+----------------------+------+
|Magnesic carbonate |66·963|
+----------------------+------+
|Calcic carbonate |23·634|
+----------------------+------+
|Sodium chloride | 3·542|
+----------------------+------+
|Sodic sulphate | 0·293|
+----------------------+------+
|Sodic carbonate | 0·598|
+----------------------+------+
|Magnesic hydrate | 1·311|
+----------------------+------+
|Ferric oxide | 0·092|
+----------------------+------+
|Alumina | 0·227|
+----------------------+------+
|Silicic acid | 0·765|
+----------------------+------+
|Water combined at 120°| 1·153|
+----------------------+------+
|Hydroscopic moisture | 1·422|
+----------------------+------+
The 'Chemical News' (xxxvi, 202) contains the analysis by Mr Paterson Muir
of a clay from Mackenzie County, South Island, New Zealand, which is
largely eaten by sheep. It consists of:--
+------------------+------+
|Silica | 61·25|
+------------------+------+
|Alumina | 17·97|
+------------------+------+
|Ferric oxide | 5·72|
+------------------+------+
|Lime | 1·91|
+------------------+------+
|Magnesia | 0·87|
+------------------+------+
|Sodium chloride | 3·69|
+------------------+------+
|Potassium chloride| trace|
+------------------+------+
|Water | 7·31|
+------------------+------+
|Organic matter | 1·77|
+------------------+------+
| |100·49|
+------------------+------+
See ANIMALCULÆ.
=EDULCORA'TION.= The affusion of water on any substance for the purpose of
removing the portion soluble in that fluid. Edulcoration is usually
performed by agitating or triturating the article with water, and removing
the latter, after subsidence, by decantation or filtration. It is the
method commonly adopted to purify precipitates and other powders which are
insoluble in water. The washing-bottle is a most useful instrument for the
edulcoration of precipitates. In its simplest form, it is a bottle fitted
with two bent glass tubes, one drawn to a fine point and reaching to the
bottom of the bottle, the other only entering the cork a few inches. By
blowing down the latter tube, the water is forced out of the former in a
fine stream. See WASH-BOTTLE.
=EEL.= _Syn._ ANGUILLA, L. A family of fishes belonging to the 'apodal'
section of the _malacopterygii_. At least three species of eels are found
in this country--the 'sharp-nosed,' the 'broad-nosed,' and the 'snig.' The
first, which is common in streams and lakes, attains the greatest
size--sometimes 25 lbs. or even 30 lbs. The 'snig' is considered superior
to other kinds for the table. As articles of food, eels are said to be
laxative and far from wholesome. The fat (EEL FAT; ADEPS ANGUILLÆ, OLEUM
A.) is among the simples of the Ph. L. 1618, and was formerly considered
'good against stripes,' and is even now used by the vulgar as a friction
for stiff joints. For the table, eels are generally dressed by stewing,
frying, baking, or potting, which is done in the usual way, the fish being
cut into pieces 2 or 3 inches long, and melted butter, onions, sweet
herbs, and anchovy sauce, added at will. The CONGER EEL is a distinct and
gigantic species of the same family. Its flesh is coarse and oily, but is
much esteemed by the inhabitants of the southern coast of Devon, on which
it abounds.
Letheby states the following to be the composition of the Eel:
+------------------+-----+
|Nitrogenous matter| 9·9|
+------------------+-----+
|Fat | 13·8|
+------------------+-----+
|Saline matter | 1·3|
+------------------+-----+
|Water | 75·|
+------------------+-----+
| |100·0|
+------------------+-----+
Payen's analysis differs from the above, in giving a larger proportion of
nitrogenous matter, and a still greater quantity of fat.
The native inhabitants of New Zealand and kindred races suffer largely
from scrofula, the prevalence of which disease amongst them has been
attributed to their partaking so largely of eel as a common article of
diet.
=EFFERVES'CENCE.= The rapid escape of gas in small bubbles from a liquid.
See DRAUGHT, POWDER, &c.
=EFFLORES'CENCE.= The spontaneous conversion of a crystalline solid into a
dry pulverulent form. Crystals which in a dry atmosphere lose their water
of crystallisation, and become crusted over with a mealy powder, are said
to be EFFLORESCENT.
