Yeah, I read that post before.
Originally Posted by Alan Johnson
I can only get Potassium Hydroxide and Potassium Metabisulphite here, but I'm not sure what the minimum purchase quantities would be.
Is there a recipe I could follow with the Potassium Hydroxide and Potassium Metabisulphite?
(I'm going to start searching for one now...)
Is this right?
Potassium Metabisulphite (32,2gr) + Potassium Hydroxide (25,8gr) + Paracetamol (15gr) + distilled water (250ml total finished volume)
One mole K2S2O5 (222.3g) plus 2moles KOH (112.2g) gives 2 moles K2SO3 (316.6) plus 1 mole water (18.0g)
Sorry I don't have time to do the complete calculation at the moment.
AFAIK the potassium version of Parodinal formula is not published,you have a research project.
Fantastic! Thank you.
I will get onto procuring the chemicals first, and then doing the necessary calculations.
I hope the supplier is willing to sell me the materials in 1 or 2kg packets!
I make this formula using Panado capsules and potassium hydroxide, and call it Panadonal-K (just for the fun of it - it really is only Parodinal with potassium instead of sodium, of course). The formula is:
Water: 100 ml
Sodium sulfite: 40 g
Dissolve at roughly 50 degC (122 degF)
Water: 60 ml
Potassium hydroxide: 17.9 g
Dissolve the hydroxide, then add 15 g (30 capsules) of paracetamol while the hydroxide solution is still hot. Stir in the powder thoroughly and break any clots. It will turn reddish and murky, which is fine.
Once the two parts are cool, combine. Use the sulfite solution to wash out all the paracetamol solution. Make the final volume up to 200 ml (not 250!). Any undissolved sulfite can be added as crystals to the final container - it will dissolve over time. The brew is ready to use within two to three days. It is important that the cap of the bottle seals really tightly, as air leaks will eventually destroy the developing agent (4-aminophenol). Do not be alarmed if it turns redder everytime you open the bottle - that is natural, and it will still be active even if it looks like cola concentrate. The Parodinal formula of Zorkikat and others is short on the active ingredient by about 20%, if you compare it to other rodinal formulas. I believe that is the reason why it does not last long. My Panadonal-K lasts now for more than a year as a half-full bottle, without any signs of deterioration.
Hope it works for you.
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Thanks for that!
I have just got off the phone with a chemical company here in Cape Town.
I can get Potassium Hydroxide and Potassium Metabisulphite next week.
I had to enquire about the Potassium Sulphite at another company, who has not yet replied to my email.
If you ever want the Paracetamol powder I use, let me know and I can send you some!
It's cheaper than panado, and it's completely pure.
Parodinal Batch 27082012-01 and Parodinal Batch 27082012-02 have still not crystallised by this morning (30 Aug).
I'll use them on my test film later today or over the weekend!
Are you planning on ordering from BM Scientific? I got some of my chemicals from them, including enough KOH to share. You can also try Minema - they are generally cheaper and will have stock, but don't buy as yet. Rather PM me your postal address and I'll send you some KOH, as well as another surprise or two. My stocks are all in 500 g + quantities, and for things like developers that is usually more than one needs for a long time. Yes, for certain I would like some paracetamol, but I will trade you for it.
About Parodinal: I would advise against metabisulphite and/or carbonates as they affect the pH and you would then have to tweak your total balance to get things right, and it is not really necessary in the first place. You really only need three things: hydroxide, sulphite and paracetamol. If the hydroxide is potassium hydroxide, the solubility of sulphite is improved because of the "common ion effect", where fewer sodium ions compete to stay in solution. Potassium salts are as a general rule more soluble than sodium salts on a molar (and hence also mass) basis, and this is why if you use NaOH you will battle to get the sodium sulphite dissolved, but if you use KOH all eventually dissolves. You can use potassium sulphite with sodium hydroxide too, based on the correct molar (not mass) quantities. I'd be happy to do the calculations for you if you do not know how. Basically you divide the mass by the molar mass of the specified chemical, and multiply by the molar mass of the one you substitute. So for KOH substituting for NaOH the correction is 56.1/40.0 = 1.40. The same principle will apply to sulphite but the factor would be different (1.26) etc. I reverse-calculated the Panadonal-K formula against two other formulas - the pre-war Rodinal formula (which differs in containing EDTA and KBr) and the formula for Rodinal published in The Darkroom Cookbook. Those two formulas have the same 4-aminophenol content (within 1 %), and the Zorkikat formula is about 80 % of that. I think that is because ZorkiKat used only sodium chemistry and couldn't get everything into solution as is supposed to be the case. If you filter the Zorkikat formula, you will be in trouble, because the excess sulphite is necessary to protect the aminophenol from oxidation. The TDC and original formulas both employ potassium as well as sodium but in different ways. However, the end product has more or less the same composition in either case, and my adaptation matches that fairly well. The difference between various formulas lies in the byproduct which is usually derived from the way in which the aminophenol is introduced. In the case of TDC it is chloride, in the Parodinal formulas it is acetate, and in metonal it will be something like sulphate. I think at the concentrations after dilution 1:50 these byproducts do not affect the developing much, but I would appreciate if someone with more insight can comment. NaCl does affect some developers, but typically at higher concentrations than what one finds in Rodinal.
For metabisulphites (they are acidic) you have to do the following correction:
2KOH + K2S2O5 => 2K2SO3 + H2O
So if you use metabisulphite, part of your hydroxide is consumed to convert to sulphite, and you have to make a correction or the pH will not be correct. Hope that is clearer now than I stated above. Not in principle a problem, but the quantities have to be correct.
Thank you. Theres a company just a few km away that can get me almost all I need. I have ordered 1kg of KOH from them. For technical grade KoH, it costs R23/kilo ex VAT. So no complaints. It'll ready for collection on Monday or Tuesday. I need to get more paracetamol and Sodium Sulphite next week as well. How much do you want of the paracetamol? Other surprises ?
Originally Posted by dorff
Don't worry about the KOH, they are easily available here. I want to make some Parodinal for friends to try, so eventually I'll be making larger batches.
Good to know that using KoH will help with solubility. Potassium Sulfite is impossible to find by comparison to Sodium Sulfite, which is also quite cheap.
Originally Posted by dorff
Goodness! Thanks for all the insight. Invaluable!
With regards to the byproduct, how does your Panadonal-K results differ from Rodinal at 1:25?
Do you filter your solution or is it not necessary?
OK, Please excuse if this is wrong...
If I were to use Potassium Metabisulfite, would the following formula be correct?
28,1 gr Potassium Metabisulphite
14,2 + 17,9gr KOH
15gr Paracetamol powder
Water to make 200ml
I'm likely going to take your advice by using the KOH and Sodium Sulphite recipe, but since the Potassium Metabisulphite is so cheap, I'm likely to give it a try...just because I'm curious.
Do I need to get Kbr also? I can't find that on the current product lists I have.