Elementary treatise on electric batteries

Preface

The English translation of Mr. Alfred Mandet's " La File Electrique " scarcely requires my commendation to render it acceptable to the English-speaking community interested in the subject, since the author's name is so well kiown to electricians.

This work will serve to guide the uninitiated in the choice and management of batteries, and even the professional electrician may find not only new matter but even old material presented in a new form, and worked to new developments.

Telegraphers generally will rind many of their frequently recurring problems solved in its pages, and its perspicuity will save both inventor and investigator from making useless experiments or errors, while at the same time the work offers to all new fields for careful research.

Although the subject treated is so useful and interesting, yet this is, I believe, the first time it has received such recognition in English as its importance demands.

The translator was happily fitted for his task, having studied under the direction of the author himself, and with whose sanction he undertook his task.

Xew York, July 23, 1880.

Preface To The English Edition

The work which we here present to the public is in conformity with the second French edition of a book the first edition of which appeared in 1878, and which has been exhausted in less than two years.

]S~o other treatise upon the "Electric Battery" has hitherto been published either in English, French or German. It has appeared desirable to meet this need, and to offer a complete guide to those who wish to thoroughly study or even to improve upon batteries, which are to-day. so extensively applied to different uses.

The order that the author has adopted in his exposition is in some sense obligatory. Single-liquid batteries are the first, historically and logically, to jn'esent themselves. In connection with this first part are naturally placed the exposition of princijiles, definitions of terms, and the study of the phenomenon of polarization, wherein lies the whole difficulty of the subject.

Next in order come two-liquid batteries, in which polarization is suppressed or reduced according to circumstances.

Definitions,

Origin of the Name Pile, First Idea of the Battery, Properties of Amalgamated Zinc, Inconstancy of Simple Batteries, Battery Cells joined in Intensity,

PAGE

1 1 2

CHAPTER II. DESCRIPTION OF VOLTA's

BATTERY AND ITS DERIVATIVES.

Column Battery,

.

Volta's " Couronne de Tasses,"

Cruikshank's Battery,

Wollaston's Battery,

Spiral Battery,

Muncke's Battery,

Sand Battery,

.

Nature of the Chemical Action in Volta's Battery,

Action of Air upon Batteries,

VI CONTENTS.

Chapter III. General Remarks Upon Batteries

PAGE

Ideas upon Electric Resistance, .... 23

General Remarks upon Electro-motivfe Force and Resistance, 24

Electro-motive Force, . . . • . . 26 Measurement of Electro-motive Forces, .. . .31

Internal Resistance of the Battery, . . . 32

Various ways of Joining Voltaic Cells, ... 34

The Voltameter, . . . . . 38

Secondary Currents, Polarized Electrodes, ... 41

Polarization of a Voltaic Cell, .... 42

Polarization in a Battery of several Cells, ... 47

Chapter IV. Sulphuric-acid Batteries

Batteries with Carbon Electrodes, .... 49

Manufacture of Carbon Electrodes, . . . .50

Use of Carbon Electrodes, . . . . . 51

Zinc-Iron Battery, ...... 53

Iron-Copper Battery, ..... 53

Other Combinations, . . . . . .53

"Walker's Platinized Carbon Battery, .... 56

Baron Ebner's Battery, . . . . . .58

Batteries analogous to that of Smee, ... 59

Remarks upon Polarization in the preceding Batteries, . 59

Chapter V. Acid Batteries Analogous To That Op Volta

Hydrochloric-Acid Batteries, ..... 61

Nitric-Acid Batteries, ..... 61

Various Acid Batteries, ..... 62-

COjNTE^TS.

vn

Chapter VI. Batteries Without Acids

Sea-salt Batteries, ....

Duchemin's Electric Buoy, Sea-water, Zinc and Copper Battery, Zinc, Iron, and Sea-water Battery, Accidental Reversing of the Current, Chemical Action in Sea-salt Batteries, Marine Batteries, ....

Sal-Ammoniac Batteries, Bagration Battery, ....

Carbon-Electrode Battery', Action of Air upon the preceding Battery, Chemical Action in Sal-Ammoniac Batteries,

OTHER BATTERIES.

Zinc-Iron- Water Battery, Iron- Tin Battery, ....

Alum Battery, .....

Remarks upon Single-Liquid Batteries,

PAGE

63 64

67 68

70 71 72

79,

PAET SECOND.

Two-Liquid B atteries.