=EGG.= _Syn._ OVUM, L. A body produced in the females of birds and certain
other animals, containing an 'embryo' of the same species, or body, from
which a similar animal may ultimately be produced. The eggs of the common
domestic fowl are nutritious and easily digestible; and when lightly
cooked by boiling and eaten with a little salt, are admirably adapted as
an aliment for the sick and delicate. When boiled hard or fried, they are
rendered less digestible, and possess no advantage in this respect over
butcher's meat. A new-laid egg, beaten up in a cup of tea, coffee, or
chocolate is an excellent ingredient in the breakfast of a person with a
poor appetite, and is very supporting. A glass of wine, beer, or porter,
similarly treated, along with a biscuit, has been recommended as a light
and nutritious luncheon or supper, well suited to the debilitated and
dyspeptic. Raw eggs may be advantageously substituted for cod-liver oil in
all the cases in which this last is ordered, occurring in persons with
delicate or irritable stomachs. The addition of fresh salad oil vastly
increases their medicinal virtues. A fresh egg is said to contain about
the same amount of nourishment as 1-1/2 oz. of fresh meat and 1 oz. of
wheaten bread, but in a more digestible form.
_Composition of the contents of the egg._
Water 74·02
Albumen 14·08
Oil and fat 10·25
Mineral matter 1·65
-------
100·00
_Composition of the white of egg._ (Thompson.)
Nitrogenous matter 20·40
Fatty matter
Saline matter 1·60
Water 78·00
------
100·00
_Composition of the yolk._ (Thompson.)
Nitrogenous matter 16·00
Fatty matter 30·70
Saline matter 1·30
Water 52·00
------
100·00
=Egg, White of= (ALBUMEN OVI), is officinal in the B. P. Yelk of egg
(_vitellus ovi_) is an ingredient in the BRANDY MIXTURE (MISTURA SPIRITUS
VINI GALLICI) of the London College. It is also a popular application to
chaps, cracked nipples, abrasions, &c., and is largely used to render
oleaginous substances miscible with water, in the preparation of
emulsions.
The average weight of the new-laid egg of a hen is about 2-1/2 oz., and
its sp. gr. is 1·080 to 1·090; the white generally weighs about 1-1/2 oz.;
the yolk, a little under 3/4 oz.; and the shell and skin, 1/4 oz. Dr Prout
found that an egg, on being kept for 2 years in a dry situation, lost
544-3/10 gr., from the evaporation of a portion of its water through the
shell. By boiling in water an egg loses from 2% to 3% of its weight.
_Choice._ The larger end of a new-laid egg feels cold when placed against
the tongue. New-laid eggs appear semi-transparent when placed between the
eye and a strong light, and have a small and perceptible division of the
skin from the shell, which is filled with air. This mode of examination
among the trade is called 'candling.' When they shake they are stale. The
eggs of turkeys and pea-hens are much esteemed for some purposes; those of
ducks and geese are coarse and inferior.
Sound eggs will sink if put into a solution, consisting of 1 oz. of salt
in 10 oz. of water; in the same solution indifferent ones will float,
whilst bad or worthless ones will swim even in pure water.
_Pres._ Eggs may be preserved for any length of time by excluding them
from the air. One of the cleanest and easiest methods of doing this is to
pack them with the small end downwards, in clean dry salt, in barrels or
tubs, and to place them in a cool and dry situation. We have eaten eggs
thus preserved that were more than a twelvemonth old, and that had been
for some months on shipboard in a tropical climate, and which yet retained
all the peculiar sweetness of new-laid eggs. With a like intention, eggs
are placed in vessels containing milk of lime or strong brine, or are
rubbed over with butter, lard, or gum water, all of which act by excluding
the air. Eggs for keeping should never be laid on their sides, and when
kept in the air should be occasionally turned to prevent the yolk
attaching itself to the side instead of floating in the albumen. Some
persons place the eggs in a netting or on a sieve or colander, and immerse
them for an instant in a caldron of boiling water before packing them
away. The practice of packing eggs in damp straw, or anything else that
can convey a flavour should be carefully avoided. The shells of eggs are
porous, and readily admit the passage of gaseous substances, especially of
fetid odours. It is from inattention to this point that a large number of
the eggs imported from the coast of France have a less delicate flavour
than those of our poultry yards. Damp chopped straw, as well as most other
organic substances exposed to warmth and moisture, readily ferment or
putrefy; and during fermentation a considerable increase of temperature
takes place, as any one may readily perceive by examining the common
hotbeds in our gardens, which are merely masses of organic matter in a
state of decomposition. Eggs, as long as they retain the embryo of the
future chick in a vital state, possess in themselves a certain degree of
warmth, which tends materially to promote the decomposition of the
substances they are packed in, particularly in the presence of moisture.
