times
stated, are very commonly found in plants, and con-
sequently are important constituents of manure; they
both exist in "most soils, though present but in small
quantity, and are generally combined with silica and
other earthy substances ; these compounds are slowly
and gradually decomposed by the carbonic acid of
the air (051) ; their decomposition may be artificially
assisted by the action of lime (873); the principal
salts of the fixed alkalies used as manures are the
carbonates, muriates, nitrates, and sulphates.
890. The ashes of some plants contain a, very large
328 COMMON SALT.
quantity of carbonate of potash: in fact, the potash
of commerce, the chief source of the alkali, is the ash
of trees; whilst kelp, the ash of sea-plants, consists
chiefly of carbonate of soda. Both pot-ashes and kelp
are good manures in moderate quantity, but their
value depends as much on the earthy phosphates
which they contain as on their alkaline salts.
891. Muriate of potash or chloride of potassium
is sometimes used as a dressing for grass-land. The
petre salt of the nitre-refiners contains a large quan-
tity of this salt. It used formerly to be obtained in
large quantities by the soap-boilers, who mixed salt
with their potash soap; the salt was decomposed and
a hard soda soap and chloride of potassium in solu-
tion were the results. The soap-maker's spent lees
were considered a valuable manure for grass-land,
and were believed to destroy moss (524).
892. Chloride of sodium or muriate of soda
(common salt), is frequently recommended as a valu-
able manure ; and in many soils, particularly those
containing little chlorine, it produces very marked
eiFects, when applied in moderation. It is by many
stated that cattle thrive better on plants which have
been manured with a small quantity of common salt,
than on those not so manured. Common salt is not
unfrequently added to dung with a view of facilitating
its putrefaction ; it is very improbable that any such
effect should be produced by salt, which in fact is
more likely to retard decomposition.
893. Common salt is sometimes recommended to
SALT AND LIME. 329
be added to liquid manure for the purpose of fixing
ammonia, because by particular processes, and by em-
ploying very strong solutions, carbonate of ammonia
and common salt may be made mutually to decompose
each other; under all ordinary circumstances, how-
ever, the two salts have no action on each other, and
it is quite useless to add common salt to animal ma-
nures, as a fixer for ammonia.
894. Salt is of course of no use as a manure on
land near the sea-coast, or exposed to winds loaded
with the salt of sea spray. On other land it is fre-
quently employed, either alone or mixed with earth
and lime ; when used in the latter manner, it is
common to make a compost, by mixing salt, earth,
and lime, some time before it is required, and allow-
ing the mixture to remain some time, sheltered from
the rain, the whole being occasionally turned: such
a mixture contains a portion of carbonate of soda.
895. When solutions of chloride of calcium (241)
and carbonate of soda are mixed together, they are
both decomposed, chloride of sodium (common salt)
and carbonate of lime (chalk) being produced. From
this fact it is evident that, under ordinary circum-
stances, chalk and common salt cannot decompose
ea.ch other; nevertheless, when chalk or lime is mixed
with salt and moist ear'th, a considerable quantity of
carbonate of soda and muriate of lime are produced,
an effect wiiich does not take place if n mixture of
the two salts is thrown into a quantity of water.
28*
330 NITRATE OF POTASH.
896. A mixture or compost of lime and salt is a
good manure; it contains carbonate of soda and chlo-
ride of calcium, both of which are useful to plants.
It is possible that salt when applied to land is always
more or less decomposed in this manner, and that,
according to the extent in which this takes place,
salt produces a beneficial effect.
897. Common salt is a necessary addition to the
soil in the cultivation of marine plants, or such as
naturally grow near the sea-shore. It is also fre-
quently used to kill insects. For all these purposes
the most impure salt may be used; the impurities for
the most part rather increase the value of the sub-
stance as manure (252).
898. Nitrate of potash has long been used as a
manure, being found to produce beneficial effects on
most soils, in quantities from one to three hundred
weight per acre. The exact nature of the chemical
effect produced by alkaline nitrates on plants is not
accurately known ; but as both nitric acid and fixed
alkali are separately valuable as manure, or at least
are found to assist vegetation, we might reasonably
expect that the nitrates should be good manures ; it
must always be remembered, however, that though
they contain both nitrogen and alkali, they cannot
well be used alone on ordinary soils, and are best
employed in conjunction with some other substance
containing phosphoric acid.
899. A great many rich and fertile soils are found
ALKALINE NITRATES. 331
to contain a small quantity of nitrate of potash, soda,
or lime, which appears to produce nearly the same
effect as the salts of ammonia, rendering vegetation
vigorous and dark colored. The way in which these
salts are formed will be easily understood when we
remember that, whenever substances containing ni-
trogen decay in the neighborhood of lime or alkaline
salts, a portion of nitric acid is formed (166, 837).
Under these circumstances, the ammonia which would
otherwise be produced is oxidized, and nitric acid
and water are formed in place of ammonia; the acid
combines with the alkali, and nitrate of potash or
soda results. These salts are frequently found in
mixtures of decomposing organic manures ; they are
formed in the same way in the soil itself.
900. The effects produced on different plants by
alkaline nitrates are very various ; to some they are
far more beneficial than others. Some plants, such
as the sun-flower, tobacco, lettuce, and many others,
always contain more or less of these salts. Others
do not contain them, but when supplied with nitrates,
are subsequently found to contain the base, without
the acid. The soda, potash, or lime is combined
with some organic acid, whilst the nitric acid has
disappeared. It is probable that in these cases the
nitrogen of the acid is assimilated by the plant, or
that it assists in the formation of gluten and albu-
men.
901. Nitrates can have but very little value as
manures on the soils which naturally contain salts of
832 ALKALINE SILICATES.
nitric acid, or which, in consequence of the substances
they contain, are constantly forming nitrates. On
soils neither containing nitrates nor other alkaline
salts, they appear to produce very beneficial results.
It has been found that wheat manured with alkaline
nitrates, contains more gluten and albumen than
wheat grown in land not so manured.
902. These remarks apply equally to nitrate of
soda and nitrate of potash ; at least similar effects
are produced by the two salts, as far as regards the
increased formation of gluten and albumen. Nitrate
of soda contains weight for weight more nitrogen than
does the nitrate of potash. It is not known in how
far soda is able to replace potash, or whether it is
indifferent which of the two alkalies is supplied to
plants.
903. Silicates of potash and soda have also been
proposed and partially employed as manures. These
salts are easily made by melting together sand and
carbonate of potash or soda (262) ; it was supposed
that they would be particularly valuable for corn and
grass crops, as these plants contain a considerable
quantity of silica, but the result of trials hitherto
made with these compounds has been such as to
render it probable that the silica which they contained
produced much less effect than the alkali. It appears
that almost all soils contain silica in a soluble form ;
and consequently that, plants are always able to ob-
tain as much silica as they require, from the soil,
except in very rare cases.
333
CHAPTER IX.
COMPOSITION OF PAETIOULAR CROPS AND MANURES.
904. Plants differ considerably from each other
in chemical composition ; not only do various plants
consist of different proportions of the proximate ele-
ments which compose them, but also the same plant
is found to contain variable proportions of these sub-
stances, depending on the peculiarities of soil, situa-
tion, mode of cultivation, manure, and the weather,
or season when they were grown. In the following
pages a brief account is given of the average mean
composition of some of the principal plants which are
cultivated as crops.
905. The first point to be ascertained is the relative
proportion of water, organic matter, and inorganic
matter in different plants. This is done by very
carefully drying a weighed portion ; the loss which
it sustains indicates the quantity of water. The dry
matter is then burnt, the weight of the ashes shows
the proportion of inorganic matter. The chemical
composition of the organic matter, as well as the in-
organic constituents, requires a separate analysis.
334 WHEAT. ^
906. The average composition of wheat, grain, and
Btraw is —
Grain.
Straw
Organic matter
. 866
835
Inorganic matter .
" , 17
45
Water .
. 117
120
1000 1000
907. According to Boussingault, the ultimate com-
position of some wheat which he analyzed was —
Grain.
Straw
Carbon
. 461
.484
Oxygen
. . 434
389
Hydrogen
. 58
52
Nitrogen
. 23
3
Inorganic matter
. 24
70
1000 1000
908. The proportion of bran and flour obtarined
from wheat varies very considerably. The flour, as
it is obtained from the mill, is usually separated by
sifting into four parts : namely, fine flour, which
amounts to from 70 to 80 per cent. ; boxings, from 6
to 10 per cent. ; sharps, from 5 to 7 per cent. ; and
6 to 8 per cent, of bran. There is usually a loss of
rather more than 3 per cent. The bran always con-
tains a considerable quantity of starch, soluble mat-
ters, &c. ; in the following analysis the term bran is
used to denote the insoluble fibrous husk alone.
WHEAT.
335
Hermhst'ddt.
VauqneUn.
Wheat.
No. Manure. Manure, Urine.
French W.
Odessa W.
Starch
666
402
710
578 •
Gluten
Albumen
95
7
351
14
110
145
Sugar
19
14
47
85
Gum
18
16
33
49
Fixed oil
10
10
Soluble ph
08-
phates
3
9
—
—
Bran
140
142
—
23
Water
42
42
100
120
1000
1000
1000
1000
909. The inorganic substances contained in wheat
are also found to vary greatly in composition and
proportion from different sorts of wheat. According
to the experiments of Sprengel, IOO5OOO parts of dry
wheat contain 1777 parts of inorganic matter; the
same quantity of wheat straw contains 3518 parts of
earthy matters. These consist of the following sub-
stances : —
Potash
Soda
Lime
Magnesia
Alumina
Silica
Sulphuric acid
Phosphoric acid
Chlorine
Grain.
Straw.
225
20
240
29
96
240
690
32
26
90
400
2870
50
37
40
170
10
30
1777
3518
WHEAT.
910. According to a more recent analysis by Way,
a sample of white wheat from Whitfield farm con-
tained in 100,000 parts, grain 1730, and in the straw
4680 parts of inorganic matter. Hopeton wheat
from the same place contained in the grain 1760, in
the straw 4160, and in the chaff 10,360 parts of in-
organic matter. 10,000 parts of these ashes respec-
tively consisted of: — -
White Wheat.
Hopeton
Wheat. ^
Grain.
Straw.
Grain.
Straw.
Silica . . . .
263
7050 .
329
6710
Phosphoric acid
. 4744
577
4444
705
Sulphuric acid .
—
331
trace
559
Lime
339
353
821
444
Magnesia . . . .
1405
329
967
327
Peroxide of iron
67
14
8
154
Potash . . . .
