Yet another Chlorohydroquinone thread, but with synthesis

I know this is an often lamented topic, but I was reading through the Kodak patent for chlorohydroquinone synthesis and well... it looked actually kinda reasonable in my tiny under equipped home lab.

I know that this synthesis is incredibly crude and I make no attempt at purifying the final product. For superadditive developers, this is likely unsuitable because at least some hydroquinone is expected to remain.

Anyway. Here's what I did since I've never seen anyone claim to do the synthesis actually describe how:

* Add stir bar to beaker
* Add 10.2g of hydroquinone to beaker
* Add 10ml distilled water
* Add 20ml glacial acetic acid
* Stir for around 5 minutes. It won't all dissolve. The solution will turn ice cold
* Add hydrochloric acid, drop wise slowly. (1st batch was 10ml. 2nd batch is 2.8ml). The solution will warm slightly
* Cover using a simple coffee filter or foil
* Turn on heating but only gently and briefly. Basically get it to where it feels a bit warm, probably around 100F and immediately turn off heating
* Stir for 1-2 hours
* For batch #1 after around 30m, the solution became clear with no precipitate. I did not see batch #2 have a similar reaction, though it may have had this reaction but briefly and I didn't see it
* After around 2 hours, the texture and appearance of the solution will be distinctly different. More gel-like with the crystals taking on a different shape. Unsure how to describe this
* Take off stirring. The solution will become fairly solid after another hour
* Use about 150ml hot water to dissolve the chunk of material. This should not be very difficult
* Neutralize batch #1 using about 13g of sodium hydroxide. (batch #2 untested). After adding 10g, add a small pinch of sulfite. Do not add more than a pinch, otherwise there can be a dangerous sulfur dioxide release. I used a 10% solution of hydroxide instead of dissolving powder.
* Mix 500ml of Defender 58-D formula using the entire batch of this solution for the chlorohydroquinone
* Add 2g additional sodium carbonate (ph seemed too low with clip tests)
* With usage, added 10ml of 20% citric acid (5ml was about right. 10ml was too much) to test different pH results

The final test was a bit low on pH but did produce a reasonable somewhat low contrast image with brown-blacks after 6m of development. The measured pH was 9.25. At least some chlorohydroquinone was produced. Hydroquinone alone would definitely not produce normal contrast images like this, at this pH. Using the crude product comes with severe limitations. There are likely multi-chlorinated species of hydroquinone present, along with the mono variant which we are aiming for. Some hydroquinone is most likely left behind. There is no guards against oxidation, though I believe oxidation in such an acidic solution would be minimal. There is sodium acetate and sodium chloride produced as products of neutralizing the solvents instead of doing a purifying distillation

A test result is below, on Fomatone Classic FB. The bottom is with 5ml of the citric acid solution and top is with 10ml. Top was developed for 6 minutes, bottom for 4.5 minutes

Hi Ashley,

I assume you're referring to US2748173. The other Eastman patent for CQ uses carbon tetrachloride, a carcinogenic solvent now practically phased out worldwide. I think you might have unintentionally reduced the procedure and omitted an important step, which is the addition of dry chlorine gas (Cl2), wherein the actual halogenation occurs. The two patents essentially propose alternative solvent systems (aqueous acetic acid and the non-polar inert CCl4) in which the actual addition takes place.

Simply dissolving HQ in acetic acid and adding HCl probably has no effect on the hydroquinone. The benzene ring isn't susceptible to attach by haloacids, and definitely not in aqueous medium without catalysis and extreme temperature/pressure conditions. Hydroquinone is a fairly activated phenol and can be halogenated by chlorine (and IIRC hypochlorous acid) without catalysts. But the chloride ion in HCl cannot simply add to the benzene core, to put it simply.

The preparation of CQ using HCl is possible, but HQ is not the starting material, rather, its oxidized form - benzoquinone. 1,4-benzoquinone (aka p-benzoquinone, aka quinone) is a much more active reagent and can undergo conjugate addition reactions with suitable nucleophiles (such as Cl-). It is also volatile, a strong irritant of skin and mucosa, stains skin, and may be long-term harmful.

US3959392 describes the synthesis in nonaqueous medium under elevated pressure. Problem is, the solvent is benzene, again not the nicest thing to hang around with. There is doubt whether the reaction proceeds smoothly in aqueous conditions.

Edit: FDC2 and posts on Photrio suggest that at least one developer (Edwal FG-7) was made using CQ prepared in-situ from benzoquinone and hydrochloric acid in an aqueous medium. Starting from hydroquinone, once can use an oxidizer, such as H2O2, to produce the benzoquinone, then treat the result with conc. HCl without intermediate purification steps, and use the result in a developer, as was probably done for FG-7. The reaction scheme may not have a simple stoichiometry, because free benzoquinone will oxidize the chlorohydroquinone during the synthesis. Treatment with a stronger reducing agent (dithionite is mentioned in the literature, but I wouldnt use that anywhere near developers as even a trace amount will likely fog and cause chemical reversal of AgX) may be needed.

