ORGANIC CHEMISTRY.
RADICALS—ACIDS—BASES—NEUTRALS.
In the introduction to these brief chapters upon Chemistry, we said
that the science was divided into two sections, the first section
consisting of the simple combinations, and the other of compound
combinations. The latter being met with chiefly in animal and vegetable
matter, as distinguished from dead or inert matter, was termed
_Organic_. This distinction will be seen below.
COMBINATIONS OF SIMPLE GROUPS.
INORGANIC.
I. Elements and their Combinations.
(1) Non-Metallic.
(2) Metallic.
II. Peculiar Decompositions of the above.
(1) By Electricity.
(2) By Light.
COMBINATIONS OF COMPOUND GROUPS.
ORGANIC.
I. Compound Radicals and their Combinations.
II. Peculiar Decompositions of the above.
(1) Spontaneous.
(2) Dry Distillation.
We have already placed before our readers the elements and their
simple combinations, and have incidentally mentioned the decomposition
by electricity and by light. In the section upon Electricity the
positive and negative poles are explained. Oxygen appears always at
the positive pole, potassium at the negative. The other simple bodies
vary. Chlorine, in combination with oxygen, is evolved at the negative
pole, but when with hydrogen at the positive pole. In the series below
each element behaves electro-_negatively_ _to those following it_, and
electro-_positively_ to those _above it_; and the farther they are
apart the stronger their opposite affinities are.
ELECTRICAL RELATION OF THE ELEMENTS.
Oxygen.
Sulphur.
Nitrogen.
Chlorine.
Bromine.
Iodine.
Fluorine.
Phosphorus.
Arsenic.
Carbon.
Chromium.
Boron.
Antimony.
Silicium.
Gold.
Platinum.
Mercury.
Silver.
Copper.
Bismuth.
Lead.
Cobalt.
Nickel.
Iron.
Zinc.
Hydrogen.
Manganese.
Aluminium.
Magnesium.
Calcium.
Strontium.
Barium.
Sodium.
Potassium.
The importance of these facts to science is unmistakable, and, indeed,
many attempts have been made to explain, from the electrical condition
of the elements, the nature of chemical affinity, and of chemical
phenomena in general.
Electrotyping is another instance of decomposition by means of
electricity, and respecting decomposition by light we know how powerful
the action of the sun’s rays are upon plants, and for the evolution
of oxygen. The daguerreotype and photographic processes are also
instances which we have commented upon. So we can pass directly to the
consideration of the compound groups.
In nearly every complex organic compound we have a relatively simple
one of great stability, which is termed the _radical_, which forms,
with other bodies, a compound radical.[22] In these complex groups we
find certain elements generally,—viz., carbon, hydrogen, nitrogen,
sulphur, and phosphorus. Some compounds may consist of two of these,
but the majority contain three (hydrogen, oxygen, and carbon). Many
have four (carbon, oxygen, hydrogen, and nitrogen), and some more
than four, including phosphorus and sulphur. Others, again, may
contain chlorine and its relatives, arsenic, etc., in addition. Now
we will all admit that in any case in which carbon is present in
composition with other simple bodies forming an organic body, and if
that body be ignited in the air, it burns and leaves (generally) a
black mass. This is a sure test of the presence of carbon, and forms
an organic compound. Similarly in decomposition nitrogen and sulphur
in combination inform us they are present by the odour they give off.
We need not go farther into this question of radicals and compound
radicals than to state that a compound radical plays the part of
an element in combination. We find in alcohol and ether a certain
combination termed _Ethyl_. This “compound radical” occurs in same
proportions in ether, chloride of ethyl, iodide of ethyl, etc., as
C_{2}H_{5}; so it really acts as a simple body or element, though
it is a compound of carbon and hydrogen. A simple radical is easily
understood; it is an element, like potassium, for instance. We may now
pass to the organic combinations classified into ACIDS, BASES, and
INDIFFERENT, or NEUTRAL, BODIES.
I. ACIDS.
There are several well-known organic acids, which we find in fruits
and in plants. They are volatile and non-volatile; acids are sometimes
known as “Salts of Hydrogen.” We have a number of acids whose names are
familiar to us,—viz., acetic, tartaric, citric, malic, oxalic, tannic,
formic, lactic, etc.
