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Dissertations and Theses Dissertations and Theses
1976 The Effect of a Magnetic Field on the Leclanche ́ Cell
Walter Edward Socha Portland State University
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Recommended Citation Socha, Walter Edward, "The Effect of a Magnetic Field on the Leclanche ́ Cell" (1976). Dissertations and Theses. Paper 2561. https://doi.org/10.15760/etd.2558
This Thesis is brought to you for free and open access. It has been accepted for inclusion in Dissertations and Theses by an authorized administrator of PDXScholar. Please contact us if we can make this document more accessible: [email protected]. A~~ ABSTRACT OF THE THESIS OF Walter Edward Socha for the Master of
Science in Physics presented March 4 , 19?6
Title: The Effect of an Appl~ed Magnetic Field on the Lecianch~ Cell
APPROVED BY MEMBERS OF TiiE THESIS COM,t_.fJ:TTEE:
Dr. ~.akoto Takeo
Dr. David Roe
The effect of a magnetic field on an electrochemical system, the
LeclanchS" cell, was investigated. Experiments show that there is an
increase in power output and charge passed when a cell is discharged
in an applied magnetic field.
Possible explanations for the effect and discriptions of attempts
to verify these explanations are presented. --~ ...... ------6---~. -H --·- .... _..... _~6
THE EFFECT OF A MAGNETIC FIELD
;' ON THE L~LANCHE CELL
by
WALTER EDWARD SOCHA
A thesis subro~tted i~ partial fulfillment of the requirements for the degree.of
MASTER OF SCIENCE in PHYSICS.
Portland State University 1976
~~t TO THE OFFICE OF GRADUATE s·ruDIES AND RESEA.RCH
The members of the committee approve the thesis of
Walter Fidward Socha. presented ·.jr.a'rch 4~. , 1976
Dr. Makoto Takeo
Dr. Pavel Sme.)teK
Dr. David Roe
APPROVED:
Dr. MarlC Gurevitoh, Head, Department of Physics
Acting Dean of Gds:O.uate Studies and Research ------·- 6• • -...... ____ ...... --- -- ... ..,...... _ .. ------·-----.. - .. - ... -- ...... ,___ .-...... --... -...... -..... _ - --
ACKNOWLEDGMENT
I uish to thank Dr. John Dash, without whose help, ·suggestions,
and Pa.tience, this thesis would not be written.
,. I• I .
1 •& ----··------· &---~& - ~-- & --~-· • - -~- &. ______
TABLE OF CONTEN·rs
PAGE
ACKNOWLEDG?IDH ...... ~ ...... • iii
LI3·r OF TABL~ ...... vi LIST OF FIGURES ...... • vii
I!HRODUC'rION • • • 1
I. ·~ULK HYDRODYNAMIC EFFECTS ...... 1 II. INHIBITION OF HYDROGEN EVOLUTION ...... 2 III. SOLUTION-MET~ "INTERFACE PHFJiOEJ!NA~ ...... 3 ~ . . . - - . .,. . "' IV. THE LECLANCHE CELL ...... 4 CELL DISCHARGE EXPERIMENTS ...... 8
I. EX?~RIM"F'.• NTAL ...... 8 II. RESULTS • • • ...... ·11
. j FURTHER INi/£STIGArION3 OF.THE LEX;LANCHE CELL ...... 23 i I. HYDROGSN EVOLUTION ...... 23 II • MASS CHANGE • • • • ·.• ...... 25 III. EXTEN'r ··OF CORROSION • . . . . . " ...... 26
I~VESTIGArIONS OF TIE CORROSION OF ZINC ...... ' . . .' . . 28 I. CORROSION EXPERIMENTS ...... 28 II. DlSCUSSION OF RESULTS ...... 36 CONCLUSION:) ...... 39
RB;F~ENCES ...... 40
APPENDIX A ...... , ...... 41
APP~DIX B • ...... ·43 • • • • • • • • • • • • ... • • • • • • • • • • i XICTNaddV
• • • • • • • • • • • • • • • • • • • • • • • • •• • • • • :il XIatmddV
• .• Q XION8ddV
.. _. J XIQN3ddV
_...... - _------..... -- --....._-- ...... - ..... _.. __ Lis·r OF TABLEs
TABLE; .PAGE l !· I.. RESUL"rs uF c ELL DISCHARGE EXPERIMENTS 12
II DATA COMPUTED FOR EX~ERIM~TS 5 THROUGH 9 ...... 13 III. VOLTAGES ACROSS EACH SEr OF CELLS IN EXPERIMENT 8 BEFORE AND AFTER A 534 MINUTE I~T~UPl'~QN. • ~.. • • • .• • •.•. • • ·18
IV ENERGY OUTPUT AND CHARGE PASSED FOR SIZE.N AND SIZED I C~LS SUMMED OVER ALL EXPERIMENTS • • • • • • • • • • • • • 21 !. v !~S3 CHANGE OF SIZE D CELLS (BURGESS 210) DURING ! . DISCHARGE AT o0 c • • • • • • • • • • • • • • • • . . . . . 25 i / VI OPE,N AREA OF LECUNCHE CELL CANS CORRODED DtE TO DISCHARGE • 27
VII MASS CHANGE OF THE ZINC SPECIMENS DUE TO CORROSION . • • • • JO VIII INDIVIDUAL DATA FOR ZINC CANS IN EXPERii··1vNT C . . . . 34 - .. - ...... ______
LIST· OF FIGURES FIGURE PAGE 1 Pictorial diagram of electrothinning of zinc and the· ~9lationship between the concentration' of zn++ (n) and the distance. from the· electrode (x). . • ·• • • . 1
2 Pictorial diagram showing. th~ ~ffective pa.th (dottP.d line.) of the io~ under the influence of a magnetic field 3 . . . "' 3 ~-~odern Leclanche cell (6) ~ ...... 5
4 Simplified illustr~tion of corrosion 7
. 5 Sch~ma.tic electric~l circuit for cell- discharge ex pc riments • • • • • • •. • • • • • · • • • • • • • • • • • ·9
6 Cell alignment in the applied m.a.~etic field • • • • 9
7 Schematic circuit of Experim,ent 9 ••• 10 :
t 8 Tne effect of a magnetic field on the amount.of .oh~rge . I . ~ . !JS.~sed by Leclanche cells • · ••••••. • ••••••• ·14
9 The effect of a :magnetic field on the energy output of Leclanch~ cP-lls • • • • • • • • • • • • • • • • ; • • ·• . 15 10 Graph of charge passed per cell versus the resistance load per cell for Experiments 5, 6, 7. 8, and 9 •••••..• 16 11 Graph of the energy output per cell versus the resistancA load "per cell for Experiments 5, 6, 7, 8, and 9 • . ••• 17
12 Roug~ plot of voltage versus ~laused time .for Experiment 9 19 . . 1J Basic approach~~ t~ the det~cti?n of hydr~gen evolu~ion 24
14 Ecpipment and positioning of Exp~riment A . . ~ . . . 29
15 Fqulpment and position of magnetic f~eld in ExpP-rime~t B • 32
16 Position of apparatus in Experiment c ..• ...... 33
17 . Interior surface of zinc cans at enq of Experim~nt C • 35
18 S~hematic pic~ure_ of differential· aeration • . • • • • • 37 FIGURE PAGE
19 . Possible ex.planation for the liquid-air. line on. the interior surface of-the zinc cans used in Experiment C. • -38
/ INTRODUCTION.
I. auLK HYDRODYNAMIC Eli'F~TS ..
A r,:.port by Dash and King (i) in 1??2 s.how~ that the .elec1roohemical deposition and thinning or mAtals at constant current is more uniform if. porformed in·a magnetic field.· Also shown is that thP.. resistance of an
electrochemical cell may·be reduced in a magnetic field.
This latter affect may be· caused by thP. reduced thickness of the
int~rface layer between the electrode.and the. bulk electrolyt~~ Fick's
law states that the net drift J; ·~xpres~~ in carr~Ars crossing a unit
area p~r·~it time is proportion~l to the concentration gradient •. · . ! J = ..:n(dn/ciX} ·. (1}
wh~re n is· the number of mol~cules p~r.unit vol~ and X· is th~ distance
in th~ direc.tion ·or_ drif~ (see Figure 1). The proportionality constant
. · D is kn.own as 't~ diffusion constant an.d .is proportional to the mobtlity
of the carriers (2). n ··~~dx~f ~ .-. ...,.. Q) .· dn 't1 0 bulk . .;. ...,~ ·9~. ~ _____ .: () () . ·value ~ - .. ------. s::. OJ •rl r-4 ·•N CD electrolyte ------_..;~ x
Figure 1. Pictorial diagram of electrothinn~g· or zinc and the. ~la.t~onship between the concentration o:r .-zn++(n) al1Cl the: distapoe from the electrode (x). dn and dx·are infinitesimals. 2
If at a constant current one obtains a lowering of impedance •. then this I!\aY. be due to a steepAr concentration gradient. Also, this observation may be due to a mixing effect.
In electrochemical celis, the current is carried by moving ions.