A correspondent of the 'Chemical News' says: "Eggs may be kept fresh for a
whole year by subjecting them to the following process. The fresh eggs are
carefully placed in a mixture of five kilogrammes of alum, dissolved in
five litres of water, heated to from 45° to 50° C., and left in that
liquid for from thirty to forty minutes; the eggs are next drained, and in
the meantime the solution of alum is heated to boiling-point. The eggs are
again immersed in the liquid and kept therein from ten to fifteen seconds;
after having been drained and cooled, they are packed in either dry bran,
sawdust, cork-dust, sifted ashes, or in cotton-wool."
M. Durand, of Blois, proposes to preserve eggs by coating them with
silicate of soda.
_To Preserve Eggs fresh for many weeks._--As the eggs are taken
from the nest, brush each one separately with a thin solution of
gum Arabic, being careful to leave no portion of the shell
uncovered by it. The half of each egg must first be done, and
left to become dry before the remainder is touched, that the gum
may not be rubbed off any part by its coming in contact while
wet with the hand as it is held to be varnished, or with the
table when it is laid down to harden.--ELIZA ACTON.
_Eggs to boil in the Shell._--Eggs brought from a cold place and suddenly
plunged into boiling water are very frequently liable to crack, and thus
to allow of the partial escape of their contents. In winter it will be
found a good plan to hold them for an instant over the steam of the
saucepan before they are placed in it, which they should be, very gently.
By boiling for three minutes, the whites will become in a partially solid
state. Exactly five minutes will harden the whites and leave the yolks
liquid. Eight or ten minutes will render them hard. Eggs should always be
boiled in water sufficient to entirely cover them. They should be boiled
15 minutes for salad-dressings.
_Eggs, to Poach._--Take for this purpose a wide and delicately clean pan
about half filled with the clearest spring water; throw in a small
saltspoonful of salt, and place it over a fire quite free from smoke.
Break some new-laid eggs into separate cups, and do this with care, that
the yolks may not be injured. When the water boils, draw back the pan,
glide the eggs gently into it, and let them stand till the whites appear
almost set, which will be in about a minute; then without shaking them
move the pan over the fire, and just simmer them from two minutes and a
half to three minutes. Lift them out separately with a slice, trim quickly
off the ragged edges, and serve them upon dressed spinach or upon minced
veal, turkey, or chicken; or dish them for an invalid upon delicately
toasted bread, sliced thick and free from crust; it is an improvement to
have the bread buttered, but it is less wholesome.
Comparative time of poaching eggs: swan's eggs, 5 to 6 minutes (in basin,
10 minutes); turkey's eggs, 4 minutes; hen's eggs, 3 to 3-1/2 minutes;
Guinea fowl's, 2 to 3 minutes; bantam's, 2 minutes.
_Obs._ All eggs may be poached _without boiling_ if kept just at simmering
point, but _one boil_ quite at last will assist to detach them from the
stewpan, from which they should always be very carefully lifted on what is
called a fish or egg slice. There are pans made on purpose for poaching
and frying them in good form; but they do not, we believe, answer
particularly well. If broken into cups slightly rubbed with butter and
simmered in them, their roundness of shape will be well preserved.--ELIZA
ACTON.
=Egg, Elas'tic.= Take a good and sound egg, place it in strong vinegar,
and allow it to remain for 12 hours; it will then become quite soft and
elastic. In this state it can be squeezed into a tolerably wide-mouthed
bottle; when in, it must be covered with water having a little soda
dissolved in it. In a few hours the egg will be restored to nearly its
original solidity; after which the liquid may be poured off and the bottle
dried, the whole being kept as a curiosity to puzzle one's friends for an
explanation how the egg got there. ('Parlour Pastime.')
