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forces of this system are directed from the
amalgam to the copper solution ; so that P
proceeding from the copper cylinder is the
positive, and N proceeding from the amalgam,
is the negative pole.
The action of this system is said to be constant, like that of

Daniel, so long at least as the vessel vv allows equally free

passage to the two fluids, and the state of saturation of the

copper solution is maintained.

1872. Bagratiori s system. A voltaic
arrangement suggested by the Prince
Bagration, and said to be well adapted
to galvano-plastic purposes, consists of
parallel hollow cylinders,^. 545., of zinc
and copper, immersed in sand contained
in a porcelain vessel. The sand is kept
wet by a solution of hydrochlorate of
ammonia.

1873. BecquereVs system. M. Bee-
Fig. 545. querel has applied the principle of two




284



VOLTAIC ELECTRICITY.



fluids and a single metal, explained in (1856) in the following

manner :

A porcelain vessel v, fig. 546., contains concentrated nitric

acid. A glass cylinder T, to which is attached a bottom of un-
glazed porcelain, is immersed in it. This cy-
linder contains a solution of common salt. Two
plates of platinum are immersed, one in the
nitric acid, and the other in the solution of
salt. The electro-motive forces take effect, the
conduction being maintained through the porous
bottom of the glass vessel T, the positive pole
being that which proceeds from the nitric acid,
and the negative that which proceeds from the
salt.

1874. Schonbein's modification of Bunsen's
battery. M. Schonbein proposes the following
modification of Bunsen's system. In a vessel




Fig. 546.



of cast-iron rendered passive, he places a mixture of three
parts of concentrated nitric with one of sulphuric acid. In
this he immerses the cylindrical vessel of unglazed porcelain
which contains the zinc, immersed in a weak solution of sul-
phuric acid. In this arrangement the cast-iron vessel plays
the part of Bunsen's cylinder of charcoal. The positive pole
is therefore that which proceeds from the cast-iron vessel,
and the negative that which is connected with the zinc.

1875. Grove's gas electro-motive apparatus. We shall con-
clude this synopsis of the simple voltaic combinations with the
gas electro-motive apparatus of Mr. Grove, one
of the most curious and interesting that has been
contrived. Two glass tubes h and o,fig. 547., are
inverted in a vessel containing water slightly
acidulated with sulphuric acid. Hydrogen gas h
is admitted into one of these, and oxygen o into
the other in the usual way. A narrow strip of
platinum passes at the top of each tube through
an aperture which is hermetically closed around
it, the strip descending near to the bottoms
of the tubes. An electro-motive force is de-
veloped between the platinum and the gases,
which is directed from the platinum to the
oxygen, and from the hydrogen to the platinum. The end of




Fig. 547.



VOLTAIC BATTERIES. 285

the platinum which issues from the hydrogen is therefore the
positive, and that which issues from the oxygen the negative,
pole of the system.



CHAP. II.

VOLTAIC BATTERIES.

1876. Volta's invention of the pile. Whatever may be the
efficacy of simple combinations of electrometers compared
one with another, the electricity developed even by the most
energetic among them is still incomparably more feeble than
that which proceeds from other agencies, and indeed so feeble
that without some expedient by which its power can be aug-
mented in a very high ratio, it would possess very little im-
portance as a physical agent. Volta was not slow to perceive
this ; but having also a clear foresight of the importance of the
consequences that must result from it if its energy could be
increased, he devoted all the powers of his invention to discover
an expedient by which this object could be attained, and happily
not without success.

He conceived the idea of uniting together in a connected and
continuous series, a number of simple electro-motive combi-
nations, in such a manner that the positive electricity developed
by each should flow towards one end of the series, and the
negative towards the other end. In this way he proposed to
multiply the power of the extreme elements of the series by
charging them with all the electricity developed by the inter-
mediate elements.

In the first attempt to realize this conception, circular discs
of silver and copper of equal magnitude (silver and copper coin
served the purpose), were laid one over the other, having inter-
posed between them equal discs of cloth or pasteboard soaked
in an acid or saline solution. A pile was thus formed which
was denominated a VOLTAIC PILE ; and although this arrange-
ment was speedily superseded by others found more convenient,
the original name was retained.