ThArefore, on observing a mixing effect in a magnetic field~ the assump- tion must be that the Lorentz fore~ q(B x vl is stirri.~g the ions as they move. Orift vel. of the hydrogen ion is given as 22.5· x 10-4 cm/s11!3C in a field of 1 volt/cm at o0 c (J). Using this.value for the velocity in the Lorentz force and a value of 1 kilogauss (kG) for the magnetic· field 26 strength normal to the velocity, one gets a value of J6 -X: io- newtons for the force deflecting the ion. Using m = 1.68 x 10-27 kilograms for the mass of th~ ion, a further sL~plistic.calculati~n yields an acceler ation of a = F/m = 214 met9rs/sec2 perpendicular to the· direction of motion. Note that the mobility was used for the velocity of th~ indi- vidual ion and no consideration was made for the mechanism of ionic con- duction. However, even though arrived at with a naive calculation., the values of the force and acceleration of the ions are significant.
II. INHIBITION OF HYDROGEN EVOLUTION
Experiments performed by Tung in 1972 ( 4), and continued by Chen and Housen in 197 5 ( 5) • showed that the Cllrrent efficiency for the deposition of chromium is greater when performed in an applied magnetic
field. This means that a greater amount of chromium is deposited for
the same amount of charge passed.
However, chromium co-deposites with hydrogen and Chen (5) found
that a magnetic field inhibits hydrogen evolution. This inhibition of ...... -...... __ ...... -~- --- ...... --...... ~----:---~- ~- ...... -...... -....._.._..._..,
:3
hydrog13n .. evolution could be oaus~d by ·a decrease. in mobility ot the ! ' hydrog~n ion.duel to a Hall eff~~t in the.~lectrolyte. The investigatio~ by D~ Laforgue-Kk.nzter (3) of the Hall effect in aqueous electrolytes supp~rts the the~ry that the conductivity of aque~us solutions is par- tia.lly du~ 1;.o t~e H~o.+ i?n and pg.rtially due t~ .~ d~y proton, the lattet;" 1
having an ~xtremely high mobility. A magnetic field could have a larg~
eff~ct on. the movement of such a proton, reducing the mobilit~ in the
direction of th~ el'"'c.trode (see. Figu~e .2) •.
!
elioctrolyte . rg.Cl> ~ +> u ~--- (!) .Q, ..-f tJ, The direction.of the m~gn~tic Cl> fi~ld is into th~ pa.per
Figure ~· Pictor.ial diagram showing the. effective path (dotted lin~) of the ion.under the· influence of a magnetiC.field •
.I!L~ . . SOLUTION-MEl'ALt·•. IN'l'ERFACE PHENOMENA
Other f>ossible ·interactions of '.a magnetic field with an electro~
eh~mical c 0 ll may take place at -th~ ,so~'ri-metal interface. One pos- J . . sibl~ Affec~ ~s·a change. in the activation ov~rpotential. This over-
potential· is th~ difference betwe~n thP deo~mposition p0tential of the
cell and th~ reversible potential (th~ potential at which the forward
and reverse rates at the electrod~ are equal)." It is connected· with the
shift 'in.· the .Fe~i level in the D,let~l electrode from ·the v~lue which it
' !
-. 4
had when the electrode reactions were taking _place' at an equal speed.
It is possible to c~ange the Fermi level of the electrons in the mata.l
by th~ us~ of an applied mag~etic field •. The ma:gnitude of this change I . ' is, .. ~ere, ·. thg product of the Bohr magneton (0.927 x 10-20 ergs/gauss)
and the ma,;netic fie~d strength. A .fiel~ of 1 ~ would then· ·change the
Fermi levei .·by approximately ·io-17 ·ergs~
· Improved understanding ·or the magnetic interaction with electrol.. !' ysis· 'W'OUli'.3 thl?ln result from the· eH.JJli'f'.l~ti,on of. one of thA follO"•ting: l. bulk hydrodynamic effects (miXing)
I I 2,. inhibition of bydrogen evolution
. ,. 3. $0-:lh(-metal interf8:ce phenomena. -;- An electrochemical system with·the eleetrolyte immobilized in. the . ·!
form of a. paste or suspended in a fiber~u~ material would decrea·se or · ..
eliminate the ~lk mixing effect. F
th~ operation of the Le~lanc}l,.: celi in ·a magtietic field was started. ,, rv·. THE L~LA.NCHE CELL (6 )
rh~ structure of a typical Lec~anch~ cell is shewn· in Figure J.
The basic celi consists.of th~ zinc can, serarator, cathode mix, and
carbon rod, with the. electrolyte impregr;ia.ting thA cathode mix and
s e}:1! ra. tor.
Th~ 'zinc can serves as the anode and to contain.the) cell. It is madP. .by :1.mp;.~t extrusion ·and' a typical alloy consists of' 1.0% l~d. 0.05% cadmium,. and the. reniaind_er zinc of 99.9~ purity.· The alloying
~l~m.ents llriprove the mechanical properties and decrease waatetul
·corrosion. ------· - •6
5
plated steei cover expansion. -chamber _ ~ pitch seal . ~-.~ seal washer ; - carbon rod --- cathode mix _Jill--~---=-~=- sei:a-~tor - -- zinc can cupp~ ·kraft washqr plated steel cover ·,jacket·
F.iP-Ure 3. Modern Leclanch~ c~ll · (6).
·The cathode mix consists of ari uniform mixture of ~nganese
dioxide (~1 ~O~), th~ a~~uai. cathode material, and .carbo~ black. (usually acetylene black).-. The latter serves ___the double purpose· of increas·ing
' ' th9 conductivity or the Mn02 and absorbing ·th~ elect~91yte. The ratio of ~~o2 to ca~bon black may vary rrom.10:1 (transistor ~se)_to 1:1
. ' ( ohotofla sh 'batteries) .• The cathodP. mix also contains ~l~ctr~lyte
· ·amounting t~ about 25i of its total w~ight.
Th~ el~ctrolyte is mad~ by dissolving a1'Uttonium ch~oride, zinc
chloride, and ~ small amount of mercuric chloride in water. This
latter converts to zinc chloride as the me~curY plates out on the zinc
on contact • .-In use, the pH or the paste· (electrolyte and cathode mix) . . near the zinc mAY vary from roughly 6 to 4, while for 'the innermost por-
tions of t~o mix, it may vary from 6.to 10 •.
The carbon rod serves as the con~uctor of electricity ~~r the
manga~ese dioxide electrode and also ~eryes·as a vent to allow hydrogen
gas,. which forms at the ~node, to escaJ>e•
The s=-pa ... ~tion of t~~ two el~trodes is accomplished by using
I I. 6
kraft pa.per (a strong pa.per made from sulfate pulp) coated on the zinc
side with methyl cellulose contaLYling mercurous(ic) chloride. The
mercury coa.tes the zinc (as with th~ mercury from the electrolyte) and
inhibits its corrosion.
The basic anode reaction of the Leclanch~ cell is the oxidation
of zinc•
'. Zn = zn++ + 2e- {2)
whil0 th~ cathode reaction is the reduction of manganese dioxide, ,, 2Mno + 2H+ + 2e- = ¥~ o + ~o (3) 2 2 3 The standard reduction half-reactions and thermodynamic data for zinc and manganese dioxide are (?) •••
0 Zn ++ + 2e - __..Zn- AG = +35.20 kcal E0 = -0.763 volts
0 Mno + 4H+ + 2e- _. ¥.n ++ + 2Hz0 A G = -.55. 73Jkcal 2 E0 = +1.208 volts
The complete reduction of the Mn.Oz is complicated and occurs in
a series of steps. The Mn is first formed, then MnOOH, and finally 2o3 ¥.n o (8). The removal of the ¥.inOOH is considered to be the rate deter 3 4 mining step of thg overall r~action (9). In ~cidic solutions. the re~
moval is effected by
2MnOOH + 2H+ = I'lll0 + 14.n ++ + 2H 0 (4) 2 2 For neutral and alkaline solutions, protons and electrons diffuse·into
the interior of the Mn0 particles, effectively removing the MnOOH. At 2 pH 3 to 6, both processes occur. In either case, formation and the re-
moval of MnOOH is itself limited by the diffusion of protons.
Corrosion at the zinc anode (sge Figure 4) in the Leclanche cell
is an important factor in its perfor?l'~nce. Corrosion requires two
I. i .... ------...... _ ...... - ...... -- ...... _ __ ... - ...... _ ... -
7
r~actions, a reduction and an oxidation. The oxidation or anode
reaction is zinc dissolution,
Zn= zn++ + 2e- (5)
One possible reduction, which. occurs at cathodic sites on the zinc
·anode, is that of hydrogen formation,
2H+ + 2e- = H 2 (6) This necessitates venting, which allows a second.reduction reaction,
that of oxygen, which may occur anywhere in the cell,
+ 4H+ + 4e- 2~ o (7) o2 = 2
~ gas · 1. © l solution ~®~@ metal
Figure ~· Simplified illustration of corrosion. The oxidation of zinc frees two electrons which combine with hydrogen ions to form atomic hydrogen. The atomic hydrogpn then recombine into molecular H • 2 ... _...... __ --...... _ ----6-· ------..
CELL DISCHARGE EXPERIMENTS
. Thq investigation of the effects of a magnetic field. on the ~ . . . Leclanche cell was begun by m~suring ·the energy OUt}?Ut and: .charge passed ·by cells·discharged with ~nd ~ithout an applied field.