=Egg Flip.= _Prep._ 1. Beer, 1 pint; eggs, 3 in no.; sugar, 2 oz.; nutmeg
and ginger, q. s. to flavour; the eggs are broken into one half of the
beer, the sugar added, and the whole beaten well together; the mixture is
then placed in a clean warmer, and heated over the fire to nearly the
boiling-point, and stirred one way all the time, care being taken not to
let it either boil or curdle; the other portion of the beer and the spices
are then added, and the whole mixed well together.
2. As above, but adding a glass of spirit. Some persons also add a little
lemon peel.
=Eggs, Packing, for Shipboard.= The following plan is now adopted by many
firms shipping eggs:--"In the bottom of the box may be placed bran, cut
hay, and sawdust. Tear up old newspapers to about 8 or 10 inches square.
The paper should be about medium--that is, not too stiff nor too soft.
Place one of these pieces of paper on the hand, and on this an egg, on one
end; close the lower hand so as to bring the paper up all round the egg;
with the other hand crumple the loose corners and edges of the paper down
over the other end of the egg; lay another piece of paper on the hand, on
which place the same egg, but the other end up; bring up the new paper and
crumple down as before. This gives a good cushion to both ends, and a fair
one over the centre. Repeat this till you have six thicknesses of paper,
reversing the egg each time, and always keeping it on the end. This gives
you a ball about 3 to 3-1/2 in. thick by 3-1/2 to 4 in. long. Care should
be taken not to press the paper too closely to the egg while covering.
Place on one end in the box or basket; place alongside and press them
together close enough to prevent their becoming loose in the box, fillings
at the ends and on top with crumpled paper."--J. P.
=Egg, Glaire of.= _Prep._ Separate the whites from the yolks, and whisk
them to a froth, let them stand 24 hours, and strain them through muslin.
Used as a glaze or varnish by bookbinders and others.
=Egg, Liquid.= _Prep._ (Jayne.) From lime, 1 bushel (slaked with water);
common salt, 2 or 3 lbs.; cream of tartar, 1/2 lb.; water, q. s. to form a
mixture strong enough to float an egg. Used to preserve eggs, which it is
stated it will do for two years, by simply keeping them in it. Simple milk
of lime answers quite as well.
=Egg Wine.= As egg flip, but using equal parts of white wine and water,
instead of beer.
=ELA'IDINE.= A fatty compound of elaïdic acid and glycerin, formed by the
action of nitrous acid or nitrate of mercury on olive oil. It is neutral;
melts at 90° Fahr.; and is very soluble in ether, scarcely so in alcohol.
It is one of the components of CITRINE OINTMENT. By saponification it is
resolved into its two constituents.
=ELA'IN.= See OLEIN.
=ELAIOM'ETER.= _Syn._ OLEOM'ETER. An instrument for ascertaining the
specific gravity of oils. See HYDROMETER and OIL.
=ELAL'DEHYD.= A peculiar crystalline substance which forms in ALDEHYD when
kept for some weeks at a temperature of 32° Fahr. It melts into a
colourless liquid at about 38°, in which state it is miscible with water,
alcohol, and ether. It is isomeric with aldehyd, but its vapour has about
three times the density of that substance, whilst it neither combines with
ammonia nor comports itself with potassa and solution of silver like
aldehyd.
=ELAOP'TENE.= See OIL (Volatile).
=ELAT'ERIN.= _Syn._ MOMORDICINE. The active principle of ELATERIUM. It was
discovered by Dr Clutterbuck in 1819, but first obtained in a state of
purity in 1830 by the late Mr Hennel.
=Elaterin.= _Syn._ ELATERIUM. (Dr Morries.) Obtained by evaporating
tincture of elaterium (made with rectified spirit) to the consistence of
thin oil, and throwing it in boiling distilled water. When cold, the
crystalline precipitate is collected, and dried with a gentle
heat.--_Dose_, to commence with 1-16th of a grain.
_Prep._ 1. (Dr Morries.) Elaterium is digested in hot alcohol, the
resulting tincture filtered, evaporated to the consistence of thin oil,
and then thrown into boiling distilled water. When the whole is cold, the
precipitate is collected and purified by redissolving it in alcohol and
precipitation by water, as before.
