Helmont, JEAN BAPTISTE VAN, Belgian chemist, was born at Brussels in 1577. At Louvain he studied medicine and its cognate sciences, but soon turned aside from them to throw himself into the movement known as mysticism, to study the works and practise the precepts of Thomas à Kempis and Johann Tauler. Then, falling in with the writings of Paracelsus, he came back to his first love, and began to study chemistry and natural philosophy. After spending several years in France, Switzerland, and England, in 1605 he returned to Amsterdam, married Margaret van Ranst, a noble lady of Brabant, and in 1609 settled down at his estate near Vilvorde, where he spent the remainder of his life in chemical investigations of various kinds. He died 30th December 1644. In spite of much theosophical mistiness and much alchemical error, Van Helmont is regarded by some historians of chemistry as the greatest chemist who preceded Lavoisier. He was the first to point out the imperative necessity for employing the balance in chemistry, and by its means showed, in many instances, the indestructibility of matter in chemical changes. He paid much attention to the study of gases, and is supposed to have been the first to apply the term gases to elastic aeriform fluids. Of these gases he distinguished several kinds. He was also the first to take the melting-point of ice and the boiling-point of water as standards for the measurement of temperature. It is in his works that the term saturation is first employed, to signify the combination of an acid with a base; and he was one of the earliest investigators of the chemistry of the fluids of the human body. Along with other physiologists of his day, he speculated much on the seat of the soul, which he placed in the stomach. An account of his contributions to the knowledge of chemistry will be found in the Histories of
Chemistry by Kopp and Höfer. His works, entitled Ortus Medicinæ, were published by his son four years after his death, and frequently since then. See Rommelaere, Études sur Van Helmont (Brussels, 1868).