OS- 
 
 
 
 LIBRARY 
 
 UN 
 
 IVERSITY OF CALIFORNIA. 
 
 Received^ NOV 18 1891 , 18 
 Accessions No.^-^^^^ Shelf No:.. 
 
 -8*3 
 
THE 
 
 CHEMISTRY OF THE SECONDARY BATTERIES 
 OF PLANTS AND FAURE, 
 
NATURE SERIES. 
 
 THE CHEMISTRY 
 
 SECONDARY BATTERIES 
 
 OF 
 
 PLANTE AND FAURE. 
 
 BY 
 
 J. H. GLADSTONE, PH.D., F.R.S., 
 
 M 
 
 AND 
 
 ALFRED TRIBE, F. INST. C, 
 
 LECTURER ON CHEMISTRY IN DULWICH COLLEGE. 
 
 MACMILLAN AND CO. 
 1883. 
 
 The. Right of Translation and Reprod^lct^Qn is Reserved. 
 
LONDON : 
 
 R. CLAY, SONS, AND TAYLOR, 
 
 BREAD STREET HILL. 
 
CONTENTS. 
 
 PAGE 
 
 INTRODUCTION vii 
 
 PART I. 
 LOCAL ACTION ......... 
 
 PART II. 
 
 THE CHARGING OF THE CELL . ............ 10 
 
 PART III. 
 
 THE DISCHARGE OF THE CELL ............. 2$ 
 
 PART IV. 
 
 THE FUNCTION OF SULPHATE OF LEAD ........ 36 
 
 PART V. 
 
 1. INFLUENCE OF STRENGTH OF ACID ......... 44 
 
 2. FUNCTION OF HYDROGEN .............. 47 
 
 3. EVOLUTION OF OXYGEN FROM THE PEROXIDE PLATE . 49 
 
 4. TEMPERATURE AND LOCAL ACTION ......... 51 
 
 APPENDIX ................. 53 
 
INTRODUCTION. 
 
 EIGHTY years ago Ritter constructed a second- 
 ary pile, and obtained from it a reversed current 
 of short duration. Since that time many eminent 
 scientific men have investigated the subject of 
 voltaic polarisation, but it was the invention of 
 the powerful cells of Plante, and the perception 
 of how valuable an addition to the resources of 
 electrical engineers a good secondary battery 
 would be, that raised the subject to one of 
 practical importance. 
 
 In the autumn of 1881, when many scientific 
 men of ability were investigating the physical 
 questions connected with the battery of Plante, 
 
INTRODUCTION, 
 
 or the modifications of it introduced by Faure 
 and others, the chemical questions remained un- 
 attacked ; while at the same time various diffi- 
 culties arose in regard to its introduction into 
 general use. It seemed to us, however, that a 
 knowledge of the chemical reactions lay at the 
 very foundation of the whole subject, and afforded 
 the best hope of resolving some of these practical 
 difficulties. Our former experience on copper- 
 zinc and other couples enabled us to perceive 
 that in the coating of lead peroxide in contact 
 with metallic lead, and surrounded by dilute 
 sulphuric acid, we had the elements of a very 
 powerful local action. Our observations on this 
 point, and on the formation of sulphate of lead, 
 the existence of which seems not to have been 
 recognised previously, were published in Nature 
 on January 5th, 1882. That communication 
 was followed by four others on March i6th, 
 July 1 3th, October igth, 1882, and April iQth, 
 1883, respectively. These are reprinted in the 
 
INTRODUCTION. 
 
 present volume with such slight verbal changes 
 as seemed necessary, and the addition of a few 
 notes in further explanation of the experiments. 
 
 It may not be entirely out of place to refer to 
 a popular misapprehension as to the nature of 
 these batteries. It is somewhat unfortunate that 
 they have been called "accumulators" or " storage 
 batteries." There is a sense, no doubt, in which 
 these names are applicable, but they seem to 
 have conveyed the idea to some minds that any 
 quantity of electric energy might be stored up 
 in the leaden elements ; whereas it is limited by 
 the amount of chemical work which can be done 
 on one or both plates. The name " secondary" 
 also seems to have exaggerated in popular appre- 
 hension the difference between these and other 
 voltaic arrangements. They are secondary in so 
 far as they have been made by means of another 
 voltaic arrangement or electric current ; but when 
 they are " formed " or " charged " they act in 
 precisely the same manner as any other voltaic 
 
 b 
 
INTRODUCTION. 
 
 battery ; that is to say, their action is entirely 
 conditioned by the chemical change that takes 
 place between the binary liquid and one or both 
 of the solid elements when these are brought into 
 contact. When these chemical changes have come 
 to an end the arrangement is no longer a battery, 
 although it is capable of being made one again 
 by an electrical current. 
 
 In looking over the very elaborate work of 
 M. Gaston Plante, Recherches sur lElectricite, 
 we have been struck by the careful and minute 
 observations of that philosopher. While he has 
 not attempted to explain the chemical problems 
 presented by his battery, he has noticed " the 
 formation of a local couple between the oxidated 
 surface and the subjacent metal." He has also 
 observed that a gas is sometimes given off after 
 the breaking of the primary current, or at first 
 closing of the secondary current. He also remarked 
 the fact, which is at first a very puzzling one, that 
 " a secondary couple once discharged may yield 
 
INTRODUCTION. xi 
 
 after a certain time, without being re-charged, 
 residual charges analogous to those given by Leyden 
 jars." He also remarked that when a secondary 
 couple is discharged immediately after its removal 
 from the primary circuit, there is observed, during 
 the first few moments, a much higher electro- 
 motive force than that which is recognised as the 
 normal force of the couple, and which he attributes 
 to the existence of such products as peroxide 
 of hydrogen. We believe that our inquiries 
 have thrown light upon the nature of all these 
 observations of Plante. 
 
 In conclusion we wish it to be borne in 
 mind that our joint work has been of a purely 
 scientific character, though we have not hesitated 
 now and then to draw some conclusions that might 
 bear on the best way of preparing or utilising 
 a secondary battery. 
 
THE 
 
 CHEMISTRY OF THE SECONDARY BATTERIES 
 OF PLANTE AND FAURE. 
 
 PART I. 
 
 LOCAL ACTION. 
 
 AMONG the important discoveries of late years 
 few have claimed so much attention, or have 
 been so full of promise for practical use, as the 
 accumulator of Plante" and its modifications. 
 Our attention was very naturally directed to 
 the chemical changes that take place in these 
 batteries, especially as it appeared to us that 
 there must be certain analogies between them 
 and some actions which we had previously in- 
 vestigated. We propose in the first place to 
 treat merely of local action. 
 
 B 
 
THE CHEMISTRY OF THE SECONDARY 
 
 It is well known that metallic zinc will not 
 decompose water, even at 100 C, but we had 
 found that zinc, on which copper had been de- 
 posited in a spongy condition, was capable of 
 splitting up the molecule even at the ordinary 
 temperature, oxide of zinc being formed and 
 hydrogen liberated. If placed in dilute sulphuric 
 acid, it started a very violent chemical action, 
 sulphate of zinc and hydrogen gas being the 
 result. We termed the two metals thus conjoined, 
 the copper-zinc couple, and this agent was fruit- 
 ful in our hands in bringing about other chemical 
 changes which neither metal singly could effect. 
 Electricians will readily understand the nature 
 of this agent, and will recognise in its effects 
 only an exaggerated form of what we are all 
 familiar with under the name of local action. 
 Now the negative plate of a Plante secondary 
 battery is a sheet of lead, upon which finely- 
 divided peroxide of lead is distributed. It is 
 well known that the electromotive force of lead 
 and lead peroxide in dilute sulphuric acid is 
 nearly three times that of zinc and copper in 
 
BATTERIES OF PLANTE AND FAURE. 3 
 
 the same liquid. We were therefore induced to 
 think that the plate must act in the same way 
 as our copper-zinc couple. We found such to be 
 the case. If a plate so prepared be immersed 
 in pure water, the decomposition of the liquid 
 manifests itself by the reduction of the puce- 
 coloured peroxide to the yellow monoxide. There 
 could be little doubt, therefore, that the lead 
 peroxide couple, if we may call it so, would de- 
 compose sulphuric acid, with the production of 
 sulphate of lead. This also was found to be 
 the case. 
 
 As the destruction of peroxide of lead means 
 so much diminution of the amount of electric 
 energy, it became interesting to obtain some 
 definite knowledge as to the rapidity or extent 
 of this action. 
 
