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Vitamin C in divided developer?


Patrick, it is a fundamental mistake for you to assume that the patent was granted for the "process of dissolving photographic chemicals in a common organic solvent." It is given for some other reasons. How can you judge a patent withotu reading it closely?

Offensive rights of patents are determined ultimately in court, when there is a dispute, but even so, if you have a good set of claims, it is more difficult for the disputer to nullify your patent. What you are saying sounds to me to be a quibble from someone who doesn't understand the system.
 
Yes, ligands of pentanedione are different from alcohols... but the point I was trying to convey was that the acceleration of oxidation was probably related to potentialtion of catalysts to various degrees by ligands. BUT your suggestion of these addives bringing in more impurities is certainly a possibility.

Maybe you can help me think this through here. Both propylene and triethylene glycols accelerated oxidation but propylene did so more. D-sorbitol also accelerated. Methylcellulose did the same (the last is not very useful comparison, I know). Primary alcohols and secondary alcohols usually slow oxidation of hydroxybenzene developers.

Chelation effect itself may not be the key point here. It's really concerned about kinetics of redox instead of stability of possible compounds. For example, salicylic acid does not seem to form strong complex with iron except in very low pH (ferrous) or very high pH (ferric) but presence of sal changes the way ascorbate is oxidized in intermediate pH.

In my understanding, infringenment of patents technically has nothing to do with whether the product, service, process, etc. is offered commercially. Whether Kodak will bring the case to court is an entirely different matter, but we've seen analogous cases in software patents. Those patents can still be effectively used to threaten individual programmers, individual formulators or small businesses (whether it is software company or a business like Photographer's Formulary). Even if the formula is kept proprietary, you know it's not that hard to analyze if a product is infringing their patents. I would not openly promote on the internet to infringe patents even in home darkrooms.

But the particular patent I mentioned is concerned about using nonaquaous solvents in split stock developers and claims aren't that broad. I see traces of claims getting stripped down because specification is written as a much more broader invention.
 
Jdef, did you run a control with the B bath lacking ascorbate but pH and buffer capacity adjusted to be same?

Also, what is your sensitometer (just curious)?
 
 
Hey Jay, I've got 500 grams of fresh salicylic acid. Send me a little glass bottle and I'll send you some. I haven't tried it yet.
 
salicylic acid

Tom-I got a small headache can I get some too? Just joking!
Best, Peter
 
Sure, send me a bottle - but don't take it for your headache!
 
Please be careful of pure salicylic acid. It is the active ingredient in compound W used for removal of warts and callouses. If you get any on your hands, particularly with any organic alcohol, you stand a chance of getting a severe burn or blister.

PE
 
Ryuji -- I understand your point. The isolable intermediates may not be catalytically active (there was a very famous study from the 1980s about this very issue -- in this case, in homogeneous catalytic hydrogenation with rhodium complexes).

In any case, I think that for a ligand to have any significant effect on the redox properties of a metal, it has to be charged. Acac (pentanedione) as a ligand is -1... the charge is delocalized across a few atoms. At typical developer pH values, alcohols will be charge-neutral, and there won't be any bonding effects that aren't also present with water. You can buy transition metal alkoxides as solid powders, but they are prepared anhydrously, and I'm pretty sure they're not stable in aqueous solution.

For these reasons, I can't see the presence of alcohols in an aqueous solution affecting the reduction potential of a metal ion all that much. Chelates like EDTA are a different story: EDTA is negatively charged at neutral pH and is a fairly soft ligand.

The alcohols you tested are fairly diverse in scope and would lead to steric differences, but I think in this case that the equilibrium for complex formation with neutral alcohols is so small that it doesn't even matter. So I would again suggest that it may be impurities in the alcohol sources that are the real culprits.

Interesting choice of alcohols, though! Methylcellulose, sorbitol... wow. Did you just have these laying around or something?
 

I'll PM you, Jay - and I'd like to try both developers.

Right on the money, PE. I handle the salycilic acid with Nitrile SafeSkins under a hood.
 
off thread...

Sorry this is off thread-- Tom would you give us a little review of JDEFS developers please? Would love to hear what you have to say.
Best, Peter
 
Just as a gratuitous hint to those of you looking for a good ligand for metals in developers. The Dequest series of sequestrants is the most powerful on the market today. They are the only series that can dissolve iron hydroxide and decolorize solutions of iron salts.

The complexation constant of the one I used was several orders of magnitude greater than the pKsp of Iron (III) and Iron (II) hydroxides. I could detect iron at 1 mg/dm^2 in paper just due to color, and the Dequests would remove it completely and deactivate it.

A tad of this in a blix or bleach with ferric edta renders it colorless and inactive. (all you have to do is figure out which one to use).

AFAIK, the inventors of Xtol and other workers on ascorbate developers are unaware of this work. IDK if it will work in this case to stabilize developers however, as my goal was something entirely different when I worked with it. I never tested it in developers, I tested it in color stabilzers to remove the oxidative effects of transition metals and the stain associated with some of them.