I. EXPERIMENTAL
Leclanch~ cells of size Nor D, chosen.at random from conmlercial lots, were usPd. Eithe~ one.cell or sets of ~~v~ral·cells of the same kind were drained through a known constant r~sistor at a constant temperature. The voltage ~s a function of time was recorded using a doublP .pen .voltage-t~e recorder ·(Houston Inst~e~ts Oanigraphic . i 2-JOOO). Two similar sets of cells were tested at the same time. One
.s~t ~as.drained in an app~ied magnetic field while the seco~ set was drained without the field. The initial experiment had the hookup leads sold~red to the size.N cells~ Subsequent experimP.nts used copper tabs firmly taped to the cell. ends. or us.ed non-magnetic alligator clips for contacts.· With .the. siz.e D cells .• the steel contact plates at both ends were removed, since these would distort thP. aoplied magn~tic fiPld.
The size N cells have the~r cans bare and have a copper contac~ pr.ass~ over the carbon post. In al~ cases. tµA hookup ~Pads w~re kept ~he sa~e length ·in thP. circuits of both.sets. &•-&•- &- --~------··--- -~--&~--~&&-----~
·9
.I.cells load· ..L. two· r:ien voltage-time recorder ·
Lcells in load .I. fi9ld
Figure S. Schematic electrical circuit for cell discharge $Xperiments. ·rhe number of cells in sP-ries varied from one to six.· In.one case (Experiment 9)9 the cells in the.field and .tr~ose. outside . the field were in series acrc;)s~ the resistance load (see Figure ?).
T!i!!'lp'?rature .control. wtlS provid~· ·by b.qrs of aluminum stock (at
rnom tem:o~~ature) or by ice-wat~r b:.iths. In ·the former ~ase,. th·~ two
cells or SAts of cells.were.held in rhysical contact w~th an a.lumi~um
b.9.r and. we.re loeated at opposite ends o·f this bar. If the ice-water. .
. .ba.th was used, the individual C'3lls Were sealed in plastic bags to . . prevent an electrical short circuit through the water.
Orientatiqn ~f the e~lls was .either pa~~llel or perpendicular to
the 4pplieQ fi~ld.
~- ~ di~ection of field
(a) f ~ 1 (b).
Figur~ 6~ Cell-alig!ll11ent in th~ appli-=d magn~tic field: (~) th~ ~Ppltea-ri~ld _parallel to thA •xis of th~ c~lls, and (b) the aoolt~ field pP.rpendicular to ~h~ ax~s of the cells •
. . i
~ 1. . --_____ ...... _ -- -- - ...... _.. _...... -- ...... -- ...... -- ...... -- ...... ____ .
10
Tho resulting·strip chart graph of .voltage versus time was·
integrated numerically in time interval' segments to giv~ t~e total
·amount of· energy output. r'rom the cells, 2 2 E = f Pdt = i f v2dt =~I. (vr + viv . + v ) (8) · R · 3R . . f · i
wh~r~ 'C' is thA time. interval used,· R is th~ resistanc~ load, is v1 thP- initial·voltage,of.the segm~nt.considcr~, and·vr is· the final volt
ag~ of thp same segm 0 nt (see ~ppendix A for·derivation). The suinmation
is ov~r all time segm~nts.
Th*? amount of charge .~ssed was calculat,qcf (Appendix A) from the
same strip cha:rt graph acc~rding to·: ·
Q. ::; 1 f :Vdt = .1. l (V1 + Vf) (9) · R .. 2R
· One experiment was perfo~,d in .a aifferent manner. In Experiment
9~ the two sets or· cells were connected together in series (see Figure
7). In this.manner, the current through both sets ·or cells .is the same.
two pen cells outside voltage-~im~ fiP-ld voltage 1 IA · · recorder ti.m~ recorder cells in field . 14 .ohms·
Figure .z. Schematic circuit of EXperiment 9. · The cells ~ the field and. those outside the field were ·connected in series · across a common resistance .load. ·. This load ··was made up of two known. res_istances, one of which .(R) .~d it~ v:olt~ge. drop ( VR). reco~ed. A two pen voltage-time .recorde~. plo~tftd the potential .di~ferenc·~s.,. VB· a.nd VJ.., v~rsus time· of the ~ells drained ·~ith and without· an appliett magnetic· field, respectively. . 11
Th~ energy out?Ut and charge pa.ss~d for thP. SPt of cells in. l?xptJ>rimr.nt 9 drained without thP- field w~:l°s calculated according to,
EA = J Pdt = f IVdt =. bR"?:' l (2VRiVAi + VRiVAr. +. VRfVAi + 2.VRfVAf). (10) and for the charge passed~
VM) (11) QA = ~ Idt =·.! } Vdt = ~ L_(vRi + R 2~ . where VRi and VRf' are.the tnitial and final.voltage drops across R for
: •I ' '! • tho. time segment con.sidered, VAi and yA.f are t~~ initi~l. a~d final potential differences of the cells for the same ti.m? segmen_t, and "'C' ts thq le~gth of th0 . time segment (s~e Apj)endix B). The energy output
~md charge ~ssed for the set drained with an aupii~ magnetic field is calculated similarly~
II. RESULTS
The results of the .experiments·measuring the energy output and charge passed by the Leclanche cells with and without an. applied magnetic .. // /' field are given in Table I. .,/ ... / . /.l",,.. Experim~nts are labeled 1 through 26. The type of cells nsed w~re, . for size N, Mallory M910F. and Eveready 904, ' and, for size D,
Burgess 210 ~nd Eveready 950. The different types o~ ~gnets s~pplying tha field are listed as I, I!, III, IV, and V (see Appendix C for illus- tra tions). The magn~ts are &s follows.:
I.· ••••• Va.rian Associat~s, electromag~~t mod~l V-400? with six inch pole pieces . ·
II ••••• Westinghouse, permanent hor~eshoe magnet
III ••• ~mi.mund Scientific, permanent ring magnet #30?30. 12
Tl>.3L?: I
!!:.3:.:.:.> 0!" c::LL OI3C·:t.;GE EXPERIY.i"..!iTS
4
19
20
21 v
22 v 30.1 perpend. i 22 2,450 i ~.1~ 1 1.540 ~ "·N, 904 J0.2 I iggg 2,J10 ·+-··! 1,540 ---- -·------.. 23 2.5 v 3 N, 904 9,13 Looo ptrpend. 22 J60 I -1.4~ 840 . ~ 0 3 N, 904 9.14 \ 1000 J65 640 24 2.5 I 1000 P"!'p9nd.. 22 i 2,990 i '44.5" 1,440 +2.~ 0 v __ U~~L I 1~0 1,4')0 J_J__ J1:1; ____ -~~-':"° _[_ .. -- !-·------s N, 904 59.6 1,400 ..0.7~ N, 9'l4 60.0 I1000'000 ,.,.,...,. " j '·"°2,1\80 . -··~ 1,)90 -·- -- ... N, 91)11 59.6 1~') Jl'"J"p.nd 22 2,990 '44.2~ 1,430·- -1.--~ I N, 9')4 6'l.O I 1000 1,400 ~s-r-·-rl .l ·---- I 2,!370
Resistors used 1n Experillants 1 through 14 are listed vith their percentage error. For Experi:llents 15 through 26, the values listed are those 111easured vit.h a c.nco ;.'heatston.. bridge (185295) accurate to the -·:-,,1)er or places given. See Appendix F. tor e'l'ror &Ml;ya1•, 13 IV ••• ~.~d Scientific, two permanent ring magnet~ #30730
V•••••• La}?~ratories For Science.• permanent magnet model "Variflux" For Experiment 1, a plot of the amount of charge passed versµs time
for th~ cells drained with ~nd without an applied roagn~tic field is l l given in Figure 8. ; The energy output of the~e cells ·versus time ·is plotted in Figure 9.
Exp~~iments 5. 6, 7, 8, and 9 WAre performed using the same field strength ·of 3.3 kG (kilogauss), but for various load resistances. For .
these experiments, th~ amount of ch~rge passed and th 0 energy output was. rec.alculated for a COIJl."'lOn time of 620 minutes. These values are
given in Table II •. For these same experiments, graphs of charge passed
and energy output per cell versu~ the ~esistance load per. cell b,.ve been
plotted {see Figures-10 and 11 res.pe~tively).
TABLE II DATA COMPUTED.FOR EXPERIMENrs 5 THROUGH 9. TIME IS 620 MINUTES
1 EXPERIMEN'l FIELD . NUMBER OF Cin,LS . LOAD CHARGE PASSED (kG) ENERGY OUTPUT (ohMs) (coulombs) (joules).
5· 3.3 6 . 4.6 i4,4oo· 0 30,600 .6 . 4.6· 10,600 19,100 6 6' 3.j ·4.6 14,700 j2,600 0 6 4.6 12,800 Zh,000 7 J.J 6 1.05 16,JOO · ·O 11,900 6 1.05 13,JOO 8,580. '8 . .3 .3 6 . 1.05 17.,400 12 .JOO 0 6 1.05 . 14.·900 9,900 9 3.3 ' 6 15 11,·aoo 39,400 0 ·6 1~ 11,800 2 9, 700 ...... t0')0 J CHARGE PASSED • (coulombs) .. •• .. • 9'?0 .. ••
800 .. • :A • •• ?00 • A • 600 • • ~ • •• .500 •••• 400 ·•· • .... SIX CELLSIN SERIES WITH·ANAPPLIED MAGNETIC FIELD JOO • .. SIX CELLSIlf SERIES WITHOUTA MAGNEl'ICFIE;LD.
