I think about the same as the others, except an inorganic chloride
replacing Mercuric Chloride
Do you mean an Aqua Regia type, with Nitric and Hydrochloric acids and Iron?
I've gone away from those types for pattern-welded barrels, to types with Nitric Acid, Ferric Chloride, and Alcohol, which are water based and seem to work well under dilution. More cycles when diluted are necessary, but the contrast stands up better under carding and polishing. Using the AR types sometimes the coating is so thick the pattern is more easily buggered when polishing for contrast.