Patent Publication Number: US-5629139-A

Title: Photographic processing solution composition

Description:
FIELD OF THE INVENTION 
     This invention relates to photographic processing solutions and in particular to photographic processing solutions containing hydrogen peroxide. It also relates to a method of using these processing solutions. 
     BACKGROUND OF THE INVENTION 
     Redox amplification processes have been described, for example in British Specification Nos. 1,268,126, 1,399,481, 1,403,418 and 1,560,572. In such processes color materials are developed to produce a silver image (which may contain only small amounts of silver) and then treated with a redox amplifying solution (or a combined developer-amplifier) to form a dye image. 
     The developer-amplifier solution contains a color developing agent and an oxidizing agent that will oxidize the color developing agent in the presence of the silver image which acts as a catalyst. An amplifier solution contains the oxidant but for its dye image forming depends on color developer carried over from the previous developer bath. 
     Oxidized color developer reacts with a color coupler to form the image dye. The amount of dye formed depends on the time of treatment or the availability of color coupler and is less dependent on the amount of silver in the image as is the case in conventional color development processes. 
     The stability of amplifier and developer/amplifier solutions is not good while that of bleach solutions can cause problems, though not to the same extent. 
     A number of ways of stabilizing amplifier and developer/amplifier solutions have been proposed in the art. 
     We have now found that the stability of a replenished amplifier, developer/amplifier, or bleach bath deteriorates as processing progresses (or as the solution is seasoned). It has now been discovered that this instability is apparently caused by silver deposited in the tank and pipework or other metallic parts of the machine. The present invention seeks to solve this problem. 
     SUMMARY OF THE INVENTION 
     This invention provides a photographic processing solution comprising a redox amplification oxidant or a compound that provides a redox amplification oxidant, and dissolved therein, a compound having a hydrophobic hydrocarbon group and a group which adsorbs to silver or stainless steel. 
     This invention also provides a method for processing an imagewise exposed silver halide photographic element comprising contacting the element with the photographic processing solution just described. 
     It is believed that the compound that adsorbs to silver inhibits the silver&#39;s catalytic effect. 
     An RX amplifier or developer/amplifier can be run in a continuous processor in which silver deposits would otherwise occur and still be as stable as in the absence of silver deposits. 
     The long chain amines, in particular, have very little sensitometric effect on the material at 0.1 g/l or even at 5 times this level. 
     The most likely catalytic agents are silver metal or stainless steel. Such materials might be found generally inside the tanks and pipework or may be localized metal parts exposed to the processing solution. 
     The materials used in the present invention could be used to stabilize peroxide solutions used as silver bleaches which tend to decompose in the presence of metals. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The photographic processing solution may be a developer/amplifier, amplifier or bleach solution. 
     The redox amplification oxidant may be a persulphate, periodate, Cobalt(III) compound or, preferably, hydrogen peroxide, or a compound providing any of them. 
     In the compound described above, the hydrophobic hydrocarbon group preferably comprises a long chain alkyl group that may be branched or unbranched and may be an alkyl group having from 8 to 20 carbon atoms, more preferably from 10 to 18 and particularly from 10 to 16 carbon atoms. Alternatively the compounds may comprise more than one alkyl group, the sum of their carbon atoms being from 8 to 20 or an alkylaryl group having from 14 to 27 carbon atoms in total. 
     It is believed that the main purpose of the hydrophobic hydrocarbon group is to ensure that the compound is not able to diffuse into the photographic material where it could affect sensitometric properties, and to make the silver and other metal surfaces hydrophobic. 
     Compounds that adsorb to silver are preferably primary, secondary or tertiary long chain alkylamines, long chain alkyl quaternary ammonium salts, long chain alkyl heterocyclic ammonium salts, long chain alkyl aminocarboxylic acids, long chain alkyl aminosulphonic acids, long chain alkyl diamines, long chain alkyl branched alkyldiamines, long chain alkyl thiols, long chain alkyl thiocarboxylic acids, long chain alkyl thiosulphonic acids, long chain alkyl-substituted nitrogen-containing heterocyclic or mercaptoheterocyclic compounds, for example long chain alkyl substituted benzotriazoles, 1-phenyl-5-mercaptotetrazoles and 5-nitroindazoles in which the long chain alkyl group contains 7-20 carbon atoms. 
     Examples of such compounds are shown in the following table: 
     
