Starting in the second half of the 15th century, the Medici Court attracted many alchemists to Florence, providing them with avant-garde factories and laboratories. Of the immense Medicean collection of alchemists' instrumentation, very little has survived: only a few glass vessels used by the Accademia del Cimento (1657-1667), and the great burning lens donated by Benedetto Bregans in 1697 to Cosimo III (1642-1723) to experiment with the combustion of gemstones, displayed here on the stand at the centre of the room. On the wall behind it hangs the "table of chemical affinities", emblematic testimony to the Lorraine dynasty's interest in pharmaceutical chemistry. The numerous instruments used in theoretical and experimental chemistry also come from the Lorraine collection. Atmospheric chemistry especially, with the discovery of hydrogen and a method for determining the amounts of oxygen and other gases present in the atmosphere, favoured the development of new measuring instruments, such as Alessandro Volta's (1745-1827) electric pistol and hydrogen lamp, Felice Fontana's (1730-1805) evaerometro, and Marsilio Landriani's (1751-1815) eudiometer.