Potassium Hydroxide in Parodinal?

ulysses · Mar 19, 2011

I just ordered some R09 (Rodinal) from Freestyle and the invoice says "Potassium Hydroxide". All of the Rodinal formulas I have specify Sodium Hydroxide. I have potassium hydroxide, which apparently can be shipped easily (at least within the states) but DEA forms are required to sell/ship sodium hydroxide. I have a bunch of acetaminophen capsules, too, since I was planning to test Parodinal against the "real" thing. Can I use potassium hydroxide in place of sodium hydroxide to make Parodinal? If no one knows (or no one replies) I'll give it a try and report back.

Ulysses

hrst · Mar 19, 2011

AFAIK the Na+ or K+ ion is quite irrelevant in most photographic reactions. The OH- is what counts here. But you want the same number of OH- ions to give the same pH, and because the Na+ and K+ have different weight, you have to compensate when you weigh the mass.

http://en.wikipedia.org/wiki/Sodium_Hydroxide 39.9925 grams per mol
http://en.wikipedia.org/wiki/Potassium_Hydroxide 56.1056 grams per mol

So, you need higher mass of potassium hydroxide than sodium hydroxide. You can calculate the ratio from the molar masses given above.

Gerald C Koch · Mar 19, 2011

Agfa used potassium hydroxide when making Rodinal. Potassium salts appear to be somewhat more active in developers than their sodium counterparts.

ulysses · Mar 19, 2011

hrst said:
AFAIK the Na+ or K+ ion is quite irrelevant in most photographic reactions. The OH- is what counts here. But you want the same number of OH- ions to give the same pH, and because the Na+ and K+ have different weight, you have to compensate when you weigh the mass.

http://en.wikipedia.org/wiki/Sodium_Hydroxide 39.9925 grams per mol
http://en.wikipedia.org/wiki/Potassium_Hydroxide 56.1056 grams per mol

So, you need higher mass of potassium hydroxide than sodium hydroxide. You can calculate the ratio from the molar masses given above.

Outstanding. That ratio is exactly what I need.

U.

Photo Engineer · Mar 19, 2011

You can use either Na or K salts in developers as long as you adjust for the molecular weight differences when you make the substitution. You CANNOT use K salts in fixes! The use of a K salt in a fix just about ruins its effectiveness as a fixing solution.

PE

Ian Grant · Mar 19, 2011

Potassium salts are more soluble which is why Potassium rather than Sodium Carbonate is used in commercial liquid developers, and Potassium alum and also Potassium Metabisulphite are used in some commercial fixers (Ilford/Kodak etc).

Rodinal has a very high sulphite content and the easiest way to achieve it is by mixing Potassium Metabisulphite with Potassium Hydroxide.

Ian

Alan Johnson · Mar 19, 2011

The acetaminophen/paracetamol developer originated from an experiment by Sreenath:
www.photokb.com/Uwe/Forum.aspx/photo-darkroom/1956/Acetaminophen-Paracetamol-developer
Later Donald Qualls named it Parodinal (post 45)
http://www.f295.org/Pinholeforum/forum/Blah.pl?v-print/m-1132019056/
It contains an excess of hydroxide so the precise amount is probably not very critical.

Marco B · Mar 19, 2011

Photo Engineer said:
You CANNOT use K salts in fixes! The use of a K salt in a fix just about ruins its effectiveness as a fixing solution.

PE

As I am always interested in the details of the chemistry going on, can you explain why this is?

Is it because the K+ cation somehow combines in a similar way and with higher affinity with the thiosulfate as the Ag+ silver ion does, hence removing thiosulfate's fixing capability?

And any comments as to the text inn this linked webpage:

"KTS® (potassium thiosulfate solution) is used in gas processing to absorb and catalytically oxidize H2S into elemental sulfur.

In photo processing, diagnostic imaging, motion picture and graphic arts, KTS is used in the preparation of rapid fixing solutions where concerns are present regarding ammonia levels. :confused: KTS, the "original" potassium thiosulfate solution.

Consult the technical data information for specific applications and the MSDS for handling and storage recommendations."

Ah... well, it says "preparation", so probably the K is substituted with the ammonium cation in the final product.

Photo Engineer · Mar 19, 2011

There are reports in Haist, VI P 566 and following pages that cite work by Frank and Schramm that show inhibition of fixing when using Potassium Thiosulfate. Haist and others report that the huge K ion is the problem. Small amounts of K as in Potassium Alum hardened fixers are not harmful apparently, but larger quantities slow down the fix considerably. Mees reports fixation slowed by 2x or more and some experiments, mine included, show that you can effectively "poison" a fix with Potassium ions.

The complex with hypo contains up to 5 or so hypo ions with associated Sodium and Potassium or Ammonium which must diffuse out of the coating without undue crowding. This is why you show increased activity in the series Calcium, Potassium, Sodium, and Ammonium. However, since Ammonium is also a silver halide solvent in itself, the change is more than predicted based on size alone.

You note that Calcium is included in this as an "inhibitor" for fixing.

This also holds true to some extent for washing the complexes out of the coating.

PE

Olympus17 · Aug 6, 2020

Konudan bu yana uzun zaman geçti. Ama birisi bana kesin bir şey söyleyebilir mi? Potasyum hidroksit veya sodyum hidroksit kullanmalı mıyım? Tabii ki, 250 ml çözelti için miktarlar ne olmalı? Teşekkür ederim .

