van Helmont, Jan

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van Helmont, Jan

Flemish Physician and Chemist 1579-1644

Renowned physician and chemist Jan van Helmont was born into the Flemish gentry in 1579. He received his medical degree at the age of twenty, then proceeded to revolutionize the field of plant nutrition. As a young university student first in Belgium, then in Switzerland, France, and England, van Helmont openly rejected the mysticism and superstition prevalent in academia at the time, being especially skeptical of natural magic and magnetic cures.

In all of his attempts to understand "the small things" that at the time were treated with "magic" and magnetism and today are studied with microscopes, van Helmont relied on the principles of balance, experiment, and quantification. Van Helmont applied chemical analysis to smoke, which he produced by burning a variety of solids and fluids. He observed that the vapors that formed when solids were burned were very different from "just air"; these vapors had distinct and unique properties depending on the solid from which they had been derived.

Van Helmont called this class of vapors by the term "gas." He referred to gas as being "wild," stating that this new type of substance "could not be contained by vessels nor reduced into a visible body." Van Helmont described and identified a variety of gases and therefore is credited as the "discoverer" of gas.

Van Helmont's desire to understand the composition of water initially motivated his experiments on plant nutrition. He was the first to use a quantitative and ingeniousexperimental approach to show that plants obtain nutrition from the chemicals in water. Van Helmont planted a young willow plant in a container. The willow shoot weighed 5 pounds and the container (including earth) had a dry weight of 200 pounds. For five years, van Helmont attended his willow plant with great care, watering it as often as necessary. Once those five years were up, van Helmont weighed the shoot. It had gone from 5 pounds to 169 pounds. Meanwhile, the dry weight of the soil had decreased by only 2 ounces. As van Helmont concluded: "There-fore 164 pounds of wood, bark, and root have arisen from water alone." Van Helmont thus demonstrated that the main source of plant nutrition was not the soil, thus countering a widely held belief among his contemporaries.

Ironically, van Helmont, even though he was extremely interested in the air, overlooked the role that air plays in plant nutrition. He had the right idea, but came to the wrong conclusion. It is known now that plants need to get nutrients from water and air in order for carbon fixation to occur.

Van Helmont's radical thinking would eventually land him in some trouble with the Spanish government and Catholic church. In 1625 the General Inquisition of Spain condemned a treatise he had published in 1621, citing van Helmont for 157 counts of heresy, impudence, and arrogance, as well as for association with Lutheran doctrine. He was kept under house arrest for years, and, perhaps because of this experience, published little of his work. When he was dying in 1644, he asked his son to edit and publish his works.

see also Physiologist; Physiology; Physiology, History of; Water Movement.

Hanna Rose Shell


Isley, D. "Helmont." One Hundred and One Botanists. Ames, IA: Iowa State University Press, 1994.

Morton, A.G. "J. B. Van Helmont." History of Botanical Science. London: Academic Press, 1981.

Pagel, W. "J. B. Van Helmont." Dictionary of Scientific Biography 6 (1972): 253-59.

van Helmont, Jan

views updated

van Helmont, Jan

Flemish physician and chemist

Jan van Helmont was an early pioneer in the study of gases, and performed numerous chemical experiments, including an analysis of smoke, distinguishing it from ordinary air by the particles it contained. However, van Helmont is best known for a single experiment demonstrating that the weight a plant gains during growth is not due to absorption of an equal amount of soil, but instead is due (at least in part) to water.

Van Helmont undertook his famous experiment in plant growth, in part, to learn more about water. In this experiment, he carefully weighed a young willow shoot, and then planted it in a large container whose soil he had also carefully dried and weighed. He watered the willow as needed for five years, and then reweighed both the willow and the soil. The willow had grown from 2.2 kilograms (5 pounds) to 77 kilograms (169 pounds), while the dry weight of the soil had lost only 57 grams (2 ounces). In this way, van Helmont demonstrated that plants do not simply take up soil as they grow, and concluded that water was the sole source of this increased weight. However, van Helmont did not suspect that gases in the air might contribute to plant growth, a fact demonstrated by Nicolas de Saussure more than one hundred years later.

see also Soil; Water

Richard Robinson


Isley, D. "Helmont." In One Hundred and One Botanists. Ames, IA: Iowa State University Press, 1994.

Pagel, W. "J. B. Van Helmont." In Dictionary of Scientific Biography, Vol. 6. New York: Scribner's, 1972.