Alternatively, an oxidizer such as peroxide may be added to an aqueous hydrochloric solution of HQ. Depending on the reaction conditions (temperature, concentration), the peroxide may oxidize the HQ to p-benzoquinone, or the HCl to Cl2, or trigger an alternative free radical mechanism (if acetic acid is present, some will be converted to peroxyacetic acid). An alternative, and possibly better oxidizer might be permanganate (KMnO4, liberates free Cl2 from HCl solutions) or dichromate (a classic oxidizing agent for phenols), though then the metals need to be separated and the product purified. I might test this procedure later this year, and also perform the chlorination to prepare a reference material.

Note: please do not attempt to mix strong acids and oxidizers. Between severe chemical burns and exposure to poisonous, corrosive gasses, there is plenty to go wrong, and even without mishaps, the chemistry involved is dangerous and not adaptable to the home environment. A fume hood and proper lab PPE are the bare minimum before even considering this route.

CQ is an interesting developing agent and has potential future applications, but since it is practically an orphan reagent, it's unlikely to become accessible in reasonable purity and price, especially since there are ways to emulate it in formulae using the commonly available chemistry. For instance, PF deems it profitable to prepare glycin, which involves alkylating agents and noxious fumes, yet don't offer CQ, because even for a well-equiped lab, kg batches would be difficult, messy, and expensive to manufacture.

Just out of curiosity what does Chlorohydroquinone with synthesis do in photographic processing?

pentaxuser

It is a (historic) developing agent, once used in a german commercial developer:

https://upload.wikimedia.org/wikipedia/commons/3/33/Adurol-Hauff_Advertisment.jpg

Nikola Dulgiarov said:

Hi Ashley,
...snip...

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Hi, so I honestly didn't expect it to work due to lack of Cl gas and lack of starting with benzoquinone, and maybe I have somehow synthesized some alternate developing agent... all I know is that what I have is no longer regular hydroquinone and it appears rather interesting. I agree that lack of an oxidizer (either starting with benzoquinone or using Cl gas) would seem to say that the reaction would result in nothing having happened... but the only alternate known chemical I could make from this is a very small amount of HQMS, which would still not produce a paper developer like this at this pH. I was actually planning to synthesize a small amount of benzoquinone and use HCl to chlorinate it... but I figured I'd try this first.

I know a reaction happened due to solution becoming self heating which lasted for around 30m and that at one point the solution turned completely clear and dissolved and then rapidly something fell out of solution without significant temperature variation. This reaction does not happen by just putting hydroquinone in acetic acid
I know that 10g of regular hydroquinone would be hard to dissolve in 150ml of water, while this goes into solution with no effort at all. -- Hydroquinone is capable of about an 8% solution in water, but monochlorohydroquinone is about 60%. I'm unsure about di and other more chlorinated species though. I've seen references that dichlorohydroquinone is much less soluble
I know the solution once brought up to proper alkaline pH of >8, the solution color changed from clear to a light tan color. This is the typical color described for developers with chlorohydroquinone
The solution produced normal contrast images with a slow induction period (chlorohydroquione is known to have a slow induction period like hydroquinone does)
The solution produced normal contrast images with reasonable dmax at pH 9.25. Hydroquinone is not properly activated until around pH 10, and even then will not produce normal contrast images.

I definitely realize that I deviated from the procedure to an extreme degree and I'm off in uncharted territory here... but whatever I have in this beaker definitely behaves a lot like chlorohydroquinone. If you would like to offer any advice on confirming that, I'm definitely interested to hear it... but I don't have the means to do a purifying distillation, recrystalization in inert atmosphere, or using dangerous solvents like Benzene and honestly if the process requires that then I'm not interested in trying.. but whatever I did seems to have done... something, which makes an interesting paper developer

pentaxuser said:

Just out of curiosity what does Chlorohydroquinone with synthesis do in photographic processing?

pentaxuser

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Chlorohydroquinone is a now unavailable developing agent related to hydroquinone. It has some unique properties which made it very interesting:

* Activation pH of 8.5
* 5x more active than hydroquinone but significantly less superadditive with phenidone, metol, and others
* Capable of behaving as a staining developer (unsure if there was ever a formula which actually used this property)
* Famously useful for fine grain film developers
* Also famous for warm tone paper developers, specifically producing tones more toward brown and even red depending on the formula
* Only developing agent known to reduce dichroic fog
* Often cited as being useful as an anti-fogging developer. At least one reference that a person had some paper that was too fogged for any developer except lith printing... but it worked in a chlorohydroquinone developer without any fog

