Why acetic acid in a paper developer?

Here's a 1990s patent from Ilford:
https://patents.google.com/patent/US5376510A/en

Scroll down to the exemplary developer under "Example I". This formula shows the concept being patented. It contains acetic acid (i.e., vinegar). Why?

Paper developers contain large amounts of carbonate to push up pH, to shorten dev times. Why add an acid which will pull down pH and lengthen dev time? Acetic acid has a pKa of 4.something, so it won't help buffering. Perhaps the purpose is to make the dev stink should anyone actually try that formula. /2

Mark

I wonder if it has something to do with dissolving Compound A (1-phenyl -4-methyl-4-hydroxymethyl pyrazolid-3)?

I wouldn't read much into this. I've spent many years in the patent business, writing, prosecuting and defending them, and they are a world of their own that isn't necessarily obvious.

The claims are the heart of the invention, they define the scope of legal protection. If it isn't in the claims, it's not patented. The example presented can be used to help understand the invention, but it's really meaningless. It's purpose could be simply to create prior art - what that means is that by describing something it makes it known, and thus unpatentable by others.

There could be many reasons related to patent practice that acid is in the text, and may have nothing to do with being strictly chemically necessary. At best, use this disclosure as a guide to further experimentation, but don't treat it as cast in stone, or even correct.

First of all @albada, this is an interesting patent. Thanks. They already knew to use DTPA to preserve ascorbic acid. This does look like a paper developer to me. They mention testing it on paper. But directionally it is interesting.

There are some possibilities for the acetic acid. It may be used in tandem with DTPA as a sequestrant that they thought was better for ascorbic acid developers. It notably chelates calcium to a very soluble calcium acetate. DTPA can also do this and there is a lot of DTPA. But it may be that the two together work better. I know from bleach development that EDTA and citric acid are more active together, for example.

They mention that a number of acids could be added to balance the pH. Another possibility is they are using it for that here. I would also guess that it’s not the most suitable for that.

It’s not in enough quantity to be active for anything else as far as I can tell.

BradS said:

I wonder if it has something to do with dissolving Compound A (1-phenyl -4-methyl-4-hydroxymethyl pyrazolid-3)?

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Interesting idea. But, that's a phenidone/dimezone derivative, but I'm not sure which one. Seems to be Dimezone-S but a weirdly ordered name for it, if so. Shouldn't need anything special to dissolve it, if so, as far as I know.

relistan said:

Craig said:

The claims are the heart of the invention, they define the scope of legal protection. If it isn't in the claims, it's not patented. The example presented can be used to help understand the invention, but it's really meaningless. It's purpose could be simply to create prior art - what that means is that by describing something it makes it known, and thus unpatentable by others.

There could be many reasons related to patent practice that acid is in the text, and may have nothing to do with being strictly chemically necessary.

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Is this an Ilford patent for the U.S.? If so I wonder if the U.K. patent has the same content if the acetic acid doesn't have any chemical significance? From what you say it sounds as if vinegar has been included to stop anyone else making it

How does this work and what might examples of the other reasons for an acid inclusion be?

To this member of "Joe Public" I am a loss to understand what the real advantage to Ilford is

Thanks

pentaxuser

pentaxuser said:

Is this an Ilford patent for the U.S.? If so I wonder if the U.K. patent has the same content if the acetic acid doesn't have any chemical significance? From what you say it sounds as if vinegar has been included to stop anyone else making it

How does this work and what might examples of the other reasons for an acid inclusion be?

To this member of "Joe Public" I am a loss to understand what the real advantage to Ilford is

Thanks

pentaxuser

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Yes, the link was to an issued US patent. Ilford filed an application in the UK, but never did anything more than that, they didn't get a UK patent. Patents are national, so a US patent is only valid inside the USA. Same with all other countries. So while Ilford had a US patent, Kodak would be entirely free to make and sell that exact developer in Canada, as Ilford doesn't have a patent there.

A reason something might be mentioned, but not claimed is to destroy patentability. As a general rule, to be patentable the material must be new, useful and not obvious, where obvious has a specific meaning, which isn't the same as in ordinary English. If the use is described in a patent document, then it is "known to mankind" and fails the new test. That means that while Ilford didn't patent that particular use of acetic acid, neither can anyone else; so Ilford is free to use it and not be locked out by someone else patenting that use.

