Of the ordinary manufacturing metals lead is the softest and possesses the least strength. It is very heavy, being more than four times the weight of aluminium. Its softness renders it particularly suitable for working into the various shapes and forms required by the plumber. It resists the action of sulphuric or hydrochloric acid to a much greater degree than most of the ordinary metals. Nitric acid when strong scarcely attacks it, but when diluted rapidly dissolves the metal. Although lead is practically unacted upon by cold strong acids it is very soon corroded when exposed to an atmosphere containing much carbonic acid. The metal readily flows under pressure in the solid state, hence lead pipes can be formed by squirting from a hydraulic press.