200 t
100·
. TIME (minutes)
_40. 8 200 240 280 J20 J60 460 440 -480 520 560 600
· Figu~e..8. ·l'he .effect of a magnetic field on the amount. of ch~~gepassed by Leclanch~cell~(Exp. 1). .... ~ 3000~~NEP£Y O~TPUT {joules) ... • .. 27001 • . .. •• 2400~. ~ .. • • 21001 • • •• .. •
180~
150 . •
..• ., .. SIX.CELLS iN SERIESWITH AN APPLIED MAGNETIC FIELD l~Oa~ • I srx:·c~sIN SE.RIEs WITHOUTA MAGNETICFIELD· 9')~ • .A
I • 600
JOOl (minutes} TIME-r 40 80 . 120 . 160 20() 2hO 280 320 360 40') ·440 .480 520 600 . . " ...... The· effect· or a ~gneticfield on the energy output of ~clanche.·cells(Exp. 1) • Figure_-9. \.n 16
CR:\RG E PASSED
(coulombs) B = 0 17400 /::,. D• B ::: 3.J kG 16800 A A
16200 ...
15600
.150001 0 .6. . 14400 ~
13000
1j200 • D 12600
12000 ~ 11400 10800 • 10200
9600 LOAD PER CELL (ohms/cell)
0.1 0.2 0.3 o.4 0.5 o.6 0.7 o.s 0.9 1.0 1.1 1.2
Figure 10. Graph of charge passed versus the resistance load per cell for E:xp~rirnents 5, 6, 7, 8, and 9. Time for each exp?rL~ent was-620 ~inutes. Te~perature was o0 c •. l· I j . 17 ~N~~GY CUTPU'r PPR CELL (joules/cell) ... l:l. 6500
6000
5500 l.l. A 5000 D 4500 • 40')~
3500 D 3000.
2500
2000 J ~ I 15·')0 I o• B = 0 A A. B = 3.3 kG 1000
500 LOAD PER CELL (ohms/cell) I 0.1 0.2 0.3 o.4 0.5 0.6 o.? o.8 0.9 1.0 1.1 1.2 Figure 11. Graoh of.the en~rgy output per cell VPrsus the resistance loa.d pt:!r c-ell for Experiments 5,· 6, 7 • 8, and 9. Time· for each I 0 experiment was 620 minutes and the temperature was o c. The cells in th~ 0xp~riinent at 1.25 ohms/cell w~re all in series (see page 10). 18
Dur~ng the operation of Experiment 8, a power failure turned otf
the electromag~et and ope~ed the Leclanche cell circuits. -DUring t~is
interruption, the cells were able to recover. The experiment was int~r-
rupted J46 minutes after its start and the length or the int~rruption. was 534 minutes. The power was then reapplied and the exper.iment allowed.
to continue •. Iri. Table.III, ther~ is listed the values of ~h~ voltages
across each se~ before and after th~ interruption ·Of the expeririient.
TABL~· III V'OL't'AGES ACROSS EACH SEl' OF CELLS IN EXPli'RIMFNT 8 BEFORE AND AFT!i'R A 534 .MINUTE INT~RUPrION. EACH SEI' HAD BEEN." CONNECTED TO A 1. 05 ± 2~ OHM. LOAD ~OR A PFRIOD OF .346 MINUTES PRIOR TO THE . RECOVERY PERIOD
I I I ·. I VOLTAGE BEFORE VOLTAGE AFTER· ~. _INCREASE · I ! CELLS WITH FIELD .J22 volts .810 volts 15~ I CELLS WITHour FIELD .275 volts .570 volts 105%
Experiment 9 is unique in that it was the only experiment run with
·th~ two se·ts of· cells in series (see Figure·?.). The energy output and
charge.passed were calculated in this experiment only·for the first 840
minutes. :rhis was due to the vo:Itage across. the ce+ls drained without
an appli~ magn~tic.field dropping to ~ero at the end or this period
12). (see Figure The experiment was allowed to .continue . beyond. this r;>o.int and for· a. p"?.riod of 1 30 min'1tes thA potential across the cells
· outside th 0 field was some U?Ullea~u:red nega~ive value. For t_he next 210 minutes, the potential across this set of cells was again positive. The experiment was then ended. 19
VOLTAGE (volts) l I 1 l i ·10 l ·upper line •• .-cells .with field .· .·lower line ••• cells without tield
1.11 2 ' • ...... _ 1.45 volts o.3·volts
I -==---·.... ' ,,...... -- • ) TIME .840 .. -970 1i8o (minutes)
Figure 12. Rough· plot of voltage versus-elapsed time for Experi- . ment 9. . The two sets of six c~lls were wired· in series with a 15 ohm r.esistance load. Th~ field used. was 3.3 kG. The dotteq. · line indicates· the section where no. voltag.es. were measured. · ·During th~s period, the,cells.llithout ~n~ppl.ied field were' acting as ari additional load for the set of ·cells positioned in the · magnigt ic ·field.
It was stat~ in tha Introduction tha~ the removal of MnOOH by
proton diffusion into th~ interior the MnO particle·is considered to or 2 . be tha rat~ determ~ing ~tep in the Leclanc~e cell •. Therefo~e, a crude
! . determinati~n of the diffusion distance (x) of thA .proton was calculated
from the recov~~y time (t = 130 minutes) during which th0 potential
S.CrOSS thq 111a~AtiC. W&S. . CellS'_. in. Experiment . 9 Without. an applied field . - ~18 2 ' negative. The diffu_sion constant (~) for protons .is 1.2 x 10 cm /sec
( 10). Then the 'diffusion distaneq· -(11) is
x = -ti 2Dt (1.2) ·= .,[i.(1.2 x 10-lB cm2sec-1 )(9.8 x. 10J· sec)' · ...... ·20
x = 1.5 x 10-7· cm
·This v~lue corresponds to several molecul~r layers.
Th~se .~~sults indicate a apparent increase in energy output arid
in th0 amount of cha.rge passed when thP. cells are d~ained in an applied . . . / . magnetic field.~ The total energy output of the Le~lanche cells in
Experiments 1 through 26 is 21? kilojoules for those drain~ in a field
and 1~8 kilojoules for. those without.. · This is a 15~ difference iii
energy output. The percentage increase in the amount of charge passed
~as 9.0~ with a total of 149,000 coulombs passed'. by those ce~ls in the field and 136,000 coulombs for those without. The total number or
Leclanche'cells used in the 26 experima~ts was 202, with·101 being
drained in an applied magn~tic field and 101 with.out.
A ma.rkied differ.ence is noted between· .the increased output of the.
I size D and size N c~lls (see Table IV) •. The latter have a ·relatively I l I s!llall increase .·in energy output ~nd in th~ amount of charge P&ssed with
th~ a ~plied magnetic .·fi~ld. Anoth~r diff1?rence between the two cell
sizes li~s in the ratios of the volume.of the. cathodic material (V)
to th~ surface a~ea of the zinc (A) with.which it is in contact. For
the sise N cells, the app~oximate·ratio is
V/A =· (2000 mm.3/(800 mm2 ) = 2.5 while for the size D cells,
vI A = (Jo, ooo nUn3 )I ( 5, o~o mm2 ) · = 6 If the bulk hydrodynamic mixing effects are negligible in the . > . . . . Leclan~h9.cell, then one possible contribution to the great~r efficien~y
of th~ cell.is thP- inhibition by the magn~tic fielrt of hydrogen evolution
~t tho ~inc anode. This might be expAOted if proton.motion to cathodic TABLE IV
ENERGYOUTPUT ANI) CHAFGE PASSED FOR SIZE N AND SIZE D CELLS SUMMED OVERALL EXPERIMENTS
SIZE NUMBEROF NUMBER ENERGY(J) CHARGE(C) '/, INCREASE EXPERIMENTS.OF CELLS FIELD .NO FIELD FIELD NOFIELD ENERGY. CHARGE
N 18 136 45,000 44,300 24,JOO 2~.100 1.6~ o.8~
·D 8 66 172,000 144,000 124,000 112,0~0 1~ 11~ ' all . 26 cells 202 .21?,000. 1'38,000 149,000 136,000 1si 9.0~
N ..... 22
sites on ~he anode is impeded by the field. The zinc-oxidation/ . -
hydrogen-reduction mechanism d~0s not directly influence the zinc
oxidation/manganese dioxide-reduction couple, but it does indirectly by increasing the amount of z·inc ions being produced. This la.st
increases the zinc ion concentration gradient, reducing its effective mobility and increasing.the resistance of the cell. .., ,I .FURTHER INVESTIGATION OF THE LECLANCHE CELL ··~ /'
·rhe pos~tive re.lationship betw~en an S:ppl.ied magnetic .fi~ld and a;n
increase. in the energy output and in ~he amount of charge passed has been
shown·. However, the r~sons for this effect are still uncertain. As~
swning that the bulk hydrodynamic effect .of mixing has been eliminated
I • or reduced·, investigations of corro.sion is Leclanche cells. ·with and with-
out th~ pr~sence ·of ·a magnetic field were attempted. ·
I. HYDROGEN EVOLUTION ! I ! As se~n·in Table I, an apnlied ~:gnetic .field of SP-Veral kilogauss : I I can increase th~ amount of charge passed ~y Leclanche cell through
vari~~s resis~ance loads_. If this is at l~ast p~.rtly- a result. of the
i.J:ihibition of.hydro~en.ev~lution, then·disc~rging.cells in a field
should hav~ ineasureably less hydrogen. gas being disch::i.rged than cells
discharging under ·the 'am.e conditions outside the f·ield. .