_Acetic acid_ (HC_{2}H_{4}O_{2}) is a very important one, and is easily
found when vegetable juices, which ferment, are exposed to the air, or
when wood and other vegetable matter is subjected to the process of
“dry distillation.” Vinegar contains acetic acid, which is distilled
from wood, as we shall see presently. Vinegar is made abroad by merely
permitting wine to get sour; hence the term _Vin-aigre_. In England
vinegar is made from “wort,” of malt which is fermented for a few days,
and then put into casks, the bung-holes of which are left open for
several weeks, until the contents have become quite sour. The liquid is
then cleared by isinglass. The vinegar of commerce contains about 6 per
cent. of pure acetic acid, and some spirit, some colouring matter, and,
of course, water. Wood vinegar (pyroligneous acid) is used for pickles.
The ordinary vinegar when distilled is called white vinegar, and it may
also be obtained from fruits, such as gooseberries or raspberries.
[Illustration: Fig. 420.—Vinegar ground.]
[Illustration: Fig. 421.—Boiler or copper.]
Acetic acid, or “wood vinegar,” is prepared as follows:—There are
some large iron cylinders set in brickwork over furnaces, and these
cylinders have each a tube leading to a main pipe in which the liquid
is received for condensation. The cylinders, which contain about seven
or eight hundredweight, are filled with logs of wood, either oak,
beech, birch, or ash, the door is closely fastened, and the joints
smeared with clay; the fires are now lighted and kept up all day,
till the cylinders are red-hot; at night they are allowed to cool. In
the morning, the charcoal, into which the wood is now converted, is
withdrawn, and a fresh charge supplied; it is then found that about
thirty or forty gallons of liquid has condensed in the main tube from
each cylinder, the remainder being charcoal and gases which pass off;
the liquid is acid, brown, and very offensive, and contains acetic
acid, tar, and several other ingredients, among which may be named
creosote; it is from this source all the creosote, for the cure of
toothache, is obtained. To purify this liquid it is first distilled,
and this separates much of the tar; it is then mixed with lime,
evaporated to dryness, and heated to expel the remaining tar and other
impurities; it is next mixed with sulphate of soda and water, and the
whole stirred together; the soda, now in union with the acetic acid,
is washed out from the lime and strained quite clear; it is afterwards
evaporated till it crystallises, and vitriol (sulphuric acid) then
added; finally the acetic acid is distilled over, and the sulphuric
acid left in union with the soda, forming sulphate of soda, to be used
in a similar process for the next batch of acid. The acetic acid is now
quite colourless, transparent, and very sour, possessing a fragrant
smell. This is not pure acetic acid, but contains a considerable
quantity of water. The acetic acid of commerce, mixed with seven times
its bulk of water, forms an acid of about the strength of malt vinegar,
perfectly wholesome, and agreeable as a condiment.
[Illustration: Fig. 422.—Vinegar-cooling process.]
[Illustration: Fig. 423.—Tan-yard and pits.]
Pure acetic acid may be made by mixing dry acetate of potash with oil
of vitriol in a retort, and distilling the acetic acid into a very cold
receiver; this, when flavoured with various volatile oils, forms the
aromatic vinegar sold by druggists. It is a very strong acid, and if
applied to the skin will quickly blister it.
Acetate of lead, or sugar of lead, is obtained by dissolving oxide of
lead in vinegar. A solution of this salt makes the goulard water so
familiar to all. Acetate of lead is highly poisonous.
Acetate of copper is _verdigris_, and poisonous. Other acetates are
used in medicine.
We may pass quickly over some other acids. They are as follows:—
TARTARIC ACID (C_{4}H_{6}O_{6}) is contained in grape juice, and
crystallizes in tabular form. The purified powdered salt is cream of
Tartar.
CITRIC ACID (C_{6}H_{8}O_{7}) is found native in citrons and lemons, as
well as in currants and other fruits. It is an excellent anti-scorbutic.
MALIC ACID (C_{4}H_{6}O_{5}) is found chiefly in apples, as its name
denotes (malum, an apple). It is prepared from mountain-ash berries.
OXALIC ACID (C_{2}H_{2}O_{4}). If we heat sugar with nitric acid we
shall procure this acid. It is found in sorrel plants.