                                           TABLE 1                                 
__________________________________________________________________________
Compound          General formula n                                       
__________________________________________________________________________
Alkyl amines      NH.sub.2 (CH.sub.2).sub.n CH.sub.3                      
                                  7-17                                    
Alkylaryl amines                                                          
                   ##STR1##       1-11                                    
Secondary and tertiary alkyl amines                                       
                  NR.sub.1 R.sub.2 (CH.sub.2).sub.n CH.sub.3              
                                  7-17                                    
 Alkyl quaternary salts                                                   
                   ##STR2##        7-17                                   
Alkyl heterocyclic quaternary salts                                       
                   ##STR3##       1-15                                    
Alkyl amino carboxylic acids                                              
                  NH.sub.2 (CH.sub.2).sub.n COOH                          
                                  7-20                                    
Alkyl amino sulphonic acids                                               
                  NH.sub.2 (CH.sub.2).sub.n SO.sub.3 H                    
                                  7-20                                    
Alkyl diamines    NH.sub.2 (CH.sub.2).sub.n NH.sub.2                      
                                  8-20                                    
Branched alkyl diamines                                                   
                  NH.sub.2 CH(NH.sub.2)(CH2).sub.n CH.sub.3               
                                  6-20                                    
Alkyl thiols      SH(CH.sub.2).sub.n CH.sub.3                             
                                  7-17                                    
Alkyl thiocarboxylic acids                                                
                  SH(CH.sub.2).sub.n COOH                                 
                                  7-20                                    
Alkyl thiosulphonic acids                                                 
                  SH(CH.sub.2).sub.n SO.sub.3 H                           
                                  7-20                                    
__________________________________________________________________________
 
    
     Further examples of heterocyclic compounds which adsorb to silver are: oxazoles, thiazoles, diazoles, triazoles, oxadiazoles, thiadiazoles, oxathiazoles, thiatriazoles, tetrazoles, benzimidazoles, indazoles, isoindazoles, selenotetrazoles, mercaptobenzothiazoles, selenobenzothiazoles, mercaptobenzoxazoles, selenobenzoxazoles, mercaptobenzimidazoles, selenobenzimidazoles, benzodiazoles, mercaptooxazoles, mercaptothiadiazoles, mercaptothiazoles, mercaptotriazoles, mercaptooxadiazoles, mercaptodiazoles, mercaptooxathiazoles, telleurotetrazoles and benzisodiazoles. 
     Specific examples of such compounds are dodecylamine, hexadecylamine, octadecylamine, dodecylammonium acetate, tetradecylammonium hydrochloride, tetradecyl-benzotriazole, 1-(4-dodecylphenyl)-3-mercaptotetrazole and tetradecyl-5-nitroindazoles, and mixtures thereof. 
     The amount of the compound needed to deactivate silver deposits is small, for example from 0.01 to 5 g/l, preferably from 0.05 to 1 g/l, and more preferably from 0.1 to 0.5 g/l. 
     When the compound does not readily dissolve in the processing solution, the solution may also contain a non-ionic surfactant. Examples of suitable non-ionic surfactants are polyoxyethylene long chain esters, alcohols, and amines and the number of polyoxyethylene groups is from 3 to 30. The compounds listed in Table 2 may be used for this purpose. Preferably, the non-ionic surfactant is a polyoxyethylene ester having an alkyl group of 8 to 20 carbon atoms. 
     
