"Hypo eliminator usually refers to a solution containing hydrogen peroxide or peroxide-releasing compound such as percarbonate, perborate or persulfate. These solutions may also contain ammonia, other alkaline agents, bromide, iodide, and other additives.
The idea behind hypo eliminator is to oxidize thiosulfate to harmless compounds that are not adsorbed by silver surface. However, it was later found that peroxide solutions damage and undermine image-forming metallic silver. Today, the use of hypo eliminators are discouraged."