US2943935A - Stabilization of photographic bleach powders containing an alkali metal ferricyanide - Google Patents
Stabilization of photographic bleach powders containing an alkali metal ferricyanide Download PDFInfo
- Publication number
- US2943935A US2943935A US659213A US65921357A US2943935A US 2943935 A US2943935 A US 2943935A US 659213 A US659213 A US 659213A US 65921357 A US65921357 A US 65921357A US 2943935 A US2943935 A US 2943935A
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- United States
- Prior art keywords
- alkali metal
- bleach
- parts
- ferricyanide
- weight
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
- G03C5/00—Photographic processes or agents therefor; Regeneration of such processing agents
- G03C5/26—Processes using silver-salt-containing photosensitive materials or agents therefor
- G03C5/40—Chemically transforming developed images
- G03C5/44—Bleaching; Bleach-fixing
Definitions
- the present invention relates to single powder photographic bleach mixtures containing an alkali metal ferricyanide as the oxidizing agent, and more particularly to the stabilization of such bleach powders.
- aqueous solution an alkali metal fern'cyanide such as lithium, potassium or sodium terricyanide as the oxidizing agent which converts the metallic silver formed during development into a silver salt which is soluble in silver halide solvents such as hypo.
- a bleach solution contains, in addition to the ferricyanide, a halogenizing or converting agent preferably an alkali metal chloride or an alkali metal bromide which converts the silver ferricyanide initially formed in the bleaching reaction into the less soluble silver chloride or silver bromide and thus impels the bleach reaction to completion.
- the ferricyanide bleach solutions contain a bufiering agent which maintains the desired pH even though small amounts of acids or alkali may be carried into the bleach by the film.
- the pH of the bleach solutions falls between a range of from 3 to 9, a pH between 4' and 6 being generally preferred.
- alkali metal phosphates such as disodium and monosodium phosphate, sodium citrate, sodium bisulfate, citric acid or phthalic acid.
- Some of the ingredients of the butter mixture act also as corrosion inhibitors and retard the corrosive action of the ferricyanide bleach on metallic developing tanks, trays and the like.
- the alkali metal ferricyanide bleaches are usually packaged and sold as dry powder mixtures. Normally, the stability of dry ferricyanide bleach mixtures leaves much to'be desired. However, their stability is further drastically curtailed by the presence of other ingredients which are added to ensure thatthe bleach possesses certain desirable photographic characteristics.
- a metal ferrocyanide is included which gives a tempering action to a freshly mixed bleach solution in order to simulate the performance of a partially used bleach.
- the rate of bleaching depends on the 7 oxidation reduction potential which in turnis a function of pH and the relative"ferrocyanide-fenicyanide concentration. No such oxidation reduction potential can be established so long as ferricyanide only is in the fresh solution, and no ferrocyanide has been formed as a result of the bleaching action;
- the desired tempering action is achieved by adding to a fresh bleach solution specified amounts of ferrocyanide thus establishing an oxidation reduction potential which otherwise would be set up only after part of the ferricyanide had been reduced to ferrocyanide.
- ferricyanide has an even greater tendency to cause caking and discoloration. It is believed that this discoloration is caused by the de- Patented July 5, 1960 2 composition of ferricyanide yielding ferrocyanide and iron salts leading in all likelihood to the formation of Prussian Blue or Turnbulls Blue.
- a gas is formed which creates a pressure'build-up in hermetically sealed packages. This gas has been identified as hydrogen cyanide which is highly toxic. 'Thus, the decomposition of ferricyanide bleach powders creates a serious health hazard.
- ferricyanide bleaching powder ingredients which afiect adversely the stability of the ferricyanide bleaching powder are alkali dichromates which are added to bleach solutions to inhibit the corrosion of processing equipment. Ferricyanide bleaches containing dichromates also cake and discolor with the formation of hydrogen cyanide.
- boric anhydride is an etiective stabilizer for photographic bleaches particularly those which contain, in addition to the alkali metal ferricyanide, a small amount of alkali ferrocyanide or alkali dichromate.
- Photogaphic bleach mixtures containing alkali metal ferricyanide as the oxidizing agent and stabilized with boric anhydride constitute the purposes and objects of the present invention.
