US Sources for Potassium Carbonate Sesquihydrate/1.5 H2O/Crystal

DowntownDan · Jul 18, 2023

Hi all,

I’m looking for a source that will supply educational or lab grade (not ultra pure or re-agent) Potassium Carbonate in 1.5 H2O form to a private individual based in the US.

Would like to try the original formulation or FX-2 for some old-school emulsions. I’m aware of the many substitutes available and have most of those on hand. I’ve searched the archives, and read both DCB and FDCB.

I’m looking to get into an argument about chemistry, the limitations of trying to replicate Crawley’s formula, or whether or not it will make a difference to use the crystal form—I’m just hoping to find a supplier where I can buy some and give it a shot myself.

I’m based in NYC and there’s another user nearby (Saganich) who posted that he was able to obtain some. But, alas, I guess I am too new to the forum to have the ability to send a PM.

Thanks in advance for any help. Much appreciated.

Kino · Jul 18, 2023

DowntownDan said:
I’m looking to get into an argument about chemistry, the limitations of trying to replicate Crawley’s formula, or whether or not it will make a difference to use the crystal form—I’m just hoping to find a supplier where I can buy some and give it a shot myself

You're looking to get into an argument? You've come to the right place!

koraks · Jul 18, 2023

Look for CAS 584-08-7

The anhydrous form will be the same thing if you adjust for the difference in molar mass. There's not much to argue about.

DowntownDan said:
I’m based in NYC and there’s another user nearby (Saganich) who posted that he was able to obtain some. But, alas, I guess I am too new to the forum to have the ability to send a PM.

If you include their username preceded by an @ they will get an alert and might respond to this thread.

DowntownDan · Jul 18, 2023

DowntownDan said:
Hi all,

I’m looking for a source that will supply educational or lab grade (not ultra pure or re-agent) Potassium Carbonate in 1.5 H2O form to a private individual based in the US.

Would like to try the original formulation or FX-2 for some old-school emulsions. I’m aware of the many substitutes available and have most of those on hand. I’ve searched the archives, and read both DCB and FDCB.

I’m looking to get into an argument about chemistry, the limitations of trying to replicate Crawley’s formula, or whether or not it will make a difference to use the crystal form—I’m just hoping to find a supplier where I can buy some and give it a shot myself.

I’m based in NYC and there’s another user nearby (Saganich) who posted that he was able to obtain some. But, alas, I guess I am too new to the forum to have the ability to send a PM.

Thanks in advance for any help. Much appreciated.

Hahahahaa

Kino said:
You're looking to get into an argument? You've come to the right place!

oh man. Laughing hard. I meant *not* looking to get into an argument.

Steve Goldstein · Jul 18, 2023

Artcraft sells Potassium carbonate in 1lb and 5lb sizes, and they're in New York (state, not city).

Potassium Carbonate

Artcraftchemicals

artcraftchemicals.com

I don't remember the hydration amount, but if you adjust the formula as koraks mentioned it'll be exactly the same.

Doremus Scudder · Jul 18, 2023

Not trying to start an argument here, but have a question: Is the potassium carbonate in the Crawley formula there for a reason other that to simply make a more concentrated stock solution? If not, would not the results be identical if one used sodium carbonate in the correct proportion?

Doremus

Alan Johnson · Jul 18, 2023

Crawley, BJP Jan 6 1961 p12:
"This use of potassium carbonate (crystalline) as in FX2 deserves comment. Potassium carbonate (cryst) B.P. K2CO3 1 1/2 H2O gives an individual type of alkalinity not matchable with any direct equivalent of potassium carbonate (dried) -as was observed by Dalzell in the twenties; the B.P. crystals must therefore be used in these formulae where specified.
The type of alkalinity provided is useful, as it is in practice less energetic than the other carbonates ( due to the formation perhaps of some restraining bicarbonate? ) and therefore allows a fairly large concentration to be present, which stabilises the activity of the solution."

"Potassium carbonate (dried) gives lower contrast than sodium, and therefore by the time the same contrast has built up will have produced better toe contrast, as they both give the same film speed; this is probably the reason for our grandfather's advice to use potassium carbonate for "detail development"."

Making Crystalline Potassium Carbonate

After playing with D23 with borax, Sodium carbonate, Kodalk, glycin, for some time now I plan to mix-up some Crawley FX-2 and try some of the variations cited for solution B. I read that I can make potassium carbonate crystalline by dissolving potassium carbonate anhydrous in seltzer and...

www.photrio.com

DowntownDan · Jul 18, 2023

@Saganich

Can you please enlighten me as to your source for the 1.5 hydrate Potassium Carbonate? Saw in another post you were able to find.