TANNIC ACID (C_{27}H_{22}O_{17}). It is assumed that all vegetables
with an astringent taste contain this acid. _Tannin_ is known for its
astringent qualities. The name given to this acid is derived from the
fact that it possesses a property of forming an insoluble compound with
water, known as _leather_. Tanning is the term employed. _Tannin_ is
found in many vegetable substances, but oak bark is usually employed,
being the cheapest. The “pelts,” hides, or skins, have first to be
freed from all fat or hair by scraping, and afterwards soaking them
in lime and water. Then they are placed in the tan-pit between layers
of the bark, water is pumped in, and the hides remain for weeks,
occasionally being moved from pit to pit, or relaid, so as to give
all an equal proportion of pressure, etc. The longer the leather is
tanned—it may be a year—the better it wears.
Skins for gloves and binding are tanned with “sumach,” or alum and
salt. Sometimes the leather is split by machinery for fine working.
_Parchment_ is prepared from the skins of asses, sheep, goats, and
calves, which are cleaned, and rubbed smooth with pumice stone.
Tannic acid, with oxide of iron, produces _Ink_, for the gall-nut
contains a quantity of the acid. All the black inks in use generally
are composed of green vitriol (sulphate of iron) in union with some
astringent vegetable matter; the best is the gall-nut, although, for
cheapness, logwood and oak bark have each been used. An excellent black
ink may be made by putting into a gallon stone bottle twelve ounces of
bruised galls, six ounces of green vitriol, and six of common gum, and
filling up the bottle with rain water; this should be kept three or
four weeks before using, shaking the bottle from time to time.
Blue ink has lately been much used; it is made by dissolving
newly-formed Prussian blue in a solution of oxalic acid. To make it,
dissolve some yellow prussiate of potash in water in one vessel, and
some sulphate of iron in another, adding a few drops of nitric acid to
the sulphate of iron; now mix the two liquids, and a magnificent blue
colour will appear, in the form of a light sediment; this is to be put
upon a paper filter, and well washed by pouring over it warm water, and
allowing it to run through; a warm solution of oxalic acid should now
be mixed with it, and the Prussian blue will dissolve into a bright
blue ink.
[Illustration: Fig. 424.—Unhairing the hide.]
Red ink is made by boiling chips or raspings of Brazil wood in vinegar,
and adding a little alum and gum; it keeps well, and is of a good
colour. A red ink of more beautiful appearance, but not so durable,
may be made by dissolving a few grains of carmine in two or three
teaspoonfuls of spirit of hartshorn.
Marking ink is made by dissolving nitrate of silver in water, and then
adding some solution of ammonia, a little gum water, and some Indian
ink to colour it. Printers’ ink is made by grinding drying oil with
lamp-black.
The powdered gall-nut is an excellent test for iron in water. It will
turn violet if any iron be present.
FORMIC ACID (CH_{2}O_{2}) is the caustic means of defence employed
by ants, hence the term _formic_. It can be artificially prepared by
distilling a mixture of sugar, binoxide of manganese, and sulphuric
acid. On the skin it will raise blisters.
[Illustration: Fig. 425.—Drying rooms for hides.]
LACTIC ACID (C_{3}H_{6}O_{3}) is present in vegetable and animal
substances. Sour whey contains it, and the presence of the acid in
the whey accounts for its power of removing from table-linen stains.
When what is called “lactic fermentation” occurs, milk is said to be
“turned.”
II.
BASES.
The definition of a base is not easy. We have described bases as
substances which, combining with acids, form salts, but the definition
of a base is as unsatisfactory as that of acid or salt. All vegetable
bases contain nitrogen, are usually very bitter, possess no smell or
colour, and are insoluble in water. They are usually strong poisons,
but very useful in medicine.
The most important are the following bases:—
QUININE is contained in the cinchona (yellow) bark. One hundred parts
of the bark have been calculated to yield three of quinine.
MORPHINE is the poisonous base of opium, which is the juice of the
poppy, and is prepared chiefly in India and China.
NICOTINE is the active principle of tobacco, and varies in quantity
in different tobaccos. Havannah tobacco possesses the least. It is a
powerful poison, very oily, volatile, and inflammable.
CONIA is prepared from the hemlock. It is fluid and volatile. It is
also a deadly poison, and paralyses the spine directly.
[Illustration: Fig. 426.—Hemlock.]