                       TABLE 2                                                     
______________________________________                                    
Name of surfactant                                                        
               Description                                                
______________________________________                                    
TWEEN ™ 80  Polyoxyethylene sorbitan monooleate                        
TWEEN ™ 20  Polyoxyethylene sorbitan                                   
               monolaurate                                                
TRITON ™ X-100                                                         
               Iso octyl phenoxypolyethoxyethanol                         
DOWFAX ™ 9N10                                                          
               Nonyl phenol ethoxylate                                    
DOWFAX ™ 9N5                                                           
               Nonyl phenol ethoxylate                                    
SYNPERONIC ™ OP8                                                       
               Octyl phenol ethoxylate                                    
ETHOMEEN ™ S25                                                         
               Polyoxyethylene oleylamine                                 
ETHOMEEN ™ T25                                                         
               Polyoxyethylene tallow-amine                               
______________________________________                                    
 
    
     The nonionic surfactants may be used in amounts of 0.01 to 10 g/l, and preferably in the amount needed to solubilize the compound having the hydrophobic hydrocarbon group. 
     The preferred color developing agents are: 
     4-amino-3-methyl-N,N-diethylaniline hydrochloride, 
     4-amino-3-methyl-N-ethyl-N-β-(methanesulphonamido)-ethylaniline sulphate hydrate, 
     4-amino-3-methyl-N-ethyl-N-β-hydroxyethylaniline sulphate, 
     4-amino-3-β-(methanesulphonamido)ethyl-N,N-diethylaniline hydrochloride, and 
     4-amino-N-ethyl-N-(2-methoxy-ethyl)-m-toluidine di-p-toluene sulphonate. 
     Peroxide-containing bleach solutions are described in European Publications 0 540 619, 0 569 576 and 0 506 909. 
     Examples of suitable peroxide oxidizing agents are peroxy compounds including hydrogen peroxide and compounds that provide hydrogen peroxide, e.g., addition compounds of hydrogen peroxide. 
     Other components that may be included in a developer/amplifier solution include a base, e.g., potassium or sodium hydroxide; a pH buffer such as a carbonate, borate, silicate or phosphate; antioxidants such as hydroxylamine sulphate, diethylhydroxylamine and substituted alkylhydroxylamines as described, for example in U.S. Pat. Nos. 4,876,174 and 5,354,646; metal-chelating compounds such as 1-hydroxyethylidene-1,1&#39;-diphosphonic acid, catechol disulphonate and diethyltriamine-pentaacetic acid. Other components may be present, for example those mentioned in Research Disclosure Item 308119, December 1989 published by Kenneth Mason Publications, Emsworth, Hants, United Kingdom. 
     A particular application of this invention is in the processing of silver chloride color paper, for example paper comprising at least 85 mole percent silver chloride, especially such paper having total silver levels from 5 to 700 mg/m 2 , and for image amplification applications levels from 10 to 120 mg/m 2 , particularly from 15 to 60 mg/m 2 . 
     Such color materials can be single color elements or multicolor elements. Multicolor elements contain dye image-forming units sensitive to each of the three primary regions of the spectrum. Each unit can be comprised of a single emulsion layer or of multiple emulsion layers sensitive to a given region of the spectrum. The layers of the element, including the layers of the image-forming units, can be arranged in various orders as known in the art. In an alternative format, the emulsions sensitive to each of the three primary regions of the spectrum can be disposed as a single segmented layer. 
     A typical multicolor photographic element comprises a support bearing a cyan dye image-forming unit comprised of at least one red-sensitive silver halide emulsion layer having associated therewith at least one cyan dye-forming coupler, a magenta dye image-forming unit comprising at least one green-sensitive silver halide emulsion layer having associated therewith at least one magenta dye-forming coupler, and a yellow dye image-forming unit comprising at least one blue-sensitive silver halide emulsion layer having associated therewith at least one yellow dye-forming coupler. The element can contain additional layers, such as filter layers, interlayers, overcoat layers, subbing layers, and the like. 
     While the present solutions may be used in conventional large scale or minilab processing environments the present processing solutions are preferably used in a method of processing carried out by passing the material to be processed through a tank containing the processing solution that is recirculated through the tank at a rate of from 0.1 to 10 tank volumes per minute. 
     The preferred recirculation rate is from 0.5 to 8, especially from 1 to 5 and particular from 2 to 4 tank volumes per minute. 
     The recirculation, with or without replenishment, is carried out continuously or intermittently. In one method of working both could be carried out continuously while processing was in progress but not at all or intermittently when the machine was idle. Replenishment may be carried out by introducing the required amount of replenisher into the recirculation stream either inside or outside the processing tank. 
     It is advantageous to use a tank of relatively small volume. Hence in a preferred embodiment of the present invention the ratio of tank volume to maximum area of material accomodatable therein (i.e., maximum path length×width of material) is less than 11 dm 3  /m 2 , preferably less than 3 dm 3  /m 2 . 
     The shape and dimensions of the processing tank are preferably such that it holds the minimum amount of processing solution while still obtaining the required results. The tank is preferably one with fixed sides, the material being advanced therethrough by drive rollers. Preferably the photographic material passes through a thickness of solution less than 11 mm, preferably less than 5 mm and especially about 2 mm. The shape of the tank is not critical but it could be in the shape of a shallow tray or, preferably U-shaped (that is, having a rack and tank design). It is preferred that the dimensions of the tank be chosen so that the width of the tank is the same or only just wider than the width of the material to be processed. 
     The total volume of the processing solution within the processing channel and recirculation system is relatively smaller as compared to prior art processors. In particular, the total amount of processing solution in the entire processing system for a particular module is such that the total volume in the processing channel is at least 40 percent of the total volume of processing solution in the system. Preferably, the volume of the processing channel is at least about 50 percent of the total volume of the processing solution in the system. 
     In order to provide efficient flow of the processing solution through the opening or nozzles into the processing channel, it is desirable that the nozzles/opening that deliver the processing solution to the processing channel have a configuration in accordance with the following relationship: 
     