Thanks both for the replies

pentaxuser

grainyvision said:

Hi, so I honestly didn't expect it to work due to lack of Cl gas and lack of starting with benzoquinone, and maybe I have somehow synthesized some alternate developing agent... all I know is that what I have is no longer regular hydroquinone and it appears rather interesting. I agree that lack of an oxidizer (either starting with benzoquinone or using Cl gas) would seem to say that the reaction would result in nothing having happened... but the only alternate known chemical I could make from this is a very small amount of HQMS, which would still not produce a paper developer like this at this pH

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HQMS is unlikely to form even if quinone was present, considering that a sulfite source was added at an acidic pH (the reductive sulfonation occurs at mildly acidic to neutral pH, >5 IIRC).
You have a solution of hydroquinone in a fairly concentrated carboxylic acid and you're adding a substantial amount of H+ with the hydrochloric acid. This is a typical (usually, sulfuric acid would be the catalyst and pushes the equilibrium towards the products) setup for esterification, where an organic alcohol (which HQ can be considered) reacts with a carboxylic acid (acetic in this case) to form the corresponding ester (mono- or diacetoxybenzene, aka hydroquinone mono/diacetate):

This would be inactive. The monoester might have activity in solution, but I believe that according to Kendall-Perutz, it would also be inactive. The remaining HQ could account for the activity you are seeing, and the acetate/chloride/citrate present in the developer you ended up making might account for the behavior you're observing.

It's very unlikely that any chlorination is taking place simply because the electronic structure of HQ or HQ(OAc) does not support attack by chloride. That said, you did not protect the reaction from the atmosphere, so some oxygen might have been able to oxidize some HQ at the surface and produce a *small* amount of some Cl-substituted material, especially over the course of several hours. It would be difficult to verify that either way.

A one-pot synthesis is possible given the proper reaction conditions.

Nikola Dulgiarov said:

HQMS is unlikely to form even if quinone was present, considering that a sulfite source was added at an acidic pH (the reductive sulfonation occurs at mildly acidic to neutral pH, >5 IIRC).
You have a solution of hydroquinone in a fairly concentrated carboxylic acid and you're adding a substantial amount of H+ with the hydrochloric acid. This is a typical (usually, sulfuric acid would be the catalyst and pushes the equilibrium towards the products) setup for esterification, where an organic alcohol (which HQ can be considered) reacts with a carboxylic acid (acetic in this case) to form the corresponding ester (mono- or diacetoxybenzene, aka hydroquinone mono/diacetate):
View attachment 290644
This would be inactive. The monoester might have activity in solution, but I believe that according to Kendall-Perutz, it would also be inactive. The remaining HQ could account for the activity you are seeing, and the acetate/chloride/citrate present in the developer you ended up making might account for the behavior you're observing.

It's very unlikely that any chlorination is taking place simply because the electronic structure of HQ or HQ(OAc) does not support attack by chloride. That said, you did not protect the reaction from the atmosphere, so some oxygen might have been able to oxidize some HQ at the surface and produce a *small* amount of some Cl-substituted material, especially over the course of several hours. It would be difficult to verify that either way.

A one-pot synthesis is possible given the proper reaction conditions.

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if a very small amount of chlorohydroquinone was synthesized, maybe it would be enough IFF hydroquinone is super additive with it. But I don't think this if the case

Nikola Dulgiarov said:

HQMS is unlikely to form even if quinone was present, considering that a sulfite source was added at an acidic pH (the reductive sulfonation occurs at mildly acidic to neutral pH, >5 IIRC).
You have a solution of hydroquinone in a fairly concentrated carboxylic acid and you're adding a substantial amount of H+ with the hydrochloric acid. This is a typical (usually, sulfuric acid would be the catalyst and pushes the equilibrium towards the products) setup for esterification, where an organic alcohol (which HQ can be considered) reacts with a carboxylic acid (acetic in this case) to form the corresponding ester (mono- or diacetoxybenzene, aka hydroquinone mono/diacetate):
View attachment 290644
This would be inactive. The monoester might have activity in solution, but I believe that according to Kendall-Perutz, it would also be inactive. The remaining HQ could account for the activity you are seeing, and the acetate/chloride/citrate present in the developer you ended up making might account for the behavior you're observing.

It's very unlikely that any chlorination is taking place simply because the electronic structure of HQ or HQ(OAc) does not support attack by chloride. That said, you did not protect the reaction from the atmosphere, so some oxygen might have been able to oxidize some HQ at the surface and produce a *small* amount of some Cl-substituted material, especially over the course of several hours. It would be difficult to verify that either way.

