show you the mode of analyzing it. This is done by distillation. When
wine of any kind is submitted to this operation, it is found to contain
brandy, water, tartar, extractive colouring matter, and some vegetable
acids. I have put a little port wine into this alembic of glass (PLATE
XIV. Fig. 1.), and on placing the lamp under it, you will soon see the
spirit and water successively come over--
[Illustration: Plate XIV. Vol. II. p. 213.
Fig. 1.
A Alembic.
B Lamp.
C Wine glass.
Fig. 2. Alcohol blowpipe.
D the Lamp.
E the vessel in which the Alcohol is boiling.
F a safety valve.
G the inflamed jet or steam of alcohol directed towards a glass
tube H.]
EMILY.
But you do not mention alcohol amongst the _products_ of the
distillation of wine; and yet that is its most essential ingredient?
MRS. B.
The alcohol is contained in the brandy which is now coming over, and
dropping from the still. Brandy is nothing more than a mixture of
alcohol and water; and in order to obtain the alcohol pure, we must
again distil it from brandy.
CAROLINE.
I have just taken a drop on my finger; it tastes like strong brandy, but
it is without colour, whilst brandy is of a deep yellow.
MRS. B.
It is not so naturally; in its pure state brandy is colourless, and it
obtains the yellow tint you observe, by extracting the colouring matter
from the new oaken casks in which it is kept. But if it does not acquire
the usual tinge in this way, it is the custom to colour the brandy used
in this country artificially, with a little burnt sugar, in order to
give it the appearance of having been long kept.
CAROLINE.
And is rum also distilled from wine?
MRS. B.
By no means; it is distilled from the sugar-cane, a plant which contains
so great a quantity of sugar, that it yields more alcohol than almost
any other vegetable. After the juice of the cane has been pressed out
for making sugar, what still remains in the bruised cane is extracted by
water, and this watery solution of sugar is fermented, and produces rum.
The spirituous liquor called _arack_ is in a similar manner distilled
from the product of the vinous fermentation of rice.
EMILY.
But rice has no sweetness; does it contain any sugar?
MRS. B.
Like barley and most other seeds, it is insipid until it has undergone
the saccharine fermentation; and this, you must recollect, is always a
previous step to the vinous fermentation in those vegetables in which
sugar is not already formed. Brandy may in the same manner be obtained
from malt.
CAROLINE.
You mean from beer, I suppose; for the malt must have previously
undergone the vinous fermentation.
MRS. B.
Beer is not precisely the product of the vinous fermentation of malt.
For hops are a necessary ingredient for the formation of that liquor;
whilst brandy is distilled from pure fermented malt. But brandy might,
no doubt, be distilled from beer as well as from any other liquor that
has undergone the vinous fermentation; for since the basis of brandy is
alcohol, it may be obtained from any liquid that contains that
spirituous substance.
EMILY.
And pray, from what vegetable is the favourite spirit of the lower
orders of people, gin, extracted?
MRS. B.
The spirit (which is the same in all fermented liquors) may be obtained
from any kind of grain; but the peculiar flavour which distinguishes gin
is that of juniper berries, which are distilled together with the
grain--
I think the brandy contained in the wine which we are distilling must,
by this time, be all come over. Yes--taste the liquid that is now
dropping from the alembic--
CAROLINE.
It is perfectly insipid, like water.
MRS. B.
It is water, which, as I was telling you, is the second product of wine,
and comes over after all the spirit, which is the lightest part, is
distilled. --The tartar and extractive colouring matter we shall find in
a solid form at the bottom of the alembic.
EMILY.
They look very like the lees of wine.
MRS. B.
And in many respects they are of a similar nature; for lees of wine
consist chiefly of tartrit of potash; a salt which exists in the juice
of the grape, and in many other vegetables, and is developed only by the
vinous fermentation. During this operation it is precipitated, and
deposits itself on the internal surface of the cask in which the wine is
contained. It is much used in medicine, and in various arts,
particularly dying, under the name of _cream of tartar_, and it is from
this salt that the tartarous acid is obtained.
CAROLINE.
But the medicinal cream of tartar is in appearance quite different from
these dark-coloured dregs; it is perfectly colourless.
MRS. B.
Because it consists of the pure salts only, in its crystallised form;
whilst in the instance before us it is mixed with the deep-coloured
extractive matter, and other foreign ingredients.
