Balard discovered chlorine monoxide in 1834, investigating its properties and reactions; and his observations on hypochlorous acid and hypochlorites led him to conclude that " bleaching-powder " or " chloride of lime " was a compound or mixture in equimolecular proportions of calcium chloride and hypochlorite, with a little calcium hydrate.
The metallic film is tested with 20% nitric acid and with bleaching-powder solution.
Arsenic is insoluble in the acid, but immediately dissolves in the bleaching-powder.
The black films of antimony and bismuth and the grey mottled film of mercury are slowly soluble in the acid, and untouched by bleaching-powder.
The black films of tin, lead and cadmium dissolve at once in the acid, the lead film being also soluble in bleaching-powder.