A one-pot synthesis is possible given the proper reaction conditions.

Click to expand...

So in theory to confirm if this ester is the chemical responsible for producing normal development, I should just do hydroquinone in acetic acid, and add sulfuric acid (I only have 40%, but maybe itd work) and then test if it can produce a developer substantially different from regular hydroquinone like I've seen in this case. [EDIT: actually, sulfuric acid is an oxidizer, so that wouldn't reproduce that behavior]

I've messed around a lot with hydroquinone-only developers and I've never seen anything like this. I've used citrate and acetate in lith developers with no observed effect, and it definitely didn't make the developer much more active and normal contrast

pentaxuser said:

Just out of curiosity what does Chlorohydroquinone with synthesis do in photographic processing?

pentaxuser

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It's reputed to be very suitable with old paper that would be fogged in any other developer.

I just realized I missed one very important footnote which actually does explain how this is possible. I'm not using pure hydrochloric acid. I'm using the much weaker muriatic acid. I didn't really consider the honestly somewhat unknown percentage of HCl in it, AND the impurities in it. The batch I have has a very slight yellow tint, which seems to likely point to dissolved iron, ferric chloride. I can at least somewhat confirm this as well because there is a very fine dust of what looks like iron hydroxide on the magnetic stir bar I used for the first batch. Ferric chloride on its own is an oxidizer though I'd assume due to the weak color that the amount actually introduced is tiny...,however, it might behave in a much more powerful way than expected due to the fenton reaction. It is well known that ferric chloride can oxidize hydroquinone to benzoquinone. At least one paper seems to indicate that this oxidation process introduces radicals which then go on to oxidize the ferrous ions back to ferric state.... I'm unsure if that is possible in the conditions here though (my understanding is that only really happened in alkali).

There are some chlorohydroquinone synthesis patents (specifically for polymer usage, not photography) which specifically avoid use of chlorine gas and pressurized setups by using oxidizing metal salts such as manganese oxide. I've not seen iron mentioned, but in theory it could work. I don't have any ferric chloride, but I do have ferric nitrate which would likely work well enough in its place if I want to manually try adding this impurity to get a stronger oxidizer effect. Though everytime I do any kind of work with iron salts I immediately regret it because clean up is always such an ordeal... but if I could figure out a way to dissolve the hydroquinone derivatives and leave behind the acidified solution with the salts and acids, that would be ideal. I don't think any solvent that can do that is friendly for home use though.

This has renewed my interest in acquiring some, as I have quite a lot of old papers.

Is it
2-Chloro-1,4-dihydroxybenzene
CAS Number:
615-67-8 ?

I see it is available from Merck from whom I have bought previously. Sigma Aldrich would not supply a hobbyist when I tried some years ago.

john_s said:

This has renewed my interest in acquiring some, as I have quite a lot of old papers.

Is it 2-Chloro-1,4-dihydroxybenzene

I see it is available from Merck from whom I have bought previously. Sigma Aldrich would not supply a hobbyist when I tried some years ago.

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The problem is the tech grade stuff available is brown mush and very oxidized. It's one thing to have impurities that are other developing agents, but the oxidation products really throw off a developer formula. I've not seen anyone have luck using the grades available cheaply. And reagent grade is extremely expensive and still on the low end of purity.

Nikola Dulgiarov said:

For instance, PF deems it profitable to prepare glycin, which involves alkylating agents and noxious fumes

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I'm not sure that they are. The MSDS suggests that they're getting it from TCI - presumably they're ordering enough for TCI (or a subcontractor to TCI) to be doing the synthesis in decent quantities.

Haist discusses Chlorohydroquinone in his Volume 1, but doesn't mention any property of its that's seems magical. Yes, it's more soluble and more active than Hydroquinone, but the superadditivity of Metol/Phenidone with Hydroquinone probably killed all interest in Chlorohydroquinone.

Raghu Kuvempunagar said:

Haist discusses Chlorohydroquinone in his Volume 1, but doesn't mention any property of its that's seems magical. Yes, it's more soluble and more active than Hydroquinone, but the superadditivity of Metol/Phenidone with Hydroquinone probably killed all interest in Chlorohydroquinone.

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The most interesting difficult to replace use of CQ seems to be as an anti dichroic fog agent. I believe it was used in the old HC-110 formula for this purpose.

I attempted a more proper synthesis from in situe benzoquinone (addition of permanganate, ensuring there is an under supply of permanganate for safety. Addition of TEA to complex with any remaining manganate and iron when brought to alkali pH) and while some CQ was produced, it seems to be less and of poorer quality with significant oxidation and polymerization. I will likely try one more simplified route if I ever get some ferric chloride, but I've mostly written it off until I get a better lab setup which looks like it'll happen next year. It's just too messy and I'm getting to an uncomfortable danger level by messing with quinone, even if briefly due to doing this all in situ and avoiding making solutions of quinone without reactants which will immediately reduce it into something less awful

grainyvision said:

The most interesting difficult to replace use of CQ seems to be as an anti dichroic fog agent. I believe it was used in the old HC-110 formula for this purpose.

