I've just gotten some copper sulfate to use in bleaching for B&W reversal (used with a chloride donor such as table salt, in an acidic solution), and it occurred to me that hydrochloric acid (sold at home improvement stores as muriatic acid, for cleaning concrete etc.) would both acidify the solution and provide chloride ions to convert the developed silver to silver chloride for later dissolution by ammonium hydroxide.
I see copper chloride has very low solubility in water, so I'd think adding any chloride donor to a copper ion solution would lead to precipitation of copper chloride -- but the desired end result is silver chloride in the developed image area of the film (which is soluble in aqueous ammonia, unlike silver bromide and iodide), so a chloride donor is critical, and I know from report that this bleach works.
Is there some reason other than cost why hydrochloric acid isn't used here?
I see copper chloride has very low solubility in water, so I'd think adding any chloride donor to a copper ion solution would lead to precipitation of copper chloride -- but the desired end result is silver chloride in the developed image area of the film (which is soluble in aqueous ammonia, unlike silver bromide and iodide), so a chloride donor is critical, and I know from report that this bleach works.
Is there some reason other than cost why hydrochloric acid isn't used here?