Such arrangements are still called VOLTAIC FILES, and



286



VOLTAIC ELECTRICITY.



sometimes VOLTAIC BATTERIES, being related to a simple
voltaic combination in the same manner as a Leyden battery is
to a Leyden jar.

1877. Explanation of the principle of the pile. To explain
the principle of the voltaic battery, let us suppose several
simple voltaic combinations, z^c 1 , z 2 L 2 c 2 , z 3 L 3 c 3 , z 4 L 4 c 4 ,
fig. 548., to be placed, so that the negative poles z shall all




Fig. 548.

look to the left, and the positive C to the right. Let the
metallic plates c be extended, and bent into an arc, so as to be
placed in contact with the plates z. Let the entire series be
supposed to stand upon any insulating support, and let the
negative pole z 1 of the first combination of the series be put in
connection with the ground by a conductor.

If we express by E the quantity of positive electricity de-
veloped by z 1 !, 1 ^, the negative fluid escaping by the con-
ductor, this fluid E will pass to c 1 , and from thence along the
entire series to the extremity c 4 . The combination z 1 !, 1 ^ acts
in this case as the generator of electricity in the same manner
as the cushion and cylinder of an electrical machine, and the
remainder of the series z 2 L 2 c 2 , &c., plays the part of the con-
ductor, receiving the charge of fluid from z^c 1 .

The second combination z 2 L 2 c 2 being similar exactly to the
first, evolves an equal quantity of electricity E, the negative
fluid passing through z 1 L 1 c 1 , and the conductor to the ground.
The positive fluid passes from z 2 L 2 c 2 to the succeeding com-
binations to the end of the series.

In the same manner, each successive combination acts as a
generator of electricity, the negative fluid escaping to the
ground by the preceding combinations and the conductor, and
the positive fluid being diffused over the succeeding part of the
series.

It appears, therefore, that the conductor p connected with the
last combination of the series must receive from each of the
four combinations an equal charge E of positive fluid ; so that
the depth or quantity of electricity upon it will be four times



VOLTAIC BATTERIES. 287

that which it would receive from the single combination
z 4 L 4 c 4 acting alone and unconnected with the remainder of the
series.

In general, therefore, the intensity of the electricity received
by a conductor attached to the last element of the series, will
be as many times greater than that which it would receive
from a single combination as there are combinations in the
series. If the number of combinations composing the series be
n, and E be the intensity of the electricity developed by a
single combination, then n x E will be the intensity of the
electricity produced at the extremity of the series.

It has been here supposed, that the extremity z 1 of the series
is connected by the conductor N with the ground. If it be not
so connected, and if the entire series be insulated, the distribu-
tion of the fluids developed will be different. In that case, the
conductor P will receive the positive fluid propagated from
each of the electro-motive surfaces to the right, and the con-
ductor N will receive the negative fluid propagated from each
of these surfaces to the left, and each will receive as many
times more electricity than it would receive from a single
combination as there are simple combinations in the series.
If, therefore, E' express the quantity of fluid which each con-
ductor p and N would receive from a single combination Z I L I C I ,
then n x E' will be the quantity it would receive from a series
consisting of n simple combinations.

Since two different metals generally enter with a liquid into
each combination, it has been usual to call these voltaic com-
binations PAIRS ; so that a battery is said to consist of so many
PAIRS.

On the Continent these combinations are called ELEMENTS ;
and the voltaic pile is said to consist of so many ELEMENTS,
each element consisting of two metals and the interposing
liquid.

1878. Effect of the imperfect liquid conductors. In what
precedes we have considered that all the electricity developed
by each pair is propagated without resistance or diminution to
the poles P and N of the pile. This, however, could only occur
if the materials composing the pile through which the electri-
city must be transmitted were perfect conductors. Now, although
the metallic parts may be regarded as practically perfect con-



288 VOLTAIC ELECTRICITY.

ductors, the liquid through which the electricity must be trans-
mitted in passing from one metallic element to another is not
only an imperfect conductor, but one whose conducting power
is subject to constant variation. A correction would therefore
be necessary in applying the preceding reasoning, the electri-
city received by the poles P and N being less than n x E', by
that portion which is intercepted or lost in transmission through
the liquid conductors. The amount of the resistance to con-
duction proceeding from the conductors, liquid and metallic,
by which the electricity evolved at the generating surfaces is
transmitted to the poles of the pile, has not been ascertained
with any clearness or certainty.