2991
1276
3214
1003
Soda
187
68
214
85
911. With such data it is easy roughly to calcu-
late about the quantity of each substance taken off
from the soil with a crop of wheat. Suppose, for
example, a crop of Hopeton wheat, consisting of 22
cwt. of grain, 30 of straw, and 15 of stubble and
roots ; the latter, of course, remaining in the soil
need not be reckoned. The grain, then, would con-
tain about 43 lbs., and the straw (including 4-cut
chaff) nearly 180 lbs. of inorganic matter ; the for-
mer containing nearly 20 lbs. of phosphoric acid,
14 lbs. of potash, 1 lb. of soda, and nearly 4J lbs. of
magnesia. The inorganic matters in the straw would
include about 120 lbs. of silica, 12 J lbs. of phos-
BARLEY.
33T
phoric acid, 10 lbs. of sulphuric acid, 6 lbs. of mag-
nesia, 18 lbs. of potash, and 1 J lbs. of soda, romoved
from each acre.
912. The composition of barley is about —
Organic matter
Inorganic matter
Water
Grain.
825
25
150
1000
913. The proportion of the proximate elements of
barley, according to the experiments of Hermbstadt,
is —
Barley.
Starch .
Gluten .
Albumen
Sugar
Gum
Fixed oil
Soluble phosphates
Husk .
Water .
1000 ;1009
914. In the process of malting barley (412, ^Ott}^ '
a large quantity of starch, which the grain naturally
contains, is converted into sugar and gum. The fol-
lowing analyses by Prout show the relative propor-
tions of these substances which he found in the raw
and in the malted grain. By Hordein, is meant a
peculiar kind of starch, which exists together with
•29
No Manure.
Manure, Urine
. 625
596
. 29
59
I
5
. 50
44
47
44
1
4
1
7
. 136
136
. 110
105
338
BARLEY.
common starch in barley. Hordein is insoluble in
hot water, whilst common starch is readily soluble
(326).
Barley.
Malt
Starch . . ' .
. 320
560
Hordein .
. 550
120
Gluten .
. . 30
10
Sugar
50
150
Gum
40
150
Kesin
. . 10
10
1000
1000
915. According to the experiments of Sprengel,
100,000 parts of dry barley contain 2349, and 100,-
000 parts of straw 5242 parts of inorganic matter,
consisting of —
Potash
Soda
Lime
Magnesia
Oxide of iron
Oxide of manganese
Alumina
Silica
Sulphuric acid .
Phosphoric acid .
Chlorine
Grain.
Straw
278
180
290
48
106
554
180
76
trace
14
—
20
25
146
1182
3856
59
118
210
160
19
70
2349
5242
916. According to two analyses by Way, Chevalier
barley contains from 225 to 243 parts of inorganic
OATS.
339
matter in 10,000 parts of the grain
of the ash consisted of —
Silica .
Phosphoric acid
Sulphuric acid
Lime
Magnesia .
Peroxide of iron
Potash
Soda
Chloride of sodium
in.
10,000 parts
r.
ir.
3273
2360
3169
2601
79
272
148
279
745
867
51
9
2077
2743
456
5
860
917. Oats consist on the average of —
Organic matter . . . . . 872
Inorganic matter 28
Water .100
1000
918. According to Boussingault, the grain of oats
is composed of —
Carbon 503
Oxygen 372
Hydrogen 63
Nitrogen 22
Inorganic matter . . . . . 40
1000
919. The proportion of the proximate elements of
oats are (Hermbstadt)-^
340
OATS.
No Manure. Manure, Urine.
600
531
19
44
2
5
64
60
70
' 57
3
4
1
6
120
170
108
130
Starch .
Gluten .
Albumen
Sugar
Gum
Fixed oil
Soluble phosphates
Husk .
Water .
920. According to Sprengel, 100,000 parts of dry-
oats contain 2580, and 100,000 parts of straw 5740
parts of inorganic matter, consisting of —
Potash .
Soda
Lime
Magnesia
Alumina
Oxide of iron
Oxide of manganese
Silica .
Sulphuric acid
Phosphoric acid .
Chlorine
Grain.
Straw
150
870
132
2
86
152
67
22
14
6
40
2
—
2
1976
4588
35
X9
70
12
10
5
2580
5740
921. According to Way, Hopeton oats contain
•227, and potato oats 245 parts of inorganic matter in
10,000. The composition of the ash was in 10,000
parts —
RYE.
341
Hopeton oat.
Potato oat
Silica
. 3848
5003
Phosphoric acid
. 2646
1887
Sulphuric acid
110
10
Lime
354
131
Magnesia
733
825
Peroxide of iron
49
27
Potash
1780
1970
Soda
384
135
Chloride of sodium .
92
7
I, Rye consists on the average of—
-
Organic matter
.
. 889
Inorganic matter
.
. 11
Water
,
. 100
1000
923. According to Boussingault, the grain of rye
consists of —
Carbon 463
Oxygen 442
Hydrogen 54
Nitrogen . . . . . .17
In'organic matter 24
1000
924. The proportion of the proximate elements of
rye is (Hermbstadt) —
No Manure. Manure, Urine.
Starch
. 563 502
Gluten
. 86 120
Carried forward
. 649 622
29'
342
RYE.
No Manure. Manure, Urine.
Brought forward
Albumen
Sugar
Gum
Fixed oil
Soluble phosphates
Husk
Water
649
622
26
35
47
33
54
46
9
11
13
42
101
108
101
103
1000
1000
925. According to the experiments of ^prengel,
100,000 parts of the grain of rye contain 1040, and
100,000 parts of straw contain 2793 parts of inor-
ganic matter, consisting of —
Potash I
Soda J
Lime
Magnesia
Alumina
Oxide of iron
Oxide of manganese
Silica
Sulphuric acid
Phosphoric acid
Chlorine
Grain.
Straw
532
(32
(11
122
178
44
12
241
42
25
34
164
2297
23
170
46
51
9
17
1040 2793
926. According to Way, the grain of rye contains
136, and its straw 313 parts of inorganic matter in
10,000. The composition of the ash from the grain
was —
MAIZE. 343
Silica . . . • . . . .922
Phosphoric acid ..... 3992
Sulphuric acid . . . ... 17
Lime . ...... 261
Magnesia . . ... . 1281
Peroxide of iron . ... . 104
Potash . . . . . . . 3383
Soda . . . . . . . 39
927. The grain of maize, or Indian corn, consists
of about-
Organic matter 857
Inorganic matter . . . . .13
Water 130
1000
928. According to the experiments of Payen, dry
maize contains —
Starch 712
Gluten ) J23
1
Albumen
Fixed oil . 90
Gum 4
Woody matter . . . . . . 59
Inorganic matter 12
1000
929. Sprengel found in 100,000 parts of maize
grain 1312 parts of inorganic matter, and in 100,000
parts of maize straw 3985 parts of inorganic matter,
consisting of —
a4^
RICE.
Grain.
Straw
. 200
189
. 250
4
. 35
652
. 128
236
. 16
6
traces
4
—
20
. 434
2708
. 17
106
. 224
54
8
6
Potash
Soda
Lime
Magnesia ,
Alumina .
Oxide of iron .
Oxide of manganese
Silica
Sulphuric acid .
Phosphoric acid
Chlorine .
1312 3985
930. The grain of rice consists of about —
Organic matter 856
Inorganic matter 4
Water .140
1000
931. According to the analyses of Braconnot, rice
contains —
}■
Starch
Gluten
Albumen
Sugar
Gum
Fixed oil .
Earthy phosphates
Husk
Water .
Carolina.
Piedmont
851
838
36
36
3
OJ
7
1
1
2^
4
4
48
48
50
70
1000
1000
BUCKWHEAT.
345
932. The more recent experiments of Payen and
Boussingault, however, indicate a larger proportion
of albumen and gluten as existing in rice ; these
chemists found 75 in place of 36 of those substances.
933. The dry grain of buckwheat consists of, ac-
cording to Zenneck —
Starch .
Gluten .
Sugar and gum
Fixed oil
Husk .
Inorganic matter
523
107
83
4
269
14
1000
934. From the experiments of Sprengel, it ap-
pears that 100,000 parts of the seed of buckwheat
contain 1354 parts of inorganic matter. 100,000
parts of the dry straw contain 3203 parts, consisting
of—
Potash .
Soda .
Lime
Magnesia
Alumina
Oxide of iron
Oxide of manganese
Silica .
Chlorine
Sulphuric acid
Phosphoric acid .
Seed.
Straw
204
332
330
62
156
704
183
1292
26
26
8
15
44
32
114
140
15
95
47
217
170
288
1354
3203
346
LINSEED.
935. The proportion of starch, &c., in,^eeds which
contain much oil is, of course, considerably less than
in the grains hitherto described. The following is
an analysis of linseed by L. Meyer
Starch
Gluten
Albumen .
Azotized matter
Gum
Sugar, &c.
Coloring matter
Resin
Wax
Fixed oil .
Husk
15
29
28
151
61
109
25
25
1
113
443
1000
936. In this analysis the quantity of oil is con-
siderably below the usual average (938). The large
quantity of azotized matter which exists in linseed
explains the value of oil-cake, both in fattening cattle
and as a manure (854). From the experiments of
Sprengel, it appears that 100,000 parts of linseed
contain 2340 parts of inorganic matter, and 100,000
parts of the stem contain 1456 parts of inorganic
matter, consisting of —
Seed.
Stalks
Potash \
Soda J
.
. 438
510
Lime
...
630
230
Magnesia
.
234
480
Alumina
.
2
2
Carried forward
. 1304
1222
HEMPSEED.
Seed.
Stalks.
Brought forward .
. 1304
1222
Oxide of iron
. trace
10
Oxide of mangenese
—
■—
Silica . . .
-^ . 120
20
Chlorine
12
20
Sulphuric acid
24
66
Phosphoric acid .
880
118
347
2340
1456
937. Hempseed contains, according to Bucholz —
Albumen
247
Gum . . . .
90
Sugar
16
Besin
16
Woody fibre .
50
Fixed oil
191
Husk
. 383
Loss in analysis
7
1000
938. The proportion of oil yielded by different
seeds varies greatly with the year, climate, soil, &c.
The following table shows the average proportion of
oil obtained from 100 parts of some of the most im-
portant oil seeds : —
Linseed
22
Almond
. 30 to 40
Poppy .
. 47 to 50
Beech-nut .
. 15 to 17
Walnut
. 40 to 70
Colza .
39
Hemp .
25
Rocket
18
Kape ..
33
White mustard
36
Castor
. 50 to 60
Black
18
Olives
10
Earth-nut .
45
Sunflower .
15
Gold of Pleasure
27
348
BEANS.