EMILY.
Pray cannot we now obtain pure alcohol from the brandy which we have
distilled?
MRS. B.
We might; but the process would be tedious: for in order to obtain
alcohol perfectly free from water, it is necessary to distil, or, as the
distillers call it, _rectify_ it several times. You must therefore allow
me to produce a bottle of alcohol that has been thus purified. This is a
very important ingredient, which has many striking properties, besides
its forming the basis of all spirituous liquors.
EMILY.
It is alcohol, I suppose, that produces intoxication?
MRS. B.
Certainly; but the stimulus and momentary energy it gives to the system,
and the intoxication it occasions when taken in excess, are
circumstances not yet accounted for.
CAROLINE.
I thought that it produced these effects by increasing the rapidity of
the circulation of the blood; for drinking wine or spirits, I have
heard, always quickens the pulse.
MRS. B.
No doubt; the spirit, by stimulating the nerves, increases the action of
the muscles; and the heart, which is one of the strongest muscular
organs, beats with augmented vigour, and propels the blood with
accelerated quickness. After such a strong excitation the frame
naturally suffers a proportional degree of depression, so that a state
of debility and languor is the invariable consequence of intoxication.
But though these circumstances are well ascertained, they are far from
explaining why alcohol should produce such effects.
EMILY.
Liqueurs are the only kind of spirits which I think pleasant. Pray of
what do they consist?
MRS. B.
They are composed of alcohol, sweetened with syrup, and flavoured with
volatile oil.
The different kinds of odoriferous spirituous waters are likewise
solutions of volatile oil in alcohol, as lavender water, eau de
Cologne, &c.
The chemical properties of alcohol are important and numerous. It is one
of the most powerful chemical agents, and is particularly useful in
dissolving a variety of substances, which are soluble neither by water
nor heat.
EMILY.
We have seen it dissolve copal and mastic to form varnishes; and these
resins are certainly not soluble in water, since water precipitates them
from their solution in alcohol.
MRS. B.
I am happy to find that you recollect these circumstances so well. The
same experiment affords also an instance of another property of
alcohol,--its tendency to unite with water; for the resin is
precipitated in consequence of losing the alcohol, which abandons it
from its preference for water. It is attended also, as you may
recollect, with the same peculiar circumstance of a disengagement of
heat and consequent diminution of bulk, which we have supposed to be
produced by a mechanical penetration of particles by which latent heat
is forced out.
Alcohol unites thus readily not only with resins and with water, but
with oils and balsams; these compounds form the extensive class of
elixirs, tinctures, quintessences, &c.
EMILY.
I suppose that alcohol must be highly combustible, since it contains so
large a proportion of hydrogen?
MRS. B.
Extremely so; and it will burn at a very moderate temperature.
CAROLINE.
I have often seen both brandy and spirit of wine burnt; they produce a
great deal of flame, but not a proportional quantity of heat, and no
smoke whatever.
MRS. B.
The last circumstance arises from their combustion being complete; and
the disproportion between the flame and heat shows you that these are by
no means synonymous.
The great quantity of flame proceeds from the combustion of the hydrogen
to which, you know, that manner of burning is peculiar. --Have you not
remarked also that brandy and alcohol will burn without a wick? --They
take fire at so low a temperature, that this assistance is not required
to concentrate the heat and volatilise the fluid.
CAROLINE.
I have sometimes seen brandy burnt by merely heating it in a spoon.
MRS. B.
The rapidity of the combustion of alcohol may, however, be prodigiously
increased by first volatilising it. An ingenious instrument has been
constructed on this principle to answer the purpose of a blow-pipe,
which may be used for melting glass, or other chemical purposes. It
consists of a small metallic vessel (PLATE XIV. Fig. 2.), of a spherical
shape, which contains the alcohol, and is heated by the lamp beneath it;
as soon as the alcohol is volatilised, it passes through the spout of
the vessel, and issues just above the wick of the lamp, which
immediately sets fire to the stream of vapour, as I shall show you--
EMILY.
With what amazing violence it burns! The flame of alcohol, in the state
of vapour, is, I fancy, much hotter than when the spirit is merely burnt
in a spoon?
MRS. B.
Yes; because in this way the combustion goes on much quicker, and, of
course, the heat is proportionally increased. --Observe its effect on
this small glass tube, the middle of which I present to the extremity of
the flame, where the heat is greatest.