         0.6≦F/A≦23 
    
     wherein: 
     F is the flow rate of the solution through the nozzle in liters/minute; and 
     A is the cross-sectional area of the nozzle provided in square centimeters. 
     Providing a nozzle in accordance with the foregoing relationship assures appropriate discharge of the processing solution against the photosensitive material. Such Low Volume Thin Tank systems are described in more detail in the following publications: U.S. Pat. No. 5,294,956, EP 559,027, U.S. Pat. No. 5,179,404, EP 559,025, U.S. Pat. No. 5,270,762, EP 559,026, WO 92/10790, WO 92/17819, WO 93/04404, WO 92/17370, WO 91/19226, WO 91/12567, WO 92/07302, WO 93/00612, WO 92/07301, WO 92/09932. 
     In the following discussion of suitable materials for use in the emulsions and elements of this invention, reference will be made to Research Disclosure, December 1989, Item 308119, published by Kenneth Mason Publications, Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire P010 7DQ, ENGLAND, which will be identified hereafter by the term &#34;Research Disclosure.&#34; The contents of the Research Disclosure, including the patents and publications referenced therein, are incorporated herein by reference, and the Sections hereafter referred to are Sections of the Research Disclosure. 
     The silver halide emulsions employed in the elements of this invention can be either negative-working or positive-working. Suitable emulsions and their preparation as well as methods of chemical and spectral sensitization are described in Sections I through IV. Color materials and development modifiers are described in Sections V and XXI. Vehicles are described in Section IX, and various additives such as brighteners, antifoggants, stabilizers, light absorbing and scattering materials, hardeners, coating aids, plasticizers, lubricants and matting agents are described, for example, in Sections V, VI, VIII, X, XI, XII, and XVI. Manufacturing methods are described in Sections XIV and XV, other layers and supports in Sections XIII and XVII, processing methods and agents in Sections XIX and XX, and exposure alternatives in Section XVIII. 
     The following Examples are included for a better understanding of the invention. 
     EXAMPLE 1 
     In this example several materials were examined as inhibitors for the silver catalyzed decomposition of a redox developer/amplifier solution (Dev/Amp). The basic Dev/Amp used is shown in Table 1. 
     