Chapter I

THE DAXIELL. BATTERY.

Introduction, .

Description of the Darnell,

Improved Daniell Cell, . . . .

Balloon Battery, ....

A Reversed form of Darnell's Battery,

Trough Battery, ....

Conventional Furure, .

SI

101 102 104 106

Vlll

CONTENTS.

Muirhead's Battery, .

Carre's Battery,

Siemens and Halske's Batteiy,

VarleyS Battery,

Minotto's Battery,

Trouve's Blotting-Paper Battery,

PAGE

107 108 109 110 111 112

Chapter II. Gravity Batteries

Callaud's Battery, .

Applications of Callaud's Battery, .

Trouve-Callaud Battery,

Meidinger's Battery, ....

Meidinger's Flask Battery, ...

Kruger's Battery, .....

Sir William Thomson's Battery,

Electro-motive Force of the Daniell Gravity Battery,

Chapter III. General Remarks Upon Daniell Batteries

Amalgamation of Zinc m the Darnell, .... 134

Copper-Plating, . . . . . . 135

Irregularity of the Chemical Action in Daniell's Batteries, . 137

CHAPTER IY.

BATTERIES DERIVED FROM THE DANIELL.

Marie Davy's Sulphate-of -Mercury Batte-ry,

"Weakening of the Sulphate-of -Mercury Battery,

Sulphate-of -Mercury Gravity Battery,

Trouve's Reversible Battery,

GainVs Battery, ....

Latimer Clark's Standard Battery,

Sulphate-of -Lead Batteiy,

Weakening of the Sulphate-of-Lead Battery,

Various Salt Batteries,

'ON

TEXT'. IX

Chapter V. Acid Batteries

PAGE

Grove's Battery, . . . . . ■ . 154

Chemical Actions in Grove's Battery, . . . 156

Bunsen's Battery, French Model, .... 158

Bud sen's Battery, German Model, . . 172

Bunsen's Battery, Faure'js Model, . . . .174

Electro-motive Force and Resistance in Nitric- Acid Batteries, 174 Maynooth's Battery, . . . . . 175

Daniell's Experiments upon the Size and Place of the Electrodes, ....... 176

Chloric-Acid Battery, . . . . 177

Chromic-Acid Battery, . . . . .177

Various Acid Batteries, . . . . . 177

Chapter VI. Oxides In Batteries

Peroxide-of-Lead Battery, . . . . 179

Peroxide-of-Manganese Battery, . . . . 180

Leclanche's Battery, ..... 180

Leclanche's Agglomerated Mixture Battery, . . 189

Clark and Muirhead's Modification of the Leclanche, . 193 Electro-motive Force, Polarization, .... 194

Chemical Action, . . . . . . 194

"Weakening of the Leclanche Battery, . . . 196

Practical Durability of the Leclanche Battery, . . 197

Chapter VII. Chloride Batteries

Chloride-of -Platinum Battery, .... 200

Chloride-of-Silver Battery, .... 201

Gaiffe's Battery, ...... 206

Chloride-of-Lead Battery, ..... 208

Perchloride-of-Iron Battery, .* . . . .208

X CONTENTS.

Chapter VIII. Depolarizing-mixture Batteries

PAGE

Potassium- Chlorate and Sulphuric- Acid Batteries,

Bichromate of-Potassium and Sulphuric-Acid Batteries .

Chemical Action in the Bichromate Battery,

Application to the Telegraph, ....

Gaugain's Experiments, . .

Use in England, ......

Fuller's Battery, .....

Military Batteries, ......

Grenet's Bottle Battery, ....

Trouve's Battery, . .

Byrne's Pneumatic Battery, ....

Agitation of the Liquid, .....

Camacho's Battery, .....

Delaurier's Battery, .....

PAKT THIKD.

Various Batteries.

Dry Piles,

Identical Electrode Batteries,

Unattacked Electrodes in Batteries,

Becquerel's Oxygen-Gas Battery,

Coke-Consuming Battery,

Gas Batteries,

Secondary Batteries,

235 237

238 239 240

242 243

TABLES.

Electric Conductivity of Solids, Specific Resistances, Conductibility of Liquids,

253 254 255

CONTENTS. XI

PAGE

Resistances of Liquids, ..... 256

Dilute Sulphuric Acid, . . . . . .257

Resistance to Different Liquids, .... 258

Electro-motive Forces, ..... 259

Remarks upon the preceding tables, .... 264

Chapter I. Introduction

A battery, or pile as it is sometimes called, is an apparatus arranged to furnish a continued flow of electricity, to which the name of "electric current" is given.