CAROLINE.
The glass, in that spot, is become red hot, and bends from its own
weight.
MRS. B.
I have now drawn it asunder, and am going to blow a ball at one of the
heated ends; but I must previously close it up, and flatten it with this
little metallic instrument, otherwise the breath would pass through the
tube without dilating any part of it. --Now, Caroline, will you blow
strongly into the tube whilst the closed end is red hot.
EMILY.
You blowed too hard; for the ball suddenly dilated to a great size, and
then burst in pieces.
MRS. B.
You will be more expert another time; but I must caution you, should you
ever use this blow-pipe, to be very careful that the combustion of the
alcohol does not go on with too great violence, for I have seen the
flame sometimes dart out with such force as to reach the opposite wall
of the room, and set the paint on fire. There is, however, no danger of
the vessel bursting, as it is provided with a safety tube, which affords
an additional vent for the vapour of alcohol when required.
The products of the combustion of alcohol consist in a great proportion
of water, and a small quantity of carbonic acid. There is no smoke or
fixed remains whatever. --How do you account for that, Emily?
EMILY.
I suppose that the oxygen which the alcohol absorbs in burning, converts
its hydrogen into water and its carbon into carbonic acid gas, and thus
it is completely consumed.
MRS. B.
Very well. --_Ether_, the lightest of all fluids, and with which you are
well acquainted, is obtained from alcohol, of which it forms the
lightest and most volatile part.
EMILY.
Ether, then, is to alcohol, what alcohol is to brandy?
MRS. B.
No: there is an essential difference. In order to obtain alcohol from
brandy, you need only deprive the latter of its water; but for the
formation of ether, the alcohol must be decomposed, and one of its
constituents partly subtracted. I leave you to guess which of them
it is--
EMILY.
It cannot be hydrogen, as ether is more volatile than alcohol, and
hydrogen is the lightest of all its ingredients: nor do I suppose that
it can be oxygen, as alcohol contains so small a proportion of that
principle; it is, therefore, most probably, carbon, a diminution of
which would not fail to render the new compound more volatile.
MRS. B.
You are perfectly right. The formation of ether consists simply in
subtracting from the alcohol a certain proportion of carbon; this is
effected by the action of the sulphuric, nitric, or muriatic acids, on
alcohol. The acid and carbon remain at the bottom of the vessel, whilst
the decarbonised alcohol flies off in the form of a condensable vapour,
which is ether.
Ether is the most inflammable of all fluids, and burns at so slow a
temperature that the heat evolved during its combustion is more than is
required for its support, so that a quantity of ether is volatilised,
which takes fire, and gradually increases the violence of the
combustion.
Sir Humphry Davy has lately discovered a very singular fact respecting
the vapour of ether. If a few drops of ether be poured into a
wine-glass, and a fine platina wire, heated almost to redness, be held
suspended in the glass, close to the surface of the ether, the wire soon
becomes intensely red-hot, and remains so for any length of time. We may
easily try the experiment. . . . .
CAROLINE.
How very curious! The wire is almost white hot, and a pungent smell
rises from the glass. Pray how is this accounted for?
MRS. B.
This is owing to a very peculiar property of the vapour of ether, and
indeed of many other combustible gaseous bodies. At a certain
temperature lower than that of ignition, these vapours undergo a slow
and imperfect combustion, which does not give rise, in any sensible
degree, to the phenomena of light and flame, and yet extricates a
quantity of caloric sufficient to react upon the wire and make it
red-hot, and the wire in its turn keeps up the effect as long as the
emission of vapour continues.
CAROLINE.
But why should not an iron or silver wire produce the same effect?
MRS. B.
Because either iron or silver, being much better conductors of heat than
platina, the heat is carried off too fast by those metals to allow the
accumulation of caloric necessary to produce the effect in question.
Ether is so light that it evaporates at the common temperature of the
atmosphere; it is therefore necessary to keep it confined by a well
ground glass stopper. No degree of cold known has ever frozen it.
CAROLINE.
Is it not often taken medicinally?
MRS. B.
Yes; it is one of the most effectual antispasmodic medicines, and the
quickness of its effects, as such, probably depends on its being
instantly converted into vapour by the heat of the stomach, through the
intervention of which it acts on the nervous system. But the frequent
use of ether, like that of spirituous liquors, becomes prejudicial, and,
if taken to excess, it produces effects similar to those of
intoxication.