Olympus17 · Aug 6, 2020

Does anyone have a clear parodinal formula?

Donald Qualls · Aug 6, 2020

I do, but it's on my home computer. I'll try to remember to post it when I'm home, tonight.

Olympus17 · Aug 6, 2020

Thank you very much. And I need a simple fixer formula for film and printing.

Olympus17 · Aug 6, 2020

It's hard to be a beginner

Donald Qualls · Aug 6, 2020

Olympus17 said:
Thank you very much. And I need a simple fixer formula for film and printing.

Fixer is easy. From memory, you want 240 g/L sodium thiosulfate (the slippery crystals, don't recall what hydration state that is), 60 g/L sodium sulfite, and optionally enough acetic or citric acid to make it distinctly acidic (I prefer mine neutral/alkaline, but there are arguments both ways).

This should have a capacity of around a dozen rolls of film or a couple dozen 8x10 prints per liter, but recommended is a clearing test: when freshly mixed, put an undeveloped film scrap into the fixer (in the light, you need to be able to see this), and time how long it takes to lose all of the milky appearance and appear as clear film base. Fix for twice that long and repeat the clearing test every few rolls. When the clearing time is twice that in fresh fixer, discard and start over.

This fixer does not work well for tabular grain films, like Delta, T-Max, or Acros -- but it's fine for cubic grain (pretty much every other B&W film).

Olympus17 · Aug 6, 2020

Should the solution be used undiluted?

Alan Johnson · Aug 6, 2020

Olympus17 said:
Does anyone have a clear parodinal formula?

The Potassium sulfite is much more soluble than sodium sulfite and solutions made using potassium instead of sodium should come out clear like my effort:
https://www.photrio.com/forum/threads/parodinal-with-potassium-bisulfite.118849/
I have not done the calculations for the hydroxide but there is so much excess of it in Parodinal just using the same weights as the sodium in the original formula should be OK IMO.

Olympus17 · Aug 6, 2020

The formula is then:
Water..............................................................250ml
Acetaminophen...30x500mg capsule contents.........15g
Potassium Bisulfite..............................................47.7g
Sodium Hydroxide...20g+15.9g............................35.9g

Can I use this formula?

Olympus17 · Aug 6, 2020

Unfortunately, I have a chance to buy only Potassium Metabisulfite.

Alan Johnson · Aug 6, 2020

Olympus17 said:
The formula is then:
Water..............................................................250ml
Acetaminophen...30x500mg capsule contents.........15g
Potassium Bisulfite..............................................47.7g
Sodium Hydroxide...20g+15.9g............................35.9g

Can I use this formula?

Yes.
There are small differences between bisulfite and metabisulfite but for this purpose they are not significant.
I have used this formula from time to time for years , it does eventually deposit a small quantity of crystals.
It seems to last a long time, several years in half full bottles.
I am beginning to suspect the chemicals don't know what is written on the bottle and behave like Rodinal.

Donald Qualls · Aug 6, 2020

Olympus17 said:
Should the solution be used undiluted?

The fixer formula I gave is working strength. Note that it is not a rapid fixer, so can't get the Ilford "almost no wash" process for RC prints; they need to fix for too long to wash clean so quickly. Look up old instructions (like from the 1960s or so) for how long to fix prints; three minutes is probably enough but I don't recall for certain. I usually give non-tabular films six minutes, but those will wash just like normal (Ilford wash is valid -- 5 inversions, dump and refill, 10 inversions, dump and refill, 20 inversions, dump and refill and add wetting agent).

Olympus17 · Aug 6, 2020

Alan Johnson said:
Yes.
There are small differences between bisulfite and metabisulfite but for this purpose they are not significant.
I have used this formula from time to time for years , it does eventually deposit a small quantity of crystals.
It seems to last a long time, several years in half full bottles.
I am beginning to suspect the chemicals don't know what is written on the bottle and behave like Rodinal.

Can I use the same gram for Potassium Metabisulfite? Can this solution be used for printing? Thank you .

Olympus17 · Aug 6, 2020

Donald Qualls said:
The fixer formula I gave is working strength. Note that it is not a rapid fixer, so can't get the Ilford "almost no wash" process for RC prints; they need to fix for too long to wash clean so quickly. Look up old instructions (like from the 1960s or so) for how long to fix prints; three minutes is probably enough but I don't recall for certain. I usually give non-tabular films six minutes, but those will wash just like normal (Ilford wash is valid -- 5 inversions, dump and refill, 10 inversions, dump and refill, 20 inversions, dump and refill and add wetting agent).

Thank you so much . In this case, I will use it without dilution and in accordance with ilford standards.

Ian Grant · Aug 6, 2020

Olympus17 said:
Unfortunately, I have a chance to buy only Potassium Metabisulfite.

Bisulphite is a less pure form of Metabisulphite which is far better.

IAn

Alan Johnson · Aug 6, 2020

Olympus17 said:
Can I use the same gram for Potassium Metabisulfite? Can this solution be used for printing? Thank you .

Yes,
I did the calculation for bisufite but actually I used Metabisulfite.
I made some prints developed in this solution (sorry, I don't recall the dilution.}
It did work but they were a bit low contrast compared with prints from proprietary print developer.

Potassium Hydroxide in Parodinal?

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