Have fun.

PE
 

PE

Do you think they would be any good as clearing agents of iron hydroxide in palladium and platinum printing? Or might they also dissolve palladium and platinum?

Sandy
 

That's exactly the kind of things that I'm warning about. Take those bath A solution and develop films in them for 10 min or something. Are they completely inactive? You should think first, and find the answer for yourself. Does sugar completely inhibit development? You should think hard and also find the answer for yourself.
 

Salicylic acid is not very soluble in plain water (it is much more soluble in alkaline solutions) and the amount typically used in my developers (0.1% max) is much less than what you find in facial lotions (typically containing 0.5% sal).
 

I didn't assume anything. You started it. It is simply the fact that one cannot patent the laws of nature. If a descritption of a patentatable device includes such elementary processes as heating, dissolving some part in a particular solvent, or the like, these elementary processes are not forever more forbiden by from use in any other process or device.
 
I agree about the alcohol itself not being very effective in chelating. There's something fishy going on here, and higher impurity carried by propylene glycol is a simple theory for it. I am not sure whether propylene glycol typically contains more Me impurities, but I think someone who heavily relies on this solvent should do some research on it...

Those alcohols are something I ordered for some photography related research... well, don't ask

Another thing I tried was to sulfoesterify primary alcohol groups prior to addition to the developer. But this agent could react with phenols, amines, and a lot of other things including metal ion species, so, although I found the effect to be favorable (useful), the result is entirely uninterpretable It was a bad experimental design, though at that point I was going to try anything on this problem!

Well, I've been trying a lot of other things as well but I haven't found silver bullets yet!
 

Ron, as I already told you on PN, people generally avoid phosphorous containing compounds in ascorbate developers. A very slow hydrolysis is enough to bring free phosphates in solution and they change the way iron behaves as the catalyst. The problem dealt with in ascorbate developers is NOT the stability constants but the kinetics of redox reaction involving catalysis. There are lots of very stable complexes that make situations worse, and some only moderately stable complexes that help the problem.
 
Donald Qualls said:
Does anyone know, can I make a water based
concentrate or stock solution of or containing
ascorbic or erythorbic acid ...
Click to expand...

You could use sodium bisulfite. An article on pharmaceutical
preservation mentions a ph of 5 and below where sulfite
will preferentially absorb oxygen. That and A. acid
should give a ph in the 3.? range.

Introducing sulfite I believe would ignore Mr. Gainer's
main reason for using A. acid. Dan
 
jdef said:
I can no longer tell if this is on topic or not, but I printed some Foma 200 negatives developed in the MC 2-bath developer I described above, for 1min A/1min B, and they print beautifully.
Click to expand...

FWIW, I've been following your description of this developer with interest. Given the wide range of topics now being discussed in this thread, perhaps you should just start another, and/or create an entry in the "Chemistry Recipes" area of the site.

One negative I see for this formula was the 1-minute developing times. Do you think those could be increased to something more reasonable by using a more dilute form of the developer? (Feel free to ignore this question if you choose to start a new thread; I'll ask it again there.)
 
Here is an experiment I did with a sodium ascorbate version 2VIT-CNa 91305.

Part Ahenidone 0.5g in 50ml isopropyl alcohol,add to sodium isoascorbate 25g in 400ml distilled water, make up to 500ml.

Part B:Sodium carbonate anhydrous 15g in 400ml distilled water,make up to 500ml.

On a film leader there was slight development in Part A alone after 5min. Precaution-high phenidone content used rubber gloves.Film-Delta 100, pictures of tree,sun/shade.Times-3min Part A. 3min Part B 75F.

Result-EI 125.The negs were not printed but looked OK,similar to the Vit-C phenidone part A described in my previos post.It is not clear how stable the Part A solutions are but it is possible the sodium ascorbate version may be more stable owing to its higher pH.
 
Sandy, I have no idea what the Dequest series of sequestrants would do to the iron in Pt and Pd prints, but it should not disturb the metal image itself AFAIK. I have never tested the Dequests except to sequester Iron which it does.

Ryuji, I know what you said.

I remind you that often things don't work out in practice the way they should work in theory. We have disagreed on a number of things which theory says will not work or would work poorly, but which work well in actual practice for one reason or another. I find it better to test something and possibly learn something new, than pass up an opportunity based on theory and miss something.

This is sometimes called 'intuition' and sometimes 'creativity'. Please don't dismiss the possibility that something just might work. Remember, theory says that insects cannot fly. That was 'proven' through math models.

See for example, "Science Friction" by Dr. Michael Shermer for an excellent and sometimes amusing treatment of this type of mindset.

PE
 
I should add that the Dequest series of sequestrants are used at very low levels in actual practice and therefore the level of phosphates, if any are indeed released, is extremely low.

In any event, in spite of the purported problems you note Ryuji, they continue to sell well to their main markets and appear to be acceptable in and by industry.

PE
 

PE,

Could you suggest a source for obtaining a small quantity of the Dequest series of sequestrants for test purposes?

Sandy
 
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