We may now take our leave of the vinous fermentation, of which, I hope,
you have acquired a clear idea; as well as of the several products that
are derived from it.
CAROLINE.
Though this process appears, at first sight, so much complicated, it
may, I think, be summed up in a few words, as it consists in the
conversion of sugar and fermentable bodies into alcohol and carbonic
acid, which give rise both to the formation of wine, and of all kinds of
spirituous liquors.
MRS. B.
We shall now proceed to the _acetous fermentation_, which is thus
called, because it converts wine into vinegar, by the formation of the
acetous acid, which is the basis or radical of vinegar.
CAROLINE.
But is not the acidifying principle of the acetous acid the same as that
of all other acids, oxygen?
MRS. B.
Certainly; and on that account the contact of air is essential to this
fermentation, as it affords the necessary supply of oxygen. Vinegar, in
order to obtain pure acetous acid from it, must be distilled and
rectified by certain processes.
EMILY.
But pray, Mrs. B., is not the acetous acid frequently formed without
this fermentation taking place? Is it not, for instance, contained in
acid fruits, and in every substance that becomes sour?
MRS. B.
No, not in fruits; you confound it with the citric, the malic, the
oxalic, and other vegetable acids, to which living vegetables owe their
acidity. But whenever a vegetable substance turns sour, after it has
ceased to live, the acetous acid is developed by means of the acetous
fermentation, in which the substance advances a step towards its final
decomposition.
Amongst the various instances of acetous fermentation, that of bread is
usually classed.
CAROLINE.
But the fermentation of bread is produced by yeast; how does that
effect it?
MRS. B.
It is found by experience that any substance that has already undergone
a fermentation, will readily excite it in one that is susceptible of
that process. If, for instance, you mix a little vinegar with wine, that
is intended to be acidified, it will absorb oxygen more rapidly, and the
process be completed much sooner, than if left to ferment spontaneously.
Thus yeast, which is a product of the fermentation of beer, is used to
excite and accelerate the fermentation of malt, which is to be converted
into beer, as well as that of paste which is to be made into bread.
CAROLINE.
But if bread undergoes the acetous fermentation, why is it not sour?
MRS. B.
It acquires a certain savour which corrects the heavy insipidity of
flour, and may be reckoned a first degree of acidification; or if the
process were carried further, the bread would become decidedly acid.
There are, however, some chemists who do not consider the fermentation
of bread as being of the acetous kind, but suppose that it is a process
of fermentation peculiar to that substance.
The _putrid fermentation_ is the final operation of Nature, and her last
step towards reducing organised bodies to their simplest combinations.
All vegetables spontaneously undergo this fermentation after death,
provided there be a sufficient degree of heat and moisture, together
with access of air; for it is well known that dead plants may be
preserved by drying, or by the total exclusion of air.
CAROLINE.
But do dead plants undergo the other fermentation previous to this last;
or do they immediately suffer the putrid fermentation?
MRS. B.
That depends on a variety of circumstances, such as the degrees of
temperature and of moisture, the nature of the plant itself, &c. But if
you were carefully to follow and examine the decomposition of plants
from their death to their final dissolution, you would generally find a
sweetness developed in the seeds, and a spirituous flavour in the fruits
(which have undergone the saccharine fermentation), previous to the
total disorganisation and separation of the parts.
EMILY.
I have sometimes remarked a kind of spirituous taste in fruits that were
over ripe, especially oranges; and this was just before they became
rotten.
MRS. B.
It was then the vinous fermentation which had succeeded the saccharine,
and had you followed up these changes attentively, you would probably
have found the spirituous taste followed by acidity, previous to the
fruit passing to the state of putrefaction.
When the leaves fall from the trees in autumn, they do not (if there is
no great moisture in the atmosphere) immediately undergo a
decomposition, but are first dried and withered; as soon, however, as
the rain sets in, fermentation commences, their gaseous products are
imperceptibly evolved into the atmosphere, and their fixed remains mixed
with their kindred earth.
Wood, when exposed to moisture, also undergoes the putrid fermentation
and becomes rotten.
EMILY.
But I have heard that the _dry rot_, which is so liable to destroy the
beams of houses, is prevented by a current of air; and yet you said that
air was essential to the putrid fermentation?
