I S T E S S I F T I S G ACTIO?i O F H T D R O G E S PEROXIDE A S D ORGXSIC PEROXIDES O S T H E LATEST PHOTOGRAPHIC IMAGE BY CARL E. BARNES WITH W. R . TVIIITEHORSE A X D T. A . LAWRANCE
The fact that both the vapor and solut’ionof hydrogen peroxide act on t,he photographic emulsion in a manner very similar to that of light has been known for some time.’ Recently Sheppard, TYightman and Quirk, of the Eastman Research Laboratories, and Dr. Luppo-Cramer have published papers dealing with the intensification of the latent image by means of this substance. Its action, as explained by Kightman and Quirk2 is briefly thus: In a n o r n d exposure of a plate to light certain of the grains are reduced sufficiently t o make them developable while others may be brought nearly to that stage and still remain unaffected by the developing solution. By treating such an exposed plate with a very dilute solutionof hydrogen peroxide all the grains are considered t o be affected in much the same manner as when exposed to light whereby the grains not having been sufficiently reduced in the original exposure now become so. If the action of the hydrogen peroxide solution is continued or its strength increased, more and more of the grains will become developable, including those not originally acted on by light, and fog results. Of the organic peroxides, apparently benzoyl peroxide is the only one whose action has been recorded. Furthermore the effect of hydrogen peroxide when using various developing agents has not been investigated to any extent. It is the purpose of this work to determine the effect of hydrogen peroxide on the latent image when using different developing solutions as well as to determine the action of several organic peroxides.
Methods Exposure. Strips of Eastman “Speedway” plates wcre exposed in a non-intermittent sensitometer of Hardy’s d e ~ i g n . ~ I.
Processing. Three procedures were employed : ( I ) strips receiving peroxide treatment and wash water before development; ( 2 ) strips receiving treatment, in the peroxide solvent (water in the case of hydrogen peroxide and varying proportions of acetone and water with the organic peroxides) for the same time 2.
S. E. Sheppard and E. P. Wightman: J. Franklin Inst., 195, 337 (1923). E. P.Wightman and R. F. Quuk: Proc. Seventh International Congress of Photography, 1928, 236.
Arthur C. Hardy: J. Opt. SOC. America and Rev. Sei. Instr., 10, 149-156 (192j)
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as in the peroxide treatment followed by the same time of wash water treatment in a separate beaker; and (3) strips receiving no treatment, Le., controls. The temperature of all solutions was maintained a t 2o.o0C. Development was continued for such times as to give to the control plates gammas of approximately 0.5, 1.0and 1 . 2 , these times being determined for the various developing solutions by plotting time-gamma curves. Strips were remo\-ed from all solutions five seconds before the expiration of the time of treatment to allow for draining and removing to the next solution into which they were placed promptly a t the end of the five seconds. In order to eliminate errors due to fluctuations in temperature, variations in the concentration of the developing solution, etc., three strips, one from each of the above methods of treatment, were developed together in the same solution. The order of treatment was as follows: I . Two-minute bath in the peroxide or peroxide solvent. Two-minute rinse in distilled water. 2. 3. Development for length of time required for desired gamma. 4. Immersion in rYc acetic acid short stop for I minute. 5 . Fixing in acid hypo (hardened) for I j minutes. 6. Thirty-minute wash in tap water. 7. Drying. 8. Density measurements. Density measurements were made on the Martens Polarizing Photometer.
Formulas Developing Solutions D-I. Metol. A . Metol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sodium Sulfite (Anhydrous). . . . . . . . . . . . . . . . . . . . . . . Water t o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8 . 0 g. 100.0 g.
Z O O O . ~ml. I 1 2 . o g. .2ooo.o ml.
B. Sodium Carbonate (Monohydrate). . . . . . . . . . . . . . . . . ITater t o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dilute: A, 7 j ml.; B, 7 5 ml.; water, 50 ml. D-2.