STRYCHNINE is found in poisonous trees, particularly in the nux-vomica
seeds of Coromandel. It produces lock-jaw and paralysis. There is no
antidote for strychnine; emetics are the only remedy.
The above are chiefly remarkable for their uses in medicine, and in
consequence of their highly poisonous character are best left alone by
unpractised hands.
A German chemist, named Serturner, was the first to extract the active
principle from Opium. The question of opium importation has lately been
attracting much attention, and the opinions concerning its use are
divided. Probably in moderation, and when used by ordinary people (not
demoralized creatures), it does little harm.
[Illustration: Fig. 427.—The Poppy.]
Opium is the juice of the “common” poppy, and derives its name from
the Greek _opos_, juice. The plant is cultivated in India, Persia,
and Turkey. After the poppy has flowered the natives go round, and
with a sharp instrument wound, or puncture, every poppy head. This is
done very early in the morning, and under the influence of the sun
during the day the juice oozes out. Next morning the drops are scraped
off. The juice is then placed in pots, dried, and sent for export.
The “construction” of opium is very complicated, for it contains a
number of ingredients, the most important being morphia, narcotine,
meconic acid, and codeia. It is to the first named constituent that the
somnolent effect of opium is due.
III.
INDIFFERENT SUBSTANCES.
There are a great number of so-called “indifferent” substances to which
we cannot be indifferent. Such bodies as these have neither acid nor
basic properties, and stand no comparison with salts. They are of great
importance, forming, as they do, the principal nutriment of animals.
Some contain nitrogen, some do not; they may therefore be divided
into nitrogenous and non-nitrogenous substances; the former for solid
portions of the body, the latter for warmth.
We will take the latter first, and speak of some of them—such as
starch, gum, sugar, etc.
STARCH is found in the roots of grain, in the potato, dahlia,
artichoke, etc., and by crushing the parts of the plant, and washing
them, the starch can be collected as a sediment. In cold water and
in spirits of wine starch is insoluble. The various kinds of starch
usually take their names from the plants whence they come. Arrowroot is
obtained from the West Indian plant _Maranta Arundinacea_. Cassava and
tapioca are from the manioc; sago, from the sago palm; wheat starch,
and potato starch are other examples.
[Illustration: Fig. 428.—Plantation of sugar-canes.]
If starch be baked in an oven at a temperature of about 300° it
becomes, to a great extent, soluble in cold water, forming what is
called “British gum”; this is largely used for calico printing and
other purposes; if boiled in water under great pressure, so that the
temperature can be raised to the same degree, it is also changed into
an adhesive sort of gum, “mucilage”; this is the substance made use
of by the government officials to spread over the backs of postage
and receipt stamps to make them adhere. The starch of grain, during
germination, or growth, contains _diastase_, which converts the starch
into gum and sugar; the same effect can be produced by heating starch
with diluted sulphuric acid.
GUM found in plants is chiefly procured from the Mimosa trees, from
which it flows in drops, and is called _Gum Arabic_. There are other
so-called “gums,” but this is the one generally referred to.
SUGAR exists in fruits, roots, and in the stalks of plants, in the
juice of the cane, maple, and beet-root particularly. The canes are
crushed, the juice is clarified with lime to prevent fermentation, and
the liquid is evaporated. It is then granulated and cleared from the
molasses. Sugar, when heated, becomes dark, and is called “caramel.” It
is used for colouring brandy, and gives much difficulty to the sugar
refiners.
[Illustration: Fig. 429.—Refining vacuum pan.]
Sugar refining is conducted as follows. The raw (brown) sugar is
mixed into a paste with water, and allowed to drain. The sugar thus
becomes white. It is then dissolved in water, with animal charcoal and
bullocks’ blood. The liquid is boiled, and put into a dark cistern with
holes at the bottom, and cotton fibres being fastened in the holes,
are hung into another dark cistern, into which the liquid runs pure
and white. It is then pumped into a copper vessel,—vacuum pan,—and
condensed to the proper consistence. Subsequently it is poured into
conical moulds, and pure syrup poured upon the crystal shapes. The
caramel is then removed through a hole at the end. The moulds or
loaves are then dried, and if not even or elegant they are turned in
a lathe. Finally they are packed up as “loaf sugar.” Sugar undergoes
no decomposition, and is the cause of non-decomposition in other
substances. For this reason it is employed in “preserving” fruit, etc.