- the photographic bleach powders which are contentplated herein contain as their essential ingredients an alkali metal ferricyanide and boric anhydride, together with other bleach adjuvants including buir'er mixtures, alkali metal halides, particularly alkali metal bromides andalkali metal ferrocyanides or alkali metal dichromates; Photographic bleach powders which we have found stable during storage for considerable periods of time may be compounded in the following proportions, it being understood that all parts are by weight and'that the resulting dry powder is to be used to make a liter of bleach solution:
- boric anhydride In compounding the above bleach powder, one may proceed by mixing the boric anhydride to the alkali metal ferricyanide and adding the other ingredients later; However, if preferred, all the ingredients may be admixed simultaneously.
- One of the most important advantages of boric anhydride lies in the fact that its stabilizing action is not impaired by changes in alkalinity and acidlty.
- the stabilizing action is not based on a dehydrating action and is not influenced by the selection of bleach ingredients with ditferent amounts of water of crystallization. While it is desirable to use a grade of boric anhydride which is completely free of water, it must be kept in mind that small amounts of moisture are absorbed by the anhydride during storage and before the mixing of the bleach. However, these small amounts of water absorbed which usually do not exceed 2 percent, but which may go up as high as 5 percent based on the weight of boric anhydride, do not interfere with the stabilizing action on the bleach powder.
- Example IV This powder mixture did not deteriorate after storage for "6 months at an average room temperature of 75 F.
- V l h is powder mixture 'was kept for 6 months at room temperaturewithout deterioration. "A mixture without boric anhydride caked badly' after a few days and discolored to a deep blue 'color with the-formation of hydrogen eyaziide gas.
- Example V1 r w Grams Potasium ferricyanide 75.0 Potassium ferrocyamde 5 .0 Sodium bromide. '2;. 1020 weightofan"alkalizmetal rlichroniate, theflpartsfbeiag from 2 to 12 parts by weight of alkali metal ferrocyanide,-
- a stable single powder photographic bleach ture containing as its essential ingredient-stolthe preparation of onelliter of bleach solution: from 30 to 120 parts by weight of alkalimetal ferricyanitle; from 2 to 20. parts 'by weight of alkali metal bromide; from 5 to 30 parts by weight of a butter-mixture comprising a salt selected from the group-consisting :of alkali metal phosphates and alkali :metal 'citr'ates, and an acid :selected from the. group 'consistingzof citric and phthalic acid; g
- a stable'sin'gleipowder photographic bleach mixture comprising an alkali metal fenicyanidq an alkali m'etal ferrocyanide, ania'lkalianetal bromide and 'a-stabiliiing' amount of boric 'anhydride inaS quantity sufficient to prevent 'cakingfand disodlorationbf said bleach mixture;
- a stable photographic bleach mixture having the following composition:
- a stable photographic bleach mixture having the following composition:
- a stable photographic bleach mixture having the following composition:
Description
tent
Lawrence G. Welliver, Binghamton, N.Y., 'assignor to General Aniline & Film Corporation, New York, N .Y., a corporation of Delaware No Drawing. Filed May 15, 1957, Ser. No. 659,213
Claims. (Cl. 96-60) The present invention relates to single powder photographic bleach mixtures containing an alkali metal ferricyanide as the oxidizing agent, and more particularly to the stabilization of such bleach powders.
Most photographic bleach solutions which are used for the processing of color film contain in aqueous solution an alkali metal fern'cyanide such as lithium, potassium or sodium terricyanide as the oxidizing agent which converts the metallic silver formed during development into a silver salt which is soluble in silver halide solvents such as hypo. Typically, such a bleach solution contains, in addition to the ferricyanide, a halogenizing or converting agent preferably an alkali metal chloride or an alkali metal bromide which converts the silver ferricyanide initially formed in the bleaching reaction into the less soluble silver chloride or silver bromide and thus impels the bleach reaction to completion.
It is essential that the bleach reaction be carried out at a pre-selected pH and consequently, the ferricyanide bleach solutions contain a bufiering agent which maintains the desired pH even though small amounts of acids or alkali may be carried into the bleach by the film. The pH of the bleach solutions falls between a range of from 3 to 9, a pH between 4' and 6 being generally preferred. Among the more frequently used ingredients of such buffer mixtures are alkali metal phosphates such as disodium and monosodium phosphate, sodium citrate, sodium bisulfate, citric acid or phthalic acid. Some of the ingredients of the butter mixture act also as corrosion inhibitors and retard the corrosive action of the ferricyanide bleach on metallic developing tanks, trays and the like.
