Ryuji, as I'm sure you know, propylene glycol and pentanedione are very different ligands. I am not an inorganic chemist, but alcohols generally do not have a significant interaction with redox-active metal ions in aqueous solution. Even with the chelation effect, I think that a metal impurity (say Fe) is much more likely to be hydrated (harder ligands) than to form a five-membered chelate with propylene glycol.
I would suggest that the differences you observed may be due more to impurities introduced into the developer solution by the various glycols, but of course I don't know for sure.
Kirk, PEG 200 is mostly the tetra- and penta-oligomers of ethylene glycol. Pretty viscous stuff, right? I'd imagine it would be pretty hard to work with due to the viscosity. I'm not sure what advantage it would provide... though it may be worth a try... (by the way, pure tetra-EG and penta-EG are available from places like Aldrich, but the mixed stuff is cheaper I think).
Finally, someone can correct me if I'm wrong, but I'm surprised about the concerns over patents here. A patent gives its owner a commercial monopoly on the inventions described in it, right? Violation of a patent can only take place when commercial activity is involved -- or am I wrong?
The use of propylene glycol as a solvent for developers is an interesting idea and one that has worked for me. My PG stock solution of ascorbic acid and phenidone has lasted two years without a significant decrease in activity (but I don't have a densitometer and don't run test strips). When I dilute it in aqueous base, it doesn't sit for more than 10 minutes before I develop my film, so I don't know about the lifetime of the working solution.
It's clear that the phenidone-ascorbic acid developers prepared as organic stock solutions are very poorly characterized and not rigorously tested. If I were a pro that demanded absolute roll-to-roll consistency, I would stay far away from these soups (and probably most other home-brews). But I (like most of the posters here, I think) am just a hobbyist in the photo world, I like goofing around with this stuff, and in this case it works. It may not work (or fail catastrophically) for some, but then again there are commercial developers have been known to do the same.
Anyway, my $0.02...
Getting back to the question of whether a PC divided developer is possible, I recently remembered that Paterson's FX-50 is advertised as being useable either in single-bath or two-bath ways, and it's a PC developer. This seems to suggest that a PC divided developer is possible, but I don't know how FX-50 does this.
I studied this subject along with our legal staff when I worked at NASA. No matter what the Patent Office does in granting a patent is not incontesatble, and it is not their job to defend that patent. They can testify, but in a case where it turns out that they were wrong, the patent will not be enforcible. If one tries to patent a device or process that any competent engineer would derive as a matter of course in the process of solving a problem, that patent application should be denied. I don't see how a person could patent the process of dissolving photographic chemicals in a common organic solvent. That is much too general and in fact could could and would have been in violation of the patent even before it was issued.
Originally Posted by Ryuji
Shooting bliind here... but a pool pH kit may be a cheapo solution?
Originally Posted by Donald Qualls
Mama took my APX away.....
Here is an experiment I did-2VIT-C 91205
Part A: Phenidone 1g in 50ml isopropyl alcohol,add to Vit C 50g in 400ml distilled water,make up to 500ml,filter cotton wool.
Part B: Sodium carbonate anhydrous 15g in 400ml distilled water, make up to 500ml.
Precaution-high phenidone content,used rubber gloves.Some of the concentrations may be way over the top as I tried to avoid a blank film. Film-Delta 100,pictures of tree,sun/shade. Times-3min Part A, 3min Part B 75F.
Result-EI 125 (I get 160 with Emofin),quite high density for an ascorbate,some base fog.The negs were not printed but the grain looks sharp-sulfite free that was the idea.I hope to repeat the test in a month or so to see if part A is stable.
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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?
Originally Posted by gainer
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)?
Contrary to what's written in common darkroom bibles, two bath development is not like mixing bath A and bath B in the emulsion layer when the film is transported. I do not know of a successful two-bath developer where film is not developed at all in bath A.
I recall some experiments by Kodak in the 1930s or 40s with 2 bath developers where the developer was especially formulated to prevent development in the first bath. They used sugar and pH control for this. The developers were quite successful, and are probably still useful. The idea was that the gelatine would absorb (adsorb?) the developing agent in the first bath and the alkali would act with it to develop the image in the second. If that was truly the mechanism, today's films may require some experimentation with the first bath, since their superhardened emulsions may not absorb the developing agent as well.
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.
Originally Posted by jdef
Everything is analog - even digital :D