If one should wish to make a complete enumeration, it would be necessary to note :

1. Hydro-electric batteries, to the study of which the present work is devoted ;

2. Thermo-electric batteries, which have as yet received but few applications.

It may be well to state, however, that batteries are not the only apparatus able to produce currents ; certain machines produce effects exactly similar.

OKIGIN OF THE NAME OF' PILE.

The word pile, though not as frequently used as the word battery, is, however, more correct.

The invention of electric piles is due to Volta, Profes-

SINGLE LIQUID BATTERIES.

sor of Natural Philosophy at Parvia, and dates from the year 1800.

One of the first that he constructed was composed of a certain number of discs made of zinc, copper, and cloth piled one upon another. In all courses of natural philosophy models of Volta's pile are shown, and

Fig. 1.

Fig. 1 shows the appearance of the instrument called the column-pile, which has to-day but an historical interest ; it is a pile of discs. *

FIRST IDEA OF THE PILE,

OK BATTEEY, AS WE SHALL HEREAFTER CALL IT.

If you immerse a thin plate of commercial zinc into

* This figure is a fac-simile of the first cut published of the battery. The original cut is to be found in the "Philosophical Transactions" for 1800.

dilute sulphuric acid, a very lively action takes place ; the zinc dissolves, and a considerable quantity of hydrogen is given off. It is indeed this process which is generally employed in the preparation of hydrogen gas.

But if, instead of ordinary zinc, which contains impurities, zinc rendered perfectly pure by distillation be employed, the action takes place very slowly, the bubbles of hydrogen remain attached to the plate of zinc and protect it from further action of the acid.

If a thin plate of platinum, or a platinum wire, be now placed in the same, as soon as the two metals touch at one point the action becomes extremely energetic ; the zinc dissolves and hydrogen is given off, but from the platinum and no longer from the zinc.

As soon as the contact of the two metals ceases, all action upon the zinc and all giving off of hydrogen are susj:>ended.

This important experiment, due to De La Rive, throws a great deal of light upon all that follows. It is equally successful when you substitute for the platinum silver, copper, or even iron ; it gives the same result when the metals have their point of contact either in the liquid or out of it.

It permits us to explain the difference in the action of the sulphuric acid upon pure zinc and injure zinc ; the heterogeneous particles (of iron or of other metals) found at the surface of commercial zinc play the same part as the platinum. You will observe, in effect, that the hydrogen is only given off within very limited points, and at the end of a certain time the surface becomes rough, which shows that the attack has been more active at some points than at others.

Let us resume the fundamental experiment of De La Rive.

Suppose the two metals to have their point of contact not in the liquid but out of it, as Fig. 2 represents. The chemical action takes j^lace in the liquid, as stated above.

It also takes place if, instead of bringing the two plates of metal into direct contact, you put one upon the upper part of the tongue and the other upon the under part.

You will experience a slight sensation like that of a feeble electric shock, and also a peculiar taste.

If you place upon the dry part of the zinc a strip of paper dipped in iodide of potassium, and then touch this dampened paper with the platinum, a blue spot is immediately produced, which shows that the iodide has been decomposed and iodine set free.

These experiments can also be made if you attach to the zinc and platinum two wires (indeed very long ones may be used), and operate with the two loose ends. If you place one of these in the neighborhood of a freely suspended magnetic needle, you will notice that the needle deviates slightly from its north-south direction as soon as the contact is established between the two loose ends of the wires.

These different observations prove that a singular phenomenon takes place in the two wires, which is the cause of various actions, physiological (upon the tongue), chemical (upon the iodide of potassium), magnetic (upon the needle).

The analogy of these phenomena with those which electric machines with circular glass plates produce, and which were known long before, is easy to comprehend. It is said that an electric current runs over the wire, and one can see from its effects that it is continual.

The two metal plates immersed in the liquid (Fig. 3)

Fig. 3.

are called electrodes ; the wires, long or short, attached to electrodes, and which permit the transference to a distance of the effects produced by the battery, are called rheqphores.

The rfieophores are generally short, and often end in a longer wire, c ccc, to which the name of conductor is given.

The name circuit of the current is applied to the whole, formed by the battery, the rheophores, and the solid or liquid conductor through which the current passes. In the experiments mentioned above, the tongue and the paper dipped in iodide of potassium formed part of the circuit.