For reasons of economy and convenience, the alkali metal ferricyanide bleaches are usually packaged and sold as dry powder mixtures. Normally, the stability of dry ferricyanide bleach mixtures leaves much to'be desired. However, their stability is further drastically curtailed by the presence of other ingredients which are added to ensure thatthe bleach possesses certain desirable photographic characteristics.
For instance, a metal ferrocyanide is included which gives a tempering action to a freshly mixed bleach solution in order to simulate the performance of a partially used bleach. The rate of bleaching depends on the 7 oxidation reduction potential which in turnis a function of pH and the relative"ferrocyanide-fenicyanide concentration. No such oxidation reduction potential can be established so long as ferricyanide only is in the fresh solution, and no ferrocyanide has been formed as a result of the bleaching action; The desired tempering action is achieved by adding to a fresh bleach solution specified amounts of ferrocyanide thus establishing an oxidation reduction potential which otherwise would be set up only after part of the ferricyanide had been reduced to ferrocyanide.
In such powder admixtures, the ferricyanide has an even greater tendency to cause caking and discoloration. It is believed that this discoloration is caused by the de- Patented July 5, 1960 2 composition of ferricyanide yielding ferrocyanide and iron salts leading in all likelihood to the formation of Prussian Blue or Turnbulls Blue. As a by-product, a gas is formed which creates a pressure'build-up in hermetically sealed packages. This gas has been identified as hydrogen cyanide which is highly toxic. 'Thus, the decomposition of ferricyanide bleach powders creates a serious health hazard. Other ingredients which afiect adversely the stability of the ferricyanide bleaching powder are alkali dichromates which are added to bleach solutions to inhibit the corrosion of processing equipment. Ferricyanide bleaches containing dichromates also cake and discolor with the formation of hydrogen cyanide.
I have discovered that boric anhydride is an etiective stabilizer for photographic bleaches particularly those which contain, in addition to the alkali metal ferricyanide, a small amount of alkali ferrocyanide or alkali dichromate. Photogaphic bleach mixtures containing alkali metal ferricyanide as the oxidizing agent and stabilized with boric anhydride constitute the purposes and objects of the present invention. V
The photographic bleach powders which are contentplated herein contain as their essential ingredients an alkali metal ferricyanide and boric anhydride, together with other bleach adjuvants including buir'er mixtures, alkali metal halides, particularly alkali metal bromides andalkali metal ferrocyanides or alkali metal dichromates; Photographic bleach powders which we have found stable during storage for considerable periods of time may be compounded in the following proportions, it being understood that all parts are by weight and'that the resulting dry powder is to be used to make a liter of bleach solution:
In compounding the above bleach powder, one may proceed by mixing the boric anhydride to the alkali metal ferricyanide and adding the other ingredients later; However, if preferred, all the ingredients may be admixed simultaneously. One of the most important advantages of boric anhydride lies in the fact that its stabilizing action is not impaired by changes in alkalinity and acidlty.
In spite of the anhydrous nature of the boric anhydride, it is surprising to note that the stabilizing action is not based on a dehydrating action and is not influenced by the selection of bleach ingredients with ditferent amounts of water of crystallization. While it is desirable to use a grade of boric anhydride which is completely free of water, it must be kept in mind that small amounts of moisture are absorbed by the anhydride during storage and before the mixing of the bleach. However, these small amounts of water absorbed which usually do not exceed 2 percent, but which may go up as high as 5 percent based on the weight of boric anhydride, do not interfere with the stabilizing action on the bleach powder.
The following examples will serve to illustrate my invention but are not restricted thereto. The quantity of the bleach mixtures represented by the following formulae is to be dissolved in sufi'icient water to give one liter of bleach solution.