Quinol. Hydroquinone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30.0 g. 100.0 g. Sodium Sulfite (Anhydrous). . . . . . . . . . . . . . . . . . . . . . . Sodium Carbonate (Monohydrate). . . . . . . . . . . . . . . . . I 5 0 . 0 g. Water t o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2ooo.o ml. Dilute 1:3
INTENSIFYISG ACTION O F PEROXIDES ON LATENT IMAGE
D-2B.
2639
Quinol. Hydroquinone, . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 0 . 0 g. 8 0 . 0 g. Sodium Sulfite (Anhydrous). . . . . . . . . . . . . . . . . . . . . . . Sodium Carbonate (Monohydrate), . . . . . . . . . . . . . . . . roo. o g. Water t o . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000.0 ml. Do not dilute
D-3. Pyro. A . Sodium Sulfite (Anhydrous). . . . . . . . . . . . . . . . . . . . . . . Sodium Bisulfite.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pyrogallol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . JTater t o . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
g. g. 2 0 . 0 g. IOOO.~ ml. 70.0 I;
.o
B. Sodium Carbonate (Monohydrate).. . . . . . . . . . . . . . . . 7 5 . 0 g. Potassium Bromide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Water t o . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use equal parts h and B
I
. o g.
1000.0 ml.
D-6 Glycin. Sodium Sulfite (Anhydrous). . . . . . . . . . . . . . . . . . . . . . . I j 0 . o g. 5 0 . 0 g. Glycin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sodium Carbonate (Monohydrate).. . . . . . . . . . . . . . . . I j o . o g. Water t o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I O O O . O ml. Dilute I : Z
I.
Experiments and Results Time-Gamma Curaes. To obtain a better comparison between the different developing agents
having varying rates of development, it was decided to develop to approximately the same gamma instead of the same time. In order to do this, timegamma curves were plotted €or each of the developing solutions. Upon examination of the accompanying time-gamma curves i t will be noticed that the curve for metol (curve I ) rises very gently since metol is a ((soft”developer. Only with long development times can a negative of high gamma or “contrasty” negative be obtained. From the value of “gammainfinity” (the value toward which the curve approaches asymptotically) it will be seen that no very high contrast may be attained by using metol. As opposed to this it will be noticed that pyro (curve 3) builds up contrast rapidly in the first few minutes of development. Maximum contrast has nearly been reached a t the end of five minutes with this developer. Because of this fact it is hard to develop to the same gamma with pyro, for even a slight error in stopping development (which at best is none too accurate since it must be done by removing a plate from one solution and immersing it in another) will cause an appreciable error in the gamma obtained. Mention is made of this here since it is an explanation of the slightly different
2640
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Curves I, z and 3 Time-Gamma Curves
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0.9 8
1.2 l.6
IKTESSIFYING ACTIOX O F PEROXIDES OX LATEST IMAGE
2641
values of gamma obtained with pyro for the same developing time in the experiments with organic peroxides. Pyro was used in these experiments in order that the results might be comparable to work which has already been carried out with benzoyl peroxide in which pyro (formula D-3) was used. Metol would doubtless have been a better developing agent to use since it has no steep portion in its time-gamma curve. The shape of the time-gamma curve for any given developing agent mag be changed by varying the proportions of the constituents in the developing solution. An example of this is shown in curve 4 which gives the timegamma curves for two concentrations of quinol. It is a peculiar fact that the more dilute solution of quinol is the more rapid developer up to a gamma of one (at five-minute development). Above this point, however, the higher concentration of quinol causes the plate to gain contrast much more rapidly than does the lower concentration. The reason for this is not quite clear but perhaps it may be explained on a basis of ionization; however, there are apparently insufficient data on the ionization of the sodium salts of quinol.’ An investigation of the difference in the rate in which these two concentrations of quinol build up contrast above and below five minutes throws important light upon the effect of previous swelling of the gelatin in water on developing speed. One theory has already been proposed by Wightman* that previous swelling of the emulsion by water-bathing increased the speed of diffusion of the developer, thus partly accounting for the increase in speed of his water-bathed plates. On the other hand it seems logical to assume that the presence of water already in the gelatin must cause a dilution effect t>ending to slow up development. As may be seen by comparing curves 5 and 6, bathing in water lowers the gamma in the more dilute quinol developer (curve s), but greatly increases the gamma with the concentrated quinol developer (curve 6). Since increase in gamma is only effected normally by an increase in developing time, any increase in gamma may be considered as an increase in developing speed. It was pointed out in reference to curve 4, that under five-minute development the more dilute quinol solution developed more rapidly, indicating more rapid difusion into the gelatin than the high concentration of quinol which developed more slowly. Above five minutes, however, the rate of penetration of the developing solution is no longer an important factor and the high concentration now goes rapidly ahead. With this in mind it is reasonable t o expect that swelling the gelatin of a plate with water before immersion in the high concentration of quinol would greatly increase the gamma of that plate over one not receiving water treatment provided the development times were kept below the point where the curves cross. And this, as has been pointed out, is just what takes place (curve 6). On the other hand, it would be expected that previous swelling of the gelatin of See S. E. Sheppard: “Electrochemical Aspects of Photographic Development,” Trans. Am. Electrochem. Soc., 30, 429 (1921). * E . P. Wightman and R. F. Quirk: J. Franklin Inst., 199, 286 (1927).