 When the peroxide of lead on the metal is 
 very small in quantity, its transformation into 
 the white sulphate goes on perceptibly to the 
 eye, but when the coating is thicker, the time 
 required is, as might be expected, too long for 
 this kind of observation. In one experiment, 
 
 B 2 
 
4 THE CHEMISTRY OF THE SECONDARY 
 
 following the procedure of Plante, we formed 
 the peroxide on the plate by a series of seven- 
 teen charges and discharges, or reversals, each 
 operation lasting twenty minutes, and the time 
 was further broken up by seven periods of repose, 
 averaging about twenty-four hours in length. 
 After the last charge we watched the local 
 action taking place, and found that the whole 
 of the peroxide passed into white sulphate within 
 seventeen hours. In another experiment the two 
 plates formed according to Plante's method were 
 immediately joined up with the galvanometer, and 
 the deflection noted. They were then at once 
 disconnected. After the repose of one hour they 
 were joined up again, and another observation 
 taken with the galvanometer. This was repeated 
 several times, with the following percentage 
 results : 
 
 Initial strength of current ... ... ... loo 
 
 After i hour's repose.., ... ... ... 97 
 
 , 2 40 
 
 ,,4 M . 14 
 
 I7 i'5 
 
 It results from this that during each of the 
 
BATTERIES OF PLANTE AND FAURE. 5 
 
 long periods of repose recommended by Plante 
 the peroxide on the lead plate is wholly, or almost 
 wholly, destroyed by local action, with the forma- 
 tion of a proportionate amount of sulphate. But 
 this is not, as it would seem at first sight, a 
 useless procedure ; for in the next stage, when 
 the current is reversed, the sulphate is reduced 
 by electrolytic hydrogen, and, by a process which 
 we explain when discussing the complete history 
 of the reaction, the amount of finely-divided 
 lead capable of being peroxidised is increased. 
 That this is actually the case is shown by the 
 following experiment. The peroxide formed on 
 a lead plate by first charging was determined 1 
 and called unity ; it was allowed to remain in 
 a state of repose for eighteen hours, then exposed 
 to the reverse current till completely reduced, 
 
 1 This determination could not, of course, be made by direct 
 analysis without destroying the plate ; but was made from the 
 amount of oxygen which was actually fixed by the lead. This was 
 arrived at by placing a voltameter in the circuit, and thus ascertain 
 ing how much oxygen was liberated by the electrolytic action. The 
 amount of oxygen not fixed by the metal was also measured, and the 
 difference between the two gave the amount which went towards 
 making the peroxide. 
 
6 THE CHEMISTRY OF THE SECONDARY 
 
 charged a second time, the peroxide again calcu- 
 lated, and so on : 
 
 Separate periods of repose. Charge. Amount of peroxide. 
 
 ... First ... ... i'o 
 
 1 8 hours Second 1*57 
 
 2 days Third 171 
 
 4 ., Fourth 2*14 
 
 2 Fifth 2-43 
 
 Similar experiments were made with plates 
 prepared according to the method of Faure. 
 The peroxide was formed by reducing a layer 
 of red lead (containing 51 grains to one square 
 inch of metallic surface), and subsequently com- 
 pletely peroxidising the spongy metal so pro- 
 duced. In one series of experiments we left 
 eight peroxidised plates to themselves for various 
 periods and determined the amount of sulphate 
 formed. This gave us the amount of peroxide 
 consumed, as follows: 
 
 Plate I. after 2 hours 7 '2 per cent. 
 
 II. 3 iS'i 
 
 III. 4 I9'8 
 
 IV. ,, 5 ,, 30-0 
 
 V. ,, 2 4 36-3 M 
 
 VI. 7 days 5 8' 3 
 VII. ii 67-3 
 ,, VJII. ,, 12 74-3 
 
BATTERIES OF PLANT& AND FAURE. 7 
 
 The experiment with the last plate was tested 
 with the galvanometer during its continuance, 
 as in the case of the plate formed by Plante's 
 method, with the following percentage results : 
 
 Initial strength of current ... ... IOO 
 
 After i day's repose ; \*. . .. ... ... 92 
 
 3 79 
 
 4 34 
 
 5 24 
 
 ',! 9 ',', " 8 
 
 12 ,, ,, I 
 
 It is evident from these observations that a 
 lead-peroxide plate gradually loses its energy by 
 local action. The rate naturally varies according 
 to the circumstances of its preparation. 
 
 Two difficulties will probably present them- 
 selves to any one on first grasping the idea of 
 this local action : I. Why should a lead plate 
 covered with the peroxide and immersed in dilute 
 sulphuric acid, run down so slowly that it requires 
 many hours or even days before its energy is so 
 seriously reduced as to impair its value for prac- 
 tical purposes? In the case of the copper-zinc 
 couple immersed in the same acid, though the 
 
8 THE CHEMISTRY OF THE' SECONDARY 
 
 difference of potential is not so great, a similar 
 amount of chemical change would take place in 
 a few minutes. 2. In a Plante or Faure battery 
 the mass of peroxide which is in contact with 
 the metallic lead plate expends its energy slowly. 
 How comes it to pass that if the same mass of 
 peroxide be brought into connection through the 
 first lead plate with another lead plate at a dis- 
 tance, it expends its energy through the greater 
 length of sulphuric acid in a tenth or a hundredth 
 part of the time ? 
 
 The answer to these two questions is doubtless 
 to be found in the formation of the insoluble sul- 
 phate of lead, which clogs up the interstices of the 
 peroxide, and after a while forms an almost im- 
 permeable coating of high resistance between it 
 and the first metallic plate. 
 
 The following conclusions seem warranted by 
 the above observations : 
 
 In the Plante" or Faure battery local action 
 necessarily takes place on the negative plate, 
 with the production of sulphate of lead. 
 
 The formation of this sulphate of lead is 
 
BATTERIES OF PLANTE AND FAURE. 9 
 
 absolutely requisite in order that the charge should 
 be retained for a sufficient time to be practically 
 available. 
 
 The rapidity of loss during repose will depend 
 upon the closeness of the sulphate of lead and 
 perhaps upon other mechanical conditions. These 
 are doubtless susceptible of great modifications. 
 We do not know how far they are modified in 
 practice, but it is conceivable that still greater 
 improvements may yet be made in this direction. 
 
PART II. 
 
 THE CHARGING OF THE CELL. 
 
 THE procedure of Plante* in forming his battery 
 is at first sight extremely simple. He takes two 
 coils of lead, separated from one another, and 
 immersed in dilute sulphuric acid ; a current is 
 sent through the liquid from one lead plate to 
 the other, and the final result is that the one 
 becomes covered with a coating of lead peroxide, 
 while hydrogen is given off against the other 
 plate. On the view that sulphuric acid merely 
 serves to diminish the resistance, and so facilitate 
 the electrolysis of water, the ready explanation 
 would be given that the two elements of the 
 water are simply separated at the two poles. 
 But it seems more in accordance with the facts 
 of electrolysis to suppose that the sulphuric acid, 
 
BATTERIES OF PLANTE AND FAURE. 11 
 
 H 2 SO 4 , is itself the electrolyte, and that the 
 oxygen results from a secondary chemical reaction. 
 As a matter of fact, if water be employed, no 
 peroxide is formed, but only the hydrated protox- 
 ide, even though a current from twenty-four 
 Grove's cells be made use of. The addition of 
 a single drop of sulphuric acid to the water is 
 enough to cause the immediate production of the 
 puce-coloured oxide. 
 
 If we take two plates of lead in dilute sul- 
 phuric acid, and pass the current from only one 
 Grove's cell, a film of white sulphate, instead of 
 peroxide, makes its appearance on the positive 
 pole, and the action practically ceases very soon. 
 If, however, the current be increased in strength, 
 the sulphate disappears, and peroxide is found 
 in its place. In Plante's procedure, spongy lead 
 and lead peroxide are indeed found on the re- 
 spective plates. But, in consequence of the local 
 action which takes place during the periods of 
 repose, lead sulphate will be produced from the 
 peroxide, and afterwards, in the course of the 
 "formation/' when the current is reversed, this 
 
12 THE CHEMISTRY OF THE SECONDARY 
 
 sulphate must be reduced to metallic lead by the 
 hydrogen. 
 
 It may seem at first sight improbable that an 
 almost insoluble salt of the character of lead 
 sulphate should be decomposed under these cir- 
 cumstances. To test this fact by direct experi- 
 ment, we covered two platinum plates with lead 
 sulphate, immersed them in dilute sulphuric acid' 
 and sent a current through. We found not only 
 that the sulphate was reduced by electrolytic 
 hydrogen, but that it was peroxidised by electro- 
 lytic oxygen. The white sulphate was, in fact, 
 decomposed to a large extent at each plate, the 
 positive being covered with deep chocolate-coloured 
 peroxide, the negative with grey spongy lead. 
 