Using the result~ of Experiment 1, a dif'~erence of about ~O coulombs passed was calo'lilate.d for two sets of six cells 'being drained
into 60. ohms. This corresponds· to 2H+ +·2e- ._. H (6) 2 (2 mo+es)(96,?00 cotilo?Qb.~/mol~). ~ (1 mole)(2 gr~ms/mol~ of H2 )
·50 cou,lombs -... 0.0005 g~ams H2 .
I . , ~ 6
••• s~v~ral cubi~ cent1:Jui:t,ers of ~rog~n gas .• assuming. tJ:iat .the
gre~.. ~er amoU11~ .or charge being passed in ~e cel~.s. i-ns.1da the :field is
'\ I I 24 a r~sult 0f the inhibition of hydrogen evolution •. So if one:were to
s~al th~ c9lls in a oontain9r, wit~ a method of measuring volume or
pressure ch!in~.e as thP- o~lls w~rq drained, it ·shoul~ be poss.ible to
t~st th~ theory.·
·Tu~ b.qsic approach wae; to seal the cells·· in a glass tube with
wir~ l~ds antering by way of ~ water fillAd. tube (see ~igure 13) and
·to detect~ change o~ volume. by a column of water or mercury. A
nitrogen atmo~phere :wa~ µsed to suppr~~s .~he a~companying reaction.
o2 + 4H+ + 4e- ~ 2820 (7) Alternately, the load resistor itself could be sealed in with the ·cells.
No oonsistant results were obta~ed due to either leakage or lack of
sensitivit~. a~d this approach was abandoned.
mercury bead -..._.__, ends 5.-::.aled after cell ~(and resistor) ·placed inside
~ water level ~> resistance load
Figure l'J. &sic approaches to ~he detection of hydrogen evolution. · 25
II. MASS.CHANGE
·The .reduction of oxygen (which enters th~ cell through th~ carbon rod) also 1ncreas9s the amount of zin~ corrod~~ "zn = zn2+ + 2e- (5)
02 + 4H+ + 4~- = 2Hi0 (?) Another possible explanation of the increas.ed charge passed rnay
lie in less cell res~stance due to an inhibition .of the above red"ction.
To investigate this possibility, size D cells were s~ripped_of
. their pa.p~r ja.ckets and metal. contact caps, and cleaned. Cells were·
pl~c~d in ice-water baths as in th~ cell discharge .exp~riments and drained into constant resistance loads. Mass measurements were made I .1 of th9 cells· .before ~nd after being .drai!ied but no consi13tant data was 1 1
obtained.·.. Data is given in Table V. Diff 0 rences in the n~ber of
cqlls .dra inoo with and without an appli~d mar.neti~ field resulted from
thr:> disc~r~(ing of cells that leaked e~eetro).yte.
TABLE' V
· J.VIASS .CHANGE OF SIZE D CELLS (BURGES.:3 210) DURING DISCHARGE AT o0 c. TIME .. WAS 108 MINUTES
t FI.ELD LOAD INCREASE IN MASS
4.5 kG 5 ohms. +'.J.006? grams · 0 5· -0.01)4 0 5 -0 .• 0306 0 5 +o.006? 3/3 10 -+-0.0075 J.3 . 10 -0.0047 J.J 10 +o.0096 J .:3 10 +o.0060 0 ·10 +o.0108 0 to +o.0082 0 10 +o.0938 26
. '. III. EXTENT OF .CORROSION
Hydrogen evoluti-on is part of the corrosion process for .zinc in
.I' .the Leclanc~e cell_ ( 9 ) •. Therefore, a crud.a measurement of ·the extent
of corrosion· of cells drain~d ·:with and w.i~hout an -applied field was.
made~
Thirty-six Eveready 950 size D cells (see Tabl~ _I,. ex!?erim~nts 6, . . 7, and 8) had been drained until the cell walls ·
were pitted with holes. After disc~rging, the.cells were cut apart
and th~ cells flattened out. The bott?m ends w19re .discarded.as they
wer~ protected from .extensive corrosion by a· cupped kraft washer (see Figure 3).
The flattened c~ll walls were.then U$~ to o~ta.in a ph~tograph~c
contact print·from.w~ich ~h~ open ~rea of the .zlnc .anodes w~s est~ted.
This was done by using a ~lastic sheet which had a grid ne~work photo
gra phicall1. laid ·on it. Theindividual squares o~.this grid had an·u~it . " 2 . . . . area of o.911·cm. r~e 18 ceils drained without th~ field had. a total
area of 11.9 ~m2 eaten away oom~~ed to 25.8 2 for' the. c~lls without T 0 T ' om ' \ the field (see Table VI).
The increased area of corrosion of the cells in th~ magnetic
fi~ld correlates qualitatively with the ~creased charge passed (see
Tab~es I ,a.nd ·VI). However, there is. cno 'W'ay presently to quantitativP-ly
conn.get the a'mount of open areac corr~ed to the ~mou~t o~ charge ~~sed.
This l~st is necess~ry ·to det~rmin·~ ·it~ ~hf!Jre w:as ·an inhil:?ition of
c'orr
just a re~ult of the amount 9f charge pass~.
:. I ...... - ..__ ... ..,. ___ ..__ ...... __ ....._ --... - ... ----
TABLEVI
/ OPEN AREA OF LECLANCHECELL CANS. CORRODEDDUE TO DISCHARGE
-~XPERIMENTFIELD NUMBEROF . ·. LOAD TIME : CHARGE_PASSED AREA NUMBER {kG) CELLS (ob.ms) '-1>Il_4CREASE (~inutes).(coulombs) · (cnf ). WITHFIELD 6 3.3 .6 4.6 1640 0 6· 20,JOO 14.11 ?6f, 4~6 1640. 17,500 .6.10
? J.J 6 1.05 9tSO 0 19,000 5.01 ?tf, ·6 1.05 . 960 15,600 .4.J.8 8 .. J.J 6 · i.05 620 17,400 0 6.75 280~. 6 1.05 620. 14,900 1.48
N ~ I 1 ·
INVESTIGATIONS OF TH~·CORROSION OF ZINC
I. CORROSION EXPER~TS
In an ~lectrochemical cell, interaction of the magnetic field with
processes at both anode and ca.thode are possiblC?. Furth.~r work, there- fore, was concentrated on only one process, that of corrosion at the zinc anode, due to time limita.tions.
SpP.cimen~ of zinc were allowed to corrode with and without an
I I applied magn~tic fieid in an electrolyte made up of ammonia chloride and ·!
zinc chloride. Thes~ two chemicals are contained ~n the electrol~e I I : ; us~ in th~ Lacla.nche cell. Chang~ in mass of thP. specim~ns was: I
m0 asured to determine the effect or the magnetic field on the corrosion prOCP.SS.
The el~ctrolyte was made up with .one moll3 of e'ach of the above
chemicals plus enou~h de-ioniz.ed water to make one liter of solution. In· all cases,. the zinc specimens for each experiment.were cleaned
and w~ighed in an identical manner. Four different experiment's we~e performed.
Experim 0 nt A
~ighteen zinc·diSCS (99.~ pure With rPSpect to Metallic impuri
NH The ti~s) wer~ allowP.d ~~ corrode in the 4Cl-ZnC12 solu~ion. disc~ T.~ere 0.03 cm thick and. 1.94 cm in diameter. They werP washed with
l.A.btonP (Van W~ters & Rogers, Cat. No. 218.50-003), rinsed with wA.ter, and .then placed in.an ultrasonic cleaner with distilled water for 5 ·
.! 29.
minutes. rh~ specimens were then dried wit~· a hot air gun. Nine of the discs were nlaced horizontally in a 15 ml beaker (Kimax #14000) with· one layer of.Kimwipes m~terial (K~berly•Clark Corp~, ·st~k.No. 34i50)
betw~en e~~h disc. The beakers wer~ filled to thA 10 ml mark with the
. elec.trolyt~. The second group of nine discs ·were prepared in the s~me
way. One group was left in a field of approximately 2 kilogauss, while
the·s~cond group of nine discs was allowed to .corrode without a n)agnetic
field. The m~gnet·used.was a Varian Associates model Y-4004 electro-
magnet with 2 inch pole pieces.
2.6~ cm ' .. -, .... 2.4 w- .. 1 0 ml mark .pol~ ,. ~ §5 ~ pole piece c:=:> piece J2.25 cm . beak~r .with specimens 15----- ml bea. ke'r Kimax #14000
FigUre 14. Equipment and positioning of Exp~rim~nt A.
'fhe mass of th~ specimens ·"ras mP-asured bE'fore and after t}}e
experiment. rable VII.gives the results ~f·this experimen~. The total
change in mass is given with a p~sitive amount indicating ~n increase .in
~ass. Tim~ for t~e exp~riment was 98t hours.
Experiment B
·rwe·nty~four recta.ngular .zinc strips· (99.~ pure with respect to
m~tallic impurities·) of ·various di.m~nsio~s ,.,.~re allow~ to corrode. in
th~ electrolytic solution. The strips were arranged. in three groups,
'1 I I !. ;• ,,.
L.:.i..::' .JII
.,...,......