It's probable that Ilford wouldn't be using acetic acid in their formulation, and there may be other acids that are more suitable. By making this disclosure of using acetic acid, if someone else came along and tried to patent using some other acid, it would probably be deemed obvious (patent definition) to have a skilled photo chemist substitute one acid for another; rendering other acids unpatentable In this way Ilford keeps the real acid they use as a trade secret, while preventing others from patenting the real acid Ilford uses and thus preventing Ilford from using that acid.

What to include and not include in patent document is very much a series of strategic decisions, tied into the reasons one is applying for a patent in the first place. Is it defensive or offensive? What is written will change depending on that intended purpose.

Craig said:

It's probable that Ilford wouldn't be using acetic acid in their formulation, and there may be other acids that are more suitable. By making this disclosure of using acetic acid, if someone else came along and tried to patent using some other acid, it would probably be deemed obvious (patent definition) to have a skilled photo chemist substitute one acid for another; rendering other acids unpatentable In this way Ilford keeps the real acid they use as a trade secret, while preventing others from patenting the real acid Ilford uses and thus preventing Ilford from using that acid.

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Thanks Craig. I have read your quote several times and remain puzzled as to how it works. It sounds as if the trick is to state an obviously unsuitable acid for the benefit of preventing any other chemist/ company from using the correct acid which is in fact what Ilford are using all along. So Ilford in this case but any company really, tells a complete lie in its patent to prevent any other company from using and patenting the real acid?

Is this really the case? It sounds as if Ilford are the real crooks here but other more upright companies are prevented from making the right developer. It is as if the law is on the side of clever lawyers who are by any definition I have seen of the word legally dishonest thus crooked

Does it work this way in the U.S. only or in Canada and the U.K. as well?

pentaxuser

If it's not actually the one they are using (which, as I said, I think it's not the most suitable), the example is still inline with the claims. They said in the patent that it could be any of a list of possible acids and then just picked one for the example. This is pretty normal in patents (I have read a ton of photographic patents). You usually have to read between the lines to see what they are really doing. There is nothing crooked here, and yes it works this way in pretty much all patent law. But it is one of the ways in which the whole patent system is broken.

Since it's a US patent with no corresponding UK or European patent, it's probably safe to say it's aimed at preventing Kodak from competing in this way.

Not quite. I wouldn't say the acid is obviously unsuitable. It probably will work, it just might not be the best possible acid for the intended use. The other thing to consider is that the patent process is lengthy, it can take 3-5 years from filing an application to getting a grant of a patent, and obviously research and development continues in that time. There is also something called "first to file", so if two people invent the same thing, the first person to file an application with the patent office will get the patent. So there is great incentive to file early in the R&D process. Maybe at the time acetic was the workable solution, and the patent was written that way, but as time went on a better acid was found.

The flip side is that a better acid was known when the patent was written, and it was decided to deliberately obscure that by suggesting the use of acetic acid. I wouldn't call it a lie, as the acid specified must work - otherwise the patent could be attacked for non-utility. Think of a patent like a recipe in a cookbook. It's a description of steps the reader is to follow to obtain the promised result. Like a cake recipe, substitutions are possible and you'll still end up with a cake at the end. Is saying to use baking soda when baking powder might make the cake rise a bit higher a blatant lie and crooked?

There might be a commercial advantage to conceal the best acid and simultaneously render it unpatentable by others - a risk is that if someone started making a developer with the other acid and Ilford decided to sue for patent infringement, Ilford's patent might be held to not cover the other acid. That is for the courts and expert wittiness to determine at that time.

The patent rules and regulations are remarkably similar around the world, so this sort of thing goes on in most jurisdictions. The reasons to be vague will vary depending on the objective of patenting and there is a calculated risk in doing so. If the patent is purely defensive and is intended to preserve the right to do what you do, then the patent would describe exactly what you do. If it's intended to keep other players out of your area of interest, then you cast the net wider. Maybe it works, maybe it doesn't.

