F-24 formula in Darkroom Cookbook has dangerous error

I'm just getting into mixing my own chemicals and was going to use the F-24 formula from Anchell's Darkroom Cookbook. His formula states that citric acid can be substituted for the sodium bisulfate in order to reduce odor. The problem is that substituting citric acid creates sulfur dioxide which smells really bad and is harmful. On his website, darkroomcookbook.com, he states people should cross out the substitution in the book and not use the citric acid. I was about to use this formula out of the book and only found this additional information by doing some additional research. I'm not sure this error is widely known but it makes me worry about what else could be wrong in the book or other published sources. https://darkroomcookbook.com/phpbb/viewtopic.php?t=175

Good advice, thanks for the heads up!

Welcome to Photrio!

Welcome to Photrio, @michaelapdx!

michaelapdx said:

I'm not sure this error is widely known

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Not sure; it's not being discussed very often. I think this is mostly because most people use ready-made fixer instead of mixing their own, and that most people prefer to use a rapid fixer.
I still have 1-2kg of sodium thiosulfate gathering dust somewhere; I'm not sure if I'll ever get through it. There's just no point bothering with a slow fixer if a rapid one is easily available!

Btw, the issue was raised a few years ago here: https://www.photrio.com/forum/threads/sodium-thiosulfate-fixer-smell-whew.179186/

There's no mention of this substitution in my 2016 copy of the DCB4 printed or electronic copies, or in the forth coming DCB5. So the correction was made around 8 years ago. It's in the DCB3.

The substitution was suggested to reduce the odor of Sulphur Dioxide from the Sodium (Meta)bisulphite. Other fixers such as T-5 contain use Acetic Acid and Sodium Sulphite alongside the Thiosulphate. You don't get Sulphur Dioxide formed when you mix these small quantities of Acetic or Citric acid with Sodium Sulphite. You would if you mixed them with Metabisulpite, substitution means either/or not both.

However the issue with using Citric acid as a substitute is it causes older Sodium Thiosulphate based fixers to go cloudy as some of the Thiousulphate breaks down, liberating Sulphur/Sulphides, which generates a strong powerful odor.

Ian

Ian Grant said:

There's no mention of this substitution in my 2016 copy of the DCB4 printed or electronic copies, or in the forth coming DCB5. So the correction was made around 8 years ago. It's in the DCB3.

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In a thread from 2012 you recommended a simple general purpose fixer of:


Agfa 304 Rapid Fixer

Sodium Thiosulphate 200g
Ammonium Chloride 50g
Potassium Metabisulphite 20g
Water to 1 litre

Would this still be a good fixer for someone that wants a safe and easy fixer to mix at home? And can it be reused!

Yes it works well, possible better to use Sodium Metabisuphite 17g (or Bisulphite)/ It's a rapid fixer so shorter fixing times.

Ian