Example I temperature for 6 months. I
' powderinixture from which the boric anhydride was a seam. bromide 15.0
Disodium'phosphate 11.0 Citric acid 8.0 J Boric anhydride 10,0
@Th' tier mixture; whicheontained potassium ferro- 'd not deteriorate after incubation at 120 F. for} 72 .=ho1 irs or storage for 3 monthsat roomtemperaidentieal' p'owd'er mixture from which the boric anhydride was omitted, was badlycaked and discolored to afgieeprblue colorwith the-formation of highly toxic hydrogen cyanide rgas. 7
" axmp'lg ll;
{This powder mixture did not deteriorate during incuba-v tionfior bile 'week at 110 F. or after storage at room. 7
By comparison, a similar otiiittedwas badlycaked and discolored to a light blue color the formation 'of highly toxic hydrogen-cyanide This powder mixture which contained potassium dichromate did not deteriorate during incubation for one week at 120 F.'or storage at'room temperature v(74 F.)
for "six months. A comparison mixture from which the boric anhydride had been omitted was Submitted to the same storage conditions. 'It caked and discolored to a deep blue color with the formation of highly toxic hydrog'en cyanide gas.
7 Example IV This powder mixture did not deteriorate after storage for "6 months at an average room temperature of 75 F.
identical pbwder mixture from which the boric anhydrid'e omitted was badly caked and discolored to a Hee blue colof after new 'da'ys.
V l h is powder mixture 'was kept for 6 months at room temperaturewithout deterioration. "A mixture without boric anhydride caked badly' after a few days and discolored to a deep blue 'color with the-formation of hydrogen eyaziide gas.
Example V1 r w Grams Potasium ferricyanide 75.0 Potassium ferrocyamde 5 .0 Sodium bromide. '2;. 1020 weightofan"alkalizmetal rlichroniate, theflpartsfbeiag from 2 to 12 parts by weight of alkali metal ferrocyanide,-
. 4 Monosidium phosphate 10.0 Phthalic acid ;'i 4.0
Boric anhydride V '12.0
.This powder mixture did not deteriorate when stored, for 6 months at room temperature. A'type mixture from g which the boric anhydride had been omitted became 7 colored and eaked badly aftera few days. C 1 g Various modifications such-'21s A substituting. iequivalent materials and varying the.proportions bf materialsarsed will be obvious to persons skilled in, the art. 7 Therefore,
the scope of the -inyefitiz jg g hmlvtf-eapsmeriylby g 1 V appendedclaims; H
I claim:
1; A stabl'esingleawda aiihotegraphifblekh ture containing as its essential eomponents .from 30 to,
parts by weight'of an alkali metal ferricyanidaffrom 2 to 20 parts by weight of an alkali metal bromide, from 4 to 25mm ofboric anhydride :an'd'ifro'm 2 to -12parts by weight of an alkali metalferrocyanide, the parts being based on the total 'wei ht of the powder. I '2. A stable single powder photographic bleach mixture containing as its-essential components from ,30 to 120' parts by weight of :an alkali metal ferricyanide, fromiqte i 20 parts by weightof an alkali metal bromide. 'fro'm'4'gto V 25 "parts of borio 'anhydride andsfrom .2 't'o 12 partsby based on the total weight of theipo a'der;
3. A stable single powder photographic .bieaeh mixture containing as its. essentialgingredients for the P1761131 ration of one liter of bleach asolution fromi30 to 12.0
parts 5 by weight of'alkali m'etal ferricyan'ide; from 2 to 20 parts by weight (if 'al'kalim'etal bromideffrom 5 to 30 a parts byweight "ofza'bufier .mixture comprising 'a salt selected from the :gi'oupfconsisting of alkali :metal plies phates and alkali metal citrates, "and an acid selected from thegroup consisting-ofcitr-ic and phthalic acid; and
from 4 to 25 parts byweightiof boric anhydride, the parts being based on the total weight of the powder. 4. A stable single powder photographic bleach ture containing as its essential ingredient-stolthe preparation of onelliter of bleach solution: from 30 to 120 parts by weight of alkalimetal ferricyanitle; from 2 to 20. parts 'by weight of alkali metal bromide; from 5 to 30 parts by weight of a butter-mixture comprising a salt selected from the group-consisting :of alkali metal phosphates and alkali :metal 'citr'ates, and an acid :selected from the. group 'consistingzof citric and phthalic acid; g
