Ordinary commercial zinc is far from being pure. The chemically pure metal is expensive. When impure zinc is used, small closed circuits are formed between the particles of foreign matter and the particles of zinc. This local action, which takes place even when the circuit of the cell or battery is broken, rapidly destroys the zinc plate and contributes nothing to the general current. This waste, which would not occur if pure zinc were used, is prevented by frequently amalgamating the zinc. This is done by cleaning the plate in dilute acid and then rubbing it with mercury. (a.) The method of amalgamating battery zincs practised by the author is as follows: In a glass vessel placed in hot water, dissolve 15 cu. cm. of mercury in a mixture of 170 cu. cm. of strong nitric acid and 625 cu. cm. of hydrochloric (muriatic) acid. When the mercury is dissolved, add 830 cu. cm. of hydrochloric acid. When the liquid has cooled, immerse the battery zinc in it for a few minutes, remove and rinse thoroughly with water. The liquid may be used over and over until the mercury is exhausted. The quantity here mentioned will suffice for 200 ordinary zincs or more. Keep the liquid, when not in use, in a glass-stoppered bottle.