                       TABLE 1                                                     
______________________________________                                    
Base Developer/Amplifier Solution                                         
______________________________________                                    
1-Hydroxyethylidene-1,1&#39;-                                                 
                       0.6    g/l                                         
diphosphonic acid (60% soln)                                              
Diethyltriamine-pentaacetic acid                                          
                       2.0    ml/l                                        
penta sodium salt (40% soln)                                              
K.sub.2 HPO.sub.4.3H.sub.2 O                                              
                       40     g/l                                         
KBr                    1.0    mg/l                                        
KCl                    0.5    g/l                                         
Catechol-3,5-disulphonate                                                 
                       0.3    g/l                                         
Hydroxylamine sulphate 1.0    g/l                                         
KOH (50%)              10.0   ml/l                                        
4-N-ethyl-N-(β-methanesulphon-                                       
amidoethyl)- o-toluidine                                                  
sesquisulphate (CD3)   4.5    g/l                                         
H.sub.2 O.sub.2 (30%)  2.0    ml/l                                        
pH                     11.4                                               
Temperature            32°                                         
                              C.                                          
Time                   45     seconds                                     
______________________________________                                    
 
    
     Nine Dev/Amps were made up with the basic composition as in Table 1 except that all the Dev/Amps had 7.3 mg/l of colloidal silver added to them to cause rapid decomposition and also some materials designed to inhibit the catalysis. The colloidal silver was diluted from a dispersion that contained 4.43% silver and 7.8% gelatin. This is normally referred to as Carey Lea Silver, or CLS. The composition of the Dev/Amps is shown in Table 2. 
     
                       TABLE 2                                                     
______________________________________                                    
Developer/Amplifier Composition                                           
Dev/Amp                                                                   
Number                                                                    
______________________________________                                    
1       composition in Table 1 + 7.3 mg/l Silver                          
2       as Dev/Amp 1 + 0.4 g/l ARQUAD ™                                
        MC-50                                                             
3       as Dev/Amp 2 + 0.4 g/l TWEEN ™ 80                              
4       as Dev/Amp 1 + 0.4 g/l ARQUAD ™ 16-50 +                        
        0.4 g/l TWEEN ™ 80                                             
5       as Dev/Amp 1 + 0.4 g/l ARQUAD ™ S-50 +                         
        0.4 g/l TWEEN ™ 80                                             
6       as Dev/Amp 1 + 0.4 g/l TWEEN ™ 80                              
7       as Dev/Amp 1 + 0.4 g/l VERSA ™ TL-73                           
8       as Dev/Amp 1 + 0.4 g/l ARMAC ™ 12D +                           
        0.4 g/l TWEEN ™ 80                                             
______________________________________                                    
 
    
     The ARQUAD™ materials are quaternary amine hydrochlorides with 3 methyl groups and a long chain alkyl group which for MC-50 is mainly C 12 , for 16-50 is mainly C 16 , and for S-50 is mainly C 18 . ARMAC™ 12D is 97% dodecylamine acetate and TWEEN™ 80 is polyoxyethylene sorbitan mono-oleate. 
     In all cases the silver was added as the last component and the changes in color of the Dev/Amp were monitored over a period of hours. It is known from previous experiments that a darkening of the color from an initial pale, through, light then dark to black indicates increasing degree of oxidation of the color developing agent (CD3). The result of the observations on the nine developer/amplifiers above is shown in Table 3. 
     
                       TABLE 3                                                     
______________________________________                                    
Dev/Amp oxidation                                                         
         Time after silver addition                                       
Dev/Amp    10 min    30 min    2 hr   24 hr                               
______________________________________                                    
1          dark →              black-                              
2          pale      pale      light  light                               
3          pale      pale      light  light                               
4          pale      light     dark   dark                                
5          pale      light     dark   dark                                
6          dark      black →                                       
7          dark      black →                                       
8          pale      pale      pale   light                               
______________________________________                                    
 