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I thought modern film and paper have embedded anti dichroic fog agents and so do some developers.

Photo Engineer said:

I must say that most films today have ingredients that prevent large scale formation of dichroic fog, but you can see this fog if you use high levels of solvent or if you use a strong solvent. Kodak has additives for developers (Microdol-X) and other films for preventing this sort of fog.

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grainyvision said:

The most interesting difficult to replace use of CQ seems to be as an anti dichroic fog agent. I believe it was used in the old HC-110 formula for this purpose.

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There's an important patent (US3161514) from Henn that talks about Chlororesorcinol and Chlorohydroquinone as anti-dichroic stain agents - the key claim is that CHQ is about as good as Resorcinol, but Chlororesorcinol (under the specific conditions used) has both significantly (and unforeseen) better anti-stain action, along with not acting as a developing agent. Chlororesorcinol is the '-X' in Microdol-X. Ron (and others) have commented that similar components are incorporated into emulsions today (and for several decades now).

Couple of other things, there's a Kodak patent that discusses a direct synthesis route to 2,5-Dichlorohydroquinone (US4518808) that claims a 94% assay & 61% yield - given that it requires Sulfuryl Chloride and hot Toluene, not something to do at home - more importantly however, it claims that most of the prior art tends to produce mixtures of different compounds that are costly to further purify. This tends to suggest that further work on CHQ was restricted by the problems of the synthesis.

The other area that has been explored (by Ilford amongst others) is adding aryl groups to Phenidones to make developers that could deliver specific colour (stronger cold tone etc).

grainyvision said:

So in theory to confirm if this ester is the chemical responsible for producing normal development, I should just do hydroquinone in acetic acid, and add sulfuric acid (I only have 40%, but maybe itd work) and then test if it can produce a developer substantially different from regular hydroquinone like I've seen in this case. [EDIT: actually, sulfuric acid is an oxidizer, so that wouldn't reproduce that behavior]

Click to expand...

Several points re testing what your reaction is accomplishing:

• you can prepare the ester by reacting HQ in acetic acid with a catalytic amount of sulfuric acid. H2SO4 is not a particularly strong oxidizer once diluted. I remember seeing a video demonstration of the diesterification on youtube. Repeat all other steps as previously to verify the reaction mix's behavior in a developer
  
• react HQ and HCl alone in aqueous medium, perhaps with a much smaller than stoichiometric amount of acetic acid. If it has any mechanistic effect in obtaining the chlorinated product (which I still highly doubt), then it should be able to perform that role at a lower concentration. Again, repeat the neutralization and developer preparation and observe the activity.
  
• Attempt to purify the reaction mix from the acetic acid + HCl reaction by solvent extraction.

Regarding your source of HCl, store-bought muriatic acid contains significant amounts of iron contamination (100s of ppm). It's an unknown worth removing for certain. Lab grade HCl isn't expensive and is available. In the end, if you want to have a viable developing agent, you should try to avoid iron contamination, or you'd need to use substantial amounts of suitable chelating agents.
Regarding metal salt oxidizing agents, I wouldn't bother, because it would require much more purification to be suitable for developer formulation. MnO2 is a classic oxidizer that's available and accessible, but I'm not sure if it would be suitable. in general, stay away from transition metals in anything developer-related. Ferric salts are also useful oxidizers, but even in trace amounts can catalyze Fenton-type oxidative processes. In preparative reactions, those processes are usually insufficient and nonselective, so iron catalysts are not used for oxidations. On the other hand,in a final developer formulation, even trace amounts can lead to accelerated aging. This still might have facilitated the oxidation of a small amount of HQ in your reaction, leading to chlorination of the resultant quinone.

KMnO4 is a good oxidizer, but again there's the problem of free Mn2+ ions floating around in the end. Usually, in oxidations, it's reduced to Mn4+ as MnO2, which is substantially insoluble in neutral aqueous conditions, and can be easily filtered off. Adding a chelator like TEA would actually increase the availability of metal ions in solution, and you can't be certain that the complex has no relevant oxidative (or other) activity.