2. (Hennel.) The alcoholic extract of elaterium is digested in ether, and
the residuum dissolved in hot alcohol; crystals form as the solution
cools.
3. An alcoholic tincture is evaporated to the consistence of a syrup, and
thrown into a mixture of equal parts of liquor of potassa and water at a
boiling temperature. Almost pure elaterin separates as the liquid cools.
_Obs._ Elaterin forms delicate, white, silky crystals, having a bitter
taste; it is fusible at about 365° Fahr.; tastes bitter; odourless;
neutral; insoluble in water; and dissolves readily in hot alcohol. Its
medicinal action is similar to that of elaterium, differing only in its
greater activity.--_Dose_, 1/16 gr. to 1/20 gr.
=ELATER'IUM.= _Syn._ SQUIRTING CUCUMBER. In _pharmacy_, 'the fresh unripe
fruit' of the wild cucumber, '_Ecbalium officinarum_--Richard,' Ph. L.
(_Momordica Elaterium_, Linn.). According to present usage, the word is
more generally applied to the feculence deposited from the juice of the
wild cucumber. It is thus applied in Ph. B. E. & D. See _below_.)
=Elaterium.= B. P. _Syn._ EXTRACT OF ELATERIUM, E. OF SQUIRTING CUCUMBER;
EXTRACTUM ELATERII (Ph. L.), ELATERIUM (Ph. E. & D.,) L. The feculence of
the juice of the above fruit.
_Prep._ 1. (Ph. L.) Slice wild cucumber before it is quite ripe in the
long direction, and strain the juice, very gently expressed, through a
fine hair sieve; then set it aside for some hours, until the thicker part
has subsided. The thinner supernatant fluid being rejected, dry the
thicker portion with a gentle heat. The processes of the other colleges
are essentially the same.[272]
[Footnote 272: At the Mitcham Gardens, elaterium is manufactured in much
the same way, only that considerable force is used in the expression of
the juice, and the product therefore less potent, though more in quantity.
The manufacture usually commences about the second week in September. (Dr
Royle).]
2. (Dr Clutterbuck.) The cucumbers (fully ripe) are cut longitudinally,
and sprinkling with cold water, and the juice allowed to strain through a
fine sieve into an earthenware vessel. The seeds and surrounding pulp are
next placed on the sieve, with the split fruit, and washed repeatedly with
cold water. The washings being received in the same vessel with the juice,
the whole is allowed to repose for a few hours, when the clear portion is
decanted and the sediment spread thinly on fine linen, and dried by
exposure to the air and a gentle heat avoiding the sunshine or a bright
light. Quality very fine. Forty fruits, by this process, yield only 6 gr.
of elaterium.
3. (Apothecaries' Hall.) The fruit, slit into halves, is placed in hempen
or horsehair bags, and submitted to slight pressure in a tincture press.
The juice, as it runs off, passes through a fine hair sieve into a
cylindrical glass jug or jar, where it is allowed to remain for two hours,
when the clear supernatant liquor is poured off, and the thick portion
containing the sediment is poured on a paper filter, supported on linen,
and allowed to drain, after which it is dried by a gentle heat in a stove.
The product has a green colour, and constitutes the finest elaterium of
commerce. A darker and inferior article is obtained from the liquor,
poured from the first sediment by placing it in shallow pans, and allowing
it again to deposit.
_Prop., &c._ Elaterium is sold in thin cakes, and when pure has a
pale-gray or greenish-gray colour, floats on water, is easily pulverised
by pressure, and forms with rectified spirits a rich, green-coloured
tincture. Elaterium obtained as a second deposit (ELATERIUM NIGRUM), is
dark and inferior. Alcohol dissolves from 50% to 60% of good elaterium.
"When exhausted by rectified spirit, the solution, concentrated, and
poured into hot dilute solution of potassa, deposits, on cooling, minute
silky, colourless crystals (of ELATERIN), weighing from 1/7th to 1/4th of
the elaterium operated on." (Ph. E.)
