The Moersch citric acid-based stop baths (60%) offers the advantage over acetic acid stop baths of being odor-free.
However, as with any other acid, emissions occur when citric acid is used in contact with carbonate-alkaline, sulfite-containing developers. Almost all paper developers contain a high amount of sodium sulfite as an oxidation inhibitor. If the odor nuisance has to be reduced, a water bath can be added to the stop bath. It should be noted, however, that the development process then continues - albeit at a much slower rate - until the pH value in the acid bath is abruptly lowered.
Thanks to the new formula, the SO2 emission as described above is no longer detectable even for the sensitive noses.
Dilution: minimum 2% solution 1+28 (36ml to 1 liter of water), a dilution of 1+40 is sufficient to stop most development processes.