Professor Ohm, who has investigated the question of the
resistance of the conductors composing a battery to the propa-
gation of the electricity through them, maintains that the in-
tensity of the electricity transmitted to the poles of the pile is
" directly as the sum of the electro-motive forces, and inversely
as the sum of all the impediments to conduction." We do not
find, however, that this law has been so developed and verified
by observation and experiment as to entitle it to a place in
elementary instruction.

1879. Method of developing electricity in great quantity.
If the object be to obtain a great quantity of electricity, the
elements of the pile should be combined by connecting the poles
of the same name with common conductors. Thus, if all the
positive poles be connected by metallic wires with one conductor,
and all the negative poles with another, these conductors will
be charged with as much electricity as would be produced by a
single combination, of which the generating surfaces would be
equal to the sum of the generating surfaces of all the elements
of the series ; but the intensity of the electricity thus de-
veloped would not be greater than that of the electricity de-
veloped by a single pair.

1880. Distinction between quantity and intensity important.
It is of great importance to distinguish between the quantity
and the intensity of the electricity evolved by the pile. The
quantity depends on the magnitude of the sum of all the sur-
faces of the electromoters. The intensity depends on the
number of pairs composing the series. The quantity is mea-
sured merely by the actual quantity of each fluid received at



VOLTAIC BATTERIES.



289



the poles. The intensity is proportional, cteteris paribus, to the
number of pairs transmitting electricity to the same pole, the
fluids being superposed at the poles, and the intensity being
produced by such superposition.

Voltaic piles have been composed and con-
structed in a great variety of forms by com-
bining together the various simple electro-
motive combinations which have been de^
scribed in the last chapter.

1881. Yalta's first pile. The first pile
constructed by Volta was formed as follows :
A disc of zinc was laid upon a plate of glass.
Upon it was laid an equal disc of cloth or
pasteboard soaked in acidulated water. Upon
this was laid an equal disc of copper. Upon
the copper were laid in the same order three
discs of zinc, wet cloth, and copper, and
the same superposition of the same combi-
nations of zinc, cloth, and copper was con-
tinued until the pile was completed. The
highest disc (of copper) was then the positive,
and the lowest disc (of zinc) the negative pole,
according to the principles already explained.

It was usual to keep the discs in their places
by confining them between rods of glass.

Such a pile, with conducting wires con-
nected with its poles, is represented in Jig. 549.
des tasses. The next arrangement




Fig. 549.



1882. The couronne
proposed by Volta formed a step towards the form which the
pile definitively assumed, and is known under the name of




Fig. 550.

the COURONNE DES TASSES (ring of cups) : this is represented
in Jig. 550., and consists of a series of cups or glasses con-

II. O



290



VOLTAIC ELECTRICITY.



taining the acid solution. Rods of zinc and copper zc, soldered
together end to end, are bent into the form of arcs, the ends
being immersed in two adjacent cups, so that the metals may
succeed each other in one uniform order. A plate of zinc, to
which a conducting wire N is attached, is immersed in the first ;
and a similar plate of copper, with a wire P, in the last cup.
The latter wire will be the positive, and the former the negative,
pole.

1883. CruikslianKs arrangement, The next form of vol-
taic pile proposed was that of Cruikshank, represented \\\fig.
551. This consisted of a trough of glazed earthenware divided
into parallel cells corresponding in number and magnitude to
the pairs of zinc and copper plates which were attached to a
bar of wood, and so connected that, when immersed in the cells,
each copper plate should be in connexion with the zinc plate of
the next cell. The plates were easily raised from the trough
when the battery was not in use. The trough contained the
acid solution.

1884. Wollaston's arrangement. In order to obtain within
the same volume a greater extent of electro-motive surface, Dr.
Wollaston doubled the copper plate round the zinc plate, without
however allowing them to touch. In this case the copper plates
have twice the magnitude of the zinc plates. The system, like
the former, is attached to a bar of wood, and being similarly
connected, are either let down into a trough of earthenware




Fig. 551.



Fig. 555



divided into cells, as represented vnfig. 552., or into separate
glass or porcelain vessels, as represented in Jig. 553. The latter



VOLTAIC BATTERIES.