 The reaction which takes place in charging a 
 Plante battery may be viewed in two ways. The 
 simplest may be thus expressed in the notation 
 which we have employed in some previous papers. 
 For convenience, the reaction is divided into 
 two stages : 
 
 Pb* 
 
 SO 4 H 2 I pi _ pi PKH SO 3 H 2 
 
 SOX I y l I 2 I S0 3 I H 2 
 
 and 
 
 2SO 3 + 2H 2 O = 2H 2 SO 4 . 
 
BATTERIES OF PLANT& AND FAURE. 13 
 
 But it may be that lead sulphate is always formed 
 in the first instance, and decomposed on the 
 continuation of the current. 
 
 Pb, | S0 4 H 3 | Pby = Pb*-! | S0 4 Pb I H 2 | Pby. 
 
 then 
 
 IQO I 
 gg* | H 2 I Pbj, 
 
 and 
 
 2SO 3 + 2H 2 O == 2H 2 SO 4 . 
 
 It seems not improbable that both these re- 
 actions may take place according to the varying 
 density, or other circumstances of the current. 
 The coating of peroxide interposes a great diffi- 
 culty in the way of the further oxidation of the 
 metallic lead. Hence Plante needs the successive 
 periods of repose, to admit by local action of 
 the formation of lead sulphate, and the oxidation 
 of the increasing amounts of finely-divided lead 
 thus brought into the field of action. 
 
 To obviate this waste of power and time, 
 Faure covers both plates with red lead, and con- 
 verts this into spongy peroxide and spongy lead 
 respectively by the current. Now the first thing 
 that happens, when the plates are immersed in 
 
H THE CHEMISTRY OF THE SECONDARY 
 
 dilute sulphuric acid, is a purely chemical action. 
 The minium suffers decomposition according to 
 the formula 
 
 Pb 3 O 4 + 2H 2 S0 4 = PbO 2 + 2PbSO 4 + 2H 2 O. 
 
 But as both the lead sulphate and lead peroxide 
 are insoluble, this change takes place mainly at 
 the surface, and requires time to penetrate. Thus 
 in an experiment performed with the object of 
 testing this point the following amounts of minium 
 were found to be converted into lead sulphate 
 in successive periods of time : 
 
 Time. 
 15 minutes . 
 
 Minium changed 
 into sulphate. 
 
 .. 1 1 '8 per cent. 
 
 30 
 60 
 
 .- 137 
 
 120 ,, 
 
 ., 18-1 
 
 It is evident that in a Faure battery we are 
 dealing with plates that consist of a superficial 
 layer of mixed peroxide and sulphate of lead, 
 the thickness of this layer depending upon the 
 time during which the sulphuric acid has been 
 allowed to soak into the minium. 
 
 It might happen, and we are told it has 
 
BA TTERIES OF PLANTE AND FA URE. 1 5 
 
 happened, that the amount of minium employed 
 has been great enough to abstract all the sul- 
 phuric acid from solution, leaving only water. In 
 that case water, of course, would be the electro- 
 lyte, and there can be little doubt that the lead 
 plate might suffer oxidation in the manner which 
 was described by us some years ago (Clum. Soc. 
 Journ., 1876) in a paper on "Phenomena accom- 
 panying the Electrolysis of Water with Oxidisable 
 Electrodes." This paper detailed the results 
 obtained on passing a current from one Grove's 
 cell between two plates of the same metal im- 
 mersed in pure water. We stated in the case 
 of lead : " The positive electrode showed signs 
 of slight oxidation, and the negative electrode 
 a few small bubbles, in fifteen minutes ; a slight 
 cloudiness was then beginning to form, which 
 afterwards increased ; some oxide was found 
 adhering in an hour ; and afterwards grey metallic 
 lead, which at the end of twenty-two hours was 
 found to have stretched across to the positive 
 electrode, forming a metallic connection which 
 was so much heated by the passage of the voltaic 
 
1 6 THE CHEMISTRY OF THE SECONDARY 
 
 current that the liquid became warm." We are 
 informed that such lead crystals have sometimes 
 been found in Faure's cells. 
 
 Supposing, however, that there is enough and 
 to spare of sulphuric acid, the mixture of lead 
 peroxide and lead sulphate presents a double 
 problem. Were we dealing with peroxide alone 
 it would be reduced on the one plate at the ex- 
 pense of two molecules of water or sulphuric acid, 
 while at the opposite pole the oxygen would simply 
 be liberated, the final result being : 
 
 Pb* | Pb0 2 | S0 4 H 2 | S0 4 H 2 | Pb0 2 | Pb, = 
 Pb^ | Pb0 2 | 2 | S0 4 H 2 | S0 4 H 2 | Pb y+1 . 
 
 The intermediate stages are probably 
 
 Pb* | Pb0 2 1 2 1 | 3 | ^O I Pb | p^ 
 and 
 
 2SO 8 + 2H a O = 2H 2 SO 4 . 
 
 But as there is always lead sulphate present, 
 this liberated oxygen is mainly used up in oxida- 
 ting that substance, and it is evident from the 
 following formula that it is theoretically sufficient 
 to peroxidise the two molecules of sulphate 
 2PbSO 4 + 2H 2 O + O 2 = 2PbO 2 + 2H 2 S0 4 . 
 
BATTERIES OF PL ANTE AND FAURE. 17 
 
 These two molecules of PbSO 4 are obtained from 
 one molecule of Pb 3 O 4 (red lead), and it appears 
 that two atoms of oxygen are sufficient to trans- 
 form this into peroxide. But the corresoonding 
 amount of hydrogen (four atoms) by no means 
 suffices to reduce a similar amount of what was 
 once red lead on the other side, for in this case 
 both the peroxide and the sulphate formed by the 
 action of the acid have to be reduced. To accom- 
 plish this at least eight atoms of hydrogen will 
 be necessary, and this will demand the electro- 
 lysis of an additional two molecules of water or 
 sulphuric acid. It might therefore be expected, 
 a priori, that the minium on the side to be oxi- 
 dated ought to be twice the amount of that to 
 be reduced. 
 
 In order to ascertain what is the real course 
 of procedure, in charging a Faure battery, we 
 took two plates of lead of equal size and covered 
 each with a known weight of minium, which was 
 found on analysis to be almost pure Pb 3 O 4 . We 
 passed a current of known strength, about one 
 ampere, through the arrangement for many hours, 
 
 C 
 
i8 THE CHEMISTRY OF THE SECONDARY 
 
 noting the amount of hydrogen gas which was 
 liberated at the one pole, and the amount of 
 oxygen liberated at the other. 1 From the data 
 it was easy to calculate the amount of electrolytic 
 hydrogen and oxygen utilised. We performed 
 the experiment several times, varying the strength 
 of the current and some other circumstances. The 
 most complete result was as follows : 
 
 1 The pieces of apparatus employed in these experiments were 
 the following : (i) a battery of Grove's cells; (2) a large glass 
 vessel, used as a cell, containing the dilute sulphuric acid, and the 
 two lead plates fixed on insulated supports ; (3) a voltameter to 
 enable us to determine the actual amounts of the products of electro- 
 lysis liberated by the current in any given time ; (4) a galvanometer 
 to indicate the strength of the current ; and (5) a resistance-box, by 
 means of which the current might be maintained at a constant 
 strength. Over each of the lead plates in the glass cell was sup- 
 ported a funnel leading into a long, graduated, glass tube filled with 
 dilute sulphuric acid and set vertically. As the current passed 
 and electrolysis took place, as much of the hydrogen and oxygen 
 gases as was not absorbed at their respective lead plates rose into 
 the tubes above them ; and the differences (corrected for tempera- 
 ture and pressure) between the amounts collected in a given time, 
 and the amounts collected during the same time in the voltameter 
 gave the amounts absorbed by the lead plates. 
 
BATTERIES OF PLANTE AND FAURE. 
 
 Tim^ 
 
 HYDROGEN. 
 
 OXYGEN. 
 
 iime 
 
 Lost. 
 
 Absorbed. 
 
 Lost. 
 
 Absorbed. 
 
 hours. 
 
 C.c. 
 
 C.C. 
 
 C.C. 
 
 C.C. 
 
 I 
 
 Nil. 
 
 312 
 
 Nil. 
 