~:··:G -; 3PSC~.El\.:3DU2 1'0 CGRR0.::>Id~ :.~;.33cr:.... ~ (:·? .:: znc
f 2F.P~;.I'UR~ FISLD. ·spscII~EN.3l~JMBSit OF TOTAL ~·j~.)3CHA1-.GS rn~ EXPmH!~NT· (OC) (kG) (type·) SF~CHiEi~.3 (graI11s)
. ~2· A 2 discs 9 -0.01.276 98t hours 0 discs ·9 -0.01133 98t. _hours 22
0 ·7 .22 3 2 top rectangl s 8 -0.02518 days days_ 22 2 bottom r 0 ctangles 8 ·-0.02337 ? 22· 0 rectangles 8 -0.02573 7 days c 4.5 cans 10 +0.0063 7 days 22 0 cans 11·· +1.0006 . ?:days 22
~ days . 22 ._, 1.5 top rectangl19s 4 -0.9151 7 22- '.) r 0 ct.g,ng:l'3S 4 -0.0076. 7 days
. w . . ·a. Jl
Aach of whic~.contained thA following zinc ·strips:
2 ~trips: 15i2 cm x 1.27 cm x 0.7 cm .2. strips~ ·15.2. c~ x 1.27 cm x O.J cm · 4 strips: 15.2 cm x 0.91 cm x O.J om. Each group made up of the above strips wer.e clP-aned as in E?cperi
ment A and placed ·in a 25 ml graduated cylinder (Py~ex #3075) with a
strip 9f Kimwipas· material between each strip. The cyltnd·ers were fil~ ed with the electrolyte to one inch above.the top of the specimens. One group was left to corrode with a field centered at the bottom edge of
the strips, one with tho. field at . the top . edge of thP strips, and the r~ma?-ning group with no app~ied·magn°tio field.
As mentioned before, the corrosion of zinc involves an oxidatio~
and a redu~tion re~ction• Two possible reduc~ions ·are that of H+ and
of o2• T.h~ l~tter w~l1ld b~ influenced by th 0 depth in ~he solution at
which th0 corrosi<:>n occuz!.ed. ·rhe field was apnlied at two regions of
the zinc strip ~o determine if there ~xists an interaction between the
fi~ld and 02 reduction. A difference in depth.should, therefore, vary
thP- streng~h of.such an interaction, .if all other.factors a~e unchanged.
Time was one week. The magnet used was a Varia~ Associates mod.el '·V-4004 electromagnet with 2 inch pole pieces. Field was approximately 2 kG. Results are given in Tabli=i VII and the experimental equipment · ' . . . is diagramed in Figtire 15.
Experiment C.
In this e~periment, the zinc containers from·Evaready 904 cells
~~r~ filled with 1 ml of th~ NH4c1 2 ~zn~l2 solution and tested for the ~rr~ct of a ~agn~tic field on·corrosion. 32
~ .. 1.85 cm ...... , pole· magnet positioned J .5J piece at top edge 1 18.4 cm ,------i ' magnet. positioned 'i I : at bo~tom edge 1 I ! . .:...... graduated cylinder fyrex #3075 ·
-~~· Equipment and. position of magnetic field in 'I ·Experiment B. · . !
The cells used were cut open at the top and the inside rnate:rials
r 0 moved. The cans were then cleaned with Labtone, rinsec;i, and th~n
plac~ in a .zinc cleaning solution ·for one minute. ·This cleaning
solution was ~de up of 100 g~ams of chromic aci~, ?t grams of sodium sulphate, 25.ml of nitric acid ·and 475 ml of distilled water. The zinc
cans were then re-rinsed and placed in an ultrasonic cleaner with dis-
·tilled water and finally rinsed again in ~istilled water. The cans were
then each dried with. a hot air gun for.10 seconds. The can ·size was 7/16 inches in diameter and J/4 inches high.
An alumin~n bar was drilled with two. ·sets of holes, one at either end,
to serve as a heat sink and holder for.the cans. Once-divided into
two groups and placed in either end of th~ ·alum:\,num bar'·. the ·cans were
filled with one ml of the ele~trolyte (using a 1 ml calibratPC! pipette).
On~ ml of· electrolyte filled th~. zinc cans to a d~pth of approximately . .
1.0 c~. A magn~tic fi~ld was centered on th0 zinc cans at one end of ' . 33
thA aluminum bar ~hile the other set of cans Wlis l~ft.to corrode without
. an applied field. ·The :magn~t used was a Varian Associates model V-400?
,•. with 6 inch ·pole. :pieces. The field strength was 4.5 kG •.
vfield magrr zinc can . cr holes drilled to· .hold cans ... 0 a.luminum bar c:.
Figure 16. Posi.tion of apparatus in ~~~rilTlent C•
AftAr a p~riod of one week, .the cans w0 re removed, rinsed, placed
in an ultrasonic cleaner for 5- milllutes, and re-rins~, all with dis-
tilled water. Then each can. was dried with a hot ~ir gun for 10 seconds
and re-weigh~ •. In Table VIII are listed, th~ .individu~l mass changes, together with the mean, average deviation, and:standard deviation .of each group of cans.
At the· completion of the experiment, the cans were cut open (see .Figure 17) and inspected. A dividing line of variable clarity was observed, separating the inside.surface.of the zinc ca"ns .into two
regions, ~ne which was. in contact with the electrolyte and the.other
which was ·expos~d only to air. .In both groups, the· liquid-air line on
the flattened cans show a visual increase in width With an·increase in
I. j 34
TABLE VIII
~DIVIDUAL DATA FOR ZINC CANS IN EXPERIMENT C
FIELD NO FIELD INDIV:IDUAL. MASS CHANGEs ·-0.0051 -0.00.31 (gr~ms) -0.0040 -0.0023 -0·~0024 .• 0.0007 +o.9003 -0.0007 +o.0008 .+o.0009 +o.001? -t-0.0010 -+0.0018 -+0.0011 +o.0021 +o.0012 +o.0025 +o.0013 +o.0042 -t-0. 0019 +o.0044 MEAN VALUE. +o.0006 +o.0001 AVERA.GE DEVIATION +o.0025 +o.0014 STANDARD DEVIATION +o.0930 +o.0016
·roTAL MASS CHANGE +o.0063 +o.0006
l l ! i.
• T . .;. .. ( . . 5 CM ,. r .. - ~·-~ ~~ .• ~J I ' --': -0.7 14 +l.O +1.2
'.-1 c1°1:~)1(~ -3.1 -2.·3 -0.7 +0.9 TI.I + 1.3 -t I. 9
DECREASE INCREASE IN MASS ~ -- ....
i.:·#. '· ... ."''·_-r . ~~ .· •J ,. ._' ... • ...... ,. ,-: . ·> . ·-.. . (>~
·.1 ...... ~: I . - ~~,;~~- ...---- ...it -11 + 0. 3 -t-0.8 I -5.1 -4.0 -2.4 NI+-1.7 +2.1. +4.2
UPPER CELLS ...... NO F /ELD " LOWER CELLS . · 4.5 KILOGAUSS- :l-.;··1~1·" .· ...... •.. ·.... ·~ ~>.- • . ;1\r ,.
- ~~- .. if. + 1.8 +2.8 +4.4
FIGURE 17. INTERIOR SURFACE OF ZlNC CANS AT END OF EXPERIMENT C. MASS 'CHANGE IS IN MILLIGRAMS.
\..t.) \Jl 36 :mass.
Exp~riment D .This experiment is. identical with Experiment B except that none
of the ·r~ctangular specimens were allowed to corrode with a magnetic
fiel~ applied at th~ bottom edge· (see Figtire.~5). ·Data is·given in i'able· VII.
·rr .. DISCUSSJ;QN. "OF Rr:suLTS
.F.xpt'.'rim~nts A, B, C, and D '·~t:?re perrormed by allowing zinc metal
to corrode in_ an ~lectrolytic solution. For Experiments A-, B, and D,
the mass .of the specimens decreased, but the results are confli~ting.
In A and J?, th~ zinc specimens which were allowed to corrode in a mag
netic field have a greater mass los~.than the· specimens corroding with
no app~ied field. Bu~ ~ Experim~nt B. the specimens outside.th~ field have the greater mass loss.
Also., fo ~xperiment B, there· is ·a. definite difference in mass
loss betwe~n t~e two groups .of zinc· strips which were allowed to c~rrode with a magnetic field centered on ·different ends which were at different
depths tn the· electrolyte. The strips with the fie~ center~ on the
. edge n~ar .thP surface had th~ greate~ ma~s loss. Both of these groups
did, however have a smaller mass loss than the third ~roup of zinc
strips ~hich ~ere allowed to cor~ode without the applied magnetic .field.
·So while the results indicate that the .~gnet~c field re4uces the
corrosion of z.inc in Experiment B, i:t does ·so to a greater extent when
it acts furth~r from the surface of the eleo.trolyte. Differential
&?.ration (see Figure 18) would cause th~ lower part.of-.t4~.zinc str;p
.~ J?
(:which i.s a~rated to a lesser degree) to corrode at a greater rate.. It
would then appea~ t~t the roagnetic field inhibits the zinc oxidation
reaction, having a lesser effect near th~ surface where the cathodic
reaction dominates. However, this 'theory conflicts with EXperimeri~s A.
and D, wh9re the field. appears tQ promote corrosion.
a.ir electrolyte more dissolved oxygen, reduction dominates zinc + + 2H. 02 . 4H+ 4e- = "20 i ~·- less oxygen, oxidation dominates Zn = zn++ + 2e-·
Figure 18. Schematic picture of differential: aeration. The availability of oxygen ·causes the upper part or·the zinc strip to be ca.thodic with respect to 'the bottom.