_Obs._ To procure a fine sample of elaterium it is necessary to remove it
as soon as it is deposited, as a heavy mucilage falls down soon
afterwards, which materially injures its quality and appearance. English
elaterium is the best. The foreign is uniformly adulterated with chalk or
starch, and coloured with sap green.
_Dose_, 1/16 gr. to 1/2 gr., formed into a pill with extract of gentian
and liquorice powder; as a hydragogue and cathartic in dropsies, twice a
day, repeated every other day for a week or ten days. Its use must be
avoided when there is much debility or any inflammatory symptoms. Larger
doses than 1/2 gr. of pure elaterium are poisonous. The _antidotes_ are
emetics, followed by demulcents, opium, and stimulants.
=EL'DER.= _Syn._ SAMBUCUS (Ph. L. & E.), L. A large shrub or small tree
belonging to the natural order _Caprifoliacæ_. It is indigenous in Europe,
and has long been valued for its medicinal properties. "The recent flowers
of the _Sambucus nigra_" (Ph. L.) or common elder are regarded as
diaphoretic and pectoral, and a distilled water (ELDER-FLOWER WATER; AQUA
SAMBUCI) is made of them. The inner bark of the same tree is purgative and
emetic, and is used in dropsy; the leaves are purgative; the juice of the
fresh berries is made into wine (ELDER WINE), and is largely used to make
FACTITIOUS PORT WINE, and to adulterate the real wine. See WATERS
(Distilled).
=ELECAMPANE'.= _Syn._ INULA (Ph. L.), L. "The root of _Inula Helenium_"
(Ph. L.). A plant of the nat. order _Compositæ_. Tonic, diaphoretic, and
expectorant.--_Dose_, 20 gr. to 1 dr., or more, either in the form of
powder or decoction; in catarrh, dyspepsia, &c. It is now seldom used.
=ELECTRANODYN.= For the cure of neuralgia, headache, migrain, faceache,
and apoplectic attacks. As a necklace for children for toothache, as a
preventive of quinsy, &c. A tissue paper converted into a nitrogenous
material (pyroxylin or _düppelpapier_) by immersion in a mixture of
sulphuric and nitric acid, and containing besides an insignificant
proportion of wax and resin. (Hager.)
=ELEC'TRIC.= _Syn._ ELECTRICAL. Exhibiting the effects of ELECTRICITY when
'excited' by friction; pertaining to, derived from, or produced by
electricity.
=Electric.= _Syn._ INSULATOR, NON-CONDUCTOR. A substance which may under
ordinary circumstances be readily made to evince electrical properties by
friction. Electrics do not transmit, or conduct, electricity; whilst, on
the other hand, ANELECTRICS are good transmitters or conductors of
electrical action. The most perfect electrics are shell-lac, sulphur,
amber, jet, resinous bodies, gums, gun-cotton, glass, silk, diamond,
agate, and tourmaline; dry fur, hair, wood, feathers, and paper;
turpentine and various oils; dry atmospheric air and other gases, steam of
high elasticity, and ice at 0° Fahr. The most perfect anelectrics or
conductors are the metals, charcoal, and saline fluids.
=Electric Eel.= The _Gynotus electricus_, a fish having the power or
giving violent electric 'shocks'; which power it exerts for killing or
stunning its prey. It is an inhabitant of the fresh-water lakes and rivers
of the warmer regions of America, Africa, and Asia.
=Electrical Machine.= An instrument for the excitation and collection of
electricity. The term is only applied to contrivances in which friction is
the immediate cause of the electrical disturbance; those which act through
chemical force, magnetism, or heat, being known by various distinctive
names, as 'voltaic battery,' 'electro-magnetic machine,' 'induction-coil,'
'thermo-electric pile,' &c.
The electrical machines in common use are composed of a hollow glass
cylinder, or circular plate of glass, turning on an axis, and rubbing
against two or more leather rubbers covered with silk, the electricity
being collected by sharp points fixed in a metal rod standing on a glass
pillar. A description of these instruments, however, would be out of place
in the present work, which does not aim at giving information that may be
easily obtained from other sources.
Cylinder machines are seldom made of greater size than 13 inches by 9, and
are about as powerful as an 18-inch plate machine. The latter are commonly
made up to 3 and 4 feet diameter, and will, with a suitable condenser,
give 15 inch sparks in air.