Sugar is obtained from beet by crushing and rasping the roots, as the
cane is treated.
[Illustration: Fig. 430.—Sugar moulds.]
[Illustration: Fig. 431.—Turning the loaves.]
SPIRIT OF WINE, OR ALCOHOL, is not a natural product. It is found by
the decomposition of grape-sugar by fermentation. There is a series of
alcohols which exhibit a regular gradation, founded, so to speak, upon
one, two, or three molecules of water. They are called respectively
alcohols, glycols, and glycerins. Thus we have—
_Alcohols._
Methylic alcohol.
Ethylic ”
Prophylic ”
Amylic ”
_Glycols._
Enthelein glycol.
Prophylene ”
Butylene ”
Amylene ”
_Glycerins._
(Ordinary Glycerine is the
only one known.)
The cetyl and melissylic alcohols are contained in spermaceti and
bees-wax respectively. The usual alcohol is the _Vinic_, a transparent,
colourless liquid, which is the spirituous principle of wine, spirits,
and beer, and when sugar is fermented the alcohol and carbonic acid
remain.
Spirits of wine has a very powerful affinity for water, and thus
the use of stimulants in great quantity is to be deprecated, for
alcohol absorbs the water from the mucous membranes of the stomach
and the mouth, making them dry and hard. The state of “intoxication,”
unfortunately so familiar, is the effect produced by alcohol upon the
nerves. We append a list of the beverages which are most in use, and
the percentage of alcohol in each according to Professor Hart:—
Port 15 per cent.
Madeira 14·5 ”
Sherry 14 ”
Claret 8 ”
Ale 6 ”
Porter 5 ”
Spirit of wine is contained in many mixtures, and for the purpose of
ascertaining how much alcohol may be in wine, or any other liquid, a
hydrometer is used (fig. 432). This instrument consists of a glass tube
with a bulb at the end. It is put into water, and the place the water
“cuts” is marked by a line on the stem, and called zero 0°. Spirit of
wine has less specific gravity than water, so in absolute alcohol the
instrument will sink lower than in water, and will descend to a point
which is marked 100. In any mixture of alcohol and water, of course the
hydrometer will rise or sink between the extreme points accordingly
as the mixture may contain less alcohol or more. So a scale can be
furnished. The instrument, as described, was invented by MM. Gay-Lussac
and Tralles, and called the “percentage” hydrometer. There are many
other instruments marked in a more or less arbitrary manner. We append
a comparative table of a few hydrometers. (_See_ page 420.)
[Illustration: Fig. 432.—Hydrometer.]
ETHER, or _sulphuric_ ether, is a mixture of spirits of wine with
sulphuric acid, and distilled. It loses water, and the product
is ether, which is volatile, and transparent, with a peculiarly
penetrating odour. It will not mix with water, and if inhaled will
produce a similar effect to chloroform.
COMPARATIVE TABLE OF HYDROMETERS.
---------+------------+------------+-----------+-----------+-----------
Specific | Percentage | Percentage | Degree, | Degree, | Degree,
Gravity. | Volume | Weight, | according | according | according
| (Tralles). | at 60° F. |to Cartier.| to Beck. | to Baumé.
---------+------------+------------+-----------+-----------+-----------
1·000 | 0 | 0 | 10 | 0 | 10
0·991 | 5 | 4·0 | ... | ... | ...
0·985 | 10 | 8·0 | 12 | ... | ...
0·980 | 15 | 12·1 | ... | 3 | 13
0·975 | 20 | 16·2 | ... | ... | ...
0·970 | 25 | 20·4 | 14 | 5 | ...
0·964 | 30 | 24·6 | 15 | 6 | 15
0·958 | 35 | 28·9 | ... | ... | 16
0·951 | 40 | 33·4 | ... | 9 | 17
0·942 | 45 | 37·9 | 18 | ... | ...
0·933 | 50 | 42·5 | ... | 12 | 20
0·923 | 55 | 47·2 | 21 | 14 | ...
0·912 | 60 | 52·2 | ... | 16 | 24
0·901 | 65 | 57·2 | 24 | 19 | ...
0·889 | 70 | 62·5 | 27 | ... | 28
0·876 | 75 | 67·9 | ... | 24 | ...
