ABSTRACT
A hundred years ago the range of non-ferrous metals extracted from the earth was in the main confined to copper, lead, tin and zinc, which had been produced from time immemorial by smelting the ores with charcoal or coal. Nickel and the light metals aluminium and magnesium are products of more recent times, the two latter having to await the advent of electrical generation before their production achieved any real prominence. Due to advances in engineering and the science of metallurgy, tremendous progress both in the method and scale of smelting has characterized the last hundred years. Several different designs of pot are available for carrying out the hot-dip treatment. Heating of pots is effected by oil, gas or immersion-type electrical heaters. The 'single sweep' machine often known as the Aetna or American-type machine follows the fundamental designs of that described by S. A. Davies in a USA. patent issued in 1925.