939. Common field beans, according to an ana-
lysis by Einhof, consist of (347)—
Starch 501
Albumen and legumine' . . . .117
Sugar I
Gum j • • • • • • • ^2
Husk . . .. . . . . 100
Water 156
Salts and loss 44
1000
940. Kidney beans were found by Braconot to
consist of — '■
Starch .
. 430
Legumine
182
Albumen
54
Sugar
2
Gum . • .
15
Fixed oil
7
Husk
,
70
Water
. 230
Salts and loss
10
1000
941. According to the experiments of Sprengel,
100,000 parts of common beans contain 2136, and
100,000 parts of bean straw contain 3121 parts of
inorganic matter, consisting of —
Seed.
Straw.
Potash . . ." .
. 415
1656
Soda ....
. 816
50
Carried forward
. 1231
1706
PEAS.
349
Brought forward
Lime
Magnesia
Alumina
Oxide of iron .
Oxide of manganese
Silica
Sulphuric acid
Phosphoric acid
Chlorine
Seed.
Straw
1231
1706
165
624
158
209
34
10
—
7
—
5
126
220
89
34
292
226
41
80
2136
3121
942. Field beans, according to Way, contain 237
in the seed, and 497 parts of inorganic matter in
10,000 of the straw. These ashes, analyzed, were
found to contain in 10,000 parts —
Beans.
Bean straw
Silica
. 42
261
Phosphoric acid
2872
49
Sulphuric acid
. 305
140
Carbonic acid
. 342
2532
Lime . . . ,
. 520
1985
Magnesia
. 690
253
Peroxide of iron
trace
61
Potash
5172
3285
Soda
54
277
Chloride of sodium
trace
1154
943. The composition of ripe peas, according to
Braconnot, is —
30
350
PEAS.
Water . . . . .
. 125
Husk
. 83
Albumen and legumine .
. 264
Starch
. 436
Sugar
. 20
Gum
. 40
Fixed oil
. 12
Salts and loss ....
. 20
1000
944. Peas consist of about 854 parts organic, 26
inorganic matter, and 120 parts water. According
to Sprengel, 100,000 parts of peas contain 2464, and
100,000 parts of pea straw contain 4971 parts of
inorganic matter, consisting of —
Potash
Soda
Lime
Magnesia
Alumina
Oxide of iron
Oxide of manganese
Silica
Sulphuric acid
Phosphoric acid
Chlorine
Seed.
Straw.
810
235
739
—
58
2730
136
342
20
60
10
20
—
7
410
996
53
337
1^0
240
38
4
2464
4971
945. White peas, according to Way, contain 197,
and the straw 752 parts of inorganic matter in 10,000.
The composition of 10,000 parts of this ash was —
LEJ^'J
11 LS.
Pea.
Pea Straw
Silica 176
253
Phosphoric acid
,
2420
131
Sulphuric acid , ,
.
470
185
Carbonic acid
. 318
3033
Lime
. 697
4692
Magnesia
. 666
836
Peroxide of iron
. 25
114
Potash
. 4402
387
Soda
—
186
Chloride of sodium
.
823
176
351
946. Lentils, according to an analysis of Einhof,
consist of —
Starch
Albumen and legumine
Gum ...
Sugar
Husk
Water
Salts and loss .
282
331
51
27
161
. 140
8
1000
947. In the preceding analysis of lentils, no men-
tion is made of fixed oil. The following analysis,
quoted by Boussingault, is therefore probably more
correct : —
Starch
400
Legumine
. 220
Gum
70
Sugar
15
Fibrous matter
120
Fixed oil
25
Inorganic matter . * . .
25
Water and loss . . .
, 125
1000
352
VETCHES.
948. According to Sprengel, 100,000 parts of
lentils contain 1528, and 100,000 parts of lentil
straw contain 3899 parts of inorganic matter, con-
sisting of —
Potash .
Soda
Lime
Magnesia
Alumina
Oxide of iron .
Oxide of manganese
Silica
Sulphuric acid
Phosphoric acid
Chlorine
Seed.
Straw
736
420
118
33
57
2040
. 85
119
12
■ 52 ■
34
races
traces
180
686
94
38
140
480
54
49
1528
3899
949. Common vetch, according to an analysis by
Crome, is stated to contain —
Starch 26
Albumen 19
Gum, &c. . . ,_ . . . . 76
Woody fibre 104
Water ^ . 775
1000
950. According to Sprengel, 100,000 parts of
vetch seed contain 5101, and 100,000 parts of vetch
straw contain 2290 parts of inorganic matter con-
sisting of —
POTATOES.
Grain.
Straw
Potash .
. 897
1810
Soda
622
52
Lime
160
1955
Magnesia
142
324
Alumina
22
15
Oxide of iron .
9
9
Oxide of manganese
5
8
Silica .
,
200
442
Sulphuric
acid
50
122
Phosphoric
5 acid
. 140
280
Chlorine .
• • •
,
43
84
353
2290
5101
951. A great number of different analyses of
potatoes have been published, as the varieties of the
tuber are found to contain very different proportions
of starch, azotized matter, &c. The ultimate com-
position of dry potato is (Boussingault) : —
Carbon
Oxygen .
Hydrogen
Nitrogen .
Inorganic matter
440
447
58
15
40
1000
952. According to the experiments of Einhof and
Lampadius, potatoes contain: —
30'
354
POTATOES.
Red. Kidney.
Sweet.
Peruvian.
Bread-
Starch . 150 91
151
150
138
Albumen, &c. 14 8
8
19
20
Gum, &c. . 41 —
19
28
Starchy fibre 70 88
82
52
69
Water . 750 813
743
760
745
1000 1000 1000 1000 1000
953. ihe composition of good potatoes varies from
about 10 to 25 starch, 3 to 8 fibre, 2 to 4 gum, 1 to
2 azotized matters (albumen, &c.) and 70 to 80 parts
of water per cent.
954. According to Sprengel, 100,000 parts of dry
potato tuber contain 2653 parts; and 100,000 of
potato haulm, 4T86 parts of inorganic matter, con-
sisting of —
Potash
Soda
Lime
Magnesia
Alumina
Oxide of iron
Oxide of manganese
Silica
Sulphuric acid
Phosphoric acid
Chlorine
Tubers.
Haulm.
12&1
138
748
0(?)
106
2928
104
,488
16
52
9
58
trace
44
27
801
174
245
128
32
50
0(?)
2653
4786
955. The batatas or sweet potato of the West India
Islands, contains, according to 0. Henry —
ARTICHOKE.
Starch
133
Albumen
9
Sugar
33
Cellular matter
68
Fixed oil
11
Malic acid, and salts
14
Water
. 732
355
1000
956. The ultimate composition of the tubers and
stem of the Jerusalem artichoke, according to Bous-
singault, is —
Carbon
Oxygen
Hydrogen
Nitrogen
Inorganic matter
Tuber.
433
433
58
16
60
Stem.
457
457
54
4
28
1000 1000
957. The tubers, according to the analysis of
Braconnot, contain a peculiar variety of starch, to
"which the name of Inulin is given. The tubers were
found to contain —
Starch (Inulin)
. 30
Albumen
. 10
Sugar, uncrystallizable
148
Gum
12
Fixed oil . . ,
1
Woody fibre
12
Inorganic matter
17
Water
770
1000
356
OXALIS CRENATA — CABBAGE.
958. Jerusalem artichoke, according to Way, con-
tains in the tubers 179 parts, in the stem 194, and in
the leaves 1500 parts of inorganic matter per 10,000.
These three ashes contained respectively in 10,000
parts—
Taber.
Stems.
Leaves.
Silica
. 150
151
1725
Phosphoric acid
. 1699
297
61
Sulphuric acid
. 377
323
221
-Carbonic acid .
. 1180
2540
2431
Lime
. 334
2031
4015
Magnesia
. 130
191
195
Peroxide of iron
45
88
114
Potash .
5589
3840
681
Soda
—
69
372
Chloride of sodium .
—
468
182
Chloride of potassiui
n 488
—
—
959. The bulbs of the Oxalis crenata were found
by Payen to contain —
Starch ....
. . . 25
Albumen
. . 15
Gum, &c.
55
Woody fibre . .
44
Water ....
. 861
1000
960. Common cabbage consists of about 62 parts
of organic matter, 7 of inorganic matter, and 931
parts of water. According to Sprengel, 100,000
parts of dry cabbage contain 7546 parts of inorganic
matter, consisting of —
TURNIPS.
357
Potash
Soda
Lime
Magnesia
Alumina .
Oxide of iron
Silica
Sulphuric acid
Phosphoric acid
Chlorine .
2370
1154
1747
22
17
8
210
959
785
274
7546
961. The composition of turnips and Swedes is
very similar ; they consist of the same proximate
elements united in nearly the same proportions. The
following table shows the composition of three varie-
ties according to Hermbstadt : —
Swede.
White.
Cabbage
Starch and fibr« .
53
72
60
Albumen
20
25
25
Sugar
90
80
90
Gum . . . .
30
25
35
Inorganic matter
5
5
5
Water
800
790
780
Loss .
2
3
5
1000 1000 1000
962. Dry turnip, according to Boussingault, con-
sists of —
Carbon 429
Oxygen . . . . . . .423
Hydrogen ... . . . 55
Nitrogen 17
Inorganic matter 76
1000
358
TURNIPS.
963. According to the same chemist, 100,000
parts of dry turnip contain 6226 parts of inorganic
matter.
consisting of-
Potash 2610
Soda 317
Lime 844
Magnesia . . . . . .333
Alumina and oxide of iron ... 93
Silica 496
Sulphuric Acid ^ . . . . 844
Phosphoric Acid 465
Chlorine 224
6226
964. According to two more recent analyses of
Way, Skirving's Swede contains in the bulb 76 and
88 parts inorganic matter, and 161 and 195 in the
top. The composition of these ashes was per 10,000
parts —
Top.
Bulb.
Top.
Bulb.
Silica ....
411
163
114
173
Phosphoric acid .
654
1251
621
1017
Sulphuric acid .
650
1126
1220
1553
Carbonic acid
616
954
1297
1196
Lime ....
. 2399
1136
3038
1433
Magnesia .
292
244
318
327
Peroxide of iron
190
28
66
51
Potash . . . .
2063
3616
2079
2688
Soda . . . .
—
499
■—
1331
Chloride of sodium .
1769
977
1031
219
-Chloride of potassium
977
—
209
—
965. The same chemist found in the green-topped
white turnip, in the tops 182, and in the bulb 50
BEET — MANGEL-WURZEL.
359
The analyses of these
parts of inorganic matter,
ashes gave —
Silica
Phosphoric acid
Sulphuric acid
Carbonic acid
Lime . • .
