Metal Ingots (30) in box

This wooden box contains fourteen pairs of pieces of zinc, copper, lead, steel and brass. Each piece of metal has a threaded hole at one side. Most pieces show traces of spark discharges. Probably, the pieces of metal were used by the first director of the museum, Martinus van Marum, in his experiments in which he investigated the effect of an electric charge on metals and metal oxides. In his experiments he discovered that metal oxides are converted into metals by an electric charge, and vice versa: metal can be converted into metal oxide. Van Marum could not explain this phenomenon until he came into contact with François Lavoisier. This French physicist had discovered that oxygen is absorbed during calcification. Elaborating on Lavoisier's discovery, Van Marum found that the electric discharge decomposes metal oxides into metal and oxygen and subsequently, that the high temperatures formed during the process could oxidise the metals again.