In ExperiJnent·C, the ~orroding zinc cans actually gained mass~ and it is assumed that zinc.compounds (formed as· the zinc oxidized) ·adhered to the metal •. The.cans that corroded within the applied field
gained significan~ly more mass than the cans outside the field (see
Table VIII). The standard dev~tion for.the values of mass change of
the individual cans in the field was almost twice that of .the cans ~~t- side the field. No explanation was developed.for this or for the.
change in width Qf thP, electrolyte-air line on the interior surface of
the zinc cans. This .. liquid-a1r linA could p(>ssibly be. caused by dif- 38 f~rPntial aeration, altho~gh this has not been investigated (see
Figure 19).
anodic air -shielded from o2
NH Cl + 4 x••• zinc oxidation products ZnC12 in solution ~inc
Figure 19. Possible explanation for thP- liquid-air lirie on the interior surface of the zinc cans used in Experiment C. Corrosion initiated at a weak point of the me~al surface might lAad to the formation, along the meniscus where th~ renewal of oxygen is easy, of a membrane of oxidized zinc products. This might then shield the zinc surface underneath from access of oxygen, making it · anodic with respect to areas with aera~ed ·pa·ssive regions. · CONCLUSIONS
An applied magnetic field apparently can affect the energy output of a Leclanch~ cell in two ways, depending on the strength of the field.
Belo~ 2 kG, the data suggests a decrease in energy output for the cells drained with an applied field (see Appendix F). This could be caused by an increase in cell impedance due to a Hall effect (page J). At field strengths of 2.5 kG or larger, an increase in energy
output is indicat~d (Appendix F). No well-grounded explaination ha.s y~t been developed and more work is necessary. Possibly, for large
enough fi~ld strengths, th~ decrease in mobility of H+ would permit a more a~tive role for a·secondary charge carrier.
The original problem of magnetic effects at a solution-metal
interfac~ is still unsolved. More work must be done in this area. , The action at the zinc-electrolyte interface in the Leclanche cell was masked by the rat9-determining step at the cathode. REF·ERENC ES
1 J. Dash and W. W. King, J. Electrochem. Soc., 112• 51 (1972). 2 A. W. Adamson, A Textbook of ?hysical Chemistry, chapter 12, section 12-ST-1, Acedemic Press, 1973 3 D. Laforgue-Kantzer, Electrochimia Acta, 1.Q., 585 (1965) 4 J. Tung, Unpublished r?.s3arch, 1972 5 R. T. Chen and K. Housen, Unpublishoo research, 197.5
6 J. Davis, Dry C~ll, Encyclopedia of Science and Technology. vol. 4, McGraw-Hill, 1971. 7 Handbook or .Chemistri and fhysics, 51st edition (1970-1971), The Chemic~l Rubber Co. 8 S. Ghosh and J. P. Brenet, Electrochimica Acta, z, 449 (1962) 9 D. B. Matthews, Rev. Pure and Appl. Chgm., 20, 103 (1970) 10 A. B. Scott, J. Electrochem. Soc., 107, 941 (1960) 11 A. W. Adamson, A Textbook of Physical Chemistry, chapter 2, section 2-7, Academic Press, 1973 APPENDIX A
THE CALCULATION. OF THE. ENgRGY OUTPUT .AND , THE AHOUNT OF CHARGE PASSED BY A LECLANCHE 'CELL
.The energy output of the Leclanche~ cells in the. cell discharge
exper.iments is given by . ~ E = f Pdt =tf v2dt = t ~Svk2dt (12) 4=r 0
where the· ·vol~ge-time plot of the exp~riment has been divided into n
segments of width ~ • R is the resistance load of the .cell drainage 'experiments, vk is the voltage as a function or time· for segment k, and L' is the width or the segment.
VOLTAGE
I· • • ·• • • • > TIME ~ Figure 20. In the calculation of energy output and.charge passed, the·volte.ge of the cell sets as a function of time is assumed to be in ·1µiear·segments. Segment k.is labeled. '
If ~k is_assumed to be equal to a linear function ·ror· each
·se~ment and v1 •. vf.to. be the initial and final voltages of those segments, then . . n ~ ~ . 2 2 (13) E = ~L Jvk dt-::: ~[ f (v1 + Simple .integration yields E-=~~cvf.2+vv +v2) (8) 3RL 1 r 1 summed over all segments. The charge passed is ·given by (15) Q = ~J Vdt ~ ~r.pkdt . k=1 0 Q =.::_~(Vi + Vr) (9) 2RL summed OVer all SPgmentS • : APPENDIX B THE CALCULATION OF TH~ B:NERGY OUTPUT AND THE A!10UNT OF CHARGE PASSED IN EXPERIMENT 9 In ev.pP.riment 9, both s~ts of cells were wired in series with a com~on res~stance load. (see Figure 7) •. For this case, the P-nergy out-. put for the sPt of cells without the field is given by EA = f. Pdt = 5 IVAdt (16) EA:: t J VAdt . wh9re, at any t~e. t, VA is the pot.ential difference· across the cells, VR is th~ voltage drop acro~s ~. and I = VR/R is t~e current • . As in Appendix A, the voltage-time ·plot has been divided into e ~qual segments of width "t', and for each segment, the voltage is assumed to be a linear function of time. Therefore, we have for VA and VR, VR· = VRi + ~VRf - VRi)t/'i: VA = VAi + (VAf - VAi)t/~ (17) wh 0 r~ for ~ach segment, .vRi and VRf ~re the initial and final vol~ges of th~ resistance load, and, VAi ~nd VAf ar0 the initial and final . . potential differences of the cells drained withou~ an applied magnetic field. Th~ en~rgy output is then given by H:A =fa I (2vRivA1 + vRivAf + vRfvAi + 2VRfVAf) (10) 44 wh~rq the summation is over all segments. rhP expres.sion for the .charge passed :t>Y the same set of cells is given by QA = 5Idt = t JVRdt (18) . QA ~ {VRi + VRf) {11) · ..!.'2RL wh~re th0 summation is over all segments. The equations for the energy output and oh~rge passed.for the ·cells drairied in an applied magnetic field are identical. APPENDIX C MAGNETS USED IN, ·EXPERIMENTS J.8 cm iE--:) .Magnet, ~periznent D. J.J5 cm ~ 4~4 cm Magnet II 0.250 inches ~ 0.750 ! .015 inches lfiagnet III, IV Edmund Scientific #30,730 \) I ~ 46 ··r- I 't l I ~ .. - l . N.agnet l. A••• Varian model y.;+007 electromagnet. with the pole pieces (six inch dia~eter) turned to ·provide a vertical· magnetic fiAld . , . B •.• Polystyrene ·container in whiCh th~· cells were placed. along with a mixture or water and ice t6 maint-!!in constant t~mpera ture . · · · · · :.. APPENDIX D INITIAL CALCULATIONS OF ENF.RGY OUTPUT AND· CHARGE PASSED FOR Tit<"' FIRST 100 MINUTES OF EXPERIMENTS· 5, 6, ?, 8~ AND 9 EXE 0 riment 5 TIME ENERGY OUTPUT CHARGE.PASSED (minutes) (joules) (coulombs) FIE~ NO FIELD FIELD NO FIELD 0 0 o. 0 0 1 40? 270 72.8 59.7 2 756 508 . 140 115 3 1080 ?JO 20.5 169 4 1390 939 269 221 5 1690 1140 331. 272 6 1970 030 392 322 7 2250 1520· 452 372 8· 2520 1700 51~ 420 9 2790. 18?6 571 468 10 3040 2050 629 516 20 5350 , :3600 . 1180 965 JO ?160 4860 1660 1370 40 8570 58?0 2090 1730 50 9700 6700 2480 2060 . 60 10?00 ?420 2830 2370 70 1i600 8060 3170· 2660 80 12400 8620 3500 2930. 90 1J100 9130 3800 J190 100 1)800. 9590· 3970 3430 48 ~oeriment 6 TIME ~ERGY OUTPUT CHARGE PASSED (minutes). (joules) · .(coulombs) FIELD NO FIELD FI~D NO FIELD 0 0 0 0 0 1 425 407 74.4 72.8 2 791 .750. 143 140 3 1130 1080 210 204 4 1450 1380 275 268 5· 1?60 16?0 338 329 6 2060 1950 401 390 2350 2230 436 450 ~ 7 .. ·. 2490 ; s· 2630 47.0 509 9 2910 2750 531 567 10 3180 3010 ·590 625 20 5640 5350 1160 1170 30 7680 71'60 1670. 1660 40 9)40 8600 .2140 2100 50 10700 9690 2560 2490 60 . 11900 10900 2950. , .2860 70 1)000 11800 . "3330 3220 80 13900 12700 3680 3560 90 14800 13500 4020 )880 1000 156.00 14300 4340 4200 :- ; 49 Experiment· 7 · TIME ~E:RGY OUTPUT · CHARGE PASSED (minutes) (joules) · (coulombs) FIELD NO FIELD FIELD NO FIELD 0 . 0 o· 0 0 1 428 373 157 146 2 743 649 290 271 3 1030 ~96 417 390 4 1290 1130 540 505 5 1540 1)40 660 616 6 1780 1550 77? 724 . 7 2000 1740 890 829 I 8 2220 ' 1000 j 1920 932 ! . 9 24JO 2100 . 1110 1030 10 2620 2260 1220 1130 20 4200 3560 2160 1990 30 5290 4440 2950. 