Magnesia
Peroxide of iron
Potash .
Chloride of sodium
Chloride of potassium
966. Common beet and mangel-wurzel, also, are
very similar in composition. The following table
shows the composition of four varieties : —
Top.
Bulb
205
96
315
765
783
1286
1464
1482
2873
673
285
226
80
66
1268
4856
1067
544
1656
Red mangel-wurzel
Castelnaudary beet
White sugar beet
Bassano beet
Organic matter. Inorganic matter. Water.
. 88 11 901
. 139 11 850
. 120 11 869
. 115 12 873
967. According to Boussingault, dried field beet
consists of —
Carbon 428
Oxygen 434
Hydrogen 58
Nitrogen 17
Inorganic matter 63
1000
968. According to the experiments of Sprengel,
100,000 parts of dry beet root contain 5986 parts of
aeo
MANGEL-WURZEL.
inorganic matter, and 100,000 parts of the
leaves contain 15,439 parts, consisting of —
Potash
Soda
Lime
Magnesia
Alumina
Oxide of iron
Oxide of manganese
Silica
Chlorine .
Sulphuric acid
Phosphoric acid
dry
Root.
Leaves.
1481
5600
3178
3290
285
2316
139
839
20
130
58
50
60
60
105
425
380
1064
123
975
167
690
5986
15,439
969. The yellow globe mangel-wurzel contains, ac-
cording to Way, 102 parts of inorganic matter in the
bulb, and 140 in its top. The long red contains in
the bulb 64, and in the top 179 parts of inorganic
matter in 10,000. These ashes analyzed were found
to contain respectively, in 10,000 parts —
Yell
aw globe.
Long red.
Top.
Bulb.
Top.
Bulb.
Silica . . . .
235
222
226
140
Phosphoric acid.
589
449
519
165
Sulphuric acid .
654
368
460
314
Carbonic acid .
692
1814
645
1523
Lime
. 872
178
817
190
Magnesia .
984
175
703
179
Peroxide of iron
146
74
96
52
Potash .
834
2354
2790
2168
Soda
. 1221
1908
301
313
Chloride of sodium .
3766
2454
3439
4951
CARROT.
361
970. The carrot, according to Hermbstadt and
Einhof, contains-
Starch
Fibre
Albumen
Gum
Sugar
Volatile oil
Water
Einhof.
Hermbstadt
3
—
46
90
9
11
—
18
81
78
—
4
861
799
1000
1000
971. According to Sprengel, 100,000 parts of drj
carrot contain 5090 parts of inorojanic matter.
100,000 parts of the leaves
consisting of —
Potash
Soda
Lime
Magnesia
Alumina
Oxide of iron
Oxide of manganese
Silica
Chlorine
Sulphuric acid
Phosphoric acid
inorganic mi
)ntain
10,420
Root.
Leaves,
2718
8236
709
921
505
5050
295
398
30
78
25
15
46
105
454
54
223
208
1082
395
963
5090 10,420
972. Two samples of white Belgian carrot, accord-
ing to Way, contained respectively, in the root 77,
and in the top 532 parts of inorganic matter; and 82
31
362 PARSNIP.
w
parts in the root, and 420 parts of inorganic matter
in 10,000 parts of the top. These ashes contained —
I. II.
Top. Root. Top. Root.
Silica . . .739 76 183 110
Phosphoric acid . 255 837 112 786
Sulphuric acid . . 268 634 457 695
Carbonic acid . . 1629 1515 2275 1772
Lime . . . 3498 976 2950 826
Magnesia . . . 250 378 303 320
Peroxide of iron . 406 74 90 166
Potash . . .728 3755 753 2800
Soda . . .946 1263 1069 1753
Chloride of sodium . 877 49^1 1714 765
973. The parsnip consists of —
Organic matter . . . . . . 195
Inorganic matter 12
Water 793
1000
974. According to Crome, the parsnip contains —
Starch 18
Albumen 21
Gum . .61
Sugar 55
Fibre 51
Volatile oil . . . . . . trace
Water . . . . . . . .794
1000
975. From the experiments of Sprengel, it appears
that 100,000 parts of dry parsnip roots contain 4643
parts of inorganic matter. 100,000 parts of the dry
leaves contain 15,661 parts consisting of —
CLOVER.
€
Root.
Leaves.
Potash ..... 2310
3207
Soda
780
2448
Lime
520
4160
Magnesia .
300
473
Alumina .
26
132
Oxide of iron .
5
' 9
Oxide of manganese
—
—
Silica
180
1400
Chlorine .
198
950
Sulphuric acid .
,
213
1198
Phosphoric acid
111
1784
363
4643 15,661
976. Clover, according to the analysis of Bous-
singault, consists of —
Carbon 474
Oxygen 378
Hydrogen 50
Nitrogen .21
Inorganic matter 77
1000
977. The composition of white and red clover, as
given by Crome, is —
White.
Red.
Starch 10
14
Albumen .
15
20
Gum
34
35
Sugar
15
21
Woody fibre
115
139
"Wax and resin
2
1
Earthy matter ,
8
10
Water .
.
,
800
760
1000 1000
364
CLOVER.
978. According to Sprengel,, 100,000 parts of
white clover in the fresh state contain 1735 parts of
inorganic matter, consisting of —
Potaah 590
Soda
Lime
Magnesia .
Alumina .
Oxide of iron .
Oxide of manganese
Silica
Chlorine . .
Sulphuric acid
Phosphoric acid
110
446
58
36
12
280
40
67
96
1735
979. According to Way, 10,000 red clover con-
tains 695, and white clover 765 parts of inorganic
matter. These ashes analyzed were found to con-
tain —
Red clover. White clover.
Silica
334
368
Phosphoric acid
635
1153
Sulphuric acid
. 418
721
Carbonic acid
1693
1803
Lime
3539
2641
Magnesia
1122
815
Peroxide of iron
97
196
Potash . .
1485
1433
Soda
140
372
Chloride of potassium
236
494
Chloride of sodium
296
—
LUCERN — SAINTFOIN.
365
980. The composition of Lucern, according to
Crome, is —
Starch . . . ,
.
22
Albumen .
19
Gum
44
Sugar . . . .
Woody fibre
Wax and resin
•
8
143
6
Earthy matter .
Water .
•
8
750
1000
981. According to Sprengel, 100,000 parts of
fresh Lucern contain 2580 parts of inorganic matter,
consisting of —
Potash .362
Soda 166
Lime . 1304
Magnesia 94
Alumina
8
Oxide of iron . . .
. . 7
Oxide of manganese
—
Silica
. 90
Chlorine
. . 86
Sulphuric acid ....
. 109
Phosphoric acid
. 353
2580
982. According to Sprengel, 100,000 parts of
fresh saintfoin or esparcette contain 1671 parts of
inorganic matter consisting of —
31*
366
SAINTFOIN — HAY.
Potash . 494
Soda 105
Lime . .527
Magnesia . . ... . . . 69
Alumina 16
Oxide of iron traces
Oxide of manganese . . . .
Silica . 120
Chlorine . . ' . . . . 38
Sulphuric acid ...... 82
Phosphoric acid 220
1671.
983. Saintfoin in flower, according to Way, con-
tains 565 parts, and, in seed, 570 parts, of inorganic
matter. These ashes consisted of —
In flower.
In seed
Silica 322
349
Phosphoric acid
935
797
Sulphuric acid
. 328
233
Carbonic acid
1520
1736
Lime
2430
2967
Magnesia
503
459
Peroxide of iron
61
58
Potash .
3190
2961
Soda
—
125
Chloride of sodium
. 78
312
Chloride of potassiui
□a
624
—
984. Hay. According to the experiments of Bous-
singault, 10,000 parts of good meadow hay contain
547 parts of inorganic matter, consisting of —
HAY.
367
Potash
. 130
Soda
10
Lime
107
Magnesia
Oxide of iron .
. 43
5
Silica
. 189
Sulphuric acid .
Phosphoric acid
Chlorine
16
32
. 15
547
985. 10,000 parts of Italian rye-grass in flower,
according to Way, contain 616 parts, and, in seed,
556 parts of inorganic matter. These ashes con-
tained in 10,000 parts —
Silica
Phosphoric acid
Sulphuric acid
Lime
Magnesia
Peroxide of iron
Potash
Soda
Chloride of sodium
In flower.
In seed
5918
6062
634
632
282
131
995
1229
223
264
78
30
1245
1077
398
13
227
558
As has been several times stated, the exact
relative proportions of these different constituents of
plants vary very considerably, depending on soil,
climate, manure, &c. Thus, for example, mangel-
wurzel root contains from 9 to 11 parts of inorganic
matter in every 1000 parts; or, abstracting the water,
from 87 to 150 parts in the dry root j hence it is easy
36B RATE OF EXHAUSTION.
to see that a crop of 25 tons may in truth take more
inorganic matter out of the land than one of 30 tons;
and that the mere weight of the crop is no proof of
the extent to which it has exhausted the soil.
987. This effect is quite independent of the mere
quantity of water in the crop, because the same result
is shown when we ascertain the relation which exists
between the inorganic matter and the dry organic
matter which the plants contain; in different crops of
mangel-wurzel it is found that the quantity of dry
organic matter which is formed for every 100 parts of
inorganic matter absorbed from the soil, varies from
568 to 1045.
988. It is consequently evident that, in order to
raise the most profitable crops, we must endeavor to
obtain the largest possible quantity of useful veget-
able matter, with the smallest relative proportion of
inorganic matter. This is a subject of the greatest
practical importance, and one well worthy of the
attention of scientific agriculturists.
989. Having now briefly stated the average com-
position of some of the most important plants culti-
vated as crops, it may be useful to enter shortly into
the composition of the most common substances em-
ployed as manure, in order more fully to show the
relation which exists between plants and the manures
employed in their cultivation. Of the simple animal
manures the most important are dung, urine, and
bones.
990. The dung of sheep (according to Zierl) con-
369
sists of 291 parts dry organic matter, 30 parts inor-
ganic matter, and 679 parts water. The earthy
matters consist of about half silica, a quarter carbon-
ate and phosphate of lime, and the remainder alka-
line salts. The urine of the sheep consists of 28
parts organic matter, 12 parts inorganic matter,
and 960 parts water, containing a portion of am-
monia ; because even in fresh urine a portion of the
azotized matter which it contains, is generally begin-
ning to decompose and form ammonia.
991. Fresh cow dung (according to Boussingault)
consists of 124 parts dry organic matter, IT parts
inorganic matter, and 859 parts water. The inor-
ganic matter contains two-thirds of silica, nearly
one-third of earthy phosphates, and a small quantity
of alkaline salts. Cows' urine consists of 53 parts
dry organic matter, 21 parts inorganic matter, and
926 parts water (Sprengel).
