Helmont, Jan Baptista van

Helmont, Jan Baptista van (1580-1644), Belgian doctor and chemist, the first scientist to distinguish between gases and air. He pioneered in experimentation and an early form of biochemistry, called iatrochemistry. Helmont believed that the basic elements of the universe are air and water. He believed that plants are composed only of water and claimed to have proved this theory by planting a willow of known weight in soil of known weight and weighing the willow and the soil five years later. The willow had gained 76.7 kg (169 lb), and the soil had lost practically no weight. He suggested that the willow had gained weight by taking in water alone. (For the modern explanation of his experiment, see Photosynthesis). His works were published posthumously in 1648 as Ortus Medicinae; vel, Opera et Opuscula Omnia (The Fount of Medicine; or, Complete Works).