 I 5 6 
 
 2 
 
 M 
 
 318 
 
 iS 
 
 I 4 I 
 
 3 
 
 
 306 
 
 48 
 
 105 
 
 4 
 
 n 
 
 300 
 
 66 
 
 84 
 
 5 
 
 
 
 300 
 
 72 
 
 78 
 
 6 
 
 2 
 
 3'3 
 
 90 
 
 6 7 
 
 7 
 
 5 
 
 295 
 
 87 
 
 63 
 
 8 
 
 3 
 
 312 
 
 96 
 
 61 
 
 9 
 
 6 
 
 33 
 
 93 
 
 61 
 
 10 
 
 21 
 
 297 
 
 99 
 
 60 
 
 ii 
 
 37 
 
 273 
 
 99 
 
 56 
 
 12 
 
 101 
 
 220 
 
 io5 
 
 56 
 
 13 
 
 "50 
 
 158 
 
 105 
 
 49 
 
 H 
 
 J 95 
 
 132 
 
 !5 
 
 58 
 
 15 
 
 210 
 
 92 
 
 100 
 
 51 
 
 16 
 
 228 
 
 90 
 
 1 06 
 
 53 
 
 17 
 18 
 
 22 5 
 2 7 
 
 ^5 
 66 
 
 IOO 
 
 108 
 
 II 
 
 19 
 
 264 
 
 5i 
 
 108 
 
 49 
 
 20 
 
 270 
 
 50 
 
 in 
 
 49 
 
 21 
 
 273 
 
 43 
 
 114 
 
 44 
 
 22 
 
 270 
 
 30 
 
 114 
 
 36 
 
 23 
 
 2 7 6 
 
 30 
 
 114 
 
 39 
 
 2 4 
 
 297 
 
 21 
 
 123 
 
 36 
 
 25 
 
 309 
 
 9 
 
 126 
 
 33 
 
 26 
 
 270 
 
 18 
 
 120 
 
 24 
 
 27 
 
 300 
 
 18 
 
 132 
 
 27 
 
 28 
 
 309 
 
 ii 
 
 138 
 
 22 
 
 2 9 
 
 3 2I 
 
 15 
 
 141 
 
 27 
 
 30 
 
 318 
 
 15 
 
 147 
 
 19 
 
 31 
 
 300 
 
 6 
 
 135 
 
 18 
 
 
 5>230 
 
 4,489 
 
 3, 1 20 
 
 i,737 
 
 The amounts of hydrogen and oxygen capable 
 of being absorbed by the materials on the plates 
 were 4,574 and 1,294 c.c, respectively. 
 
 C 2 
 
20 THE CHEMISTRY OF THE SECONDARY 
 
 We read the indications of this table in the 
 following way : At first, both the reduction and 
 oxidation take place very perfectly, with little loss 
 of either of the elements of water. The absorption 
 of the hydrogen proceeds with little diminution, 
 until by far the greater part of the lead peroxide 
 and sulphate are reduced, but the last portions are 
 very slowly attacked, probably because they are 
 imbedded in a mass of reduced lead. On the 
 side that is being oxidated it is otherwise : a 
 considerable waste of oxygen soon shows itself, 
 but nevertheless a continuous slow absorption of 
 that element takes place long after the theoretical 
 amount of it has been fixed. A very small 
 amount of this excess is to be attributed, according 
 to our experiments, to the oxidation of the 
 metallic plate itself; but we attribute the greater 
 portion to the local action which must be constantly 
 going on between the peroxide and the lead plate 
 with the formation of sulphate of lead, the sulphate 
 in its turn of course being attacked by the 
 electrolytic oxygen. Thus the excess of oxygen 
 in the fifth column of the above table, 1737 as 
 
BATTERIES OF PLANTE AND FAURE. 21 
 
 against 1294 c.c., may be looked on as a measure 
 of the local action which has taken place during 
 the charging, and the figures in the lower portion 
 as roughly indicating its progress from hour to 
 hour. Local action will of course take place at 
 first on the opposite plate, but it requires no more 
 hydrogen to reduce two molecules of lead sulphate 
 than one molecule of lead peroxide, and the 
 possibility of local action gradually diminishes as 
 the reduction proceeds. 
 
 All our other experiments told the same story 
 as far as the absorption of hydrogen is concerned, 
 but there are differences on the other plate. In 
 one or two instances, not half of the theoretical 
 amount of oxygen was absorbed. On searching 
 into the circumstances on which this depended, we 
 were unable to arrive at any other conclusion than 
 that it was connected with the condition of the 
 surface of the lead plate. 
 
 Experiments with a current of about two amperes 
 showed that a larger quantity of both hydrogen 
 and oxygen was fixed in a given time, but there 
 was a larger proportionate loss, especially in the 
 
22 THE CHEMISTRY OF THE SECONDARY 
 
 case of oxygen. Experiments with a current of 
 about half an ampere, on the contrary, gave a less 
 rapid action, but a much smaller waste of force 
 through the escape of free gas. 
 
 A complete study of the results of these experi- 
 ments would be instructive, but the following 
 comparisons may suffice to illustrate the points 
 just mentioned. The theoretical amount of oxygen 
 required for the red lead used is about 1,200 c.c., 
 and the table shows the length of time in which 
 300, 600, and 1,000 c.c. were fixed by different 
 strengths of current, together with the accom- 
 panying loss. 
 
 Strength of 
 current. 
 
 Amount of 
 oxygen stored. 
 
 Time. 
 
 Loss of 
 oxygen. 
 
 Amperes. 
 
 C.C. 
 
 hours. 
 
 C.C. 
 
 2 
 
 300 
 
 I "5 
 
 174 
 
 I 
 
 , r 
 
 2 
 
 18 
 
 1 
 
 
 
 3-8 
 
 15 
 
 2 
 
 600 
 
 4'i 
 
 617 
 
 I 
 
 ,, 
 
 5 '5 
 
 249 
 
 \ 
 
 
 
 7-6 
 
 47 
 
 2 
 
 1,000 
 
 I3-9 
 
 3,081 
 
 I 
 
 ,, 
 
 I2'2 
 
 900 
 
 4 
 
 " 
 
 16-0 
 
 400 
 
BATTERIES OF PLANTE AND FAURE. 23 
 
 In some cases we mixed the red lead with a 
 little water, and allowed it to dry. In other 
 experiments we mixed it at once with dilute 
 sulphuric acid, but without finding any particular 
 practical advantage. 
 
 The forming of a good secondary battery is a 
 matter evidently depending upon very nice adjust- 
 ment of conditions. It is but a few of these that 
 we have carefully studied ; nevertheless, we feel 
 ourselves in a position to make one or two sugges- 
 tions in regard to the economic aspects of the 
 question. It is evident that the energy stored up 
 in a cell is determined mainly by the amount of 
 peroxide present. This appears to be obtained 
 with the smallest amount of waste when the 
 current is not too strong ; in fact, in our experiments 
 it was obtained when the density of the current 
 was about 6| milli-amperes per square centimetre, 
 calculated on the original surface of the lead plates. 
 
 There would seem to be no commensurate 
 advantage in continuing the current after the 
 oxygen has ceased to be absorbed pretty freely, 
 because the presence of some unoxidised sulphate 
 
24 BA TTERIES OF PL ANTE AND FA URE. 
 
 of lead, although it increases the resistance, rather 
 impedes than promotes local action. 
 
 On the other hand, however, it is necessary that 
 the reduction of the minium on the opposing 
 plate should be complete, for a mixture of lead 
 peroxide and metallic lead would be peculiarly 
 conducive to the production of lead sulphate, and 
 thus increase the resistance ; while if any peroxide 
 should escape destruction it would diminish the 
 electromotive force of the cell. 
 
 It would appear probable, therefore, that the 
 most economical arrangement would be obtained 
 by making the red lead to be hydrogenated much 
 smaller in amount than that to be oxidated. On 
 trying the experiment with only half the quantity, 
 we obtained a most satisfactory result as far as the 
 charging was concerned. How far such an arrange- 
 ment may be really desirable we consider more 
 fully in treating of the chemistry of the discharge. 
 
PART III. 
 
 THE DISCHARGE OF THE CELL. 
 
 THE two plates of a Plante or Faure battery 
 consist essentially of lead peroxide as the negative 
 element, and metallic lead in a spongy condition 
 as the positive. These are brought into com- 
 munication with one another through the lead 
 plates which support them, together with the 
 connecting wire. 
 
 The lead "peroxide reacts both with the lead 
 plate that supports it, and with the lead on the 
 opposite plate. At first sight, it might be ex- 
 pected that the reaction between it and the 
 supporting plate would be the greater, as the 
 space between them is so small, and the resist- 
 ance of the intervening liquid in consequence 
 almost inappreciable. The action is, indeed, 
 
26 THE CHEMISTRY OF THE SECONDARY 
 
 probably greater at the first moment, but, as 
 explained in the first part, sulphate of lead is 
 immediately produced, and that which lies at or 
 near the points of junction, forms no doubt a 
 serious obstacle to further local action, and admits 
 of the lead on the opposite plate coming more 
 fully into play. 
 
 If we consider a priori what is likely to be the 
 reaction between lead peroxide and lead, with water 
 as the connecting fluid, we should expect : 
 Pb0 2 | H 2 | H 2 | Pb = PbO | H 2 | PbH 2 2 . 
 