Every apparatus which produces a current is indeed a battery. However, the simple apparatus mentioned above (Fig. 3) is, to be more exact, a cell, or an element, of a battery, and a number of these cells grouped together is properly a battery.

It is said that the circuit- is open when at any point whatever the conductor be disconnected ; all the effects of the current then cease and the current does not circulate. The current is closed when the two parts of the conductor, which were separated, are brought into contact with each other and the current commences to flow.

It is said that a battery is in short circuit when the conductor connecting its poles has a null resistance ; that is, when it is very short. We will frequently have occasion to use this expression in the course of the present work.

It has thus come to be said that, in the conductor, the current flows from the positive pole of the battery (-[-plate of copper) to the negative pole (-plate of zinc) ; a transference of a peculiar fluid from one to the other of these points is thus implicitly admitted. Let us say, in passing, that this way of looking at things, after having been abandoned in science, shows a tendency towards reacceptance with a few changes, so that the conventional Ianguage, which had not been changed, finds itself again in accordance with the theoretical ideas admitted.

The cell formed of the electrodes of zinc and copper immersed in sulphuric acid is more particularly known under the name of Yolta ; by changing the nature of the liquid and the electrodes, you can obtain an indefinite number of cells which produce the same kind of energy.

PEOPEKTIES OF AMALGAMATED ZINC.

We have shown, in that which precedes, how differently the pure zinc and the ordinary commercial zinc act in the voltaic cells.

The result is that when pure zinc is employed there is no local current at its surface, and that the electricity which is produced passes entirely into the circuit between the poles, and also that the hydrogen is given off from the copper.

If, on the other hand, impure or commercial zinc be employed, the giving off of hydrogen takes place, for the most part, upon its surf ace ; there is reason to conclude, from this, that a very large proportion of the chemical action is lost for the production of the electric current.

Thus, in the construction of batteries, the use of pure zinc presents very important advantages ; but the price of this material is almost fabulous, and it can almost be called a curiosity of the laboratory.

Happily, a very simple artifice has been discovered, by which the properties of pure zinc may be given to commercial zinc. It suffices to amalgamate it — that is, to spread mercury over its surface in such a manner as to form a layer of amalgam of zinc. This amalgam is an alloy, or, in other words, a combination of zinc and mercury.

The experiment shows that the amalgamated zinc immersed in sulphuric acid diluted with water, is scarcely attacked, and if it be employed as the positive electrode of a voltaic cell, it occasions no local actions ; the giving off of hydrogen takes place entirely upon the negative electrode, of copper or platinum.

In short, amalgamated zinc presents, for use in batteries, the same advantages as the chemically pure zinc, and with a few exceptions zinc should always be amalgamated.

INCONSTANCY OF SIMPLE EATTEEIES.

All the cells of which we have spoken, formed of two electrodes immersed in a liquid, present an immense drawback ; namely, their action decreases very rapidly from the beginning of the action.

The causes of this decrease are twofold, which we will analyze summarily here.

The first is the loss of acid from the dilution. It can be easily understood that water acidulated in the proportion of 1 to 100 will act less energetically than water acidulated in the proportion of 1 to 10. This cause of the weakening of the battery is not felt until the expiration of a certain time, and it is easily avoided by adding, from time to time, acid to the dilution.

The second is the deposit of hydrogen upon the copper. If the current be interrupted during a length of time sufficient for the freeing of the hydrogen, it will be seen, as soon as the current is again closed, that the intensity assumes its original worth ; it suffices indeed to agitate the plate of copper in order to cause the gas to free itself and to give to the current its initial intensity.

Constant batteries are those in which this second cause of weakening, called polarization of the electrode, is removed. The presence of the hydrogen upon the electrode opposes a double resistance to the passage of the current, a passive resistance and an active resistance; it is the latter that is properly called polarization of the electrode. To depolarize the electrode, is to provide against these resistances by suppressing the freeing of hydrogen.

It is very important to comprehend perfectly everything pertaining to this question ; therein lies the whole difficulty concerning the improvement and perfecting of batteries. We will return to it in the course of our exposition.

Various reasons have combined to designate the positive electrode as that one which represents the negative pole of the cell (zinc, in Yolta's battery), and negative electrode as that one which represents the positive pole (copper or platinum, in the cells which have occupied us up to the present).

