Helmont, Jan Baptista van (yän bäptĭsˈtä vän hĕlˈmônt) [key], 1577–1644, Flemish physician, chemist, and physicist. He attributed physiological changes to chemical causes, but his conclusions were colored by his speculative mysticism. He discovered carbon dioxide, distinguished gases as a class of substances (as contrasted with solids and liquids), and is credited with introducing the term gas in its present scientific sense. His chief work is Ortus medicinae (1648).
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