I’m also in NYC, but I don’t have a registered business, which a lot of the labs require. I’ve been through every supplier US and Canada listed in the DCB.

DowntownDan · Jul 18, 2023

Steve Goldstein said:
Artcraft sells Potassium carbonate in 1lb and 5lb sizes, and they're in New York (state, not city).

Potassium Carbonate

Artcraftchemicals

artcraftchemicals.com

I don't remember the hydration amount, but if you adjust the formula as koraks mentioned it'll be exactly the same.

Thanks, Steve. I have anhydrous on hand, I’m addition to Kodalk, sodium carbonate, and other substitutes for which I have formulas. I spoke with ArtCraft a few weeks ago, and they were not able to obtain a source for the sesquihydrate.

When Crawley formulated the developer, he seemed to think there was a legitimate difference in the hydrate vs. dry form, and said so explicitly, that the 1.5 H20 should not be substituted.

I’m not saying he’s right, but when it comes to developer formulations, I’m one of those people who has to tsee it both ways before I’ll be satisfied.

Michael Howard · Jul 18, 2023

Alan Johnson said:
Crawley, BJP Jan 6 1961 p12:
"This use of potassium carbonate (crystalline) as in FX2 deserves comment. Potassium carbonate (cryst) B.P. K2CO3 1 1/2 H2O gives an individual type of alkalinity not matchable with any direct equivalent of potassium carbonate (dried) -as was observed by Dalzell in the twenties; the B.P. crystals must therefore be used in these formulae where specified."

Chemically, this statement makes no sense whatsoever. What is "an individual type of alkalinity"??? Seriously, no sense. Swap in the molar equivalent of anhydrous, you will have exactly the same solution. This isn't alchemy or homeopathy.

koraks · Jul 18, 2023

DowntownDan said:
When Crawley formulated the developer, he seemed to think there was a legitimate difference in the hydrate vs. dry form, and said so explicitly, that the 1.5 H20 should not be substituted.

I’m not saying he’s right, but when it comes to developer formulations, I’m one of those people who has to tsee it both ways before I’ll be satisfied.

Alright, that's fair enough; point taken. Like @Michael Howard I'm extremely skeptical as to the veracity of Crawley's claims, but your wish to test it as he described is very explicit and renders any discussion on the chemistry moot (for now).

Perhaps there's a possibility to dissolve water-free potassium carbonate and then crystallize it, perhaps by dissolving a large amount in hot water and then cooling the water, forcing crystallization. I suppose this might form the sesquihydrate (?) along similar lines as production does in the first place.

Alan Johnson · Jul 18, 2023

LP Clerc, Photography Theory and Practice, Vol 4, 1930-1971 section 587:

"Potassium Carbonate is usually obtained in the anhydrous form , K2CO3 , molecular weight = 138, as a white deliquescent powder which should be stored in a well sealed container. It absorbs moisture and carbon dioxide very readily to form the bicarbonate and, unless a specially purified sample is obtained, most specimens contain a considerable proportion of the bicarbonate."

Maybe Crawley considered the crystalline form available in 1960 to be more stable, IDK.

Michael Howard · Jul 18, 2023

That may very well be their reasoning. Carbonate to Bicarbonate, however, would be miniscule approaching zero in typical storage conditions. Not enough to really even calculate. It would be less than the contaminate bicarbonate present in both anhydrous and sesquihydrated versions. Having said that, I can understand the desire to test EXACT formulas. I'm just still stuck on that really weird (and unscientific) "an individual type of alkalinity". I'll probably still be chuckling at that phrase tonight lol

Alan Johnson · Jul 18, 2023

With sodium carbonate the hydrocarbonate can be formed,p763, potassium carbonate is not discussed but may be similar:

A comprehensive treatise on inorganic and theoretical chemistry : Mellor, Joseph William, 1873-1938. n 86858599 : Free Download, Borrow, and Streaming : Internet Archive

Includes bibliographic references and index

archive.org

DowntownDan · Jul 18, 2023

Alan Johnson said:
LP Clerc, Photography Theory and Practice, Vol 4, 1930-1971 section 587:

"Potassium Carbonate is usually obtained in the anhydrous form , K2CO3 , molecular weight = 138, as a white deliquescent powder which should be stored in a well sealed container. It absorbs moisture and carbon dioxide very readily to form the bicarbonate and, unless a specially purified sample is obtained, most specimens contain a considerable proportion of the bicarbonate."

