There is one in Derek Watkins book, the Gilbert Hopper one and that one is with 10 ml of a 10% solution of sulphuric acid. Emil Mayer also gives a recipe, but with hydrochloric acid. From what Emil says, heavy silver deposits may not bleach fully. And when doing liquid emulsion I guess it would be possible to get these thicker deposits. All of this is theory and reading - I have only used the non-acid bleach, on Foma papers.

On a related note, some of the sensitizer recipes for oil printing contains citric acid.