 On experiment this is found to be actually the 
 case, yellow oxide appearing on the negative plate, 
 and white hydrate on the positive. 
 
 If, however, the reaction takes place in presence 
 of dilute sulphuric acid, the result will inevitably 
 be sulphate on both sides, for even if oxide be 
 first formed, it will be 'attacked by that acid. Of 
 course this production of lead sulphate on each 
 side might be expected gradually to produce a 
 perfect electrical equilibrium. This, in fact, does 
 take place under certain circumstances, but not 
 under others. The reaction on the negative plate 
 
BATTERIES OF PLANTE AND FAURE. 27 
 
 is always of this character, as far as our analyses 
 have shown. We have invariably found the 
 deposit to consist of sulphate of lead mixed with 
 unaltered peroxide. If, however, the cell be 
 allowed to discharge itself rapidly, the lead on 
 the positive plate is converted, not only into the 
 sulphate, but, very partially, into lead peroxide. 
 This is sometimes evident to the eye from the 
 puce colour of the superficial layer, and we found 
 also that this was confirmed by several chemical 
 tests. 
 
 It is difficult to conceive how the reduction of 
 the peroxide of lead on the one plate to oxide or 
 sulphate, should be attended by a direct oxidation 
 of lead on the other plate up to peroxide itself, 
 as that would involve a reversal of the electro- 
 motive force. It is more easy to imagine that 
 the peroxide results from the oxidation of sul- 
 phate of lead already formed, through the agency 
 of electrolytic oxygen. 
 
 When this peroxide is formed on the positive 
 plate, it is not difficult to foresee what must happen. 
 A state of electrical equilibrium will be approached 
 
28 THE CHEMISTRY OF THE SECONDARY 
 
 before the peroxide of lead on the negative plate 
 is exhausted. But the two sides are in very dif- 
 ferent positions with regard to local action. On 
 the negative plate, the peroxide being mixed with 
 a great deal of lead sulphate, it will suffer decom- 
 position only very slowly through the agency of 
 the supporting plate, but the lead peroxide on the 
 positive plate, being mixed not only with lead 
 sulphate, but with spongy metallic lead, will be 
 itself speedily reduced to sulphate. Hence, on 
 breaking the circuit, when local action alone can 
 take place, the peroxide formed on the positive 
 plate during the discharges will be destroyed much 
 more easily than the original peroxide on the 
 other plate. The difference of potential between 
 the plates will be restored, and on connection 
 the cell will be again found in an active 
 condition. 
 
 Now it has been frequently observed that par- 
 tially discharged accumulators do give an increased 
 current after repose, that is, after the circuit has 
 been broken and re-established. It remained for 
 us to ascertain whether the chemical change above 
 
BATTERIES OF PLANTE AND FAURE. 29 
 
 described coincided in any way with the physical 
 phenomena. For this purpose we prepared plates 
 according to the method of Faure, and examined 
 carefully the changes of electromotive force and 
 strength of current, which took place during their 
 discharge under known resistances, and the 
 chemical changes that took place under the same 
 circumstances. 
 
 We found that the initial electromotive force of 
 freshly prepared cells was 2*25, 2*25, 2*2 I, and 2*31 
 volts, averaging 2*25, but that after standing for 
 thirty minutes or so, or after being allowed to 
 discharge for a few minutes, it was reduced to 
 about 2*0 volts. We take this to represent the 
 normal electromotive force of the arrangement of 
 lead, lead peroxide, and dilute sulphuric acid, and 
 believe that the higher figure obtained at the first 
 moment is due to the hydrogen and oxygen 
 occluded on the respective plates, and which either 
 diffuse out, or are speedily destroyed. 1 
 
 We found, however, that in the discharge the 
 electromotive force diminished in a manner that 
 
 1 For further remarks upon this point, see p. 48. 
 
 ^^* 
 
 OS THE 
 
 tjm.IRSITYj 
 
30 THE CHEMISTRY OF THE SECONDARY 
 
 depended upon certain conditions. Thus, in an 
 experiment in which the external resistance was I 
 ohm, and the internal 0*58 ohm, the E.M.F. sank 
 in forty-five minutes from 2-25 to 1*92, but after 
 being disconnected for thirty minutes, it was found 
 to have risen to 1*96, and after eighteen hours' 
 repose, it had actually risen to 1*98 volts. These 
 observations were made many times in succession 
 during the course of the experiment, which lasted 
 six days. 
 
 With twenty times the external resistance, that 
 is 20 ohms, the diminution of electromotive force 
 was much slower ; but after discharging for three 
 days, the fall was more pronounced, and the rise 
 on repose very apparent. 
 
 With 100 ohms resistance, the electromotive 
 force varied very little for three days. 
 
 It is more difficult to obtain satisfactory chemical 
 evidence of a quantitative character. It is clear 
 that as chemical examination means the destruc- 
 tion of the substances, the same plate cannot be 
 analysed in two consecutive stages. Nor can two 
 plates be easily compared with one another, 
 
BATTERIES OF PL ANTE AND FAURE. 31 
 
 although they have been formed under the same 
 circumstances. Even the same positive plate, 
 whether during or after discharge, presents to the 
 eye very different appearances in different parts. 
 To a certain extent we obviated this difficulty by 
 cutting the plate in two longitudinally, analysing 
 the one half at once, and allowing the other to 
 repose for a given time before examining it for 
 peroxide of lead. 
 
 As to the estimation of peroxide in the presence 
 of metallic lead, we finally adopted as the best 
 method that of reducing it by means of oxalic 
 acid, although we were not certain that the whole 
 amount is obtained in this way, even though the 
 solution be kept hot for a considerable time. 
 
 By this method many chemical examinations 
 were made of .the positive plate. The results are 
 as follows : First of all, when the external resist- 
 ance did not exceed 20 ohms, the peroxide of lead 
 was generally visible in patches, and its presence 
 was demonstrated and approximately measured by 
 various chemical tests. On repose, the quantity 
 of this peroxide visibly diminished, and in the 
 
32 THE CHEMISTRY OF THE SECONDARY 
 
 majority of instances the chemical analyses also 
 showed a smaller amount. In all cases sulphate 
 of lead makes its appearance early in the action, 
 and gradually increases in quantity, becoming 
 finally the only product of the discharge. 
 
 The deposit on the negative plate shows the 
 presence of nothing but sulphate of lead in 
 addition to the unchanged peroxide. At the 
 conclusion of the action, we have always found 
 more or less of the substance unaltered. Thus, 
 as one instance, after a discharge lasting five 
 days, and approximately complete, we found 
 that only 68 per cent, of the deposit was lead 
 sulphate. 
 
 We conclude, therefore, that the chemical action 
 of the discharge is essentially what is expressed by 
 the following theoretical formula : 
 
 Pb0 2 | H 2 S0 4 | H 2 S0 4 | Pb = PbO | H 2 | H 2 SO 4 | PbSO 4 , 
 
 which oxide of lead in the presence of sulphuric 
 acid becomes sulphate of lead, according to the 
 equation 
 
 PbO + H 2 S0 4 = PbS0 4 + H 2 0, 
 
BA TTERIES OF PLANTE AND FA URE. 33 
 
 the final result being sulphate of lead on both 
 plates. This reaction is, however, sometimes com- 
 plicated by the formation of a small amount of 
 peroxide of lead on .the positive plate. We believe 
 this to be due to the oxidation of sulphate, an 
 action which was explained in the preceding part. 1 
 Another conclusion has reference to the resusci- 
 tation of power observed on repose. This is not 
 due to any purely physical action, but is a neces- 
 sary consequence of the formation of PbO 2 on the 
 positive plate. As sooner or later the result of the 
 action becomes solely PbSO 4 , this temporary for- 
 mation of peroxide does not seriously affect the 
 quantity of electrical force that may be regained 
 from the accumulator, but it does affect the even- 
 ness of its flow. The flow is more regular if the 
 
 1 On the 1st of March of this year Professor Frankland read a 
 paper at the Royal Society, in which he confirmed the reactions 
 given in this and the preceding part. He expresses them, however, 
 as the electrolysis of hexabasic sulphuric acid, in accordance with 
 the views of Burgoin. We have looked into the evidence upon 
 which these views are founded, but are not satisfied of its conclusive- 
 ness. We therefore prefer our original formulae as involving a 
 smaller amount of theory. 
 
 D 
 
34 THE CHEMISTRY OF THE SECONDARY 
 
 discharge be made slowly, but in that case the loss 
 on the negative plate from local action will 
 probably be greater. 
 