=ELECTRI''CITY= (-tr[)i]s'-[)i]t-e). The name given primarily to one of
the great forces of nature, and secondarily to that department of physical
science which embraces all that is known respecting this particular force.
Many theories respecting the nature of electricity have been advanced for
the purpose of explaining electrical phenomena. The theory of Dr Franklin
supposed the existence of a single homogeneous, imponderable fluid, of
extreme tenuity and elasticity, in a state of equable distribution
throughout the material world. This fluid is assumed to be repulsive of
its own particles, but attractive of all other matter. When distributed in
bodies, in quantities proportionate to their capacities or attraction for
it, such bodies are said to be in their 'natural state.' When we increase
or diminish the natural quantity of electricity in any substance,
excitation is the result, and the substance, if 'overcharged,' is said to
be electrified 'positively,' or if 'undercharged,' 'negatively.' These
theories, and all others based upon the assumption that electricity is a
form of matter, have been found to be inadequate for the elucidation of
electrical phenomena.
At the present day, however, two kinds of electric forces are recognised,
and distinguished as negative and positive, but they are both assumed to
be analogous in principle, and very generally assumed to be simply due to
different analogous motions of matter. For a full exposition, however, the
reader must refer to some of the especial works on the subject.
=ELECTRICITY, Iron reduced by.= Gelatin capsules of the size of a 2-grain
pill, filled with powdered blacksmith scales (black oxide of iron).
(Hager.)
=ELECTRO-CHEM'ISTRY.= That branch of chemistry which treats of the agency
of electricity in effecting chemical changes.
=ELECTRO-ETCH'ING.= See ETCHING.
=ELECTROL'YSIS.= (-tr[)o]l'-e-s[)i]s). Electro-chemical decomposition. The
voltaic current has the power of loosening and separating the constituents
of certain compound bodies when these are interposed in the circuit. The
substances which are thus susceptible of decomposition are termed
electrolytes. They are all binary compounds, containing single equivalents
of their components, which are held together by very powerful affinities.
The amount of electrical power required to effect decomposition varies
greatly with different electrolytes: solution of iodide of potassium,
melted chloride of lead, hydrochloric acid, water mixed with a little
sulphuric acid, and pure water, demand very different degrees of
decomposing force, the resistance increasing from the first-mentioned
substance to the last, which latter it has been denied can be decomposed.
One of the indispensable conditions of electrolysis is fluidity. When a
liquid is electrolysed its components are discharged solely at the
limiting surfaces, where, according to the usual figurative mode of
speech, the current enters and leaves the liquid, all the intermediate
portions appearing quiescent. The terms 'anode' and 'cathode' have been
proposed respectively for the surfaces which are supposed to receive and
let out the current of positive electricity. The anode is therefore
directly against or opposite the positive pole of the battery, or,
according to the improved nomenclature, the positive electrode; and the
cathode against the negative pole, or electrode. The bodies which are set
free by the action of the current are termed ions; those which go to the
anode and appear at the positive electrode being distinguished by the term
anions, and those which go to the cathode and appear at the negative
electrode by the term cathions. This nomenclature has, however, been but
partially adopted, and is making but slow way, if any, many preferring the
old terms of electro-positive for anions, and electro-negative for
cathions.
The relative decomposing effects produced by the same current in different
electrolytes are exactly expressed by the chemical equivalents of the
electrolytes. Thus, if a current be made to traverse acidulated water,
iodide of potassium, and chloride of lead, these three electrolytes will
suffer decomposition at the same time, but by no means to the same extent;
for the current which decomposes but 9 parts of water will separate into
their elements 166 parts of iodide of potassium and 139 parts of chloride
of lead. The electrolysis of metallic salts is now carried out on a large
scale in the beautiful arts, which we notice under the general head of
ELECTROTYPE.
=ELECTROMOTIVE ESSENCE= (Romershausen). An embrocation for restoring the
suspended functions of the skin by stimulating the flow of vital
electricity and the functions of the nerves. A solution of oils of
turpentine and rosemary in the ninth dilution of alcohol previously
coloured red with some vegetable dye. (Reithner.)
=ELECTRO-PLA''TING and GILDING.= See ELECTROTYPE.
