Glacial acetic acid concentration in Agfa 305

Xícara · Oct 3, 2024

Hello,

I'd like to mix up the following Agfa 305 hardening fixer formula (posted by @Ian Grant ) to fix X-ray film:

305 Hardening Fixer

Water ------------------------------800ml
Sodium Thiosulphate ---------------200g
Sodium sulphite (anhyd)----------- 20g
Acetic acid (glacial) ----------------15ml
Potassium Alum (dodecahydrate)--10g
Water enough to make up to 1 Litre

Ref. https://www.photrio.com/forum/threads/agfa-304-305.106122/post-1404302

I'm uncertain about the concentration of the glacial acetic acid. My chemical supplier stocks glacial acetic acid in solutions ranging from 1-6%.

Is the above a concentrated glacial acetic acid solution? If so, would this mean that I'd require 300ml of a 5% solution? ie. 15ml / 0.05

Also, can domestic alcohol vinegar (4% acetic acid) be used a substitute or would it introduce too many impurities? I use a dilution of this generally for my paper stop baths.

Thanks

Ian Grant · Oct 3, 2024

Glacial Acetic Acid is water free, so 100%. A 10% solution is 10ml Glacial in 100ml. You would need 375ml of a 4% solution.

White vinegar isn't particularly pure, it would probably work OK.

Ian

runswithsizzers · Oct 3, 2024

The concentration of glacial acetic acid is, by definition, just about the strongest concentration available. That is, it is anhydrous, and contains little or no water. So any acetic acid that is described by some percentage such as "5%" is not glacial acetic acid. Think of glacial acetic acid as a > 99% solution.

Edit: sorry, cross posted. BTW glacial acetic acid requires significantly greater care when handling, compared to more commonly available concentrations. Use eye and skin protection and avoid breathing fumes.

fgorga · Oct 3, 2024

The "glacial" in glacial acetic acid specifies that it is 100% acetic acid. Dilute solutions are referred to simply as acetic acid.

Your calculation regarding using a 5% solution is correct. Just remember to reduce the amount of water specified in the recipe in order to keep the final volume the same.

Vinegar will probably work as a substitute. The concentration of acetic acid in vinegar is nominally 4%. However that are certainly small differences between brands and probably between batches of the same brand. If you go this route, I would pick a brand of vinegar and (if it works) stick with it.

runswithsizzers · Oct 3, 2024

"The concentration of acetic acid in vinegar is nominally 4%"

I have noticed household "distilled vinegar" sold in my area (USA) is now often described on the label as 5% or 6%.

Xícara · Oct 3, 2024

Thanks for the confirmation @Ian Grant and @runswithsizzers. The products are listed here as diluted solutions of the glacial acetic acid, which make sense, I think. I believe the pure form is a controlled substance, so I wouldn't be able to buy it.

Just one other doubt: Is a wash of 10 minutes sufficient with this fixer?

Cheers,

Ian Grant · Oct 3, 2024

When you use a hardening fixer you need longer wash times, they will depend on whether it's used for films or paper.

Ian

Xícara · Oct 3, 2024

Ian Grant said:
When you use a hardening fixer you need longer wash times, they will depend on whether it's used for films or paper.

In my case film. The film is cut into an approximately 6x9 sheet and suspended by a clip in beaker and into which I run a tap with filtered water. There's a good circulation of water in the beaker and I've been doing this in the past for 10 minutes using kodak hardening fixer. Perhaps I should have been doing this for longer, but only became aware of this issue recently.

Glacial acetic acid concentration in Agfa 305

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