Refer back to the RSC paper on the chlorination of phenol. It's open access, so I'm attaching it below. Ignore the suggested Mn catalyst, they tested a bunch of metals in order to get away from using organic solvents. Even on the absence of metal salts, the conversion is about 70%, which is not bad for a one-step preparation. Note that the amount of chloride ion in excess of stoichiometric can likely govern the ration of mono to di-substituted hydroquinone. I think the procedure is replicable and relatively accessible. Alternatively, there are published preparations of quinone in isopropanol with iodine as catalyst and peroxide as oxidant. This works and affords a relatively pure benzoquinone (you still have to recrystallize it to lower the iodine contamination), which can then be reductively chlorinated. Note that all this requires more advanced equipment and safety than a beaker and hotplate.

All said, I would rather buy impure CQ and purify it by reduction (if partially oxidized) and recrystallization (probably from naphta, dioxane, THF) than attempting to make it. I wouldn't use a material of undefined composition in any serious photographic composition, especially film developers.

Lachlan Young said:

I'm not sure that they are. The MSDS suggests that they're getting it from TCI - presumably they're ordering enough for TCI (or a subcontractor to TCI) to be doing the synthesis in decent quantities.

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I recall PE discussing the synthesis when I first proposed to do it at my home lab back in 2013. My impression was that PF were working in-house and Ron had seen the process in person. Compared to CQ, glycin is a breeze to prepare and purify, if one doesn't mind working with a known mutagen and 5L beakers/RBFs.

Lachlan Young said:

There's an important patent (US3161514) from Henn that talks about Chlororesorcinol and Chlorohydroquinone as anti-dichroic stain agents - the key claim is that CHQ is about as good as Resorcinol, but Chlororesorcinol (under the specific conditions used) has both significantly (and unforeseen) better anti-stain action, along with not acting as a developing agent. Chlororesorcinol is the '-X' in Microdol-X. Ron (and others) have commented that similar components are incorporated into emulsions today (and for several decades now).

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AFAIK, both chlororesorcinol and substituted benzophenones have been claimed as the antistain agents in Microdol-X (cf Ron and BT/Haist in FDC2). I do wonder if PVP, as used in HC-110, can work effectively in a high-sulfite solvent type of developer. Povidones are probably the most accessible agent. Some laxatives* use PVP (Enterodez) and it is used as a food additive, known under E1201. Povidone-iodine can be separated into the parent polymer and an iodide salt via a simple acid-base reaction.

*Oddly enough, another class of laxatives uses PEG, which is an accelerant in some developer formulas (lith, E6 FD, etc).

Nikola Dulgiarov said:

I recall PE discussing the synthesis when I first proposed to do it at my home lab back in 2013. My impression was that PF were working in-house and Ron had seen the process in person. Compared to CQ, glycin is a breeze to prepare and purify, if one doesn't mind working with a known mutagen and 5L beakers/RBFs.



AFAIK, both chlororesorcinol and substituted benzophenones have been claimed as the antistain agents in Microdol-X (cf Ron and BT/Haist in FDC2). I do wonder if PVP, as used in HC-110, can work effectively in a high-sulfite solvent type of developer. Povidones are probably the most accessible agent. Some laxatives* use PVP (Enterodez) and it is used as a food additive, known under E1201. Povidone-iodine can be separated into the parent polymer and an iodide salt via a simple acid-base reaction.

*Oddly enough, another class of laxatives uses PEG, which is an accelerant in some developer formulas (lith, E6 FD, etc).

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PEG is called an accelerant in lith developers, but really it behaves more as a restrainer. Adding it to a lith developer will slow it down. I'm unsure how to use it in anything other than lith develoeprs.

I am personally interested in some easily accessible and pure form of anti-stain agent specifically for creating an ECP-2 based reversal process. ECP-2 film is extremely susceptible to dichroic fog. Even dilute and minimally solvent developers tend to look a little grey after usage with Kodak 2383. However, my point of this CQ research was more of just "is this possible". If I accidentally created a different interesting warmtone developer instead of CQ, that is an ok discovery to me. I don't intend to use this on film, only paper where if there is some synthesis failure, I don't lose anything valuable.

On the note of using ferric salts as an oxidizer. I wonder if the iron impurities function as a catalyst that enable the reaction to occur. Regardless, whatever I have from the 1st batch definitely has some iron contamination in it, yet didn't immediately die, and even the next day left out in the open it still worked. I wonder if it could be possible that chlorohydroquinone is less affected by iron compared to hydroquinone. I've mixed (on purpose) iron containing lith developers and hydroquinone behaves extremely strangely in those cases, but is invariably dead within 24 hours. The fun thing is that iron in some cases can function as a battery for hydroquinone. I had a developer which worked, then died, then worked again after 2 hours (pharohlith if you're interested)

Alternatively it could be that no chlorohydroquinone at all is being produced, but some kind of superadditive developing iron salt is produced. Ferrous sulfate of course is a developer, but would hydrolise at the pH I'm using here but I don't think would behave like this.