One of these reasons has been indicated above, which is that the current enters the liquid of the battery by the negative pole, and goes out by the positive ; in other words, the positive electrode is that by which the electricity enters the cell.

However excellent may be this reason and those which we will give further on for the choice of these denominations, it is not to be denied that they are difficult to employ. In reality, this difficulty may be avoided by speaking of the positive pole and negative pole, when you want to designate the corresponding electrodes ; that is what the majority of practical men do. But if you wish to employ absolutely correct and scientific terms, take great care not to apply them wrongly, as you will only arrive at confusion by an awkward research for precision in the language.

We find in the excellent book, " Darnell's Introduction to Chemical Philosophy," another denomination which ought to be employed more frequently than it is, because it presents the expression of a fact and does not depend upon theoretical ideas, which are always open to discussion.

He calls the generating electrode that one which plays a part in the chemical action ; it is the zinc in the cell that we have considered.

He calls the conducting electrode that one which is not attacked, and which serves, however, to complete the cell.

The first can also be called soluble electrode.

BATTERY CELLS JOINED IN INTENSITY.

We have described above the most simple cell that can be prepared, composed of two electrodes of copper and zinc immersed in acidulated water.

The cell of Yolta's column-battery does not differ essentially from this one ; it is composed of two discs, one of copper and the other of zinc, separated by a circular piece of cloth saturated with acidulated water.

Two " rheophores," or copper wires, are soldered to these two discs and conduct the current to apparatus upon which it is to act.

But as we have summarily indicated from the commencement, Yolta placed upon this first group of three discs (zinc, wet cloth, copper) a second group entirely identical and disposed in the same order ; then a third, a fourth, and so on.

These discs, in various quantities, the one at the top being of copper and the one at the bottom of zinc, constitute the battery of Volta.

Volta discovered, by delicate means, that the force of the current increased as the number of cells was augmented, and made one of the most brilliant inventions of modern times.

He thus showed that it was possible to add one source of electricity to another and to a third in such a manner as to obtain a multiple source of an indefinitely increasing power.

Although three quarters of a century have passed since this discovery, it is not certain whether all of its resources have been exhausted, and it is probable that unlooked-for consequences may yet be brought to light.

It is remarkable that he made at the same time an invention and a discovery ; he invented an apparatus, a machine, an implement, which has received and will receive many applications : at the same time he discovered one of the most fruitful principles of physics, to which he opened a new road.

If you should wish to show the increase of force of a battery with the number of cells or groups of three discs, the most simple means consists in causing the current to act upon a galvanometer or detector. The deflection of the galvanometric needle would be seen to increase in proportion to the number of cells ; that is indeed a fundamental truth, verified by experiments at every moment.

The copper electrode of the cell of Yolta (Fig. 3) is the positive pole, the zinc electrode is the negative pole of the cell.

When the cells are piled up or joined in intensity as in Volta's battery, the positive pole of the battery is that of the last cell, and the negative pole is that of the first cell.

In order to give an exact definition of the positive pole of a battery, or of a cell of a battery, it is necessary to say that it is that one whence the current starts circulating in the exterior conductor, and that the negative pole is that one towards which this same current flows, as shown by the arrows, Fig. 3.

To be complete, it must be added how the direction of the current may be recognized. The wire through which the current flows being placed directly over a freely suspended magnetized needle, causes the north pole of the needle to deflect towards the west, when the current flows from south to north.

These preliminaries being established, we may enter upon the description of the principal arrangements of Volta's Battery.

Chapter II. The Voltaic Battery And Its Derivatives

COLUMN BATTERY.

We have described this battery in the preceding pages. We add that it may be vastly improved upon by soldering the disc of copper of each cell to the disc of zinc of the following cell ; all faulty contacts of the metal plates are thus avoided.

The discs of cloth should be smaller than the metal discs. It is noticed, however, after a short time that the weight of this column squeezes out the liquid from the cloth; this liquid runs out over the edges of the discs and soon disappears, so that the battery rapidly weakens, and after a certain time produces no effect whatever.

YOLTA'S " COURONNE DE TASSES."

It is generally admitted that the column battery was the first one that Yolta arranged. This is, however, not correct ; the " couronne de tasses" was the first ; and according to us is much preferable. A series of glasses or cups were placed in a circle, forming a kind of a crown ; plates of copper and zinc were so arranged that, being connected at the top, the plate of zinc was placed in one cup and the plate of copper in the next.

