51.1 MB (3.6 MB compressed)
3921 x 4555 pixels
33.3 x 38.6 cm ⏐ 13.1 x 15.2 in (300dpi)
SHEILA TERRY / SCIENCE PHOTO LIBRARY SHEILA TERRY / SCIENCE PHOTO LIBRARY
This apparatus was used to purify sulphur obtained from the vicinity of the Italian volcanoes at Etna in Sicily and the solfatara of Pozzuoli near Naples in the early 19th century. This sulphur contains many impurities, for example soil, gravel, sand, natural sulphides, etc. Purification consists of heating the sulphur to the temperature where it becomes volatile thus enabling the process of sublimation to occur. In this apparatus, two earthenware or fire-clay jars A A' are placed in the furnace which is lighted when the jars have been filled with the sulphur and their tops sealed (luted). Sublimation occurs when heated sufficiently for the sulphur to vaporise. The vapour passes into the condensing jars B B' where it solidifies into a pure state.
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