992. The composition of cows' urine, and the
nature of the changes which it undergoes when suf-
fered to putrefy, either alone or diluted with water,
are shown in the following table (Sprengel) : —
Fresh. Putrefied. Putrefied.
Alone.
With water.
Urea
4000
1000
600 .
Albumen
10
—
Mucus .
190
40
30
Benzoic acid
90
250
120
Lactic acid .
516
500
500
Carried forward
4806
1790
1250
370
HORSE DUNG— PIG DUNG.
Fresh.
Putrefied
Putrefied.
Alone.
With water
Brought forward
4806
1790
1250
Carbonic acid
5256
165
1533
Ammonia
205
487
1622
Potash
664
664
664 .
Soda .
554
554
554
Silica .
36
5
8
Alumina
2
—
—
Oxide of iron
4
1
—
Oxide of manganese
1
—
—
Lime
65
2
8
Magnesia
36
22
30
Chlorine
272
272
272
Sulphuric acid
405
388
332
Phosphoric acid .
70
26
46
Acetic acid, or vinegar
—
1
20
Sulphuretted hydrogen
—
1
30
Insoluble earthy phos-
180
150
phates and carbonates
Water . . . .
92,624
95,442
93,481
100,000 100,000 100,000
993. Fresh horse dung consists of 284 parts dry
organic matter, 18 parts inorganic matter, and 698
parts water. Of the inorganic matter about one-
ninth is carbonate and phosphate of lime, one-twelfth
alkaline salts, and the remainder silica (Zierl).
Horses' urine consists of 27 parts dry organic
matter, 33 parts inorganic matter, and 940 parts
water.
994. Fresh pigs' dung, consisting of the excre-
ment and urine together, contains 93 parts dry
organic matter, 87 parts inorganic matter, and 820
NIGHT SOIL— HUMAN URINE.
871
parts water. Pigs' urine contains 56 parts dry
organic matter, 18 parts inorganic matter, and 926
parts water (Sprengel). The inorganic matters con-
sist chiefly of alkaline salts.
995. Human excrement (according to Berzelius)
contains 227 parts dry organic matter, 100 parts
inorganic matter, and 733 parts water. Its consti-
tuents are —
Albumen ......
9
Extractive . . . .
27
Mucus, fat, resin
140
Bile
9
Vegetable remains ....
70
Soluble salts
12
Water
733
1000
996. The inorganic matter contained in 1000 parts
consequently weighs 150, and contains 100 parts
earthy phosphates, 12 parts carbonate of soda, 8
parts sulphate and phosphate of soda, and sulphate
of potash.
997. Human urine (according to Berzelius) con-
sists of 49 parts dry organic matter, 7 parts salts of
ammonia, 11 parts inorganic matter, and 933 parts
water. Its composition in detail is —
Urea
3010
Mucus
32
Lactic acid, lactate of ammonia, animal \
matter insoluble in alcohol . . J
1714
Carried forward, ....
4756
372
BONES.
Brought forward, .
4756
Chloride of sodium
445
Sulphate of potash
371
Sulphate of soda .
316
Phosphate of soda
294
Phosphate of ammonia
165
Muriate of ammonia .
150
Earthy phosphates
100
Uric acid
100
Silica . . . _ .
3
Water
93,300
100,000
998. The composition of bones varies considerably
in the proportion of the constituents, though all bones
consist chiefly of phosphate and carbonate of lime,
together with gelatine and a portion of fat. Sheep's
bones consist of about —
Phosphate of lime
560
Carbonate of lime
130
Organic matter .
310
1000
999. The bones of oxen and
cows (according to
Berzelius) contain : —
Phosphate of lime
573
Phosphate of magnesia
20
Soda and chloride of sodium
35
Carbonate of lime
39
Fluoride of calcium
trace
Organic matter
333
1000
1000. The bones of horses contain nearly the
YARDDUNG. 373
same proportion of phosphate of lime. They con-
sist of :—
Phosphate of lime 546
Carbonate of lime 113
Salts ..... 19
Organic matter 322
1000
1001. The bones of pigs contain 520 parts of
phosphate of lime, 10 parts carbonate of lime, and
470 parts organic matter and water ; those of calves,
540 phosphate of lime, and 460 animal matter and
water. The bones of fishes, generally speaking, con-
tain less earthy matter than those of land animals.
The bones of the cod-fish contain 480 phosphate of
lime, 55 carbonate of lime, 20 phosphate of mag-
nesia, 6 salts of soda, and 440 organic matter and
water.
1002. The composition of farmyard dung, and
all mixtures of animal and vegetable manures, is very
variable. The following analysis of Boussingault
may be considered as expressing very nearly the
average composition of good yard dung: —
Fresh. Dry.
Carbon 74 358
Hydrogen 9 42
Oxygen 53 258
Nitrogen ...... 4 20
Inorganic 67 322
Watfer 793 —
1000 1000
32
374 GUANO.
1003. The composition of the inorganic part of
such manure, like that of the organic, varies con-
siderably. The following shows the composition of
10,000 parts of the inorganic matter in yard dung
(Richardson) : —
Potash 322
Soda . . 273
Lime 34
Magnesia ........ 26
Sulphuric acid 327
Chlorine 315
Soluble silica 2705
Phosphate of lime . . . . . . 711
Phosphate of magnesia 226
Phosphate of iron 468
Phosphate of manganese . . . . trace
Phosphate of alumina (?) .... trace
Carbonate of lime 934
Carbonate of magnesia ' 163
Sand 3099
Alkali and loss ...... 397
10,000
1004. The putrefied dung of birds has of late
years been much employed as manure, under the name
of guano. The composition of this substance varies
greatly, according to the extent to which decomposi-
tion has proceeded, and the degree to which it has
been exposed to the atmosphere. The following
table shows three different analyses of guano : —
GUANO.
'61
Bertels.
Oellacher.
Ure.
Urate of ammonia .
32
122
147
Oxalate of ammonia
. 134
177
32
Oxalate of lime
. 164
13
10
Phosphate of ammonia .
. 64
60
143
Phosphate of ammonia i
tnd| 42
116
45
magnesia .
•1
Phosphate of lime .
. 100
202
220
Muriate of ammonia
65
22
30
Chloride of sodium .
1
4
—
Carbonate of ammonia .
—
8
10
Carbonate of lime .
—
16
—
Sulphate of potash .
42
40
60
Sulphate of soda .
11
49
—
Sulphate of ammonia
—
—
20
Phosphate of soda .
53
—
—
Humate of ammonia
—
11
—
Wax and resin
6
7
—
Sand. Insoluble residue
. 58
17
12
Alumina
1
• —
—
Water ....
•1 227
'43
85
Organic matter
'.93
186
1000
1000
1000
1005. The value of guano as manure depends on
the ammonia which it contains, or the presence of
matter capable of forming ammonia by its slow putre-
faction, and on the presence of phosphoric acid. No
manure is more subject to fraudulent adulteration
than guano. One of the most common modes of
doing this is by the addition of earth or brickdust.
The presence of these substances may be roughly
ascertained in guano by burning a portion. The
376
WOOD-ASHES.
ashes left by pure guano are white, or nearly so ;
while, if soil or brickdust has been added, the oxide
of iron, which they always contain, will give the
ashes more or less a red-brown color.
1006. The composition of wood-ashes varies very
considerably, according to the wood from which it is
obtained. The composition of three kinds of wood-
ashes, as given by Sprengel, is : —
Oak.
Beech.
Scotch fir
Potash .
. 162
221
22
Soda . .
67
33
22
Lime
. 174
250
232
Magnesia
Alumina
. 14
50
(23)
50
Oxide of iron .
81
38
170
Oxide of manganese
Silica
269
138)
55
66
Chlorine .
24
19
23
Sulphuric acid
Phosphoric acid
Carbonic acid .
34
19
. 155
77
56
140
22
28
365
1000
1000
1000
1007. In the process for making potash or pearl-
ash (199), the greater part of the soluble salts con-
tained in the wood-ashes is washed out ; the remainder
is a valuable manure, and often contains a consider-
able quantity of phosphoric acid. The refuse ashes
from soap factories consist of the same matters. The
following table exhibits the composition of three
kinds of " lixiviated ashes," according to Berthier : —
PEAT-ASHES.
f
Oak.
Beech.
Scotch fir
Lime .
.
. 548
426
423
Magnesia
.
. 6
70
105
Oxide of iron
,
—
15
1
Oxide of manganese
—
45
4
Silica .
,
38
58
46
Phosphoric acid
.
8
57
10
Carbonic acid
.
396
329
360
Charcoal, &c.
•
4
—
51
1000
1000
1000
377
1008. The ashes of peat, as might be expected,
contain less alkaline salts than those of wood ; they
usually contain a considerable quantity of gypsum
(237). The following table shows the composition of
three sorts of Dutch ashes analyzed by Sprengel : —
Best.
Middling.
Inferior.
Potash .
2
2
1
Soda
. 10
39
4
Lime
136
86 ~
61
Magnesia
49
16
39
Alumina
45
35
41
Oxide of iron .
66
54
41 "
Oxide of manganese
J 10
43
2
Silica .
. 471
559 ,
704
Chlorine
12
30
5
Sulphuric acid
72
64
34
Phosphoric acid
20
8
13
Carbonic acid
41
64
55
Charcoal
66
—
1000
1000
1000
1009. Kelp, the ashes of sea-weeds (218, 891) re-
32*
876 KELP.
sembles wood-ashes in containing a large quantity of
alkaline salts ; but it contains little or no phosphoric
acid. The following analyses are by Dr. Ure : —
Carbonate of soda 1
Sulphuret of sodium j * * *
Sulphate of soda . . . .
Chlorides of sodium and potassium
Carbonate of lime . . . .
Sulphate of lime . .
Alumina and oxide of iron
Silica . . . . .
Sulphur and loss .
Rona.
Heisker.
55
85
190
80
375
365
100
240
95
-^
100
90
—
80
85
60
1000 1000
INDEX
A.
Absorption of manure, 780.
Acetate of iron, 489.
— lead, 311,489.
-- lime, 490.
— soda, 490.
Acetates, 489.
Acetic acid, 476.
— fermentation, 375, 393, 408,
478.
Acid, acetic, 476.
— benzoic, 992.
— butyric, 378.
— carbonic, 37, 103, 106, 681,
699,711.
— citric, 496.
— humic, 679.
— lactic, 329, 377, 445, 570.
— margaric, 515.
— malic, 502.
— muriatic, 186, 216.