291



method has the advantage of affording greater facility for dis-
charging and renewing the acid solution.




1885. Heliacal pile of Faculty of Sciences at Paris. The
heliacal pile is a voltaic arrangement adapted to produce
electricity of low tension in great quantity.
This pile, as constructed for the Faculty of
Sciences at Paris under the direction of M.
Pouillet, consists of a cylinder of wood b,Jig.
554., of about four inches diameter and fifteen
inches long, on which is rolled spirally two thin
leaves of zinc and copper separated by small
bits of cloth, and pieces of twine extended
parallel to each other, having a thickness a
little less than the cloth. A pair is formed in
this manner, having a surface of sixty square
feet. A single combination of this kind evolves
electricity in large quantity, and a battery
composed of twenty pairs is an agent of pro-
digious power.

The method of immersing the combination
in the acid solution is represented \r\fig. 555.

1886. Piles are formed by connecting to-
gether a number of any of the simple electro-
motive combinations described in the last
chapter, the conditions under which they are
connected being always the same, the positive
pole of each combination being put in me-




Fig. 555.



tallic connexion with the negative pole of the succeeding one.



o 2




292 VOLTAIC ELECTRICITY.

When the combinations are cylindrical, it is convenient to set

them in a framing, which
will prevent the acci-
dental fracture or strain of
the connexions. A bat-
ill ' \A W I/.I ULiil^ tery often pairsof Grove's

r "" ^ [/ or Bunsen sis represented

F; 556 with its proper connex-

ions in fig. 556.

1887. Conductors connecting the elements. Whatever be
the form or construction of the pile, its efficient performance
requires that perfect metallic contact should be made and
maintained between the elements composing it by means of
short and good conductors. Copper wire, or, still better, strips
cut from sheet copper from half an inch to an inch in breadth,
ai-e found the most convenient material for these conductors,
as well as for the conductors which carry the electricity from
the poles of the. pile to the objects to which it is to be con-
veyed. In some cases, these conducting wires or strips are
soldered to metallic plates, which are immersed in the exciting
liquid of the extreme elements of the pile, and which, there-
fore, become its poles. In some cases, small mercurial cups are
soldered to the poles of the pile, in which the points of the con-
ducting wires, being first scraped, cleaned, and amalgamated,
are immersed. Many inconveniences, however, attend the use
of quicksilver, and these cups have lately been very generally
superseded by simple clamps constructed in a variety of
forms, by means of which the conducting wires or strips may
be fixed in metallic contact with the poles of the pile, with each
other, or with any object to which the electricity is required to
be conveyed. Where great precaution is considered necessary
to secure perfect contact, the extremities of the conductors at
the points of connexion are sometimes gilt by the electrotyping
process, which may always be done at a trifling cost. I have
not, however, in any case found this ne-
cessary, having always obtained perfect con-
tact by keeping the surfaces clean, and using
screw clamps of the form in fig. 557. This
is represented in its proper magnitude.

1888. file may be placed at any distance
Fig. 557. from place of experiment It is generally




VOLTAIC BATTERIES. 293

found to be inconvenient in practice to keep the pile in the
room where the experiments are made, the acid vapours being
injurious in various ways, especially where nitric acid is used.
It is therefore more expedient to place it in any situation
where these vapours have easy means of escaping into the
open air, and where metallic objects are not exposed to them.
The situation of the pile may be at any desired distance from
the place where the experiments are made, communication
with it being maintained by strips of sheet copper as above
described, which may be carried along walls or passages, contact
between them being made by doubling them together at the
ends which are joined, and nailing the joints to the wall. They
should of course be kept out of contact with any metallic object
which might divert the electric current from its course. I have
myself a large pile placed in an attic connected by these means
with a lower room in the house, by strips of copper which
measure about fifty yards.

1889. Memorable piles: Davy's pile at the Royal Institu-
tion. Among the apparatus of this class which have obtained
celebrity in the history of physical science, may be mentioned
the pile of 2000 pairs of plates, each having a surface of 32
square inches, at the lloyal Institution, with which Davy
effected the decomposition of the alkalies, and the pile of the
Royal Society of nearly the same magnitude and power.

