Anyone tried kodak e6 patent(US5948604)?

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Rudeofus

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Ok, I guess you're talking about Spur developers, Adotech, Silvermax etc. I don't know if anyone synthesising HQMS for personal use have been able to create effective substitutes for these developers. Other than these, is there anything from the distant or not so distant past in the public domain?

As you probably know, E-6 FD is one of the best B&W developers out there, that's why Kodak formulated it this way. Ron told me, that unlike HQ the oxidation product of HQMS doesn't have developer properties, and this causes HQMS to give better sharpness than HQ.

The only issue with E-6 FD is, that it is a very very powerful developer, which would develop your B&W film to normal contrast within less than a minute. The way to handle this is dilution: E-6 FD working solution diluted 1+9 makes a very decent B&W developer. I typically use it at 26°C for 10-12 minutes, and this gives me at least normally developed negatives. I like the development at 26°C, since at summer time not even my cold water always comes out colder than that.

Since I have - I believe - already mentioned this at least once, you can consider this a formula in the public domain :-D
 
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The Wheatcroft patent has been discussed here several times, and IIRC was initially brought up by PE.
Although it can be shown theoretically that the conversion does not take place, it can also be verified experimentally: prepare a batch of developer per the patent and a second batch, where the H2O2 is added to the sulfite in absence of HQ and the rest of the developer mixed. Run parallel sensitometric tests. Alternatively, the free HQ can be extracted with ethyl acetate and quantified.
Oxygen can be used and the reaction proceeds as expected, but again, it is pH dependent and produces hydroxide, so either a strong buffer system has to be used or pH correction has to be applied continuously. This still means the liberated Na+ has to be bound up as some salt, the acetate or borate being the least troublesome. I thought I can be clever and use SO2 gas to neutralize the NaOH back to sulfite but it cannot work in a batch process, and it becomes a frustrating juggling act to do it continuously.

It seemed too simple to be true. Thanks for sharing your experience and perspectives.

Since I have - I believe - already mentioned this at least once, you can consider this a formula in the public domain :-D

:smile:
 

River Mantis

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@lamerko , I have to agree with Rudi that the procedure, as outlined by the AI, is broadly unclear, and will not result in any meaningful yield of the sulfonate.

Glacial acetic acid is a pretty good polar, protic solvent and is used in substitutions reactions, most notably in aromatic nitrations, since it tolerates nitric acid and forms the active nitration species in that case. The solubility of HQ in GAA is not mentioned in the CRC databooks, but I was able to quickly find a reference(https://pubs.acs.org/doi/pdf/10.1021/ja01333a057), where it is stated that 60g dissolved in 250g of solvent on heating, so that may be a reason to use it. However, the solubility of HQ in water at room temperature is about 70g/L, so not orders of magnitude difference. HQ-sulfonic acid is very water soluble, in fact it hydrolyzes on standing as an aqueous solution, so it is only prepared to then be converted to a salt (sodium, potassium, calcium are the most common).

I think the silicon mind was thinking about nitration and not sulfonation. Nitrations are usually carried out at low temperatures and slowly to prevent side products and increase yield. Sulfonations are much harder to effect in practice. For example, to prepare benzenesulfonic acid, benzene must be treated at boiling point with oleum, which is sulfuric acid with added sulfur trioxide - basically the anhydride of H2SO4. HQ is a bit easier, the two hydroxyl groups activate the ring quite well, so regular concentrated acid will do the trick. In both cases, the reason for the high concentration of H2SO4 is to act as a dehydrating agent - the sulfonation is an equilibrium reaction and the resulting HQ-sulfonic acid can hydrolyze back to HQ and sulfuric acid in the presence of water, so an excess of H2SO4 is used to sequester the water (or the reaction is carried out under vacuum to remove water as it forms). This is well known and the earliest preparations of HQ sulfonates (Seyda, 1880s), outline the procedure in sufficient detail. Even the 10-20% water suggested would represent a stoichiometric excess to the amount of HQ that can be dissolved, even at reflux. At room temp or near the ice point, you will end up with an acidic slurry of HQ, water and acid, the activation energy is much higher. There are only two (reasonable, non-esoteric) methods to obtain HQMS at room temperature, either by reductive sulfonation of the quinone with tight pH control, or by anodic sulfonation at a platinum or carbon electrode, with a bit looser pH dependence.

The two above points make preparation of HQ-sulfonates difficult, because both the free acid and its salts are very water soluble. You can use the common ion effect to precipitate them out of solution (prepare a concentrated solution, then add sulfate salts and sulfuric acid), but the usual recrystallization yields are in the 10-20% range. Another unfortunate complication is that sulfates are almost always produced as a byproduct and have almost identical physical properties to the sulfonates, regarding solubility. Weissberger, et al, to prepare about 100g of HQMS-Na, use 7 liters (2 gal) of boiling hot methanol, to extract the salt from a reaction mix. Only the calcium salt (also known as calcium dobesilate) has reasonable solubility in simple alcohols, and can be separated out more easily (but converting it back to the more useful K or Na salt is a pain).

The sulfonation of HQ, without further purification is described in the attached patent. I have followed it successfully at molar scales. For b/w developers, the stoichiometric sulfate present can be accounted for and does not present a problem. For color work, the product has to be purified by extraction.

Hey. Nice to see you here. I used the information from these two patents. What I came to is redissolving the sulfonation product (it's almost solid at room temperature) in the 4x excess of sulphuric acid (in the described disilfonate synthesis process it's present from the beginning) at around 50º C and neutralising with stoichiometric amount of KOH in the form of 50% solution (yes, that's sketchy). After cooling to about 30º C the precipitate formed. Just filter it and wash with isopropyl alcohol. Got 47% this way, still not sure if I got any disulfonate contamination. And there is a hope that with the excess of acid (and some amount of water) sulfate just won't precipitate, as bisulfate is very soluble.
 

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River Mantis

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I'm not too sure about the purity of my chemicals. Traders give specific numbers - purity and what impurities they contain, but apparently a lot of chemicals arrive in sacks and larger cuts of unclear quality. Some of them sell them simply in bags, others in not very good quality containers. Hygroscopic chemicals have probably absorbed a lot of moisture. Surprisingly though, what I've mixed so far is probably very close to the expected results.
For Citrazinic acid - until recently there was a chain store in the UK - Silverprint, which unfortunately recently went bankrupt. They had a crude chemicals section - they offered Citrazinic acid at a very good price. £23.00 - 100g including VAT. It is not known with what purity...
I currently have ATMP and DTPA-5Na, but I will test without them to see how long they would last.

CZA is the easiest here to synthesize. The method from 1893 (!) paper works surprisingly well, except that I kept the temperature at 135º because there is a clue in some later paper that above 150º the CZA (amide) may not form at all. Got about 20% this way
 

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River Mantis

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Weissberger, et al, to prepare about 100g of HQMS-Na, use 7 liters (2 gal) of boiling hot methanol, to extract the salt from a reaction mix. Only the calcium salt (also known as calcium dobesilate) has reasonable solubility in simple alcohols, and can be separated out more easily (but converting it back to the more useful K or Na salt is a pain).

BTW do you remember the exact book?
 
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