MRS. B.
True; but it must not be in such a proportion to the moisture as to
dissolve the latter, and this is generally the case when the rotting of
wood is prevented or stopped by the free access of air. What is commonly
called dry rot, however, is not I believe a true process of
putrefaction. It is supposed to depend on a peculiar kind of vegetation,
which, by feeding on the wood, gradually destroys it.
Straw and all other kinds of vegetable matter undergo the putrid
fermentation more rapidly when mixed with animal matter. Much heat is
evolved during this process, and a variety of volatile products are
disengaged, as carbonic acid and hydrogen gas, the latter of which is
frequently either sulphurated or phosphorated. --When all these gases
have been evolved, the fixed products, consisting of carbon, salts,
potash, &c. form a kind of vegetable earth, which makes very fine
manure, as it is composed of those elements which form the immediate
materials of plants.
CAROLINE.
Pray are not vegetables sometimes preserved from decomposition by
petrification? I have seen very curious specimens of petrified
vegetables, in which state they perfectly preserve their form and
organisation, though in appearance they are changed to stone.
MRS. B.
That is a kind of metamorphosis, which, now that you are tolerably well
versed in the history of mineral and vegetable substances, I leave to
your judgment to explain. Do you imagine that vegetables can be
converted into stone?
EMILY.
No, certainly; but they might perhaps be changed to a substance in
appearance resembling stone.
MRS. B.
It is not so, however, with the substances that are called petrified
vegetables; for these are really stone, and generally of the hardest
kind, consisting chiefly of silex. The case is this: when a vegetable is
buried under water, or in wet earth, it is slowly and gradually
decomposed. As each successive particle of the vegetable is destroyed,
its place is supplied by a particle of siliceous earth, conveyed thither
by the water. In the course of time the vegetable is entirely destroyed,
but the silex has completely replaced it, having assumed its form and
apparent texture, as if the vegetable itself were changed to stone.
CAROLINE.
That is very curious! and I suppose that petrified animal substances are
of the same nature?
MRS. B.
Precisely. It is equally impossible for either animal or vegetable
substances to be converted into stone. They may be reduced, as we find
they are, by decomposition, to their constituent elements, but cannot be
changed to elements, which do not enter into their composition.
There are, however, circumstances which frequently prevent the regular
and final decomposition of vegetables; as, for instance, when they are
buried either in the sea, or in the earth, where they cannot undergo the
putrid fermentation for want of air. In these cases they are subject to
a peculiar change, by which they are converted into a new class of
compounds, called _bitumens_.
CAROLINE.
These are substances I never heard of before.
MRS. B.
You will find, however, that some of them are very familiar to you.
Bitumens are vegetables so far decomposed as to retain no organic
appearance; but their origin is easily detected by their oily nature,
their combustibility, the products of their analysis, and the
impressions of the forms of leaves, grains, fibres of wood, and even of
animals, which they frequently bear.
They are sometimes of an oily liquid consistence, as the substance
called _naptha_, in which we preserved potassium; it is a fine
transparent colourless fluid, that issues out of clays in some parts of
Persia. But more frequently bitumens are solid, as _asphaltum_,
a smooth, hard, brittle substance, which easily melts, and forms, in its
liquid state, a beautiful dark brown colour for oil painting. _Jet_,
which is of a still harder texture, is a peculiar bitumen, susceptible
of so fine a polish, that it is used for many ornamental purposes.
_Coal_ is also a bituminous substance, to the composition of which both
the mineral and animal kingdoms seem to concur. This most useful mineral
appears to consist chiefly of vegetable matter, mixed with the remains
of marine animals and marine salts, and occasionally containing a
quantity of sulphuret of iron, commonly called pyrites.
EMILY.
It is, I suppose, the earthly, the metallic, and the saline parts of
coals, that compose the cinders or fixed products of their combustion;
whilst the hydrogen and carbon, which they derive from vegetables,
constitute their volatile products.
CAROLINE.
Pray is not _coke_, (which I have heard is much used in some
manufactures,) also a bituminous substance?
MRS. B.
No; it is a kind of fuel artificially prepared from coals. It consists
of coals reduced to a substance analogous to charcoal, by the
evaporation of their bituminous parts. Coke, therefore, is composed of
carbon, with some earthy and saline ingredients.