I don't have any solvents which can extract the hydroquinone derivatives and leave behind the acids. I could potentially neutralize those to form sodium chloride and acetate, but given how easily soluble chlorohydroquinone is, I'm unsure how to separate it from the salts without something more involved like distillation.

I don't care greatly about purity and byproducts, but from the step wedges I produced from my test batch of the developer, I think it could be a very interesting tool to have. I'm sure any reasonable manufaturer would want a pure sample of the compound for repeatability, and to have a consistent shelf life. I don't necessarily need that

And for TEA, unless ferrous-TEA can be used as a developer, it's presence doesn't matter too much to me. The primary reason for me using TEA is just to prevent iron hydroxide and metallic iron formation. I know TEA is used in some homebrew formulas specifically as a chelating agent. An xtol clone for instance uses a small amount of it

edit: Also, if chlorohydroquinone is superadditive with hydroquinone, then that would explain a lot about the seemingly impossible results I'm seeing. Just a tiny amount might be enough to get good results at low pH. However, I've seen absolutely nothing published on the topic of how hydroquinone and chlorohydroquinone interact in a developer

Nikola Dulgiarov said:

I recall PE discussing the synthesis when I first proposed to do it at my home lab back in 2013. My impression was that PF were working in-house and Ron had seen the process in person. Compared to CQ, glycin is a breeze to prepare and purify, if one doesn't mind working with a known mutagen and 5L beakers/RBFs.

Click to expand...

A lot will depend on what the current demand for Glycin is & the batch sizes PF make/ made. They may well be the subcontractor for TCI - or demand has risen to the point that it's worthwhile for a larger scale synthesis operation to make it.

Nikola Dulgiarov said:

AFAIK, both chlororesorcinol and substituted benzophenones have been claimed as the antistain agents in Microdol-X (cf Ron and BT/Haist in FDC2). I do wonder if PVP, as used in HC-110, can work effectively in a high-sulfite solvent type of developer. Povidones are probably the most accessible agent. Some laxatives* use PVP (Enterodez) and it is used as a food additive, known under E1201. Povidone-iodine can be separated into the parent polymer and an iodide salt via a simple acid-base reaction.

*Oddly enough, another class of laxatives uses PEG, which is an accelerant in some developer formulas (lith, E6 FD, etc).

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Ron's source was Henn, so I think we can state chlororesorcinol was most likely the anti-stain agent initially used in Microdol-X. US3552969 is Henn's patent that explains the choice of PVP in HC-110.

PEG has been used as a developer accelerator in commercial B&W reversal FD's, but not in E-6 (as far as has been disclosed). PVA, PVP and PEG (and other similar polymeric extenders) are also added to commercial emulsions to provide development acceleration & fuller access to the silver in the emulsion etc.

grainyvision said:

PEG is called an accelerant in lith developers, but really it behaves more as a restrainer. Adding it to a lith developer will slow it down. I'm unsure how to use it in anything other than lith develoeprs.

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There will be a coefficient for how long it takes for a specific MW of PEG to be taken up by the gelatin, for the gelatin to swell, and for the developer itself to access the emulsion. There may be a specific relationship with the formation of an HQMS-alike, which while slower acting (probably so slow it'd completely collapse without the accelerator), is able to penetrate the emulsion more uniformly & deliver the steadier image build-up you have observed.

On the matter of oxidisers and lith printing, I do wonder if they have an interaction with emulsion brighteners (which seem to have close relationships to antioxidants) - and that if this has any bearing on the differences between the lithability of RC and FB (the latter having often heavily ballasted brighteners in the emulsion/ supercoat layers in MG FB Classic, Cooltone, Galerie- and the former possibly having them in the RC paper surface, rather than the emulsion/ supercoat layers).

Lachlan Young said:

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So is resorcinol a thing you can just add to a developer to prevent stain or is it particular about the conditions? It seems there is one hobby friendly source for resorcinol.

Very interesting about the PEG. So basically PEG slows access of the developer to the emulsion, but by slowing that access can make it so that it all kind of happens in a uniform way, thus acting as either a restrainer or accelerator... I think I'm understanding that. Swell dynamics is definitely something I do not have a full grasp on

It really is rather odd that Ilford RC papers work, but most of the FB papers don't. The big thing I don't understand is how these papers consistently work without fail when bleaching and doing second pass lith. I can't get a handle. I've ever tried bleaching before exposure before and this did not seem to magically make the paper first pass lithable. That was also a few years ago though so I can't remember much of the details.


On the topic of chlorohydroquinone, I concede. It is very likely that I never created any significant amount. I ran a series of control test which were expected to be big failures... except, they all worked. And finally I mixed a very similar developer to 58-D but using 10g/500ml hydroquinone and it actually worked, even when mixing acids (no hydrochloric or acetic acid was introduced for control sake) and alkali to bring the pH down to about 9.5. It was able to produce very warm tones, like I observed with my first test batch. The developer still worked at this level but not ideally. I believe that this developer could work more ideally by creating a strong buffer system, as reserve alkali seems to matter more than absolute pH.