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Curve 5 H?OI with Hydroquinone-normal conc
H201
Curve 6 w-ith Hydroquinone-high ronc.
03
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16
INTENSIFYING ACTION OF PEROXIDES ON LATEST IMAGE
2643
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a plate to be developed in the weaker solution, which already penetrates quite rapidly, would tend to slow development since the dilution effect on the already dilute developer would outweigh any increase in the rate of diffusion. This is borne out by curve 5 . Thus both effects take place and the final result is determined by the concentration of the developing agent. This being true it should be possible to make the developing solution of such strength that previous swelling of the emulsion in water would produce no effect whatever. Curve 8 shows the action of such a developing solution; the curve of the water-bathed plate coincides with that of the control plate. This concentration is more easily arrived at with metol, probably, because of its gradually rising time-gamma curve. Effect of hydrogen peroxide using different developing solutions. From the time-gamma curves the following development times were obtained to secure a gamma of 0.5, 1.0and 1 . 2 for each of the developing solutions to be used in this set of experiments: 2.
Development Time-Minutes Developer
Metol, D-I Quinol, D-2 Quinol, D-ZB Pyro, D-3 Glycin, D-6
y =0.j
3 2
y=1.0
112
9
2
5 5
7
114
2
314
I/2
7
1/2
112 I
2
4 *This time is for a gamma of 0.4 for the control plate. I
y=1.2
1/2
I4 112
I*
The concentration of the hydrogen peroxide used in these experiments was approximately 0.0167,, made up from Eimer and Amend’s 3.63Y0 C. P. Hydrogen Peroxide which was acid to litmus. The order of treatment has been given above. After exposure and treatment of the strips, density measurements were made as before and the densities plotted against log exposure time, giving families of H and D curves for the different development times. The straightline portions were extended until they cut the base line and the H and D speeds and the gammas calculated. These appear on the curves together with calculated speed ratios. An examination of the average speed ratios on the accompanying curves shows the following results: Developing Solution
Metol, D-I Quinol, D-2 (normal conc.) Quinol, D-2B (high conc) Pyro, D-3 Glycin, D-6
Intensifying Action of H202-i.e. Speed Ratio: H201/control 1.69 1.26 I .36 1.87
0.96
2645
INTENSIFYING ACTION O F PEROXIDES ON LATENT IMAGE
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From the above it will be noticed that hydrogen peroxide produces an increase in speed with all developing agents except glycin. The values, however, vary considerably and are not in accord with the conclusion of Xightman and Quirk’ that latent image intensification is largely independent of the developer used. Wightman and Quirk suggest that one might expect some variation in the amount of intensification when one developer is used instead of another, but state that this should follow more or less the variations in the developability of ordinary latent image with various developers. Pyro and met,ol show the highest degree of intensification but an examination of their time-gamma curves will show that these two developers are widely different, in their action. Glycin shows a very slight falling off in speed. Accordingly, in view of these data, it would seem that latent image intensification is dependent to a considerable extent on the nature of the developing s o l u t i o n used. 3 . A c t i o n of Organic Peroxides.