=ELECTROPH'ORUS.= A simple instrument for exciting electricity, generally
used in the chemical laboratory for charging small Leyden jars when gases
have to be exploded by the electric spark. To construct it, a plate of
tinned iron is made into a circle of about 12 inches diameter; a raised
border is then turned up for about half an inch, and the extreme edge is
turned outwards over a wire to avoid a sharp border. A mixture of equal
parts by weight of shell-lac, Venice turpentine, and resin, is made by
gently heating them together with stirring until well fused and thoroughly
incorporated. This composition is poured into the plate, to quite fill it,
and kept melted until all bubbles have disappeared. Another portion of the
instrument, serving the same purpose as the conductor of an electric
machine, is a circle of wood, rather smaller than the resinous plate,
rounded at the edge, and neatly covered with tin-foil. An insulating
handle, formed of a piece of stout glass rod, is cemented into the centre
of this wooden disc. Before using the instrument it must be carefully
dried and slightly warmed. The resinous surface is excited by beating it
obliquely with a folded piece of warm flannel. When this has been done for
about a minute, the warm dry cover of the instrument is to be placed upon
the resinous plate, and touched with the finger. If the cover is then
raised a few inches, and the knuckle approached, a powerful spark of
positive electricity will pass; and if the cover be again replaced,
touched, and raised, a second spark will pass. This may be repeated many
times without again exciting the resinous plate. By receiving the sparks
with the knobs of a Leyden jar, a charge strong enough to give a powerful
shock, or explode a gaseous mixture, may be rapidly obtained. Other forms
have been given to the instrument, but the essential part of every one is
a plate of some resinous substance.
=ELECTROTYPE.= _Syn._ ELECTRO-MET'ALLURGY, GALVAN'O-PLAS'TIC. The art of
working in metals by the aid of electricity. Strictly speaking, the term
electrotype is only applicable to one branch of 'electro-metallurgy'--that
which relates to the production of copies of engraved plates, medals,
coins, and other works--but it is now commonly employed in the sense
indicated by our definition. According to this extended signification of
the term, the art of electrotype includes ELECTRO-PLATING, and
ELECTRO-GILDING.
_General Principles._--If a current from a voltaic battery be passed, by
means of platinum electrodes, through water to which some sulphuric acid
has been added, electrolysis, takes place, hydrogen appearing at the
cathode, and oxygen at the anode. If into the acid liquid some crystals of
sulphate of copper be now thrown, electrolysis will still go on, but only
one of the elements of the water, namely oxygen, will be evolved; for the
hydrogen, on being released, will take the place of the copper in the
solution, and the copper thus liberated will be deposited on the platinum
plate or wire which constitutes the negative electrode. This experiment
may be continued until all the copper is extracted from the solution. Let
this experiment be repeated with a copper plate for the positive
electrode, and it will be found that neither of the gases will be evolved.
The hydrogen, as before, will take the place of the copper in the
solution; the oxygen, instead of escaping at the anode, will combine with
the copper of the electrode and the sulphuric acid to form sulphate of
copper. The chemical forces called into action by the current are so
beautifully balanced, that in the last experiment the quantity of copper
supplied by the positive electrode exactly equals the quantity withdrawn
from the solution and deposited upon the negative electrode. The whole art
of electrotype consists in applying the metals thus released from their
solutions to artistic or useful purposes. To obtain compact and brilliant
deposits, many precautions have to be observed. The solutions must be kept
saturated, or nearly so; the mould to be copied, or object to be coated,
must not be too small, or out of proportion to the size of the zinc plate
of the battery; in fine, the power employed must be carefully regulated
according to the work to be done. In all arrangements the moulds or
objects which receive the deposits act as negative electrodes, and are
consequently in connection with the zinc of the battery or generating
cell.
_Electrotype Processes._ Although reguline deposits of many metals can be
obtained through the agency of voltaic electricity, we shall only treat of
those of copper, silver, gold, and platinum. When copper is deposited, the
object is generally to produce a substantial copy of a medal, an engraved
plate, or other work of art; but when solutions containing the precious
metals are electrolysed, the deposits are nearly always used for covering
the surface of inferior metals. We shall notice the operations connected
with the deposition of copper, and those relating to electro-plating under
separate heads.