 As to practical conclusions, we may note i. 
 Although as stated on page 24, the most econo- 
 mical arrangement for the initial charging of the 
 cell is to " make the red lead to be hydrogenated 
 much smaller in amount than that to be oxidated," 
 yet, as foreshadowed at the same time, this 
 arrangement is not desirable for the discharge of 
 the cell. Nor is it for its subsequent charging, 
 since, as will have been seen, the substances to be 
 acted upon are now very different. On the nega- 
 tive plate there will be the sulphate of lead pro- 
 duced by the discharge, plus sulphate of lead 
 produced by local action, together with more or 
 less unaltered peroxide. On the positive plate 
 there will be the sulphate of lead produced by 
 the discharge, together with excess of lead, if any. 
 Unless, therefore, the peroxide of lead unacted 
 upon is allowed to be very considerable, the 
 quantity of lead compound on the two sides 
 
BA TTERIES OF PLANTE AND FA URE. 35 
 
 ought to approach equality. 2. Care should be 
 taken that sulphuric acid is in sufficient excess to 
 allow of there still remaining some of it in solution 
 after all the available lead has been converted into 
 sulphate. If it is removed and only water is 
 present, an oxide or hydrate will be produced 
 with probably some serious consequences to the 
 cell* 
 
 D 2 
 
PART IV. 
 
 THE FUNCTION OF SULPHATE OF LEAD. 
 
 WE have already frequently remarked on the 
 formation of lead sulphate, and its importance in 
 the history of a secondary cell. 
 
 In Part I. we showed that the local action that 
 takes place at first energetically between the 
 metallic lead and the adhering peroxide is gra- 
 dually diminished by the formation of sulphate of 
 lead. 
 
 In Part II. we stated that in the original forma- 
 tion of a Faure cell sulphate of lead is oxidated 
 on the one plate and reduced on the other. We 
 also described an experiment in which two 
 platinum plates were covered with lead sulphate, 
 immersed in dilute sulphuric acid, and placed in 
 the circuit of a galvanic current, the result being 
 
BATTERIES OF PL ANTE AND FA URE. 37 
 
 that "the white sulphate was decomposed to a 
 large extent on each plate, the positive being 
 covered with deep chocolate-coloured peroxide, 
 the negative with grey spongy lead." 
 
 In Part III. we showed that on the discharge of 
 a cell, lead sulphate is the ultimate product on 
 both plates. 
 
 It might naturally be inferred from our previous 
 statements that in the re-charging of a cell this 
 lead sulphate would be oxidated on the one plate 
 and reduced on the other, as in the original forma- 
 tion. This matter, however, has given rise to 
 some controversy. All subsequent experimenters 
 admit the oxidation of the lead sulphate, but Dr. 
 Oliver Lodge could not obtain any reduction of it, 
 when pure sulphate was employed. 1 Sir William 
 
 1 A correspondence upon this subject is to be found in Nature 
 of July 20, August 10, and October 19, 1882. Dr. Lodge also 
 quotes experiments by Professor McLeod, and reverts to the subject 
 in the Engineer of January 5, 1883. There are some interesting 
 observations on the Chemistry of the Cell by Professor Herschel 
 in Nature of April 6, 1882. The matter was also brought forward 
 and discussed in a paper entitled " On Secondary Batteries, with 
 special reference to Local Action," at the meeting of the British 
 Association at Southampton on August 25, 1882 ; vide Report, 
 p. 447. 
 
38 THE CHEMISTRY OF THE SECONDARY 
 
 Thomson also, when experimenting, with two 
 platinum plates and layers of sulphate, obtained 
 only a doubtful indication of reduced metal. The 
 question as to whether the sulphate is reduced or 
 not on re-charging a Faure cell is one of vital 
 importance ; for if the sulphate formed at each 
 discharge accumulates on the positive plate it 
 would clog up the space, and, what is perhaps 
 worse, a fresh surface of the lead would have to be 
 oxidated (or rather, converted into sulphate) at 
 each discharge. Thus the positive plate will be 
 continually corroded, and its life will be limited. 
 
 We have already replied to Dr. Lodge in Nature 
 (vol. xxvi. p. 342), but we thought it desirable to 
 repeat the experiment with the platinum plates 
 especially with a view to determine whether the 
 reduction was effected slowly or with any rapidity. 
 We fastened 20 grms. of the white sulphate upon 
 a negative plate by binding it round tightly with 
 parchment-paper, placed it vertically in the sul- 
 phuric acid, and passed a continuous current of 
 somewhat under an ampere. The hydrogen was 
 at no time wholly absorbed indeed the greater 
 
BA TTERIES OF PLANT A AND FA URE. 
 
 39 
 
 part of it certainly escaped but after the lapse of 
 twenty-four hours, small patches of grey metallic 
 lead became distinctly visible through the wet 
 parchment-paper ; and these gradually spread in 
 an irregular manner. At the end of ten days it 
 was found that the whole of the sulphate, except a 
 few small patches on the surface, was reduced to a 
 grey spongy mass. Although there could be no 
 reasonable doubt that this was metallic lead, a 
 portion of it was tested chemically, and proved to 
 be such. 
 
 It thus appears that the reduction of the pure 
 sulphate of lead is an absolute fact, although it 
 does not take place so easily as the oxidation. 
 
 In an actual cell the sulphate of lead is of 
 course mixed with other bodies. Thus, in the 
 formation of a Faure battery, the minium is con- 
 verted by the sulphuric acid more or less com- 
 pletely into peroxide of lead and sulphate. We 
 have already described an experiment in which 
 4489 c.c. of hydrogen were absorbed on a plate, 
 the materials of which were capable of absorbing 
 only 4574 c.c. if the whole of the sulphate as well 
 
40 THE CHEMISTRY OF THE SECONDARY 
 
 as the peroxide was reduced. In our note-book 
 we have the particulars of four other experiments 
 made in each case with the same, or nearly the 
 same, amount of material, in which 4199, 4575> 
 4216, and 4387 c.c. respectively were absorbed, 
 although perhaps in not one of these cases was 
 the experiment continued until the action was 
 absolutely complete. As, however, it may be 
 objected that the amount of sulphate produced 
 upon these plates was an unknown quantity, we 
 have in a recent experiment treated the minium 
 in the first instance with a considerable amount of 
 sulphuric acid. This gave us a mixture which, on 
 analysis, was found to contain 18*5 per cent, of 
 sulphate of lead. This mixture, when submitted 
 to the reducing action of a current yielded a mass 
 of spongy lead that contained only a mere trace 
 of sulphate. 
 
 As it seemed desirable fully to establish the fact 
 that the sulphate of lead formed on the discharge 
 of a cell is reduced in the subsequent charging, we 
 took the quondam lead plate of a fully discharged 
 cell, determined the proportion of sulphate to 
 
BATTERIES OF PLANTE AND FAURE. 41 
 
 unaltered spongy lead, and submitted it to the 
 reducing action of a current. The amount of 
 sulphate on the plate before passing the current 
 was found to be 5 1 per cent, but, after the passage 
 of a current of about an ampere for sixty hours, 
 not a trace of it remained. 
 
 Hence it may be concluded that, during the 
 alternate discharging and re-charging of a Plante 
 or Faure cell, sulphate of lead is alternately 
 formed and reduced on the lead plate, and that 
 the plate itself is not seriously corroded. It 
 would, however, appear desirable not to allow the 
 whole of the spongy lead to be reduced to sulphate 
 during the discharge, for two reasons, viz. : (i) 
 because the supporting plate stands a chance of 
 being itself acted on if there is not a sufficient 
 excess of spongy metal ; and (2) because the 
 presence of this excess tends to facilitate the 
 reduction of the sulphate. 
 
 We have already shown that sulphate of lead is 
 produced by the local action that takes place be- 
 tween the peroxide and its supporting lead plate 
 during repose. The same local action also takes 
 
42 THE CHEMISTRY OF THE SECONDARY 
 
 place during the charging of the plate, as was 
 pointed out in our second communication, and this 
 sulphate is, in its turn, attacked by the electro- 
 lytic oxygen. In this way the absorption of 
 oxygen in forming the negative plate ought never 
 to come to an end. In order to see whether 
 this was the case, we allowed an experiment to 
 continue for 115 hours, although the main action 
 was over in about forty hours. For the last two 
 days of the experiment, the amount of oxygen 
 absorbed was pretty constant, being about 9 c.c. 
 per hour, which is equivalent to 0*24 grms. of 
 sulphate of lead formed and oxidated. The 
 whole charge . on the plate was forty grms. of 
 peroxide. This local action also takes place 
 during the discharge, as is evidenced by the 
 sulphate of lead formed on the negative plate 
 always exceeding in amount that formed on the 
 positive plate. 1 
 
 Through this local action taking place during 
 the formation of the cell, during repose, and 
 
 1 For details of the experiments from which these conclusions 
 were drawn, see Appendix. 
 
BATTERIES OF PLANTE AND FAURE. 43 
 
 during the discharge, the lead plate which sup- 
 ports the peroxide must be continually corroded 
 more and more ; and it is doubtless due to the 
 insolubility of the sulphate formed that the de- 
 struction of this kind of secondary battery is so 
 materially retarded in practice. 
 