The other thing to remember is that simply because you write something broad into the patent application, the expectation (and the actual practice) is this that the scope is narrowed by the examiner at the patent office. It's like selling used goods in the small ads - you'll almost never get a buyer willing to pay your asking price right away, you negotiate a bit; so you ask for more than you expect to sell it for. Patents are the same, ask for more scope than you really want and the examiner will cut you down to what you really wanted in the first place.

I had a quick look at the claims, and the use of acetic acid isn't claimed. A pH range is however claimed, so my guess is the acetic acid mentioned in the example is used to adjust the pH.

Craig said:

I had a quick look at the claims, and the use of acetic acid isn't claimed. A pH range is however claimed, so my guess is the acetic acid mentioned in the example is used to adjust the pH.

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Yes the pH is claimed, and the Description of the Preferred Embodiments includes:

"If the diluted concentrated solution has too high a pH, then a quantity of potassium metabisulphite can be added to the concentrated solution to decrease the pH. Alternatively, the pH may be adjusted by use of the free ascorbic acid compound, or by the use of the free acid of a metal complexing agent (described below), or by the use of alkali metal bicarbonate."

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And then further down:

Other suitable metal complexing agents include without limitation phosphonic acids such as 1-hydroxyethylidene 1,1-diphosphonic acid, diethylenetriamine penta(methylenephosphonic acid) ethylene diamine tetra(methylene phosphonic acid) and nitrilo tris (methylenephosphonic acid), and alkali metal salts thereof.

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My understanding is that they can meet that by using acetic acid because they say "include without limitation"

You can put anything in the description. The purpose of the description section is to describe how the invention works, and to provide a basis for the claims. You have to describe something before you can claim it. The description can amplify and define terms that will be used in the claims, but only the claims form the scope of legal protection. The description can be full of lots of fluff that isn't in the claims.

If Ilford went to sue someone for patent infringement, all that matters is what is written in the claims. If there is uncertainty what a term in the claims means, then you can look to the description for a definition, but you can't sue anyone on the basis of what is written the description alone.

If I'm looking at a patent for the first time to see what it's about, I read the claims first. Only then if there is something of interest will I read the rest of the description.

Thanks both. It still doesn't sound "terribly upright" practice to me. I have heard of being business being "red in tooth and claw" but now it seems we have a practice that is red in "law, tooth and claw"

Anyway I'll leave it at that as I was simply trying to satisfy my curiosity about what patent law was all about and it is not the main point of albada's thread

pentaxuser

That makes sense @Craig , I read them to try to understand what they are really doing since I’m not a lawyer and that’s the part that might be useful to me personally.

@pentaxuser yeah I hear you. Patents were supposed to protect innovators while encouraging the sharing of information. They do pretty much the opposite now.

relistan said:

Patents were supposed to protect innovators while encouraging the sharing of information. They do pretty much the opposite now.

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I wouldn't have necessarily said that. Patents are always addressed to "A person of ordinary skill in the art". That person might be a member of the general public, or it might be a Ph.D. depending on the subject matter of the patent.

It means that the person reading the patent will have the average level of knowledge of a practitioner in that area, so there is much base knowledge that can be assumed that the reader knows. For this patent, a skilled photo chemist would understand that various acids can be used to lower pH, they don't all need to be listed.

For the patent in this thread, it looks like the real invention was making a concentrated, liquid developer containing ascorbic acid, and it says how to make one.

Much of the reality in the patent world comes from the fact that it takes so long for a patent to be approved. They have to be written in such a way that they provide quick protection but still will be flexible enough to be usable three or more years down the way, after you've done a whole bunch of refining.

We can disagree on that. As a software engineer I think the system stinks in the current incarnation. It generally gets used as a cudgel to prevent people from making progress in an area rather than as a way to broaden understanding in the industry while being protected from someone competing with you using your your idea for a limited time—which is what patents were supposed to do originally.

But yes this patent explains roughly how to make a concentrated ascorbic acid developer. Which is why I said I think it’s interesting. Thanks @albada for posting.

I'm not a patent attorney and wasn't weird enough (if you can believe that) to be a chemistry major, and I was banned from high school chemistry.
Maybe making it less basic would make it less slimy, so it will rinse in stop quicker or be happier in water-only stop?