0·863 | 80 | 73·5 | 30 | 27 | 32
0·848 | 85 | 79·5 | 35 | 30 | 35
0·833 | 90 | 85·7 | ... | 34 | 38
0·815 | 95 | 92·4 | 40 | 38 | 42
0·793 | 100 | 100·0 | 44 | 44 | 48
---------+------------+------------+-----------+-----------+-----------
Chloroform is transparent, and will sink in water. Diluted alcohol
with hypo-chloride of lime, will produce it. When inhaled, chloroform
produces a pleasing insensibility to pain, and is useful in surgery.
A certain compound of alcohol with mercury dissolved in nitric acid
will cause decomposition, and white crystals will eventuate. These
compound crystals are termed _fulminating mercury_.
* * * * *
We must now pass rapidly over the few remaining subjects we have to
notice, such as fats and soaps, wax, oils, etc.
Fats are of the greatest use to man, particularly in cold climates, for
upon them depends the heat of the body. Fatty acid, if liquid, is known
as oleic acid; if solid, stearic acid. Soaps are compounds of fatty
acids. Many “fats” are consumed as food, others as fuel or for lighting
purposes, in the shape of oils. Such oils are not primarily useful
for burning. Petroleum and other mineral oils are found in enormous
quantities in America.
There are what we term fixed oils, and essential or volatile oils. A
list is annexed as given by “Hadyn’s Dictionary of Science”:—
FIXED OILS.
_Drying._
Linseed oil.
Poppy oil.
Sunflower oil.
Walnut oil.
Tobacco-seed oil.
Cress-seed oil.
_Non-Drying._
Almond oil.
Castor oil.
Colza oil.
Oil of mustard.
Rape-seed oil.
Olive oil, etc.
ESSENTIAL OILS.
Oil of anise.
Oil of bergamot.
Oil of carraway.
Oil of cassia.
Oil of cedar.
Oil of cloves.
Oil of lavender.
Oil of lemon.
Oil of mint.
Oil of myrrh.
Oil of nutmeg.
Oil of peppermint.
Oil of rose.
Oil of turpentine.
Vegetable oils are obtained by crushing seeds; animal oils come from
the whale and seal tribe. Paraffin oil comes from coal. Linseed is a
very drying oil, and on it depends the drying power of paint. We know
olive oil will not dry on exposure to the air. Oiled silk is made
with linseed oil. When oil is drying in the air considerable heat is
evolved, and if oiled substances be left near others likely to catch
fire, spontaneous combustion may ensue. Oil of turpentine is found in
the pine and fir trees, and many of the oils above mentioned are used
by perfumers, etc., the rose oil, or attar of roses, being an Eastern
compound.
[Illustration: Fig. 433.—Crushing mill.]
Allied to the volatile oils are the RESINS, which are non-conductors of
electricity. They are vegetable products. They are soluble in alcohol,
in the volatile oils, or in ether, and these solutions are called
_varnishes_; the solvent evaporates and leaves the coating. Turpentine,
copal, mastic, shellac, caoutchouc, and gutta-percha are all resinous
bodies. Amber is a mineral resin, which was by the ancients supposed to
be the “tears of birds” dropped upon the seashore. Moore refers to this
in his poetic “Farewell to Araby’s Daughter”—
“Around thee shall glisten the loveliest amber
That ever the sorrowing sea-bird has wept.”
Amber is not soluble either in water or alcohol; it is, however,
soluble in sulphuric acid. It takes a good polish, and when rubbed is
very electrical. It is composed of water, an acid, some oil, and an
inflammable gas, which goes off when the amber is distilled.
The well-known camphor is got from a tree called the “Laurus Camphora”;
it is a white, waxy substance, and can be obtained by oxidizing certain
volatile oils. It is generally produced from the Laurus Camphora in a
“still.” The behaviour of a piece of camphor in pure water is curious,
but its motions can be at once arrested by touching the water or
dropping oil on the surface. This phenomenon is due to the surface
tension of the liquid, which diminishes when it is in contact with the
vapour of the substance.
NITROGENOUS SUBSTANCES.
There are certain albuminous compounds which we must mention here.