from 4 to 25 parts by weight of b'oric a'nhyd'r ide; and
the parts being based on .the total weight ofthepowder. .5. A stable singlepowderphotographic bleach mixture containing as its essential ingredients for the preparation '7 of one-liter 'of bleach solution: from 30:10 120 parts by weight of alkali metal ferricyanideyfrom 2 to 20- parts by weight -of- -'alkali-metal bromide;ffromi to 30 parts :by weight of a buffer mixtnrec0mptising a-salt selected from the group consisting of alkali'met'al plies-. phates and alkali metal citrat'eg and an acid selected from the group consisting eof-Zcitric' andfphthalic acid;-
from 4 to 25.p'a'rts by 'weight'ofboric anhydride; and from 2 to 12 pa'rtsbyweight of alkalimetaldichromate, the parts being based onthetotalweight ofithelpowder; 7
'6. A stable'sin'gleipowder photographic bleach mixture comprising an alkali metal fenicyanidq an alkali m'etal ferrocyanide, ania'lkalianetal bromide and 'a-stabiliiing' amount of boric 'anhydride inaS quantity sufficient to prevent 'cakingfand disodlorationbf said bleach mixture; 1
A stable single powder phetographic bleach mixture 7 comprising "an L'alkali met'al ferricyanide, an' alkali metal bromide, a butfer mixmre co n rising amemberselected from the group consisting of '=alkali metal phosphates and alkali metal citrates and a member selected amine I group of citric acid and phthalieacid, :and a stabilizing amount of bo'ric anhydride in fa quantitysufiieient .to prevent calsiirg andaltscblorzition otiatidhkheh:mixture;
8. A stable photographic bleach mixture having the following composition:
Grams Potassium fern'cyanide 50.0 Potassium ferrocyanide 5.0 Sodium bromide 15.0 Disodium phosphate 11.0 Citric acid 8.0 Boric anhydride 10.0
9. A stable photographic bleach mixture having the following composition:
10. A stable photographic bleach mixture having the following composition:
Grams Potassium fenricyanide 50.0 Potassium ferrocyanide 5.0 Sodium bromide 15.0 Monosodium phosphate 10.0 Phthalic acid 2.0 Boric anhydride 10.0
References Cited in the file of this patent UNITED STATES PATENTS 1,656,235 Plagwitz Ian. 17, 1928 2,606,118 Rogers Aug. 5, 1952 2,611,699 Zappert Sept. 23, 1952 2,650,878 Boyer et a1. Sept. 1, 1953 2,843,482 Kridel July 15, 1958
Claims (1)
1. A STABLE SINGLE POWDER PHOTOGRAPHIC BLEACH MIXTURE CONTAINING AS ITS ESSENTIAL COMPONENTS FROM 30 TO 120 PARTS BY WEIGHT OF AN ALKALI METAL FERRICYANIDE, FROM 2 TO 20 PARTS BY WEIGHT OF AN ALKALI METAL BROMIDE, FROM 4 TO 25 PARTS OF BORIC ANHYDRIDE AND FROM 2 TO 12 PARTS BY WEIGHT OF AN ALKALI METAL FERROCYANIDE, THE PARTS BEING BASED ON THE TOTAL WEIGHT OF THE POWDER.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| BE567236D BE567236A (en) | 1957-05-15 | ||
| US659213A US2943935A (en) | 1957-05-15 | 1957-05-15 | Stabilization of photographic bleach powders containing an alkali metal ferricyanide |
| DEG24469A DE1062114B (en) | 1957-05-15 | 1958-05-06 | Stable photographic bleach |
| GB14652/58A GB834972A (en) | 1957-05-15 | 1958-05-07 | Stabilization of photographic bleach powders containing an alkali metal ferricyanide |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US659213A US2943935A (en) | 1957-05-15 | 1957-05-15 | Stabilization of photographic bleach powders containing an alkali metal ferricyanide |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US2943935A true US2943935A (en) | 1960-07-05 |
Family
ID=24644524
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US659213A Expired - Lifetime US2943935A (en) | 1957-05-15 | 1957-05-15 | Stabilization of photographic bleach powders containing an alkali metal ferricyanide |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US2943935A (en) |
| BE (1) | BE567236A (en) |
| DE (1) | DE1062114B (en) |
| GB (1) | GB834972A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3271153A (en) * | 1963-01-18 | 1966-09-06 | Eastman Kodak Co | Photographic processing baths for stabilization processing |
| US3342598A (en) * | 1965-06-14 | 1967-09-19 | Eastman Kodak Co | Phosphorous and maleic acid buffers for ferricyanide photographic bleaches |