2690 40 6120 5090 J640 3.310 50 6810 5590 42?0 J840 60 7380 5950 4840 4290 ·, 70' 78?0 6220 5370 4690. 80 8280 6410 5850 5020 90 8620 6550 6290: 5290 100 8900 6650 6690 5530 50 Experiment 8 TIME · ENERGY OUTPUT CHARGE PASSED (mfnutes) (joul~s) (coulombs) . FIELD NO FIELD FIELD NO FIELD 0 0 0 0 0 1 362 324 143 136 2 628 562 267 252 3 870 779. .384 364 4 1100 982. 498 471 5 1310 11?0 609 575 6 1520 1350 718 . 6?6 7 1120 1.520 824 114 . 8 1900 t670 928 869 l . ·9 2090 1830 1030 962 10 2260 1970 1130 1050 20 3650 . .3130 2020 187,0 30 4620 3950 27.60· 2550 .. 40 5.360 4600 3410 .3160 50 5970 5150 4000 .3720 60 64?0 5620 4.540 4240 70 6900 6020 5030 4720 . 80 7260 ·6J80 .5490 5i79 90 7580 6700 5910 5590· 100 •' 7860 6970 ~310 5990 51 ~pqriment 2 TIME ENERGY OUTPUT · CHARGE PASSED (joules) (coulombs) (minu~es) FIELD NO FIELD f) 0 0 0 1 J60 )59 54.3 2 684 681 10.5 3 992 9R5 155 4 1290 1280 204 5 1570 1550 252 6 ·1~40 l~JO 300. 7 2100 ·2090 345 ·8 2360 2310. 391 9. 2620 2560 4J6 10· l· 2870 .2810 482 i 20 5170 5090 916 30 7190 .7o60 1320·· 40 8980 ~770 1?00 50 10520 10200 2050 60 11820 11~00 2380 70 1)020 12500 1680 80 14120 1350.~ 2970. 90 15120 14400 3250 100 16020 15200 J52U A PPENDJ;:x E ERROR ANALYSIS ~rror in the calculation of th~ energy passed and in the amount of charge passed by th~ Leclanch~ cells ·in Experiments 1 through 26 may arise·from 3 sourc~s: 1. The value of the resistance load of the.cells 2. rhe accuracy of the. strip chart recorder in recording voltage· and time pa.ss19d 3. Th~ substitution of a summation for an integral in th~ calcu lation of the ~nergy outout and of thP amount of charge passed. ThP. ~~sistance loads were known to within 1i except for experiments 7 ~nd B, wh~re the values were given to 2% • . Th~ :strip chart r~corder used·(~ouston Instruments Om.nigraphic 2-)008) was accurate to !o.2~·f9r ·the voltage (full scale) and ±o.~~ for the time. ·The e~timation· of the extent of error due to the substitution. of a ·summation for an integ~tion: (equations 8 and 9) was not straght forward. The·. sUmma.tions were usually taken over time intervals of 10 m~nut~s. ro illustr~te the possiple inaccuracy, sample calculations ·were ~ade of energy output for the cells drained wit~out an applied magn~tic field in Experiment ?. This experiment was ohoosen because it has ~ l~rge initial voltage drop in the first few minut~s of the exper im0nt due to a low resi~tance load (1.05 ohms !2%). The energy outJ>ut was calculated far the.first 100 minutes according to equation 8, ', 53 E -_ _'l:"L< vf2 + v vf +vi·2> JR 1 wh13re 1:' is 1;.he size of the time interval. A comparison was ma.de be.:.. twe~n th~ values obtained with T = 10 minutes and "'t' = 1 minute. This will provide a rough. estimate of the expected error.in using a su.nmJ8.tion ov~r int~r,vals of 10 minutes instead of integration (the limit as "'l: -+ 0) in equation 8. Values. of energy output were calculated for 10 mi~ nute portions of thP ex90riment • . \ ENERGY {.joul~s) Por~ion of PC?rcentage ~xperiment minutes minute Difference n ~st 10 minute portion 2970 2280 JO% second 1300 1J90 6. 51' third ~73 970 1.~ fourth 655 651 0~6% .'fi7'th 447 449 0.5'% sixth 370 '370 seventh 26B 268 eighth 193 191 ·Lo·t ninth 135 133" 1.5~ tenth 98 98 Except for the first 10 minutes of the experiment, the difference · b~breen the values for the energy using ~ = 1 minute ·and 1:' = 10 mi nutes is l~ss than 1 % over the. entire e~periment. Because of th.e large difference in the first few minutes, ~xperim~nts using low resistances loads (around 1 'ohm) had the energy .output and charge passed for the .54 first 10. minutes calculated with 1: = 1 minute. The error involved in calculating the. charge passed is much less since it is pro.portional to only the first power.of the voltage (see equation 9). All experimental calculations ·a~e therefore rated at 1~. Th~ magnitudes given for.thA field strengths used are accurate . to a tenth of a kilogauss except for thP. ring magnets (III and IV in fable I). Thq fi~ld strengths for these last vary· greatly but are approximately one kilogauss at their centers·, incraasing to about 2 kilogauss next to the inner surface. of th~ magnets. The temperature given for cells drained in an ice-water bath is o0 c and any variation due to atmospheric pressure or Joule heating is considered minimal •. ·Experiments performed at room temperature are 0 . list~d as 22 C and may vary within a degree. However, in all cases, '• th~ ~xperiments were performed in pairs with one group of cells drained '. I in a magnet~c field and with the second group drained in an identical manner but without the applied magnAtic field. APPENDIX F STATISrICAL ANALYSIS In Talbe I are listed the results of 26 experiments. ·rhe experimental conditions of these, however, are widely varied. In order to investigate the reproducibility of these results, those experiments performed under sL"'Tlilar conditions were arranged in groups. The mean and standard deviations of the energy outputs of these similar experiments were then calculated. Group 1 (as given in Table I) Experiment No. Field (kG) Energy (joules) 2 4.5 12,900. 0 12,000 J 4.5 . 10,400 0 11 ,500 4 4.5 12,000 0 11,600 With field: mean E = 11, 770 joules standard deviation c;- = 1 ,270 Without field: mean E = 11,700 joules standard deviation v = 265 56 Grou~ (data recalculated for only the initial 100 minutes) Experirn~nt No. Field (kG) Energy (joules) 10 1.5 1,240 0 1,110 11 1.5 1,130 0 1,320 12 1.0 1,430 0 1,520 13 1.0 1,110 0 1,120 With field: mean E ~ 1,230 joules standard deviation v = 147 Without field: mean E = 1,270 joules standard devia. tion o- = 194 Group 3 (as given in Table I) Exp~ri.'lllent No. Field (kG) Energy (joules) 17 1.1 4,750 0 4,630 18 1.1 4,620 0 4,?00 19 1.1 4,790 0 4,860 With field: mean E = 4,720 standard deviation ~ = 89 Without field: mean E = 4,730 standard deviation ·~ = 118 57 Group 4 (as given in Table I) Exp9riment No. Field (kG) Ene:rgy (joules) 20 2 • .5 2,370 0 2,340· 21 2 .5 2,400 0 2,370 22 2.5 2,4.50 0 2,310 With field: mean E = 2,410 joules standard deviation ~ = 40 Without field: mean E = 2,340 joules standard deviation ~ = 30 Group 5 (as given in Table I) Experiment No. Field (kG) Energy {joules ) . 24 2 •. .5 2,990 0 2,860 25 2.5 2,g60 0 2,880 26 2.5 2,990 0 2,870 With field: mean E = 2,925 joules standard deviation v = 92 Without field: mean E = 2,870 joules standard deviation er = 10 In all the above groups, the mean values have deviations that overlap. This is interpreted as a result of the variability of the individual cells. However, the data still strongly suggests an influence of the energy output due to the presence of an applied magnetic field. This is more clearly seen by considering those experiments in which the field used is less than 2 kG. ror these experiments, ?o% 58 (? out of 10) show a negative effect on the en~rgy output. For the experim~nts with B ~ 2.5 kG, 75% (12 out of 16) show a increase in energy output. EXPERIMENTS PERFORMED f/ITH B < 2.5 kG (from Table I, page 12) Experiment No. Number of cells Percentage increase in in each set energy output 10 3 -0.6% 11 3 -5.5% 12 3 -2.2~ 13 3 -3.9% 14 2 +o.6% 15 3 -11% 16 6 +7.4% 17 6 +2.6% 18 6 -1.7% 19 6 -1.4% 59 EXP~IMENTS PERFOR.i'fED WITH B ~ 2. 5 kG (from Table I, page 12) Exp'3rim'3nt No. Number of cells . Percentage increase in in each set energy output 1 6 +12% 2 1 +?.4% 3 1 -9.6% 4 1 +J.4i 5 6 -O.J% 6 6 +271.> 7 6 -.46% 8 6 +24% 9 6 . -t47% 20 3 +1.3'1> 21 3 +1.J~ 22 J +6.1'% 23 3 -1.41(, 24 3 -+4.5% 25 3 -0.?"fo 26 3 .f-4.2%