    
     Clearly Dev/Amp 8 is the best followed by 2 and 3. 
     EXAMPLE 2 
     In this example the effect of dodecylamine on the catalytic activity of silver deposits in the Dev/Amp tank of a low volume thin tank processor having the solution between tank walls about 2 mm apart is demonstrated. The Dev/Amp tank was cleaned out with hydrochloric acid and the washed several times with water. The Dev/Amp tank was filled with the Dev/Amp shown in Table 1 and the chemical loss rates were measured by taking samples at various times and analyzing for hydroxylamine sulphate (HAS), hydrogen peroxide and CD3 levels. After the start run the processor was filled with fresh Dev/Amp, as in Table 1 and paper was processed for 6 tank turnovers (TTOs), this comprised run 1. The Dev/Amp was removed and a fresh Dev/Amp added as in Table 1 and the chemical loss rates were measured as before. The sequence was repeated for run 2 and run 3. The Dev/Amp used to measure the chemical loss rates after run 3 was discarded and a fresh Dev/Amp added as in Table 1 but with 0.1 g/l of dodecylamine (Aldrich 98%) and 0.2 g/l of TWEEN™ 80. The dodecylamine was dissolved in an equimolar amount of acetic acid and mixed with the TWEEN™ 80 before adding to the Dev/Amp. It can be seen from Table 4 that there is a progressive increase in the chemical loss rates with the extent of paper processing up to run 3. The inclusion of compounds dodecylamine and TWEEN™ 80 completely removes the catalytic effect of the paper processing and gives chemical loss rates almost the same as at the start. 
     
                       TABLE 4                                                     
______________________________________                                    
Chemical Loss Rates in Processor                                          
            HAS      H.sub.2 O.sub.2                                      
                              CD3                                         
            (g/l/hr) (ml/l/hr)                                            
                              (g/l/hr)                                    
______________________________________                                    
Start         0.0247     0.027    0.01                                    
After         0.0611     0.0575   0.016                                   
run 1                                                                     
After         0.125      0.207    0.021                                   
run 2                                                                     
After         0.202      0.418    0.034                                   
run 3                                                                     
After         0.0216     0.0222   &lt;0.01                                   
run 3 plus                                                                
dodecylamine                                                              
and TWEEN ™ 80                                                         
______________________________________                                    
 
    
     EXAMPLE 3 
     In this example the effect of dodecylamine on the silver-catalyzed decomposition of a redox Dev/Amp is examined. Four Dev/Amps were prepared based on the one in Table 1 and these are as follows: 
     Dev/Amp 10 the same as in Table 1, this is the control Dev/Amp. 
     Dev/Amp 11 as Dev/Amp 10 but with 0.2 g/l TWEEN™ 80 and 0.1 g/l dodecylamine. 
     Dev/Amp 12 as Dev/Amp 11 but the dodecylamine was first dissolved in glacial acetic acid before adding to the Dev/Amp, this adds 0.03 g/l of glacial acetic acid to the Dev/Amp. 
     Dev/Amp 13 was as Dev/Amp 12 but with five times the level of TWEEN™ 80(1 g/l) and five times the level of dodecylamine (0.5 g/l) and acetic acid (0.15 g/l). 
     To each of these Dev/Amps 0.73 mg/l of colloidal silver known as Carey Lea silver (CLS) was added in order to accelerate the decomposition. The color of these Dev/Amps was monitored over time and it was apparent that Dev/Amp 10 (the control) darkened noticeably in 10 minutes and particularly after 4 hours. The other 3 Dev/Amps 11, 12 and 13 stayed pale straw color over this time. 
     Sensitometric strips of an experimental low silver color paper multilayer, total silver laydown l 118 mg/m 2  (11.0 mg/sq.ft), were exposed to a step wedge tablet with built-in filters to allow neutral, cyan, magenta and yellow images and were processed in Dev/Amps 10 to 13 over a period of hours and days. The complete process cycle used was as follows: 
     
         ______________________________________                                    
Develop       45 seconds                                                  
Stop          30 seconds                                                  
Bleach-fix    45 seconds                                                  
Wash          120 seconds                                                 
Dry                                                                       
______________________________________                                    
 
    
     where the Stop was 15 g/l sodium metabisulphite and the bleach-fix was RA4 bleach-fix. 
     The Dmax of these strips is given as a function of time in Table 5. 
     
