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Portrait of the Belgian alchemist and chemist Jan Baptista van Helmont (1579-1644). Helmont believed in alchemy and his entire life was characterised by the search for the philosopher's stone which was believed to be an elixir of eternal life. However his work represented a transition from alchemy to chemistry since he always practised the experimental method. Helmont also believed that all matter was based on the two basic elements air and water. To prove this he set up an experiment in which he grew a willow tree for five years. He showed that the increase of its weight did not come from the earth and thought it came entirely from the rainwater he had given to the tree.
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