On the topic of control tests:

I mixed hydroquinone into acetic acid, then added a very small amount of sulfuric acid, heated slightly and then left to stand for an hour. The solution turned into a gel, like I had observed in previous tests. This solution was capable of creating an ideal warmtone developer (likely due to increased reserve alkali/buffering since the acid had to be neutralized)

I mixed hydroquinone into water and a very small amount of acetic acid. I then added the muriatic acid. I then added a small amount of ferric nitrate solution. The behavior of this solution was strange. There was powder (assumed hydroquinone) which would not dissolve and the solution was a deep reddish brown. I decided to filter off the powder. The powder turned yellow, red, then brown upon addition to alkali. When sulfite was introduced the solution cleared to a pale yellow. This is very consistent with hydroquinone. It was easily soluble in water and muriatic acid. The fitrate solution was... odd. Upon standing it seperated into what seemed to be phases with a darker brown oil bubble looking solution at the bottom and a more pale yellow solution on top. The two phases very easily mixed (hard to seperate without a proper seperatory funnel) but would always seperate. I decided to test both the top yellow and bottom brown layer. Both had no problem dissolving with water introduced. The brown layer was much more weakly active as a developer. The brown one also remained mostly brown when sulfite and alkali was introduced with minimal color change. I believe the brown layer was likely an oily polymerization product.

Either way. I'm officially no longer trying to do anything on this topic unless I eventually get a proper fume hood and other proper PPE. However, the fact that a moderate sulfite, low pH, hydroquinone only developer is capable of very warm tone results with normal or somewhat lower contrast is an extremely interesting discovery which makes this research at least a bit worth it. If I figure out a good formula along these lines I'll make a separate thread for that. I've only seen one other hydroquinone only developer that wasn't a lith developer, and it didn't work with modern papers when I tested it.

Lachlan Young said:

Ron's source was Henn, so I think we can state chlororesorcinol was most likely the anti-stain agent initially used in Microdol-X. US3552969 is Henn's patent that explains the choice of PVP in HC-110.

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I agree that chlororesorcinol is the most likely antistain agent in Microdol-X. More broadly, US3161513 was filed by Henn a few months following that first "nonstaining developer" patent and details the use of 2,4-dihydroxybenzophenone. So, jut between those two patents, we have resorcinol, its chloro- derivative, and the substituted benzophenone. All three are commercially available, though, granted, resorcinol is likely the easiest to obtain by the hobbyist. I'm not sure if either would be suitable as a component in developers for color film, however. It is certainly worth trying. Dichroic fog is a non-issue in most other conditions, as others have noted, due to improved emulsion technology.

In the HC-110 patent, reference is made to an article (PSA Journal, Vol. 14, No. 4 (1948), pages 201-209) discussing dichroic fog and preventive agents. If anyone has PSA membership, that article would be greatly appreciated. I wonder if the mechanism(s) whereby these compounds prevent stain formation is known. If that knowledge is available, we could potentially predict other compounds that would be effective. Additionally, povidone was used in HC-110, according to the patent, because prior known antistain agents failed in developers containing amines. However, nothing suggests that it wouldn't be functional in a sulfite-solvent fine-grain developer of the D-23/25 type or in Ashley's attempted reversal developer for ECP film. Based on the patent, it might be active in fairly low concentrations (250mg/L concentrate equals about 8mg/L of working strength Dilution B). Eyedrops often use PVP as the active lubricant/hydration enhancer. A quick search brings up Bausch+Lomb Soothe, Long Lasting eye drops, containing 2% povidone, and a minimal amount of inactive ingredients (borates, EDTA, antimicrobials). A 15 ml bottle is thus equivalent to the amount of PVP in a liter of HC110. I'd suggest buying a bottle and trialing it in 0.5 mL increments in a developer+film combination known to cause dichroic fog.

Re CQ, superadditivity, low-pH HQ developers, I don't think hydroquinone and chlorohydroquinone would be superadditive, at least not in the traditional concept of the theory. The chlorine substitution shouldn't make the molecule any more strongly adhering to AgX, indeed, the electronegative Cl might increase electrostatic repulsion at the boundary. At the same time, it stabilizes the semiquinone which explains its increased activity compared to HQ (behaving more like pyrogallol but without the increased susceptibility to oxidation). I don't know much about the behavior of HQ at pH lower than 10. Do you use a pH meter (and what kid) or test strips to check the pH? What is the purity of your HQ and can you verify that there isn't something else going on to contribute to the developer's activity at low pH?