This battery is truly the model of all those existing

SINGLE-LIQUID BATTERIES.

to-day, and will be our model for reference in the description of others.

It is interesting to note that Volta did not think of the column-battery until afterwards, and then it was with a view to produce an instrument that might be easily transported into hospitals for medical purposes.

Fig. 4.

CKUIKSHAlSrK'S BATTEKY.

Tin's battery is composed of a wooden trough, internally coated with marine glue and divided into cells separated by metallic partitions ; these partitions are composed of two thin plates, one of zinc and the other of copper, soldered together. They are arranged in such a manner as to have all the plates of zinc on the same side and all the plates of copper on the other. The cells thus disposed in the wooden trough are nearly filled with acidulated water, and if they are water-tight the battery thus constructed is very satisfactory.

It is not necessary to enumerate the inconveniences of Cruikshank's battery, which is no longer in use ; we would only point out the impossibility of changing the plates of zinc when they have been partially destroyed by the action of the acid.

THE VOLTAIC BATTERY AND ITS DERIVATIVES. 15

WOLLASTON'S BATTERY.

The difficulty mentioned above is not to be found in the battery combined by Wollaston.

The pairs of metallic plates (zinc and copper) are attached to a cross-bar of wood, which allows them to be

Fig. 5.

lifted out or immersed all at the same time in the glass vessels.

This arrangement is excellent, and is still employed very frequently.

Wollaston made another change in the combinations adopted before his time : he placed the plate of zinc in the centre and surrounded it with a thin sheet of copper, thus giving to the negative element a surface double that of the zinc. The reasons of this disposition are several, upon which we will remark :

1. When two plates are immersed in a liquid, the

SINGLE-LIQUID BATTERIES.

two sides facing each other alone combine in producing the current ; the other sides could be covered with an insulating coating without notably diminishing the current. In "Wollaston's disposition, the two sides of the zinc become active.

To this it might be opposed that an inverse disposition would present the same advantages, and that a plate of copper might be placed between the two plates of zinc

Fig. 5

Fig. 5 so as to make use of the two sides of the copper and only the half of the surface of the zinc. But as the zinc is subject to local action or waste, its size should be reduced to just that amount which is requisite to maintain the current required. There is, on the other hand, no disadvantage whatever in increasing the immerged surface of the copper, as this metal is not attacked by the dilute sulphuric acid.

There is, we repeat, an advantage in reducing the surface of the zinc as much as possible ; for when the battery is not in use and the electrodes, however, remain immerged in the liquid, the attack upon the zinc continues, although

THE VOLTAIC BATTEKY AKD ITS DEEIVATIVES. 17

with less intensity, and this dissolving of tn%zinc is pure loss. As this waste is evidently in proportion to the immerged surface, it is best to have the least possible surface of zinc ; or better, to have no part of that surface which may be useless for the producing of the current.

2. "We have stated above that hydrogen is given off from the positive electrode, and that this polarization of the electrode was a cause of weakening of the current of the battery.

If the hydrogen would free itself as it is generated, the production of the electricity would not be perceptibly diminished ; but it does not free itself — that is, not wholly — and what remains, tends to reduce considerably the intensity of the current. It is evident that the smaller the surface the more rapidly a certain quantity of hydrogen, being produced upon the positive electrode, will act ; in other words, the larger the surface to be polarized, the more slowly the effect of the polarization will be felt.

This is the second reason given for the disposition of Wollaston, in which the surface of the zinc is entirely surrounded by the surface of the copper. We will return to this subject farther on, in speaking of the action of the air upon batteries.

SPIRAL BATTEKY.

The two electrodes of this battery are rolled parallel to each other in the form of a helix, and separated by a tissue of osier ; in the centre is a wooden handle to which the whole apparatus is attached, and by which it may be lifted. It is immersed in a bucket of acidulated liquid and thus you have electrodes with very large surfaces

SINGLE-LIQUID BATTERIES.

separated by a very short distance ; the interior resistance of the battery is consequently ranch reduced, and the quantity of electricity produced very considerable.

This battery presents some of the advantages of that of Wollaston, inasmuch as both surfaces of the zinc are

Fig. 6.

used ; on the other hand, both surfaces of the copper are also used.

Cells of this description may be joined in intensity as those of an ordinary battery ; but they were more frequently nsed separately.

The spiral battery has indeed been entirely abandoned since the inventions of Grove, and Bunsen of Poggendorff (with bichromate of potash).