— nitric, 163, 217, 772.
-r- oleic, 516.
— - oxalic, 130, 503.
— phosphoric, 195, 245.
— pyroligneous, 325, 488.
— silicic, 259.
— stearic, 514, 518.
— sulphuric, 179.
— sulphurous, 173, 288.
— tartaric, 498.
Acid, uric, 609.
Acids, 109.
— organic, 493.
— test for, 113.
Action of plants on the air, 39, 745.
Active principles, 543, 635.
Adulteration of guano, 1005.
Affinity, chemical, 3, 7.
After damp in mines, 133.
Air, 21,29,638.
— contains ammonia, 150, 638.
— contains carbonic acid, 37,
638.
— contains water, 41, 638.
— inflammable, 81.
— necessary to life, 107, 606.
— composition of, 26, 29, 37.
— resists compression, 22.
— weight of, 54, 69.
Alabaster, 237.
Albumen, 559.
— vegetable, 346.
Alcohol, 368, 396, 403.
Ale, 427.
— bottled, 121.
— ripening of, 434.
Alkali, test for, 116.
— volatile, 151.
Alkalies, 198.
— vegetable, 543.
Alloys, 314.
Almonds, 938.
Alum, 213, 257, 457.
Alumina, 264, 324, 542, 654.
— absorbs ammonia, 654,
880.
— in soil, use of, 654.
— phosphate of, 256.
— silicate of, 267.
— sulphate of, 257.
Aluminum, 254.
— oxide of, 254.
380
INDEX.
Ammonia, 83, 148.
— absorbed by alumina,
654, 880.
— absorbed by charcoal,
&c., 162.
— carbonate of, 148, 154.
— fixingof, 790,876, 888.
— in air, 160, 638.
— in rain-water, 150.
— loss of, 790.
— muriate, 156.
— phosphate, 161, 793.
— salts of, 154, 790, 885.
— sulphate, 159.
— urate of, 610, 1004.
Ammoniacal liquor, 154, 854, 886.
Analyses, 17, 317, 906.
Animal heat, 607, 787.
— manures, 777, 786, 795,
799, 817.
— principles, proximate, 557.
— substances, 555.
Animals, breathing of, 107, 606.
— fattening of, 601,614, 936.
Annotta, 680, 588.
Apple jelly, 336.
Aqua-fortis, 163.
Argol,498.
Arrack, 410.
Arrowroot, 331.
Arteries, 606.
Artichoke, Jerusalem, 334, 956.
Ashes, 879.
— lixiviated, 1007.
— of coal, 881.
— plants, 546.
— sea-weed, 879, 1009.
— turf, 880, 1008.
Ashes of wood, 199, 891, 1006.
Atom, 138.
Attraction, 3, 5.
Azote, 27, 146.
B.
Balloons, 58, 82.
Bamboo, 548.
Barilla, 218.
Barley, 333, 413, 913.
— straw, 913.
— sugar, 344.
Barm, 366,441.
Barometer, 55.
Base, 109, 148, 198, 225, 269.
Basting meat, 627.
Batatas, 955.
Bay salt, 215.
Bean, field, 330, 939, 942. '
— straw, 941.
Beans, kidney, 940.
Beech ashes, 1006.
Beech nuts, 938.
Beer, 411.
— Bavarian, 437.
Beet, 966.
Beet-root sugar, 342.
Bell metal, 314.
Bile, 607.
Binary compounds, 316.
Biphosphate of lime, 245, 834.
Bitartrate of potash, 389, 498.
Bittern, 251.
Black currant jelly, 336.
Bleaching by chlorine, 185.
— by sulphur, 175, 542.
Blende, 305.
Blood, 565, 606.
Blubber, 823.
Bones, 195, 242, 595, 826, 877.
— as manure, 826.
~ boiled, 826.
— of calves, 1001.
— fishes, 1001.
— horses, 1000.
Bones of oxen, 999.
— pigs, 1001.
— sheep, 998.
Bones and sulphuric acid, 832.
Bran, 909.
Brandy, 396.
Brass, 314.
Bread, 438.
— baking of, 453.
— rising of, 456.
— unfermented, 468.
— use of alum in, 456.
Bricks, 255.
Brimstone, 171.
British gum, 360.
Bromide of magnesium, 72.
Bromides, 193.
Bromine, 193.
Brown Stout, 433.
INDEX.
381
Buckwheat, 933.
Buds, 720.
Burning, 38.
— lime, 9, 118,233.
— ofplants, 544, 906.
Burnt clay, 880.
— sugar, 344.
Butter, 574.
— clarified, 679.
— how colored, 580.
— melted, 630.
— sak, 581.
Butyric acid, 378.
C.
Cabbage, 960.
— red, 114.
Calamine, 305.
Calcium, 226.
— chloride of, 241.
Calomel, 300.
Camphor, 612.
Candles, 517.
— burning of, 30 94.
Cane, 550.
— sugar, 340.
Caoutchouc, 537.
Caramel, 345.
Carbon, 37, 86.
— in plants, 39, 91, 316.
Carbonate of ammonia, 155.
— iron, 274.
— lead, 311.
— lime, 118, 229, 530, 595.
— magnesia, 249.
— potash, 200.
— soda, 218.
Carbonates decomposed by acids,
117,228.
Carbonic acid gas, 37, 103.
— necessary to plants, 106.
681,699, 711.
— • decomposition of, 38, 700.
Carbonic oxide, 127.
Carburetted hydrogen, 83, 131.
Carcases, 800.
Carrot, 336, 580.
Caseine, 568.
— vegetable, 347.
Castor-oil, 510, 938.
Caustic potash, 201.
Cellars, foul air in, 120, 176.
Cellulose, 322.
Chalii, 88,118, 758,875.
Chamomile, 430.
Changes, chemical, 3.
Charcoal, 35, 86, 879, 883.
-^ absorbs ammonia, 162,
463, 654.
— burning of, 129.
— disinfecting powers of,
162.
Charring, 90.
Cheddar cheese, 586.
Cheese, 582.
Cheltenham salts, 224.
Cherry-tree gum, 335.
Cheshire cheese, 687.
Chestnuts, 331.
Chloride of calcium, 241.
— gold, 292.
— magnesium, 251.
Chloride of potassium, 205, 892.
— silver, 296.
— sodium, 189, 216.
— zinc, 307.
Chlorides, 186.
Chlorine, 185.
Churning, 574.
Chyle, 607.
Chyme, 607.
Circulation of the blood, 607.
Cider, 394.
Cinnabar, 301.
Citric acid, 496.
Clay, 255.
— burnt, 880.
— iron ore, 274.
Climate differences of, 42, 736.
Clover, 976.
Coagulation of albumen, 3^47, 560.
Coal-ashes, 881.
Coal-gas, 83, 134, 164, 537.
Coal-tar, naphtha, 134, 537.
Cocoa-nut oil, 511.
Cognac brandy, 397.
Cohesion, 89.
Coke, 129, 287.
Colophony, 538.
Color of soils, 662.
Colors, changing of, 113.
— vegetable, 113, 324, 641.
882
INDEX.
Colza, 938.
Combination, 3, 12, 35, 125, 138,
769.
— changes produced by,
6.
Combining numbers, 125, 138.
— weights, 144—369.
Combustion, 26, 32.
— results of, 32, 40, 94.
Common salt, 216, 893.
Composition of animal matter, 554.
— organic matter, 316.
— plants, 317.
— soils, 666, 758.
— stones, 267, 650.
Compounds, binary, 316.
— definite, 124, 135.
Compounds, saline. 111.
— ternary and quater-
nary, 316.
— their composition, 17.
Contagion, 176.
Contagious matters, 185.
Cookery, 617.
Copper, 302, 458, 550.
— in plants, 550.
-- oxide, 302..
— pyrites, 302.
— salts of, 303.
— sulphate of, 304, 458.
Copperas, 270, 794.
Coprolites, 877.
Corn, 266, 755, 904, 907.
Corrosive sublimate, 186, 301.
Cotton, 321, 323, 324.
Couching, 692.
Cream, 574.
— cheese, 687.
— of tartar, 498.
Crops, rotation of, 753.
Cubic nitre, 217,903.
Cultivated lands, 748.
Curd ofmiIk,568, 583.
Currants, 496.
Daguerreotype, 295.
Dahlia, 334.
Death of plants, 741.
Decay, 11,105, 145, 765.
Decay, influence of lime, 235, 837,
846, 872.
— like burning, 105.
— of humus, 677.
— of plants, 145, 354.
— results of, 11, 105, 354.
— under water, 131.
Decomposition, 9, 12.
— induced, 15, 358.
— of rocks, 649, 750.
— spontaneous, 15, 358.
Deliquescence, 203, 251.
Dew, 44.
Dextrine, 360.
Diamond, 87.
Diastase, 360, 416, 686, 725.
Digestion, 604, 631.
— derangement of, 633.
Diseases of plants, 740, 744.
Distillation, 73, 396.
Ditch scrapings, 865.
Double salts, 112.
Dough, 438.
Drainage water, 825, 867.
Draining, 857,
Dunder, 409.
Dung, 800, 812, 989.
— cow, 812, 991.
— farmvard, 802, 1002.
— horse, 812, 993.
— ■ pigs', 812, 994.
— sheep, 812, 990.
— rabbit, 812.
Dutch rushes, 550.
Dyeing, 324, 542.
E.
Earth, 225.
Earth-nut, 938.
Earths, 225, 268.
— alkaline, 225, 246.
Earthy matter in the air, 644.
— silicates, 650.
— substances in plants, 644,
732.
Effervescence, 229.
Egg, white of, 560.
Elaine, 516, 594.
Electricity, influence on plants, 703.
Elements, 16, 19, 135.
INDEX.
383
Embryo, 684, 724.
Epsom salts, 250, 876.
Equivalent, 125, 138, 144, 369.
Excrement, 607, 787, 799, 812.
Excrements of sea fowl, 814.
Exhaustion of soils, 748, 986.
Expansion, 62, 65.
Explosions of fire-damp, 132.
Faints, distiller's, 403.
Fallowing, 752.
Farmyard dung, 802, 1002.
Fat, 601, 613.
— of animals, 594, 936.
Feathers, 820.
Feeding off with sheep, 756, 813.
Ferment, 366.
Fermentation, 15, 364, 423, 765.
— acetic, 375, 393,
408, 478.
— lactic, 377, 570.
— of bread, 438, 447,
452.
— produces carbonic
acid, 121, 364,
372.
putrid, 845, 380.
— vinous, 364, 372,
385, 440.
Fertility, 750.
Fibre, woody, 319.
Fibrin, animal, 564.