| US4125402A (en) * | 1976-08-19 | 1978-11-14 | Ciba-Geigy Ag | Method of processing silver dye bleaching materials and preparations suitable for the dye and silver bleaching |
| EP1403705A2 (en) * | 2002-09-27 | 2004-03-31 | Eastman Kodak Company | Odorless photographic bleaching composition and color photographic processing |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3335004A (en) * | 1963-12-09 | 1967-08-08 | Eastman Kodak Co | Method for stabilization processing of color emulsions |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1656235A (en) * | 1926-05-06 | 1928-01-17 | Firm E Taeschner Chemisch Phar | Process for reducing photographic silver image layers |
| US2606118A (en) * | 1951-02-09 | 1952-08-05 | Eastman Kodak Co | Stabilizing agent for single powder photographic developers |
| US2611699A (en) * | 1949-12-30 | 1952-09-23 | Gen Aniline & Film Corp | Regeneration of exhausted silver bleaching solutions |
| US2650878A (en) * | 1949-12-09 | 1953-09-01 | Du Pont | Method of producing etched printing plates |
| US2843482A (en) * | 1956-03-30 | 1958-07-15 | Eastman Kodak Co | Photographic bleach composition |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE201168C (en) * | ||||
| DE222901C (en) * | ||||
| FR724863A (en) * | 1930-12-31 | 1932-05-04 | Union Chimique Belge Sa | Booster for photography |
| GB507152A (en) * | 1937-12-09 | 1939-06-09 | Bela Gaspar | Light-sensitive multilayer photographic material |
| USRE22977E (en) * | 1945-11-08 | 1948-02-24 | Bleaching bath and process for | |
| US2518686A (en) * | 1945-11-08 | 1950-08-15 | Gen Aniline & Film Corp | Aldehyde antistain baths for developed color photographic material |
| US2551091A (en) * | 1949-09-14 | 1951-05-01 | Du Pont | Process for color developing, including treatment with a quaternary ammonium salt |
| BE500365A (en) * | 1949-12-30 | |||
| BE519734A (en) * | 1952-05-07 |
-
0
- BE BE567236D patent/BE567236A/xx unknown
-
1957
- 1957-05-15 US US659213A patent/US2943935A/en not_active Expired - Lifetime
-
1958
- 1958-05-06 DE DEG24469A patent/DE1062114B/en active Pending
- 1958-05-07 GB GB14652/58A patent/GB834972A/en not_active Expired
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1656235A (en) * | 1926-05-06 | 1928-01-17 | Firm E Taeschner Chemisch Phar | Process for reducing photographic silver image layers |
| US2650878A (en) * | 1949-12-09 | 1953-09-01 | Du Pont | Method of producing etched printing plates |
| US2611699A (en) * | 1949-12-30 | 1952-09-23 | Gen Aniline & Film Corp | Regeneration of exhausted silver bleaching solutions |
| US2606118A (en) * | 1951-02-09 | 1952-08-05 | Eastman Kodak Co | Stabilizing agent for single powder photographic developers |
| US2843482A (en) * | 1956-03-30 | 1958-07-15 | Eastman Kodak Co | Photographic bleach composition |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3271153A (en) * | 1963-01-18 | 1966-09-06 | Eastman Kodak Co | Photographic processing baths for stabilization processing |
| US3342598A (en) * | 1965-06-14 | 1967-09-19 | Eastman Kodak Co | Phosphorous and maleic acid buffers for ferricyanide photographic bleaches |
| US4125402A (en) * | 1976-08-19 | 1978-11-14 | Ciba-Geigy Ag | Method of processing silver dye bleaching materials and preparations suitable for the dye and silver bleaching |
| EP1403705A2 (en) * | 2002-09-27 | 2004-03-31 | Eastman Kodak Company | Odorless photographic bleaching composition and color photographic processing |
| EP1403705A3 (en) * | 2002-09-27 | 2004-04-21 | Eastman Kodak Company | Odorless photographic bleaching composition and color photographic processing |
| US20040086810A1 (en) * | 2002-09-27 | 2004-05-06 | Haye Shirleyanne E. | Odorless photographic bleaching composition and color photographic processing |
| US6828084B2 (en) | 2002-09-27 | 2004-12-07 | Eastman Kodak Company | Odorless photographic bleaching composition and color photographic processing |
Also Published As
| Publication number | Publication date |
|---|---|
| DE1062114B (en) | 1959-07-23 |
| BE567236A (en) | |
| GB834972A (en) | 1960-05-18 |
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