1890. Napoleon's pile at Polytechnic School. In 1808, the
Emperor Napoleon presented to the Polytechnic School at
Pai'is a pile of 600 pairs of plates, having each a square foot
of surface. It was with this apparatus that several of the
most important researches of Gay Lussac and Thenard were
conducted.

1891. Children's great plate battery. Children's great
plate battery consisted of 16 pairs of plates constructed by
Wollaston's method, each plate measuring 6 feet in length and
2| feet in width, so that the copper surface of each amounted
to 32 square feet ; and when the whole was connected, there
was an effective surface of 512 square feet.

1892. Hare's deflagrator. The pile of Dr. Hare of Phila-
delphia, called a deflagrator, was constructed on the heliacal
principle, and consisted of 80 pairs, each zinc surface measui'-
ing 54 squai'e inches, and each copper 80 square inches.

1893. Stratingfis deflagrator. Stratingh's deflagrator con



294 VOLTAIC ELECTRICITY.

sisted of 100 pairs on Wollaston's method. Each zinc surface
measured 200 square inches. It was used either as a battery of
100 pairs or as a single combination (1879), presenting a total
electromotive surface of 277 square feet of zinc and 544 of
copper.

1894. Pepys' pile at London Institution. Mr. Pepys con-
structed an apparatus for the London Institution, each element
of which consisted of a sheet of copper and one of zinc,
measuring each fifty feet in length and two feet in width.
These were wound round a rod of wood with horsehair be-
tween them. Each bucket contained fifty-five gallons of the
exciting liquid.

1895. Powerful batteries on Daniel and Grove's principles.
These and all similar apparatus, powerful as they have been,
and memorable as the discoveries in physics are to which
several of them have been instrumental, have fallen into
disuse, except in certain cases, where powerful physiological
effects are to be produced; since the invention of the piles of
two liquids, which, with a number of elements not exceeding
forty, and a surface not exceeding 100 square inches each,
evolve a power equal to the most colossal of the apparatus
above described.

The most efficient voltaic apparatus are formed by combining
Daniel's, Grove's, or Bunsen's single batteries, connecting their
opposite poles with strips of copper as already described.
Grove's battery, constructed by Jacobi of St. Petersburg,
consists of 64 platinum plates, each having a surface of 36
square inches; so that their total surface amounts to 16 square
feet. This is considered to be the most powerful voltaic ap-
paratus ever constructed. According to Jacobi's estimate, its
effect is equal to a Daniel's battery of 266 square feet, or to a
Hare's deflagrator of 5500 square feet.

1896. Dry piles. The term DRY PILE was originally in-
tended to express a voltaic pile composed exclusively of solid
elements. The advantages of such an apparatus were so ap-
parent, that attempts at its invention were made at an early
stage in the progress of electrical science. In such a pile,
neither evaporation nor chemical action taking place, the ele-
ments could suffer no change ; and the quantity and intensity
of the electricity evolved would be absolutely uniform and in-
variable, and its action would be perpetual.



VOLTAIC BATTERIES. 295

1897. Deluc's pile. The first instrument of this class con-
structed was tlie dry pile of Deluc, subsequently improved
by Zamboni. This apparatus is prepared by soaking thick
writing-paper in milk, honey, or some analogous animal fluid,
and attaching to its surface by gum a thin leaf of zinc or tin.
The other side of the paper is coated with peroxide of man-
ganese. Leaves of this are superposed, the sides similarly
coated being all presented in the same direction, and circular
discs are cut of an inch diameter by a circular cutter. Several
thousands being laid over one another, are pressed into a close
and compact column by a screw, and the sides of the column
are then thickly coated with gum-lac.

The origin of the electromotive force of the pile is various.
Besides the contact of heterogeneous substances, chemical
action intervenes in several ways. The organic matter acts
upon the zinc as well as upon the manganese, reducing the
latter to a lower state of oxidation.

1898. Zamboni's pile. Piles, having two elements only,
have been constructed by Zamboni. These consist of one
metal and one intermediate conductor, either dry or moist. If
the former, the discs are of silver paper laid with their metal
faces all looking the snrno way ; if the latter, a number of pieces



Online LibraryDionysius LardnerHand-book of natural philosophy and astronomy (Volume 2) → online text (page 29 of 45)