PART V. 
 
 I. INFLUENCE OF STRENGTH OF ACID. 
 
 IN Part II., when treating of the charging of 
 the cell, we pointed out that in the electrolysis 
 of dilute sulphuric acid between lead electrodes, 
 two totally different reactions might be obtained. 
 The positive metal becomes thinly coated with 
 lead sulphate when the current employed is of 
 small density, but with lead peroxide when the 
 density of the current is of greater magnitude. 
 This latter action is, of course, what takes place 
 in the ordinary formation of a Plante battery. 
 The chemical change, therefore, which goes on 
 at the positive electrode is to a certain extent 
 dependent upon the strength of the current. It 
 appeared also of both theoretical and practical 
 interest to determine whether the chemical change 
 was also influenced by the strength of the acid 
 
BATTERIES OF PLANTE AND FAURE. 45 
 
 employed. Our experiments consisted in passing 
 a current of uniform strength, about I ampere, 
 between electrodes of lead, 12 square inches 
 in size, in varying strengths of sulphuric acid, 
 and estimating in each case the amount of oxygen 
 fixed by the positive electrode. We determined 
 this for successive five minutes of time, and as 
 such actions are not always very uniform, we 
 made in each instance more than one experiment. 
 The results are given in the following table : 
 
 
 
 Percentage of oxygen fixed. 
 
 of acid. 
 
 Expt. 
 
 First 
 
 Second 
 
 Third 
 
 Fourth 
 
 Total 
 
 
 
 5 mins. 
 
 5 mins. 
 
 5 nuns. 
 
 5 mins. 
 
 
 i to 5 
 
 I. 
 
 38-1 
 
 28-6 
 
 28-6 
 
 33'3 
 
 128-6 
 
 
 II. 
 
 39'5 
 
 30-2 
 
 2 5 -6 
 
 30-2 
 
 I25-5 
 
 I to 10 
 
 I. 
 
 43'4 
 
 387 
 
 29-2 
 
 34 
 
 1 45 '3 
 
 
 II. 
 
 44' I 
 
 39'3 
 
 29*3 
 
 34'9 
 
 147-6 
 
 I to 50 
 
 I. 
 
 48'3 
 
 39*6 
 
 35 '3 
 
 22-4 
 
 H5'6 
 
 
 II. 
 
 46*2 
 
 43 '9 
 
 23 
 
 30 
 
 143 i 
 
 
 III. 
 
 54 
 
 40 
 
 35'3 
 
 35'5 
 
 165 
 
 I tO 100 
 
 I. 
 
 42 
 
 38-3 
 
 33'9 
 
 29-5 
 
 1437 
 
 
 II. 
 
 42-4 
 
 40 
 
 37-8 
 
 35'5 
 
 1557 
 
 
 III. 
 
 5' 
 
 44-2 
 
 34 '9 
 
 34 '9 
 
 165-1 
 
 I to 500 
 
 I. 
 
 46-6 
 
 32-6 
 
 27 
 
 27 
 
 132-6 
 
 
 II. 
 
 46-4 
 
 27 
 
 27 
 
 18 
 
 118-4 
 
 I tO 1000 
 
 I. 
 
 90*6 
 
 8ri 
 
 76-4 
 
 57'5 
 
 35 '6 
 
 
 II. 
 
 90-8 
 
 77 
 
 72-3 
 
 63-1 
 
 303-2 
 
46 THE CHEMISTRY OF THE SECONDARY 
 
 It appears from this that the strong sulphuric 
 acid (i to 5) is not quite so favourable to the 
 action as the more dilute (i to 10), but that 
 between this latter proportion and i to 500 there 
 is no great difference in the amount of oxygen 
 fixed, and therefore of corrosion of the plate. 
 The appearance of the plate in every instance 
 indicated the formation of only lead peroxide. 
 With sulphuric acid diluted with 1000 parts of 
 water, the amount of oxygen fixed, and therefore 
 of corrosion, was at least doubled, while the 
 chemical action was very different. On parts of 
 the electrode, streaks of a mixture apparently of 
 the yellow and puce-coloured oxides were seen. 
 On other parts a white substance formed and 
 was easily detached, falling in clouds into the 
 liquid. Where this latter action took place, the 
 plate was visibly the most corroded. This white 
 substance gave an analysis SO 4 equivalent to 
 73*6 per cent, of lead sulphate, suggesting the 
 idea that it was a basic sulphate of the composition 
 2PbSO 4 ,PbO, which would require 73*1 per cent. 
 As the peroxidation of the lead is required, and 
 
BATTERIES OF PLANTE AND FAURE. 47 
 
 the corrosion of the plate is to be avoided as much 
 as possible, it is evident that this extremely dilute 
 acid must be avoided. It has already been shown 
 that if the sulphuric acid is entirely removed 
 from solution, as sometimes happens in an ac- 
 cumulator, the lead is simply converted into the 
 hydrated protoxide, and therefore corroded without 
 any good effect. 
 
 2. FUNCTION OF HYDROGEN. 
 
 In the formation of a secondary cell, after the 
 complete reduction of oxide or sulphate to 
 metallic lead, bubbles of hydrogen gas are seen 
 to escape from the lead plate. It has been 
 assumed that a portion of this element is occluded 
 by the lead, or in some other way enters into 
 association with it, and it has been supposed that 
 this hydrogen compound may play an important 
 part in the subsequent production of electro- 
 motive force. It therefore appeared desirable to 
 obtain experimental evidence as to whether hydro- 
 gen is so absorbed. The process we adopted for 
 this purpose was founded upon the observation 
 
48 THE CHEMISTRY OF THE SECONDARY 
 
 of Graham that hydrogen associated with palla- 
 dium reduced ferri- to ferro-cyanide of potassium, 
 and that generally in the occluded condition 
 the element was more active chemically. We 
 had previously ascertained that hydrogen asso- 
 ciated with other elements, as platinum, copper, 
 and carbon, was capable of reducing potassium 
 chlorate to chloride. This method seemed to 
 give trustworthy results, and therefore we applied 
 it in this instance. As the result of several 
 trials, however, we found that the amount of 
 hydrogen associated with the reduced lead was 
 almost inappreciable. Small as this quantity is, 
 however, it is by no means impossible that it 
 may be the cause of the exceedingly high elec- 
 tromotive force observed for the first few moments, 
 on joining up a completely-formed cell imme- 
 diately after its removal from the circuit of the 
 charging current. This, however, may be due, as 
 Plante imagined, to the gaseous hydrogen itself. 
 The principal if not the only function of the 
 hydrogen of the water or sulphuric acid is therefore 
 that of reducing the lead compounds. 
 
BATTERIES OF PLANTE AND FAURE. 49 
 
 By a totally different process Prof. Frankland 
 has very recently come to the same conclusion 
 as ourselves in regard to the exceedingly small 
 amount of occluded hydrogen. 
 
 3. EVOLUTION OF OXYGEN FROM THE PEROXIDE 
 PLATE. 
 
 Plante" noticed a small escape of gas from the 
 negative plate of his cell immediately after its 
 removal from the influence of the charging 
 current. This he attributed to a decomposition 
 of water by means of local circuits between the 
 peroxide and the subjacent lead plate in contact 
 with it. 
 
 The explanation given by us of the local action 
 which goes on at the negative plate does not 
 account for the escape of any gas either oxygen 
 or hydrogen. We therefore thought it of interest 
 to ascertain the nature, and if possible the origin 
 of the gas noticed by Plante. 
 
 We found that the escape of gas from a Plante 
 negative plate was very slight, and soon ceased ; 
 but we observed that it became much more 
 
 E 
 
50 THE CHEMISTRY OF THE SECONDARY 
 
 pronounced when the temperature of the electrolytic 
 liquid was raised. In order to get a sufficient 
 quantity of the gas for examination, we prepared 
 a negative plate according to the procedure of 
 Faure, and then heated it in dilute acid, with an 
 arrangement for collecting the gas as it was 
 evolved. The amount of gas was still very small 
 in comparison with that of the peroxide, but a 
 sufficient quantity was collected to enable us to 
 ascertain that it was oxygen. We next heated 
 some of the electrolytic peroxide apart from the 
 lead plate, and again noticed a similar evolution 
 of gas, which was also found to be oxygen. This 
 shows, therefore, that it was not a result of 
 local action. 
 