                                           TABLE 5                                 
__________________________________________________________________________
Dmax as a function of time                                                
Dmax(N) × 100                                                       
DEV No.                                                                   
Time  10       11       12       13                                       
(hrs) R  G  B  R  G  B  R  G  B  R  G  B                                  
__________________________________________________________________________
 0    251                                                                 
         266                                                              
            268                                                           
               262                                                        
                  272                                                     
                     275                                                  
                        258                                               
                           266                                            
                              266                                         
                                 245                                      
                                    264                                   
                                       268                                
  0.5 263                                                                 
         267                                                              
            268                                                           
               263                                                        
                  271                                                     
                     274                                                  
                        261                                               
                           272                                            
                              274                                         
                                 248                                      
                                    266                                   
                                       269                                
 4    235                                                                 
         237                                                              
            239                                                           
               252                                                        
                  261                                                     
                     263                                                  
                        255                                               
                           265                                            
                              267                                         
                                 244                                      
                                    260                                   
                                       262                                
20    112                                                                 
         126                                                              
            145                                                           
               253                                                        
                  264                                                     
                     261                                                  
                        249                                               
                           255                                            
                              251                                         
                                 244                                      
                                    262                                   
                                       259                                
92     68                                                                 
          82                                                              
             94                                                           
               259                                                        
                  266                                                     
                     256                                                  
                        255                                               
                           262                                            
                              241                                         
                                 240                                      
                                    256                                   
                                       251                                
125   -- -- -- 247                                                        
                  254                                                     
                     240                                                  
                        259                                               
                           262                                            
                              245                                         
                                 229                                      
                                    248                                   
                                       242                                
172   -- -- -- 252                                                        
                  257                                                     
                     239                                                  
                        262                                               
                           262                                            
                              243                                         
                                 232                                      
                                    249                                   
                                       244                                
__________________________________________________________________________
 
    
     It is clear from these data that the catalytic activity of the colloidal silver is prevented by the inclusion of dodecylamine. The presence of acetic acid used to dissolve the dodecylamine in Dev/Amp 12 does not appear to have a significant effect as shown by comparison with Dev/Amp 11 which did not contain acetic acid. The higher level of dodecylamine and TWEEN™ 80 in Dev/Amp 13 does appear to result in consistency lower red Dmax. 
     EXAMPLE 4 
     In this example three Dev/Amps are compared for their standing stability and initial sensitometry in the presence of potential stabilizers against silver catalyzed decomposition but without any added silver. The Dev/Amp compositions are shown in Table 6. 
     
                       TABLE 6                                                     
______________________________________                                    
Developer/amplifier Composition                                           
Dev/Amp                                                                   
No.                                                                       
______________________________________                                    
14         Control as in Table 1                                          
15         14 + 0.2 g/l ARMAC ™ 12D + 0.2 g/l                          
           TWEEN ™ 80                                                  
16         14 + 0.2 g/l ARQUAD ™ 16-50 + 0.2 g/l                       
           TWEEN ™ 80                                                  
______________________________________                                    
 
    
     The results of the standing test are shown in Table 7. 
     
                       TABLE 7                                                     
______________________________________                                    
Dmax (× 100) as a function of time                                  
DEV No                                                                    
Time  14           15           16                                        
(days)                                                                    
      R      G      B    R    G    B    R    G    B                       
______________________________________                                    
0     253    266    270  245  262  265  235  262  267                     
3     257    265    261  244  261  258  --   --   --                      
4     264    266    261  254  265  261  --   --   --                      
5     267    268    253  256  266  250  --   --   --                      
7     273    268    241  262  263  241  --   --   --                      
10    269    263    227  259  256  234  --   --   --                      
______________________________________                                    
 
    
     It can be seen that ARMAC™ 12D causes perhaps a small loss in Dmax. The Dev/Amp containing ARMAC™ 12D is clearly the one most similar to the control. ARQUAD™ 16-50 causes an initial drop in activity but the Dev/Amp (16) was essentially inactive after 3 days. 
     EXAMPLE 5 REDOX AMPLIFIER SOLUTION 
     This is an example of the invention and compares amplifiers 3 and 4 (the invention) with amplifiers 1 and 2 (comparative examples). 
     Four solutions were made up of the following composition. 
     