Maybe Crawley considered the crystalline form available in 1960 to be more stable, IDK.

He actually said the reason for using crystal was that he wanted some bicarbonate impurities due to the desirable buffering properties.

DowntownDan · Jul 18, 2023

DowntownDan said:
He actually said the reason for using crystal was that he wanted some bicarbonate impurities due to the desirable buffering properties.

I thought about just subbing out for anyhdrous and then swapping some portion of that wirh potassium bicarbonate, but I would have no idea what percentage might be fruitful. At least it would be 100 pct replicable and controllable.

john_s · Jul 18, 2023

I found that the potassium carbonate I purchased, not labelled "dessicated" or "anhydrous" but with printed formula K2CO3 produced a weaker Pyrocat that I expected. I found that the potassium carbonate was apparently somewhat hydrated to some degree by dissolving it and accurately measuring the density and comparing it to a solubility/density graph at engineeringtoolbox. I found that I had to multiply my solution by 1.26.

As far as Crawley's explanation is concerned, it always looked odd. Maybe a dash of bicarbonate would get you close (maybe a slight buffer effect?)

DowntownDan · Jul 18, 2023

john_s said:
I found that the potassium carbonate I purchased, not labelled "dessicated" or "anhydrous" but with printed formula K2CO3 produced a weaker Pyrocat that I expected. I found that the potassium carbonate was apparently somewhat hydrated to some degree by dissolving it and accurately measuring the density and comparing it to a solubility/density graph at engineeringtoolbox. I found that I had to multiply my solution by 1.26.

As far as Crawley's explanation is concerned, it always looked odd. Maybe a dash of bicarbonate would get you close (maybe a slight buffer effect?)

Yes. I had that thought, and I have some fresh bicarbonate in the cabinet. But where to start? 5 pct? Ten?

Sean · Jul 19, 2023

DowntownDan said:
But, alas, I guess I am too new to the forum to have the ability to send a PM.

All set Dan

john_s · Jul 19, 2023

DowntownDan said:
Yes. I had that thought, and I have some fresh bicarbonate in the cabinet. But where to start? 5 pct? Ten?

The instructions refer to bicarbonate as an impurity, so I'd hazard a guess at a few percent of the carbonate amount. It might not make any difference though.
It would have been better if the original instructions said x_gram of sodium bicarbonate (I know it was potassium but it wouldn't make much difference and the sodium salt is more easily obtainable: even my mother in law has some)

Steve Goldstein · Jul 19, 2023

Wikipedia told me that heating hydrated Potassium carbonate above 200C converts it to anhydrous. Since my supply of Artcraft-sourced Potassium carbonate has been around a while, I weigh out rather more than I'll need for my Pyrocat-HD "B" solution, put it in an oven-proof glass baking dish, and place into a preheated 225C (450F) oven for 30-40 minutes. I pull it out every so often to stir it around with a stainless steel spoon. It makes interesting popping noises at first. Maybe 10 minutes after the noises stop I decree it dessicated, let it cool a bit, weigh out what I need, and dump the remainder back into the container from whence it came. The resulting Pyrocat seems to be repeatable from batch to batch.

I have no information as to possible bicarbonate impurities. It's not something I lose any sleep over.

DowntownDan · Jul 20, 2023

Sean said:
All set Dan

Thanks!

Alan Johnson · Jul 20, 2023

The pH of 0.1M sodium carbonate is 11.5 but if just 10% is converted to bicarbonate the pH drops to 10.83:

https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC1258214&blobtype=pdf

If potassium carbonate is similar, again the drop in pH would again be around 0.67 units.
IDK, but it reads like it might be photographically significant.

DowntownDan · Jul 21, 2023

Alan Johnson said:
The pH of 0.1M sodium carbonate is 11.5 but if just 10% is converted to bicarbonate the pH drops to 10.83:

https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC1258214&blobtype=pdf
If potassium carbonate is similar, again the drop in pH would again be around 0.67 units.
IDK, but it reads like it might be photographically significant.

I found a source here in US and had it shipped. I will mix both ways at some point and report back on the pH.

US Sources for Potassium Carbonate Sesquihydrate/1.5 H2O/Crystal

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