— vegetable, 347.
Finings, 693.
Fir-ashes, 1006.
Fire, 36.
Fire-damp, 69, 132.
Fish refuse, 816.
Fixed oil, 506.
Fixing ammonia, 790, 876, 888.
Flame, 61, 93, 100.
Flax, 319.
Flesh, 664.
Flint, 262, 550.
Flooring malt, 692.
Flour, 348, 440, 909.
— damaged, 456.
Flowers, 716.
— effect of, on the air, 716.
Fluorides, 193.
Fluorine, 193.
Food of animals, 611.
— chemical use of, 605.
— - of plants, 782, 784.
Formation of seed, 712.
Formation of soils, 649, 750.
Foul smells, 182, 773.
Freezing, effects of, 65.
— of water, 63.
Fruit, 336, 341, 712, 729.
— ripening of, 717.
Fuel, 86.
Fumigating by chlorine, 185.
Fumigation by sulphur, 176.
Fungi, 796.
Fur, from water, 232.
G.
Galvanized iron, 314.
Game, preserving, 807.
Gas, 26.
— coal, 83, 134,537.
— inflammable, 132.
— manufacture of, 134.
— liquor, 854, 886.
— strength of, 889.
— tar, 537.
Gastric juice, 608.
Gelatine, 589.
Geneva, 406.
Germination, 682, 697.
— accelerated, 696.
Gin, 406.
Glass, 219, 262.
Glauber's salts, 224.
Gliadine, 347.
Gloucester cheese, 586.
Glue, 590.
— refuse, 820.
Gluten, 346, 349.
Glycerine, 613.
Gold, 292, 314.
— chloride, 293.
— of pleasure, 938.
— mosaic, 308.
Gooseberries, 496.
Grain of wheat, 907.
Grains, spent, 418.
Grape sugar, 340, 382, 371.
384
INDEX.
Grapes, 382^ 498.
Grass, 266, 887, 904.
Gravity, 54.
— specific, 84^ 405.
Greaves, 819.
Green manures, 854.
— vitriol, 270, 794.
Growth of plants, 736.
Guano, 610, 789, 814.
Gum, 335.
— Arabic, 335.
-— British, 360.
— cherry-tree, 335.
— formation of, 359.
— resins, 640.
Gun-cotton, 322.
Gunpowder, 208.
Gutta percha, 134.
Gyle tun, 423.
Gypsum, 237, 794, 876.
H.
Hair, 560.
Hard water, 239.
Hartshorn, 164.
Hay, 549, 984.
Heat, 48, 62.
— animal, 107, 606, 787.
— influence of, on plants, 702.
— latent, 48.
— sensible, 48.
Hedges, foul, 807.
Hemp-seed, 957.
Hollands, 407.
Honey, 394.
Hoofs, 589.
Hops, 420, 430.
Hordein, 915.
Horn, 589, 820.
Humates, 680.
Humic acid, 679.
Humus, 672.
— decay of, 677.
— excess of, 740.
— use of, 678.
Hydrogen, 69, 82.
Hydrogen, carburetted, 83, 131.
— lightness of, 84.
— sulphuretted, 182,211.
Ice, 45.
Iceland moss, 331.
Indian corn, 325, 929.
— rubber, 134.
Indigo, 542.
Inflammable air, 81.
Inorganic matter in plants, 644,
870.
— manures, 871.
Inulin, 334, 967.
Iodides, 193.
Iodine, 193.
— in sea water, 193.
Iron, 274.
— combustible, 282.
— galvanized, 314.
— in coal, 287.
— in plants, 274, 553.
— in soils, 286.
— in water, 286.
— moulds, 506.
— ores, 274.
— oxides of, 277, 288, 324, 542.
— peroxide of, 277.
— protoxide of, 277.
— pyrites of, 283.
— rust, 279.
— contains ammonia, 280.
— slags, 276.
— smelting, 275.
— sulphate of, 270, 285, 289.
— sulphuret, 284.
Irrigation, 860.
Isinglass, 391, 590.
Ivory, 695.
J.
Juniper, 407.
Kelp, 218, 879.
Kidneys, 609.
Kiln-drying, 692.
Kirschwasser, 398.
INDEX.
385
L.
Lactic acid, 329, 377, 445.
Latent heat, 48.
Lead, 310.
— action of water on, 313.
— acetate, 311.
— carbonate, 311.
— oxides, 310.
— red, 310.
— sulphate, 272.
— sulphuret, 310.
— white, 311.
Leather, 592.
Leaven, 441.
Leaves, 699.
— fall of the, 743.
— office of, 713.
Lees of wine, 389.
Legumine, 347, 598.
Lemons, 496.
Lentils, 946.
Lettuce, 901.
Light, effects of, 187, 295, 701.
— influence on plants, 602, 606,
623, 683, 700.
Lighting a fire, 36.
Lignin, 319.
Lime, 7, 226.
— action on soil, 872.
— and salt, 897.
— biphosphate of, 245, 834.
— burning, 118,233.
— carbonate of, 230, 530, 595.
— caustic, 7, 226.
— citrate, 497.
— hydrate of, 235.
— in plants, 242, 504, 551, 871.
— muriate of, 241.
— nitrate of, 163, 240.
— oxalate of, 504, 551.
— phosphate of, 242, 551, 595.
839, 877.
— silicate of, 267, 276, 873.
— slaking, 235.
Limestone, 227, 874.
— magnesian, 246, 874.
Lime, sulphate of, 237, 876.
— super-phosphate- of, 832.
— when useful, 871.
— when not to be used, 837,
885.
33
Limes, juice of, 496.
Linen, 321.
Linseed, 935.
Liqueurs, 398.
Liquid manure, 767.
— tanks, 783.
Litharge, 310.
Liver, 607.
Loss of manure, 783, 789, 798, 802.
Lucern, 980.
Lungs of animals, 107, 566, 606.
M.
Macaroni, 333.
Magnesia, 246.
— carbonate of, 247, 249.
— in plants, 253, 552.
— muriate of, 247, 251.
— phosphate of, 247, 253,
878.
— silicate of, 267.
— sulphate of, 247, 250,
878.
Magnesian limestone, 248.
Magnesium, 246.
— chloride of, 251.
-^ oxide of, 246.
Maize, 333, 927.
Malt, 401,412, 433, 915.
Malting, 690.
Malic acid, 502.
Manganese, 309.
— in plants, 916, 920,
929,936, 941.
— in soils, 309.
— oxide of, 191.
Mangel-wurzel, 966.
Manure, 754, 762.
— farmyard, 802, 1002.
— fossil, 877.
— green, 847, 852.
— heating of, 802, 845.
— inorganic, 856, 868.
— liquid, 788,797, 811.
— loss of, 782.
— preservation of, 781, 802.
— strong, 800, 817.
— vegetable, 839.
Manures, animal, 718, 777, 786,
795, 799.
386
INDEX.
Manures, organic, 764, 780.
— saline, 890.
Maple sugar, 341.
Maraschino, 398.
Marble, 88.
Mark of grapes, 383, 479.
Margarine, 515, 594.
Marl, 871.
Mashing, 401, 415.
Mead, 394.
Meat boiling, 619.
— roasting, 627.
Medicines, action of, 634.
Mercury, 298.
— chlorides, 300.
— oxides of, 299.
— sulphuret of, 298, 301.
Metallic alloys, 314.
— oxides, 269.
— salts, 270.
Metals, 196, 291.
Milk, 568.
Millet, 333.
Minium, 310.
Mixture, 4, 125.
— of soils, 857.
Molasses, 343, 409.
Mordants, 324, 542.
Mortar, 236.
Mosaic gold, 308.
Mould, 673. . ,
Mouldering, 765.
Mouldiness, 797.
Mucilage, 337.
Muriate of ammonia, 156.
•— lime, 241.
— magnesia, 251.
— soda, 216.
Muriates, 186.
Muriatic acid, 186.
Muscle, 564, 602.
Muscovado sugar, 343.
Murk, 383, 479.
Must, 385.
Mustard, 510, 938.
N.
Naphtha, 537.
Nascent state, 769, 774.
Natural vegetation, 747.
Night-soil, 807.
— disinfected, 810.
Nitrate oflimcj 163, 240.
— potash, 206, 240, 899.
— soda, 217, 903.
— silver, 296.
Nitrates, 163.
— in plants, 901.
Nitre, 206, 899.
— beds, 240.
— cubic, 217.
Nitric acid, 163,217,772.
— in manure, 837, 899.
Nitrogen, 27, 146.
Noveau, 398.
Nutrition of plants, 636, 681, 720.
— animals, 600, 604.
Oak-ashes, 1006.
Oats, 333, 917.
Odors of plants, 509.
Oil, 506.
— cake, 851.
— castor, 510, 938.
Oil of cloves, 512.
— cocoa-nut, 511.
— dregs, 823.
— drying, 508, 610.
— fat, 508, 510.
— fixed, 508.
— linseed, 510, 935, 938.
— mustard, 510, 938.
— of lavender, 512.
— • lemons, 610.
— turpentine, 407, 512, 533.
— vitriol, 179.
— olive, 510, 938.
— poppy, 510, 938.
— rape, 510, 938.
— rock, 537.
— seeds, 938.
— volatile, 509,512.
Oleine, 516, 594.
Opodeldoc, 531.
Ores, roasting of, 302, 310.
Organic acids, 49,3.
— manures, 764, 780.
Organic matter, 315, 722.
— substances in soils, 667.
— transformations, 356,
INDEX.
387
Organized matter, 722.
Oxalate in lime in plants, 551.
Oxalic acid, 130, 503.
Oxalifi, 959.
Oxide, carbonic, 127.
— of copper, 302.
— iron, 277.
— lead, 310.
— manganese, 191, 309.
— mercury, 299.
— silver, 294.
— tin, 308.
Oxides, metallic, 269.
Oxygen, 27, 68.
P.
Paint, white, 312.
Palm juice, 410.
Paper bleached by chlorine, 185.
Paring, 880. 4
Parmesan cheese, 587.
Parsnip, 336, 973.
Paste, 348.
Pearl ash, 200.
Peas, 330, 943.
Peat-ashes, 880, 1008.
Pectine, 336.
Peroxides, 272.
Perry, 394.
Persalts, 272.
Petre, 206.
— ealt, 891.
Pewter, 314.
Phosphate of alumina, 256.
— ammonia, 161.
— lime, 105—242, 556,
595, 831.
— magnesia, 263, 552.
Phosphates, 194.
— earthy, 551,732.
Phosphoric aqid, 195, 245.
in plants, 195, 242.
— in bone, 195, 242.
— in water, 79.
Phosphorus, 194.
