Joannes Baptiste van Helmont and Franciscus Mercurius van Helmont, 17th century.
© Science Museum / Science & Society Picture Library
Belgian chemist and physician Joannes Baptiste van Helmont (1579-1644) (left), invented the word 'gas', and was the first scientist to show that digestion was asociated with acid in the stomach. He was also the first to take the melting point of ice and the boiling point of water as standards for temperature. Having himself worked under Paracelsus, van Helmont's work was to greatly influence future scientists. His most famous published work is 'Ortus Medicinae'. His youngest son, Franciscus Mercurius van Helmont (1614-1699) (right) was a teacher of the deaf.