 The gas has generally some odour of ozone, 
 and, on testing the dilute acid between the plates 
 of a Plante cell, we always found traces of 
 something that bleached permanganate of potas- 
 sium, and which might be either ozone or peroxide 
 of hydrogen. 
 
 The origin of the gas noticed by Plante may 
 be easily attributed to the oxygen which always 
 
BATTERIES OF PLANTE AND FAURE. 51 
 
 passes off in quantity from the peroxide plate 
 during the process ol "formation." It is only 
 necessary to suppose that some of this becomes 
 condensed on the peroxide, and is gradually 
 eliminated from it when the surrounding conditions 
 are changed. But the matter is capable of another 
 explanation. If peroxide of hydrogen be really 
 formed in the liquid, it will exert its well-known 
 influence on higher oxides, namely, that of 
 reducing them and itself at the same time. As 
 a matter of fact, if peroxide of lead is dropped 
 into peroxide of hydrogen, oxygen is evolved. 
 
 4. TEMPERATURE AND LOCAL ACTION. 
 
 Plante has recently pointed out that an elevation 
 of temperature facilitates the formation of his 
 secondary cell (fomptes Rendus, August, 1882). 
 The character of the chemical changes which 
 take place at the negative plate led us to think 
 it exceedingly probable that this increase in the 
 rate of formation arose from an augmentation in 
 the amount of local action. Experiment showed 
 such to be the case. Pairs of similar negative 
 
 E 2 
 
52 BATTERIES OF PLANTE AND FAURE. 
 
 plates on Plant's model were allowed to remain 
 in repose at 11 C. and 50 C. respectively, and 
 the formation of the white sulphate was visibly 
 more rapid at the higher than at the lower tem- 
 perature. The same is also true with negative 
 plates prepared by Faure's process. Thus we 
 found that two similar plates kept in repose 
 for an hour, the one at 11 C. and the other at 
 50 C., formed by local action 2*6 and 7*4 per 
 cent, of lead sulphate respectively. On two other 
 plates the proportions were 7*6 and 9*5 per cent, 
 respectively. These observations of course by no 
 means exclude the idea that an increase of tempera- 
 ture may also facilitate the other chemical changes 
 that take place in the formation of a lead and 
 lead-oxide cell. 
 
APPENDIX. 
 
APPENDIX. 
 
 THE experiment referred to on page 42 was 
 made in the same manner as that on page 19. 
 The results of the observations were as follows : 
 
 1st hour 
 
 2nd ,, 
 
 3<"d 
 
 4th ,, 
 
 5th 
 
 6th ,, 
 
 7th 
 
 8th 
 
 9th 
 
 loth 
 
 nth ,, 
 
 1 2th ,, 
 
 J 3th ,, 
 
 I4th ,. 
 
 i6th 
 
 I7th ,, 
 
 H 
 
 evolved 
 (in Voltr.). 
 
 H 
 
 absorbed. 
 
 
 evolved O 
 (in Voltr.). absorbed. 
 
 160 
 
 1 60 
 
 80 
 
 78 
 
 I8 5 ... 
 
 I8 5 
 
 92-5 ... 
 
 88 
 
 150 ... 
 
 150 
 
 75 
 
 7 1 
 
 170 
 
 170 
 
 ... 85 ... 
 
 79 
 
 170 
 
 170 
 
 ... 85 ... 
 
 79 
 
 175 
 
 175 
 
 ... 87-5 ... 
 
 78 
 
 180 
 
 180 
 
 90 
 
 79 
 
 170 
 
 170 
 
 ... 85 ... 
 
 74 
 
 185 ... 
 
 185 
 
 92-5 ... 
 
 70 
 
 175 
 
 173 
 
 ... 87-5 ... 
 
 58 
 
 200 
 
 197 
 
 IOO 
 
 69 
 
 180 
 
 176 
 
 90 
 
 57 
 
 185 ... 
 
 181 
 
 92-5 - 
 
 42 
 
 168 
 
 164 
 
 ... 84 ... 
 
 3 1 
 
 175 
 
 171 
 
 ... 87-5 ... 
 
 34 
 
 175 
 
 169 
 
 ... 87-5 ... 
 
 30 
 
 165 ... 
 
 158 
 
 ... 82-5 ... 
 
 25 
 
56 APPENDIX. 
 
 H 
 
 evolved H evolved O 
 (in Voltr.). absorbed. (in Voltr.). absorbed. 
 
 1 8th hour 
 
 183 
 
 173 
 
 91*5 
 
 28 
 
 I9th 
 
 185 
 
 173 
 
 92-5 ... 
 
 27 
 
 20th ,, 
 
 183 
 
 ... I6 9 
 
 ... 91-5 ... 
 
 26 
 
 2lSt ,, 
 
 185 
 
 I6 7 
 
 92-5 ... 
 
 29 
 
 22nd ,, 
 
 180 
 
 153 
 
 90 ... 
 
 20 
 
 23rd ,, 
 
 180 
 
 145 
 
 90 
 
 20 
 
 24th ,, 
 
 180 
 
 119 
 
 90 
 
 17 
 
 25th ,, 
 
 168 
 
 no 
 
 ... 84 ... 
 
 19 
 
 26th ... 
 
 173 
 
 IO2 
 
 86-5 ... 
 
 IS 
 
 3'st ,, 
 
 185 
 
 35 
 
 92-5 ... 
 
 14 
 
 4ist ,, 
 
 177 
 
 o 
 
 88-5 ... 
 
 II 
 
 54th 
 
 190 
 
 o 
 
 95 
 
 10 
 
 6 7 th ... 
 
 183 
 
 o 
 
 9i-5 
 
 7 
 
 78th ... 
 
 224 
 
 o 
 
 112 
 
 12 
 
 90th ,, 
 
 220 
 
 
 
 no 
 
 10 
 
 95th 
 
 216 
 
 o 
 
 108 
 
 8 
 
 103rd 
 
 223 
 
 
 
 ... 111-5 - 
 
 9 
 
 "5th 
 
 2I 3 
 
 o 
 
 ... 106 
 
 6 
 
 In the above table the amounts of hydrogen 
 and oxygen absorbed were calculated as before 
 by means of the hydrogen evolved in the volta- 
 meter during the same period. The oxygen 
 evolved was calculated from the hydrogen, and 
 is placed in the table in order to render the fifth 
 column more clearly intelligible. After the 
 twenty-sixth hour, though the action of the 
 current continued without interruption, intervals 
 
APPENDIX. 57 
 
 of about half a day were allowed between the ob- 
 servations. These, however, as before were made for 
 an hour at a time, so that each line of the second 
 portion of our table is strictly comparable with 
 each line of the first, though the whole covers an 
 additional period of nearly four days. It will be 
 seen that the results are in accordance with those 
 previously obtained. The hydrogen was completely 
 absorbed during the first nine hours, and almost 
 completely for some ten hours longer. Its ab- 
 sorption then began to rapidly fall off. At the 
 end of the twenty-sixth hour the volume absorbed 
 amounted to 4,255 c.c., and for some hours after- 
 wards at least there was a small absorption still 
 going on, probably enough to make up the 
 theoretically possible amount of 4,500 c.c. On 
 the opposite plate the absorption of oxygen was 
 never perfect ; but the loss became gradually 
 greater and greater. Although at the end of 
 twenty-six hours the amount of oxygen actually 
 absorbed (1,246 c.c.) about equalled what was 
 requisite to peroxidise the whole of the minium, 
 the absorption still went on, and did not exhibit 
 
58 APPENDIX. 
 
 any signs of ever coming to an end. A small 
 amount was found to be continuously absorbed 
 as long as our experiment lasted. Taking the 
 amounts shown in the fifth column as fairly re- 
 presenting the action, it may be calculated that 
 the oxygen absorbed from the twenty-sixth to 
 the- end of the H5th hour was 901 c.c. ; which of 
 course, if our interpretation be correct, implies a 
 large amount of action between the peroxide and 
 its subjacent lead plate. 
 
 Our best observations on the amount of sulphate 
 formed on the negative and positive plates re- 
 spectively, were made with the experiments on 
 page 30, the material on each plate after the 
 discharge was analysed, and gave the following 
 percentages of sulphate of lead : 
 
 Ohm. 20 Ohms. 100 Ohms. 
 
 Negative plate..'. 
 Positive 
 
 33-0 p. c. 307 
 
 28*8 ,, 20'0 
 
 y 
 
 The formula of decomposition during the dis- 
 charge would of course require the same amount 
 of sulphate of lead on each plate. Some experi- 
 ments were also made to determine whether the 
 
APPENDIX. 
 
 59 
 
 local action was in any way diminished by the 
 co-existence of the discharge. We failed, how- 
 ever, in getting good quantitative results, but fully 
 assured ourselves that during the first ten minutes 
 the double action was taking place. 
 
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