                       TABLE 8                                                     
______________________________________                                    
Solution composition                                                      
           Solution Number                                                
Component    1        2        3      4                                   
______________________________________                                    
1-Hydroxyethylidene-                                                      
             0.6 g/l  0.6 g/l  0.6 g/l                                    
                                      0.6 g/l                             
1,1&#39;-diphosphonic acid                                                    
(60% soln.)                                                               
Pentasodium diethyl-                                                      
             2.0 ml/l 2.0 ml/l 2.0 ml/l                                   
                                      2.0 ml/l                            
triaminepentaacetic                                                       
acid (40% soln)                                                           
K.sub.2 HPO.sub.4.3H.sub.2 O                                              
              40 g/l   40 g/l   40 g/  40 g/l                             
KBr            1 mg/l   1 mg/l   1 mg/l                                   
                                        1 mg/l                            
KCl          0.3 g/l  0.3 g/l  0.3 g/l                                    
                                      0.3 g/l                             
pH           11.4     11.4     11.4   11.4                                
Dodecylamine  --       --      0.1 g/l                                    
                                      0.1 g/l                             
TWEEN ™ 80                                                             
              --       --      0.4 g/l                                    
                                      0.4 g/l                             
H.sub.2 O.sub.2 (30%)                                                     
             2.0 ml/l 2.0 ml/l 2.0 ml/l                                   
                                      2.0 ml/l                            
Carey Lea Silver                                                          
              --      7.3 mg/l 7.3 mg/l                                   
                                       --                                 
______________________________________                                    
 
    
     The level of hydrogen peroxide was monitored over a period of time and the results are shown in Table 9. The start values at solution age 0 are in fact about 3 minutes old which is the time it takes to add the colloidal silver and then take a sample and analyze it for hydrogen peroxide. 
     
                       TABLE 9                                                     
______________________________________                                    
Hydrogen Peroxide Analysis                                                
           Hydrogen Peroxide Level                                        
           (ml/l, 30%)                                                    
Solution Age 1      2          3    4                                     
______________________________________                                    
  0          2.09   1.73       1.84 1.90                                  
  1 hr       1.97   0.36       1.83 1.94                                  
  2 hrs      2.01   0.20       1.72 1.93                                  
4.3 hrs      1.94   0.10       1.73 1.96                                  
  6 hrs      1.96   0          1.74 1.91                                  
  7 hrs      1.97   0          1.73 1.90                                  
 70 hrs      1.91   0          1.58 1.84                                  
  6 days     1.85   0          1.56 1.80                                  
 11 days     1.88   0          1.42 1.75                                  
______________________________________                                    
 
    
     Solution 1 is the control without any added colloidal silver and it shows about a 10% loss in 11 days. Solution 2 is the same as the control but with 7.3 mg/l of colloidal silver (Carey Lea Silver) and it has decomposed completely after about 4.5 hours. Solution 3 is the same as solution 2 except that catalytic inhibitor, dodecylamine is included. It can be seen that solution 3 is very much more stable than solution 2 with a loss of peroxide of about 30% in 11 days (assuming 2.0 ml/l at the start). This shows that dodecylamine very substantially deactivates the colloidal silver. Solution 4 is the same as solution 1 except that it contains dodecylamine (silver is absent from both 1 and 4) and is slightly less stable than the control solution 1. 
     The Example shows that dodecylamine stabilizes amplifier solutions containing hydrogen peroxide (but without color developing agent) against catalyzed decomposition. 
     The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.