I would like to share a small compendium of solubility data of photographic reagents in hot (40-60 o C propylen glycol. The purpose is to have a long-life solution on hand when the need comes to modify an existing developer or to try a new one at small scale.
3% phenidone
2.5% dimezone S
20% hydroquinone
10% ascorbic acid ( see footnote)
10% catechol
10% benzotriazole
Footnote: will not dissolve in reagent grade PG, addition of about...
It is also possible to make long lasting solutions of Metol and of Glycin in Propylene Glycol by first reacting them with a little water and triethanolamine to remove the polar part.
I don't think the maximum amounts that can be dissolved in PG have been determined yet.
https://www.photrio.com/forum/threads/metol-in-glycol-now-horrible-brown.50262/
It is also possible to make long lasting solutions of Metol and of Glycin in Propylene Glycol by first reacting them with a little water and triethanolamine to remove the polar part.
I don't think the maximum amounts that can be dissolved in PG have been determined yet.
https://www.photrio.com/forum/threads/metol-in-glycol-now-horrible-brown.50262/
Are there any figures for phenidone? I didnt see references on the list.
I aslo had tried amidol, from references I found a good while back at 15%, but thats not near enough to make it worthwhile for print developer.
I was able to dissolve 50g of Hydroquinone in 200ml of Propylene Glycol at 45-50C and topped it to 250ml. Should be possible to dissolve a little more HQ with the same volume of Glycol albeit at higher temperatures.
Can I keep the HQ Glycol syrup in the refrigerator? Any chances of crystal formation due to refrigeration? Once I refrigerated 5% Metol aqueous solution (with some Metabisulphite) and within a night crystals formed. Wondering Glycol syrup would fare any better.
My figure of solubility comes from earlier posts of Gerald Koch here at Photrio and my own experience. I could not find any literature references. The same is true for dimezone S. Perhaps you could help.Gary, when I tried to dissolve 5g Phenidone in 100ml hot Propylene Glycol, it initially dissolved but as the liquid started loosing temperature, a puffed up slurry formed. I had to use additional Glycol to again dissolve the Phenidone.
So far it haven't, at least in my hands. I think it is triethanolammonium metol sulfate that is soluble in PG.Reacting with a little water and metaborate sounds like it might work to remove the polar part of metol. I think it is a new idea and nobody tried it yet to get metol to dissolve in glycol.
The Kodak bulletin entitled "Solubility of Eastman Hydroquinone and derivatives" states that solubility of HQ at 24 degree Celsius is 23% w/w, and in my case it was stored at 16 degree Celsius for 9 months without any change in color. Thus I think that refrigeration is unnecesary, and some HQ will precipitate out, if you refrigerate. The same is true for metabisulfite-supplemented solution of HQ, there is no need to refrigerate.
Regarding solubility of Hydroquinone in different solvents, this might be of some help to the interested:
https://www.eastman.com/Literature_Center/D/D170.pdf
According to the above document, Ethyl Alcohol (34%) and Diethylene Alcohol (32%) can take more HQ than Propylene Glycol (23).
Thank you, Radhu, for the link. We are talking about the same bulletin. Indeed there are solvents which take more hydroquinone, but ethanol is combustible and regulated in most countries, and diethylene glycol is more toxic than propylene glycol. My idea was to use a solvent that is relatively easy to obtain, non-volatile and low toxicity. If you can't get PG, metabisulfite supplemented solution in water is still a better idea, IMO, than using alcohol.
I agree completely with you regarding the choice of Propylene Glycol over either Ethanol or Diethylene Glycol from the pov of safety. Interestingly, MSDS of HC-110 states that it contains 5-10% of Diethylene Glycol.
Hello,
has anyone tested benzotriazole solution - how long does it last?
has anyone tested benzotriazole solution - how long does it last?
So I may have a problem with my benzotriazole. I made a 2% aqueous solution some time ago, but after about a month it completely crystallized. What I have is yellowish granules. However, my supplier is a bit dubious - as it is not sold in specialist shops, I got it from an antiques cleaning company. The label says 99%, but...I'm not sure about in glycol, but benzotriazole in water seems to last forever. I've had a bottle for years. It's established that you can dissolve 50g into 100g of ethylene glycol (which is much more than the 2g you can dissolve in 100g of water) -- but I don't know about into propylene glycol.
I made a 2% aqueous solution some time ago, but after about a month it completely crystallized. What I have is yellowish granules.
The solubility is 2% in water at 25 degrees, though. So if it gets colder, it's supersaturated.
But is there any way to test what I actually have?
Are there any figures for phenidone? I didnt see references on the list.
I aslo had tried amidol, from references I found a good while back at 15%, but thats not near enough to make it worthwhile for print developer.
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