I n this group of experiments plates receiving the following treatment were developed for I minute and for z 3 / 4 minutes in pyro: (I). Two-minute treatment in a 17~ solution of the organic peroxide dissolved in varying proportions of acetone and water (depending on the amount of water which could be added to the actone solution of the peroxide without causing precipitation). E. P. Wightman and R. F. Quirk: h o c . Seventh International Congress of Photography, 1928, 242.
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Curve I O Crotonyl Peroxide
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Curve I I Succinnyl Peroxide Acid
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2647
I N T E N S I F P I N G ACTION O F PEROXIDES ON LATENT IMAGE
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Curve 1 2 Triacetonyl Peroxlde
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0 I
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CARL E . BARSES WITH W. R . WHITEHORSE A S D W. A. L.4WRASCE
( 2 ) . Two-minute treatment in acetone-water of the same proportions as used in the solvent for the organic peroxide.
(3). KO treatment (control). H and D curves were plotted as in previous experiments from which gammas
and speeds were determined. These have been arranged in the following table: Peroxide
H and D Speed Ratios (average)
Crotonyl Succinnyl Acid Triaceton yl m-Chlorbenzoyl
I
Gamma Ratio: min. 2% min.
.oo
0.96 2.8
I.j
I .02
1.4
0.80
2.14
0.98
0.99
0.70
I
.93
I
From an examination of curve sheets 10-13 it will be seen that the only peroxide which produces what might be termed a practical photographic intensification ( i t . , each density being greater on the peroxide-bathed plate than the corresponding density for the same exposure on the control plate) is m-chlorbenzogl peroxide. In no other case is this true. According to the speed ratios, however, succinnyl peroxide-acid and triacetonyl peroxide should also show intensification. That any intensification shown by these last two peroxides is of a different nature than that shown by m-chlorbenzoyl peroxide is obvious from the curves. For example, the densities of the succinyl peroxide acid-bat'hed plates are in every case markedly less than corresponding densities of the control plate. Yet because of the slope of the curve, or the gamma, the inertia point is brought further to the left, thus indicating greater speed. I t is evident that the q a ~ n m a smust also be taken into consideration, and true intensification only attributed to a substance which shows an increase in speed when its H and D curve has the same slope or the same gamma as the control. In fact, this is the only result which could be considered in accordance with the present theory of latent image intensification-namely, that the action of the peroxide raises the developability level of all grains. True intensification has been effected, then, when the speed ratio shows an increase and when the ratio of the gamma of the control plate to the gamma of the peroxidetreated plate i s I . The only peroxide investigated which meets both these requirements is m-chlorbenzoyl peroxide. 4,
Summary. I ,
Water treatment prior to development has two effects: (a). that of facilitating the penetration of the developing solution, as suggested by Wightman and Quirk, which hastens development; this effect shows itself, however, when the concentration of the developing agent is sufficiently high to supersede the (b).
dilution effect in which the action of the developing agent is retarded by dilution due to water already in the gelatin, thus
INTENSIFYING ACTION OF PEROXIDES ON LATENT IMAGE
2649
causing a lowering of the gamma below that which would normally be obtained for a given development time with an untreated plate. 2.
I n view of further data obtained in these experiments it would appear that latent image intensification by means of hydrogen peroxide is dependent to a considerable extent on the developer used.
3 . It would seem that a plate has undergone true intensification only
when it not only shows an increase in H & D speed but when its H & D curve has the same slope or the same gamma as the curve of the control plate. 5 . Acknowledgment.
The authors are indebted to Professor C. B. h-eblette of the Texas A. and M.College for suggesting work along the line of latent image intensification and to the Pilot Laboratories for the rare organic peroxides used in these experiments. They are also indebted to Prof. Arthur C. Hardy and Prof. A. G. Hall of the Massachusetts Institute of Technology for the use of apparatus with which data for the curves were obtained. Bates College, Lewiston, Maine.