These are albumen, fibrine, and caseine. Albumen is the white of egg;
fibrine is, when solid, our flesh and muscular fibre, while caseine is
the substance of cheese. These are very important compounds, and the
albuminous bodies are of the very highest importance as food, for the
solid portion of blood, brain, and flesh consist, in a great measure,
of them. Albumen, fibrine, and caseine contain carbon, hydrogen,
nitrogen, and oxygen, with sulphur and phosphorus.
ALBUMEN. The most familiar and the almost pure form of albumen is in
the white of eggs, which is albuminate of sodium. It also exists in
the _serum_ of the blood, and therefore it is largely found in the
animal kingdom. It can also be extracted from seed or other vegetable
substances, but it is essentially the same. Albumen is very useful as
an antidote to metallic poisons. It forms about 7 per cent. of human
blood. It is soluble up to about 140° Fah.; it then solidifies, and is
precipitated in a white mass. Albumen is used in the purification of
sugar, etc.
FIBRINE is found in a liquid condition in blood. The vegetable fibrine
(gluten) is prepared by kneading wheat flour in a bag till the washings
are no longer whitened. Like albumen it is found both in a solid and
liquid state.
_Caseine_ is seen in the skin which forms upon milk when heated, and
forms about 3 per cent. of milk, where it exists in a soluble state,
owing to the presence of alkali; but caseine, like albumen, is only
soluble in alkaline solutions. As we have said, it is the principal
constituent of cheeses. Caseine is precipitated by the _lactic_ acid
of milk, which is produced by keeping the milk too warm. Caseine, or
curds, as they are called, are thus precipitated. The milk is said to
be “sour,” or turned.
MILK, the food of the young of all mammalia, is composed chiefly of
water, a peculiar kind of sugar, butter, and caseine. It is this sugar
in milk which causes the lactic acid mentioned above. The actual
constituents of milk are as follows:—
Water 873·00
Butter 30·00
Sugar 43·90
Caseine 48·20
Calcium (phosphate) 2·31
Magnesia 0·42
Iron 0·07
Potassium (chloride) 1·44
Sodium 0·24
Soda (with caseine) 0·42
-------
1000·00
The sugar of milk is non-fermenting, and can be procured from whey by
evaporation.
DECOMPOSITION.
We have seen that animals and plants are composed of many different
substances, and so it will be at once understood that these substances
can be separated from each other, and then the decomposition of the
body will be completed. When the sap sinks or dries up in plants they
are dead. When our heart ceases to beat and our blood to flow we die,
and then, gradually but surely, decay sets in. There is no fuel left
to keep the body warm; cold results, and the action of oxygen of the
air and light or water decays the body, according to the great and
unalterable laws of Nature. “Dust thou art, and unto dust shalt thou
return,” is an awful truth. The constituents of our bodies must be
resolved again, and the unfailing law of _chemical attraction_ is
carried out, whereby the beautiful organism, deprived of the animating
principle, seeks to render itself into less complicated groups and
their primary elements.
This resolution of the organic bodies is decomposition, or “spontaneous
decomposition,” and is called decay, fermentation, or putrefaction,
according to circumstances. The Egyptians, by first drying the bodies
of the dead (and then embalming them), removed one great source of
decay—viz., water, and afterwards, by the addition of spices, managed
to arrest putrefaction.
Fermentation is familiar in its results, which may be distilled for
spirituous liquors, or merely remain fermented, as beer and wine. Fusel
oil is prepared from potatoes, rum from cane sugar, arrack from rice.
The power of fermentation exists in nature everywhere, and putrefaction
is considered to be owing to the presence of minute germs in the
atmosphere, upon which Professors Tyndall and Huxley have discoursed
eloquently.
Plants are subjected to a process of decomposition, which has been
termed “slow carbonization,” under certain circumstances which exclude
the air. The gases are given off, and the carbon remains and increases.
Thus we have a kind of moss becoming peat, brown coal, and coal. The
immense period during which some beds of coal must have lain in the
ground can only be approximately ascertained, but the remains found in
the coal-measures have guided geologists in their calculations.
Having already mentioned some products of distillation, we may now
close this portion of the subject and pass on to a brief consideration
of minerals and crystals. We have left many things unnoticed, which in
the limited space at our disposal we could not conveniently include in
our sketch of chemistry and chemical phenomena.
FOOTNOTES:
[22] Cyanogen, ethyl, and cacodyl, are compound radicals.