Jan Baptist van Helmont (January 12, 1577 – December 30, 1644) was a Flemish chemist, physiologist, and physician. Alternative given names for him are given as Jean-Baptiste van Helmont, Johannes Baptista van Helmont, and Joan Baptista van Helmont. He worked during the years just after Paracelsus and iatrochemistry, and is sometimes considered to be "the founder of pneumatic chemistry". Van Helmont is remembered today largely for his ideas on spontaneous generation, his 5-year tree experiment, and his introduction of the word "gas" into the vocabulary of scientists.

A member of a noble family, van Helmont was born at Brussels in 1577. He was educated at Louvain, and after ranging restlessly from one science to another and finding satisfaction in none, turned to medicine, in which he took his doctor's degree in 1599. The next few years he spent in traveling through Switzerland, Italy, France, and England.

Returning to his own country, van Helmont was at Antwerp at the time of the great plague in 1605, and having contracted a rich marriage settled in 1609 at Vilvoorde, near Brussels, where he occupied himself with chemical experiments and medical practice until his death on the 30th of December 1644.

Van Helmont presented contradictions. On the one hand he was a disciple of Paracelsus (though he scornfully repudiates his errors as well as those of most other contemporary authorities), a mystic with strong leanings to the supernatural, an alchemist who believed that with a small piece of the philosopher's stone he had transmuted 2000 times as much mercury into gold. On the other hand he was touched with the new learning based on experiment that was producing men like William Harvey, Galileo Galilei and Francis Bacon.

Van Helmont deserves to be regarded as the founder of pneumatic chemistry, as he was the first to understand that there are gases distinct in kind from atmospheric air. The very word "gas" he claimed as his own invention, and he perceived that his "gas sylvestre" (carbon dioxide) given off by burning charcoal, was the same as that produced by fermenting must and that which sometimes renders the air of caves unbreathable.

For van Helmont, air and water were the two primitive elements. Fire he explicitly denied to be an element, and earth is not one because it can be reduced to water.

Van Helmont was a careful observer of nature, and an exact experimenter who in some cases realized that matter can neither be created nor destroyed. He performed an experiment to determine where plants get their mass. He grew a willow tree and meticulously measured the amount of soil, the weight of the tree and the water he added. After five years the plant had gained about 170 pounds. Since the amount of soil was basically the same as it had been when he started his experiment, he deduced that the tree’s weight gain had come from water. Since it had received nothing but water and the soil weighed practically the same as at the beginning, he argued that the increased weight of wood, bark and roots had been formed from water alone.

It was an old idea that the processes of the living body are fermentative in character, but he applied it more elaborately than any of his predecessors. For him digestion, nutrition and even movement are due to ferments, which convert dead food into living flesh in six stages. But having got so far with the application of chemical principles to physiological problems, he introduces a complicated system of supernatural agencies like the archei of Paracelsus, which preside over and direct the affairs of the body. A central archeus controls a number of subsidiary archei which move through the ferments, and just as diseases are primarily caused by some affection (exorbitatio) of the archeus, so remedies act by bringing it back to the normal.

At the same time chemical principles guided him in the choice of medicines -- undue acidity of the digestive juices, for example, was to be corrected by alkalines and vice versa; he was thus a forerunner of the iatrochemical school, and did service to medicine by applying chemical methods to the preparation of drugs.

Over and above the archeus, he taught that there is the sensitive soul which is the husk or shell of the immortal mind. Before the Fall the archeus obeyed the immortal mind and was directly controlled by it, but at the Fall men also received the sensitive soul and with it lost immortality, for when it perishes the immortal mind can no longer remain in the body.

In addition to the archeus, which he described as "aura vitalis seminum, vitae directrix", Van Helmont had other governing agencies resembling the archeus which were not always clearly distinguished from it. From these he invented the term blas, defined as the "vis motus tam alterivi quam localis." Of blas there were several kinds, e.g. blas humanum and blas meteoron; the heavens he said "constare gas materiâ et blas efficiente."

He was a faithful Catholic, but incurred the suspicion of the Church by his tract De magnetica vulnerum curatione (1621), which was thought to derogate from some of the miracles. His works were collected and published in Amsterdam as Ortus medicinae, vel opera et opuscula omnia in 1648 by his son Franz Mercurius van Helmont, in whose own writings (e.g. Cabbaiah Denudata (1677) and Opuscula philosophica (1690)) mystical theosophy and alchemy appear in confusion.

One area on which Van Helmont wrote extensively was the subject of digestion. In Oriatrike or Physics Refined (1662, English translation of Ortus medicinae ...), van Helmont addresses earlier ideas on the subject, such as that food was digested due to the body's internal heat. If such was the case, van Helmont argued, how could cold-blooded animals live? His own opinion was that digestion was aided by a chemical reagent, or "ferment", within the body, such as inside the stomach. Harré suggests that in this way, van Helmont's idea was "very near to our modern concept of an enzyme." Van Helmont proposed and described six different stages of digestion.; originally published in 1901 by Cambridge University Press</bgref>

In 2003, the historian Lisa Jardine claimed a recently discovered portrait represented Robert Hooke. However, Jardine's hypothesis was disproved by William Jensen of the University of Cincinnati and by the German researcher Andreas Pechtl of Johannes Gutenberg University of Mainz. The portrait in fact depicts Jan Baptist van Helmont.

* Redgrove, I. M. L. and Redgrove, H. Stanley (2003). Joannes Baptista van Helmont: Alchemist, Physician and Philosopher, Kessinger Publishing.

* Pagel, Walter (2002). Joan Baptista Van Helmont: Reformer of Science and Medicine, Cambridge University Press.

* The Moldavian prince and scholar, Dimitrie Cantemir, wrote a biography of Helmont, which is now difficult to locate.

* Identification of a portrait of van Helmont - earlier misidentified as a picture of Robert Hooke.

* Ferguson, John (1906). Johann Baptiste van Helmont, Bibliotheca Chemica: A Catalogue of the Alchemical, Chemical and Pharmaceutical Books in the Collection of the Late James Young of Kelly and Durris, Esq., LL.D., F.R.S., F.R.S.E., Glasgow: James Maclehose and Sons, page 381.

* Moore, F. J. (1918). A History of Chemistry, New York: McGraw-Hill.

* Thomson, Thomas (1830). The History of Chemistry, London: Henry Colburn and Richard Bentley.