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My innner chemist just got interested.
Looking at https://www.ready.noaa.gov/documents/TutorialX/files/Chem_henry.pdf which shows how much each gas dissolves into water, here are the relative solubilities of some common gasses that aren't acidic nor basic:
Gas Solubility (molar/atm) reactive?
Oxygen 0.0001 YES (so don't use this)
Hydrogen 0.0008 YES
Nitrogen 0.0003 NO
Argon 0.001 NO
Butane 0.001 Maybe (I really don't know here because I don't know the reduction potentials of the developers, but think it's higher than 0.8v)
In using gasses to purge oxygen out of the headpace of a solution, the main consideration is how much dissolves. If you add a very soluble gas over the solution, it will dissolve, creating a vacuum in the headspace. That vacuum will pull air into the bottle, and your developer-preservation plan is foiled. So, avoiding those gasses that will react with your developer (O2 and H2), nitrogen is the next best of the common gasses. Nitrogen also has one MASSIVE advantage over all the other gasses: it's already saturated in the solution! It got there when the water came out of your aerating faucet (provided you didn't boil the water before making your developer).
In the labs I worked in we always used nitrogen to displace oxygen unless we were using a reaction where nitrogen was one of the reactants (like nitrogenase studies).
So, who sells canned nitrogen gas?
P.S. This always works best when you sparge the solution with the headspace preservative, ie. blow the gas deep into the solution. Little red straws for the win.
Been looking for someone to do this for a while. I understand you can use Butane as a liquid chemical preservative, but I'd rather not use flammable gas and investing in a rechargeable cylinder and regulator for Argon was too much.
Just ordered a few cans; anyone else try this?
Bloxygen - Inert Gas Preservation
Save your leftover paints, finishes or food from getting ruined by oxygen or moisture. Simply spray, seal and store for up to 10 years. Never have hardened paint or rubbery finishes ruin your day. Safe for food, coffee, cannabis. Tested by manufacturers. Industry best practice.www.bloxygen.com
Some of us on FADU have discussed this problem a few times.The most commonly used "spray" (in Germany I think) to preserve photographic chemicals was Tetenals “Protectan”.
It can simply be summarised by calling it “expensive dust off” or Propane + Butane.
IMHO it should be safe as long as there’s no fire hazard around and displaces oxygen whilst being heavier than air.
Terry,Some of us on FADU have discussed this problem a few times.
I have used and tried various food and wine preservers, as well as Protectan. The former went wrong in dispensing the gas quite a few times, but the company selling it were very good in replacing a few cans for me.
Protectan worked well, but like the former, it too became expensive long term.
I then read the posts about using butane lighter gas, which is easily found for at least 1/10th the cost, so it became a no brainer. I too worried a little about it being flammable, but no one seems to have ever had a fire problem with it over the many years that it's been used, probably partly because very little is used at a time, so it might be worth a rethink on your part.
As for getting an tank of argon, I also looked at that, and couldn't find a small amount of it, and like you implied, it would be a bit overkill, even though the gas itself appears to be relatively cheap like this, but unless you are a welder using it all the time...
Terry S
UK
I've been using marbles in amber glass bottles to mechanically keep oxygen out. Is this better/worse/same as using gas?
I use Butane. I tried Bloxygen but it didn't last long. As in, went to use it and nothing came out after maybe four or five small uses. Not worth it. Butane is a no brainer and it works fine. Glass/butane keeps things for a looooong time.
They will start to dissolve quickly alright. But the real question is whether the absorption rate and final concentration by the time recrystallization is finished is significant enough. The likely answer is 'not even close'. Personally I'd not even bother boiling the water.As I've read it, gasses will start to dissolve quickly after the water stops boiling.
For dry chemicals that are perishable, I'm planning to get oxygen absorber packets. I
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