Collodion Iodizer Precipitate Fail

[36cm2]

Novice wetplate user hoping that someone with better chemistry knowledge and collodion experience than me can assist with a question. I was trying to prepare an iodizer solution based on a Scully & Osterman (S&O) positive collodion formula. Their formula was not specifically for the type of long-term iodizer solution I was seeking (adding all but collodion), but rather for a typical part A iodizer and a part B ether/collodion solution. Based on the chemicals I had in hand and my need to stabilize some extra ethyl ether for longer term storage, I used the following extrapolation that I made from the S&O formula (please note that what is below is not an S&O formula, because if I just messed up the approach or calculations or other considerations I wouldn't want that attributed to them in any way):

- Part A - 100 ml test tube. Add 14.3 g of warm distilled water. Mix in (with glass rod) 10.7 g of Cadmium Bromide (very toxic, wear mask), dissolve completely, then mix in (with glass rod) 14.3 g of Potassium Iodide, dissolve completely.

- Part B – Pour 355 g of ether (full 500ml bottle) into bottle. Add 394.6 g of denatured alcohol into the ether.

- Mix Part B into Part A in modest amounts back and forth and shake gently until mixed.

- [I HAVE NOT DONE THIS YET]When ready for use with collodion add to collodion in a ratio of 1 part collodion to 1.27 parts iodizer. Should be no precipitants.

My problem is that when I mixed Parts A and B a fairly large amount of precipitate formed and no matter how much I mixed the solution the precipitate would not dissolve (I mixed with an HTPE autostirrer at length without effect). Is that precipitate supposed to result in an iodizer of this type or have my Part A chemicals come out of solution and left me with a failed iodizer experiment or worse? Any insight you can provide is helpful. Many thanks to all for your time.

Also, I'm not sure if it's ok to post wetplate questions in this portion of the forum (and I know there are other forums out there more specifically targeted toward wetplate), but I've known Apug for years and would be grateful if help can be found here. Thanks.

All the best,
Leo

 

[removedacct1]

Leo,
The Potassium iodide is insoluble in Ether/Ethanol, so there will always be some precipitate when adding the solvents to the water/KI component. This happens when mixing Old Workhorse as well. Odds are the collodion will remain cloudy for a few days (up to 2 weeks, in my experience) as well. This is not a problem, but it should be allowed to age for at least a week before using it.

Why did you modify the Scully/Osterman formula? You've changed the ratio of alcohol to Ether, and I don't see the reason for this.

Also, the Scully & Osterman formula uses equal parts of Ether and Ethanol, so if you need to store Ether for a long time and don't want to worry about the formation of peroxides, simply make a 50/50 solution of the two solvents and bottle it up. It will last forever in that state. You can dissolve the salts to complete the recipe at a later date without concern. I would also recommend NOT using denatured alcohol because it is a potential problem that - depending on the denaturant added to the alcohol - it may have undesirable effects on the collodion. Best to acquire Ethanol (grain alcohol) for this.

 

[36cm2]

So extremely helpful Paul. Thank you. It is truly appreciated. I didn't experience the cloudiness you describe for more than an hour or so, but maybe that doesn't matter. I don't believe I changed the ratio of ether to alcohol (at least I didn't intend to). The relative measurements of those materials were converted from ml (in the original formula) to grams using the relative density ratios of the two materials (0.71 for ether and 0.79 for denatured alcohol). If this doesn't make sense or is simply wrong, I'm happy to be corrected. I am aware of the denatured alcohol point and am using one that was indicated to me would not cause problems, but I will stay mindful of it if things don't work. I have mixed Old Reliable and a Quinn collodion variety using the denatured without issue so far, so hopefully its working correctly.

I guess once the solution in question has aged for a bit, I'll strain out the precipitate and see if it's working correctly. Thank you again for the help. I was concerned that I might have inadvertently created something more problematic. Again, thank you for the help in these early days for me.

 

[36cm2]

Oh, and thank you very much for the note on just mixing the Ether and Ethanol 50/50 for storage. I wasn't sure if that would be enough to adequately stabilize it or whether you needed the iodizer dry chemicals to stabilize appropriately. That's very helpful to know should it happen again. Although I won't be buying as much ether next time - it was really an initial order mistake.

 

[removedacct1]

Oh, and thank you very much for the note on just mixing the Ether and Ethanol 50/50 for storage. I wasn't sure if that would be enough to adequately stabilize it or whether you needed the iodizer dry chemicals to stabilize appropriately. That's very helpful to know should it happen again. Although I won't be buying as much ether next time - it was really an initial order mistake.

You're welcome.

My apologies, I misread your original statement about solvent ratios. Here, we measure fluids by volume, not weight, so my eyes read that as ml, not grams!
You shouldn't need to filter out the precipitate from the Collodion: over a few weeks it will all settle to the bottom of the container, so as long as you don't shake the container it will stay there. Simply decant a couple hundred ml of collodion into another bottle suitable as a pour bottle, and replenish it from your stock bottle as needed. DO NOT use your stock bottle to pour plates from and catch drained off excess in: you will end up with dust and unwanted flotsam in the stock bottle. The collodion in the pour bottle will also get thicker as the solvents evaporate during pouring and will eventually need to be thinned with that 50/50 Ether/Alcohol you have set aside! Storing a volume of 50/50 solvents comes in handy in many ways!

 

[36cm2]

Really so helpful, Paul. Thank you again.