Solubility of photographic chemicals in propylene glycol

[Pixophrenic]

Pixophrenic submitted a new resource:

Solubility of photographic chemicals in propylen glycol - stock solutions, non-aqueous solvent

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...

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[Alan Johnson]

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/

 

[Pixophrenic]

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/

This may be somewhat off-topic, but I found that storage of metol is quite good, up to several months, in 0.25% aqueous metabisulfite. This is a practice dating to 1950s or earlier. My limited experience with TEA was not really positive, in that TEA solution with whatever developing agents should still be insulated from air, because if it is not, a layer of oxidized chemical quickly forms at the top. in contrast, propylene glycol solution stays colorless even i partially filled vessels for a long time. .

 

[Pixophrenic]

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/

I have found in Mark Overton's article on "Mocon" that about 15% solution of sodium metaborate can be made in propylene glycol. Will this help dissolve metol and glycin in it? Alan, have you tried that?

 

[Alan Johnson]

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.

 

[Raghu Kuvempunagar]

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.

 

[glbeas]

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.

 

[Raghu Kuvempunagar]

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.

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.

 

[Pixophrenic]

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.

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.

 

[Pixophrenic]

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.

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.

 

[Pixophrenic]

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.

So far it haven't, at least in my hands. I think it is triethanolammonium metol sulfate that is soluble in PG.

 

[Raghu Kuvempunagar]

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).

 

[Pixophrenic]

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.

 

[Raghu Kuvempunagar]

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.

 

[Pixophrenic]

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.

My guess it would be a convenient way to dispense solutions of phenidone (or derivative) and hydroquinone (or derivative) during production.

 

[lamerko]

Hello,
has anyone tested benzotriazole solution - how long does it last?

 

[Don_ih]

Hello,
has anyone tested benzotriazole solution - how long does it last?

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.

 

[koraks]

has anyone tested benzotriazole solution - how long does it last?

In water - many years. It's very stable as @Don_ih mentions. Currently, I keep my benzotriazole in a solution of ethanol because it's also better soluble in this than in water. I merely used this because I had it on hand and it appears to be stable just as well. Benzotriazole seems to be one of those things that are just easy to keep around in whatever sort of solution you make with it.

 

[lamerko]

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.

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...

 

[koraks]

The benzotriazole I have is pure white and granular. In water, I've only made a 1% solution, which took quite some time to fully dissolve, but it was stable for a year or two and by then I had used it all up.

Note that your 2% solution in water is right at the solubility limit of 20g/l, so I'm actually not surprised you ran into crystallization issues.

 

[Don_ih]

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.

 

[lamerko]

Actually, to be honest, I needed a 0.2% solution. I will make a new one. But is there any way to test what I actually have?

 

[lamerko]

The solubility is 2% in water at 25 degrees, though. So if it gets colder, it's supersaturated.

Yes, the temperature of the storage room was below 15 degrees...

 

[koraks]

But is there any way to test what I actually have?

Depends a bit on what you want to test. If you want to verify that it's really benzotriazole: no, I don't know of any way to verify in a home setting the identity of an unknown solid.
If you want to verify the concentration of your remaining solution, the only way I could think of is to filter out the crystallized solids and then evaporate a carefully measured volume of the solution. Then weigh the solids after evaporation and calculate the concentration it must have been.

The practical solution is really to purchase some benzotriazole from any reputable seller and mix whatever solution you like with it. Given how cheap and easy to get this stuff is, I don't see any reasons to waste much time on messing about with it.

 

[Sidd]

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 had tried making 10% solution of phenidone in propylene glycol but couldn't dissolve all, even warming up the solution. Then I tried to make 5% solution, warming the glycol mildly at about 40 to 50 degree Celsius, when I was successful. The solution is stable and working properly for few months now.