Study on rate of development of a photographic film by the rotating ring-disk electrode technique

AKIRA ~Wkii~~~,FvMlro *SAWA and K$EN&I HONDA Deparfmt& of Synthe& Chemistry,~ Faculty of Engineering. The University Hongo, Bz+yo:ku,

Tokyo

of Tokyo,

2 13 (Japan)

(Received?I& Debember1981) .. -.

We me&u&the rate of developmentof photographicfilm by meansof the. rotatingringdisk ele&ode technique, in which a_.silver halidegelatinem&on film v&s usedasthe disk electrodeand platinumwas used for the ring electrode. When hydro’quinoneprras addedasa developingagent, the reductioncurrentat the r&g electrode-mcmased.This indicatedthe formation of quinone at the film disk as,a resultof the development.This electrochemicalmethod providesan in situ measurement_ of the deveiopmentrate of the photographicfilm. The measuremen_ts of the film optical density.or the mass of silverhave been used to de&nine the rate of developmentof photographic.fihns[I] _ The developing .speed ‘curves, the optical d+&y-time

c-es

or the &mount of re-

duced s$ver_time c.urvesare obtained after the fihG are processed.Thus, the rate cannot be measuredduring-thedevelopment.process, The mechanismof the film developmentcan be studied by electrochemical methods:For example, Raithel and Jaenicke[2] investigatedthe electrodereaction of the developingagentsand sulfite_on a rotating metal disk electrode (RDE), and discus& su@radditivity and-so on; Hamano etaI. [S] used the_ anodizedsilverhalideelectrodeand studiedthe cathodicreactionof silverhalide : grai;ls.’ ..--.. -. In this work oje used the rota&g ring-diskelectrode (RRDE) technique [4] to me_a+rethe r&e of developmentof a photographicNm duringthe development process. The product formed duringthe developmentprocess(at the disk) was detected at the ring electrode. When hydroquinoneis used G a developingagent, the developmentreaction can be expressed&oichiometricaUyby the.following equation: 2AgX+H,QA-2’Ag+.Q+2HX where kgX is silverh&de, I&Q is hydroquinone,and Q -isquinone. One mole of the q&one f&&d& the disk ConeSponds& two moles of_the reduced silver-formed.onthe disk. A certainfr&$iou of the quinoneis reducedat-the ring electrode Sits potent&&~is_so.adju&dto givethe limitingcurrentof the &i&&n .& ~ * y’

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The rate of developmentof the photographicfihn is therefore proportional to the ring current(correctedfor the residualcurrent),or the net total charge is proportionalto the advancementof ttie developmentprocess.The proportional constantdependson the collection efficiency of the RRDE [4] and/or film flatnessof the disk. The ring electrodewas made of a I% ring (‘7 mm innerdiameter,and 9 mm outer diameter).A platinumelectrode was used as the counter electrodeand a saturatedcalomel electrode(SCE) was used as the referenceelectrode. The solution was deaeratedwith nitrogen. A sheet of X-ray film (Fuji X-ray film Em.No. 42848), which containeda largeamount of silverhalide, was punched into a disk of 6 mm diameter.Emulsion on one side of the film disk was strippedoff, and the disk was fixed in the centerhole of a Teflon holder with a cyanoacrylateadhesive.As the film was handledunderdaylightconditions, it was fogged completely. An aqueoussolution of pH 10.3, containing2.3 X 10s2 .M Na&O, and 1.2 X 10m2M NaHC03 (1 M = 1 mol dmm3),was used as the supportingelectrolyte solution. A certain amount of hydroquinoneaqueous solution was added from a syringe.The developmentbeganas soon as the hyclroquinonewas introduced. A Nikko-keisokuRRDE-1 was used as the rotatingdevice and SC-2 as the control instrument. A Nikko-keisoku DPGS-1 dual potentiostat and a NPS-2 scanning unit were used. The temperatureof the cell was controlled within + 0.5OC. Figure1 is an example of the ring current-time curve. The ring potential was fixed at -0.5 V. Usuallythere was a induction period (I) followed by an increaseof the reductioncurrent(II). The ring current-ring potential curve confirmed this cathodic ring currentto be due to the reductionof quinone which was formed duringthe film development. Figure2 showsthe advancementof development, obtained by usingthe integral(charge)of the resultsof Fig. 1. Here, the verticalaxis is the normalized chargewhereunity representscomplete developmentof the film. It was observedthat the inductionperiod became shorter,and the rate of development increasedas the temperaturewas increased.This temperatureeffect is more

10 20 Time of Development /min

30

Fig. 1. Example of ring current-time curve for the reduction of quinone formed at the film disk. The solution contained 2 x lo-’ M hydroquinone, 2.3 X lo+ M Na,CO, and 1.2 x lo* M NaHCO,. Ring potential -500 mV, temperature 2O”C, rotating-speed 1000 rpm.

189

Fig. 2. Normalized charge-time quinone in solution.

curves at various temperatures with 2

20 10 Time of Development /min

X

lo-

iU hydro-

30

Fig. 3. Normalized ring current--time curves at different temperatures.

easilyseen if one piots the normalizedring currentvs. the time of development, as shown in Fig. 3. An Arrheniusplot of the maximumcurrentof Fig. 3 givesan apparentactivation en&&y of ea. 38 kJ/mol.Ti$s value was slightly lower than that reported (40-80 kJ/mol [ 51) in chemical development;probably becatie the X-ray film was fogg& and the electrodewas rotated at a high speed. REtiERENCES

1 2

3 4

5

T.H. James, The Theory of the Photogra&ic Process. Macdbz~. 404436. H. Raithel and W. Jsenicke. 2. Pbyr. Cbem.. 111 (1978) i93.

New

Yo*Landon.

H. Ha&no. H. T&e and S. Kikuchi. J. Photogr.Sd.. 27 (1979) 203. Albery and ML Hkbmsn. pineDisk Ekctmdea. Oxford Universlt~

W.J. GAP.

Stevensoia,

Proc. Interhat.

Con&

Pkotogr.

6cLziLtch.

Focal

Ress.

Press. 1961.

1977. PP.

Oxford, 1971.