Pickling cabbage, 114.
Pine-apple, 498.
Pipes, bursting of, 65.
Pitch, 536.
Plants, composition of, 91.
Plants, death of, 740.
— decay of, 104.
— decompose carbonic acid,
106,699,711.
— effect of, on the air, 745.
-— elements of, 91.
— food of, 636, 681, 720, 782.
— growth of, 699, 707.
Plaster of Paris, 238.
— stone, 237.
Plough, subsoil, 761.
Plums, 336.
Polenta, 333.
Pond mud, 825, 865, 867.
Poppy seed, 938.
Porter, 427.
Potash, 199.
Potash, binoxalate of, 504,
— bitartrate of, 498.
— carbonate of, 200.
— caustic, 201.
— in plants, 199, 214, 546.
— • in the soil, 214.
— muriate of, 205, 892.
— nitrate of, 206—240, 899.
— salts of, 214.
— silicate of, 549.
— sulphate of, 213.
Potashes, 891.
Potassium, 202.
— chloride of, 205, 892.
Potato, 330, 333,952.
— haulm, 954.
~ spirit, 408.
— starch, 330.
— sweet, 955.
Pottery, 255.
Principles, active, 543, 635.
Proportions, 138.
Protein, 599.
Proto-salts, 272.
Protoxides, 272.
Proximate animal principles, 557,
Pruning, 715.
Putrefaction, 11, 350, 380, 765,
771, 798.
— influence of lime in,
234, 240.
Putrefying animal matter, 836, 899.
Putrid fermentation, 380.
— urine, 797, 992.
Putty powder, 308.
388
INDEX.
Pyrites, 283.
— copper, 302.
Pyroligneous acid, 325, 488.
Pyrolignites, 489.
Pyroxylic spirit, 325, 538.
Q.
Quartz, 258.
Quaternary compounds, 316.
Quicklime, 7, 233.
Quicksilver, 298.
R.
Rain-water, 71, 74, 230.
Raisins, 382,
Rape-seed, 938.
— vine, 482.
Red cabbage, 114.
— lead, 310.
Refuse of gas-works, 885.
Rennel, 584.
Resins, 632.
Respiration, 107, 606.
Results of combustion, 32, 40, 94.
— putrefaction, 3S0, 767.
Rhubarb, 503.
Rice, 329.
Ripening of fruit, 718.
River mud, 867.
— water, 77.
Road drift, 865.
Rock salt, 215.
Rocket, 938.
Rocks, disintegration of, G49, 750.
Roman vitriol, 304.
Roots, 705, 729.
Rotation of crops, 753.
Ruby, 254.
Rum, 409.
Rushes, Dutch, 550.
Rust of iron, 279.
Rye, 330, 922.
— straw, 925.
S.
Saccharine matter, 339.
Safety-lamp, 99.
Sago, 331.
SaintfoJn, 982.
Sal-ammoniac, 156.
Stiline compounds, 110.
— draughts, 14.
— manures, 890.
Salt, 215, 893.
— and lime, 897.
— bay, 215.
Salt, common, 189, 215, 581, 631.
895.
— in sea water, 215.
— rock, 215.
— spirit of, 188.
— sea, 215, 252.
— solution of, in water, 30.
Saltpetre, 206.
Salts, 110.
— double. 111.
— Epsomj 250.
•^ Glauber's, 224.
— of hartshorn, 154.
— iron, 289.
— lemons, 505.
— magnesia, 250.
— potash, 214.
— soda, 223.
— sorrel, 605.
— the metals, 270.
— sub-, 111.
— super- or bi-. 111.
Sand, 262.
Sapphire, 264.
Sawdust, 847.
Schiedam, 407.
Sea-fowl, excrements of, 610, 789.
Sea-water, 71.
Sea-weed, 218, 853.
Seeds, 347.
— formation of, 712, 735.
— germination of, 682.
— steeping, 696.
Seidlitz powders, 14,
Selection by roots of plants, 733.
Semolina, 333,
Shell sand, 871.
Shells, 876.
Silex, 258.
Silica, 258.
— in plants, 266, 548.
— in soil, use of, 265, 652.
Silicate of alumina, 267.
INDEX.
389
Silicate of lime, 267.
— magnesia, 267.
— potash, 263, 549.
— soda, 263.
Silicates, 262—267, 904.
Silicic acid, 269.
Silicon, 259.
Silk dyeing, 542.
Silver, 294, 314.
— chloride of, 296.
— nitrate of, 296.
— oxide of, 294.
— salts of, 294.
— sulphuret of, 294, 297.
Size, 593.
— resin, 539.
Skimmed milk, 682.
Skin, 689.
Slaking of lime, 7, 235.
Slag, 276.
Smells, foul, 186.
Smoke 98, 102.
Straw ashes, 649, 907.
— of barley, 916.
— buckwheat, 934.
— lentils, 948.
— maize, 929.
— oats, 920.
-- rye, 925.
— vetch, 951.
— wheat, 907.
Strong manures, 800.
Sub-salts, HI.
Subsoil, 757, 648, 856.
— • ploughing, 761.
Substratum, 758.
Suffocation from charcoal, 120.
Sugar, 340.
— barley, 344.
— candy, 345.
— formation of, 361, 374.
— of lead, 489.
— of milk, 570.
— refining, 344.
— refiners' waste, 816.
Sulphate of alumina, 257.
— ammonia, 159.
— copper, 794.
— iron, 794.
— lime, 237, 270, 794,
876.
Sulphate of magnesia, 250.
Sulphate of potash, 213.
— potash and alumina,
257.
— soda, 190, 220.
Sulphates, 180.
Sulphur, 171, 284.
— in plants, 775.
Sulphuret of iron, 283.
— lead, 310.
— silver, 297.
Sulphurets, 184.
Smelting, 310.
Soap, 10, 219, 520.
— boiling, 521.
— decomposition of, 10, 529.
— soft, 628.
— transparent, 531.
— yellow, 527, 539.
Soap-makers' ash, 879.
Soda, 189, 215, 218.
— carbonate of, 218.
— in rocks, 223.
— in plants, 547.
— in soils, 223.
— muriate of, 216.
— nitrate of, 217.
— silicate of, 262, 904.
— sulphate of, 190, 220.
Sodium, 189, 216.
— chloride of, 190, 216.
Soft water, 630, 626.
Soil, 225, 642.
Soils, analysis of, 666.
— color of, 662.
— composition of, 666.
— exhaustion of, 748, 912, 986.
— formation of, 649, 750.
— mixture of, 668, 758.
— nature of, 655,
Solder, 314.
Soot, 154, 885.
Sorrel, 503.
Soup, 623.
Specific gravity, 84, 405.
Spices, 632.
Spirit proof, 404.
— pyroxylic, 325.
Spirit of salt, 188.
— wine, 367, 396, 403.
Sponge, 447.
Spring water, 76, 239.
Springs, 75.
S90
INDEX.
Stall feeding, 615.
Starch, 326.
Steam, 43, 60.
Stearic acid, 514, 518.
Stearine, 514, 594.
Still, 73.
Stilton cheese, 587.
Sulphuret of tin, 308.
Sulphuretted hydrogen, 182, 211,
773.
Sulphuric acid, 179.
Sulphurous acid, 173, 288.
— checks fermentation,
395.
Sunflower, 901.
— seed, 938.
Super-salts, 110.
Super-phosphate of lime, 245, 832.
Super-tartrate of potash, 389, 498.
Swedes, 96 K
T.
Tabasheer, 548.
Tannin, 592.
Tanning, 592.
Tapioca, 331.
Tar, 534.
Tarnish on silver, 297.
Tartar, 389, 500.
Tartaric acid, 498.
Tartrates, 501.
Teeth, 595.
Ternary compounds, 316.
Tests, vegetable, 116.
Thermometer, 52.
Thunderbolt, 286.
Tiles, 255.
Tin, 308.
— oxide of, 308, 324, 542.
— plate, 314.
— sulphniet of, 308.
Toast, 474.
Toasted cheese, 582.
Tobacco, 901.
Toddy, 410.
Treacle, 397.
Tropical countries, 736.
Tubers, 725.
Turf ashes, 880.
Turmeric, 116.
Turnips, 961.
Turpentine, 633.
— oil of, 134,407, 512,
533.
U.
Urate of ammonia, 601, 1004.
Urea, 609, 997.
Uric acid, 609i
Urine, 609, 766, 800.
— cows', 991.
— horses', 993.
— human, 997.
— putrid, 992.
— pigs', 994.
— sheep, 990.
Use of leaves, 713.
— plants, 39, 745.
Usquebaugh^ 406.
V.
Vapor condensed by cold, 44.
— in the air, 41.
Vegetable alkalies, 543.
— manure, 839.
Vegetables, boiling of, 625.
Veins, 606.
Vermilion, 301.
Vetch, 949.
Vinegar, 325, 376, 4S8.
— distilled, 485.
Vinous fermentation, 367, 372.
Vitriol, blue, 304.
— green, 285.
— oil of, 179.
— white, 366.
Volatile alkali, 151.
— oil, 506, 512.
W.
Walnuts, 938.
Wash, distillers', 402.
Water, 45.
— action on lead, 313.
— air in, 80.
— composition of, 66. ,
— freezing of, 63.
INDEX.
391
Water, hard, 232, 432, 629, 626.
— impurities in, 71.
— mineral, 76.
— necessary to plants, 81.
— New River, 77.
— phosphoric acid in, 79.
— - pure, 73, 232.
-- rain, 71, 74, 230.
— sea, 71,251.
— soft, 239, 528, 626.
-- spring, 76, 239.
— Thames, 77.
— well, 78.
Wax, 611.
Weed-ash, 218.
Weeds, 39, 802.
— burning of, 804.
— putrefaction of, 803.
— spread of, 805.
Wheat grain, 907.
— straw, 907.
— starch, 326, 333.
Whey, 685.
Whiskey, 406.
White lead, 311.
White of egg, 560.
Wine, 383.
— brandy, 397.
— domestic, 392.
— fermentation of, 385.
— fining of, 391.
-— pricked, 393.
— ripening of, 390.
Wine, vinegar, 479.
Wood ashes, 199,838.
— spirit, 325.
Woody fibre, 319.
Wool, 818, 899.
— dyeing, 542.
— mill refuse, 816.
— rags, 819.
— soap, 816.
Wort, 401.
— foxiness of, 422.
X.
Xyloidine, 322.
Y.
Yeast, 366,425,441.
— as manure, 850.
— artificial, 467.
— bad, 460.
— dry, 465.
Zinc, 305.
— chloride of, 307,
— oxide of, 306.
— sulphate of, 306.
THE END
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