Van Helmont’s Experiment Jan Baptista van Helmont, Jan also spelled Joannes (born Jan. 12, 1580 [1579, Old Style], Brussels [Belg.]—died Dec. 30, 1644, Vilvoorde, Spanish Netherlands [Belg.]) He was a Flemish physician, philosopher, mystic, and chemist who recognized the existence of discrete gases and identified carbon dioxide. In what is perhaps his best-known experiment, van Helmont placed a 5-pound (about 2.2-kg) willow in an earthen pot containing 200 pounds (about 90 kg) of dried soil, and over a five-year period he added nothing to the pot but rainwater or distilled water. After five years, he found that the tree weighed 169 pounds (about 77 kg), while the soil had lost only 2 ounces (57 grams). He concluded that pounds of wood, barks, and roots “164 arose out of water only,” and he had not even included the weight of the leaves that fell off every autumn. Obviously, he knew nothing of photosynthesis, in which carbon from the air and minerals from the soil are used to generate new plant tissue, but his use of the balance is important; he believed that the mass of materials had to be accounted for in chemical processes. Van Helmont was the first to recognize that many reactions produce substances that are, in his words, “far more subtle or fine…than a vapor, mist, or distilled oiliness, although…many times thicker than air.” To describe these substances, he invented the word gas (from and identified a number of gases, “chaos”) including carbon dioxide. (Ironically, carbon dioxide was the major substance overlooked in his willow tree experiment.) His work on gases was taken up by the British natural philosopher Robert Boyle, among others, and the word gas, after being reintroduced by the 18th-century French chemist Antoine-Laurent Lavoisier, became a standard chemical term.
Van Helmont’s Experiment Jan Baptista van Helmont, Jan also spelled Joannes (born Jan. 12, 1580 [1579, Old Style], Brussels [Belg.]—died Dec. 30, 1644, Vilvoorde, Spanish Netherlands [Belg.]) He was a Flemish physician, philosopher, mystic, and chemist who recognized the existence of discrete gases and identified carbon dioxide. In what is perhaps his best-known experiment, van Helmont placed a 5-pound (about 2.2-kg) willow in an earthen pot containing 200 pounds (about 90 kg) of dried soil, and over a five-year period he added nothing to the pot but rainwater or distilled water. After five years, he found that the tree weighed 169 pounds (about 77 kg), while the soil had lost only 2 ounces (57 grams). He concluded that “164 pounds of wood, barks, and roots arose out of water only,” and he had not even included the weight of the leaves that fell off every autumn. Obviously, he knew nothing of photosynthesis, in which carbon from the air and minerals from the soil are used to generate new plant tissue, but his use of the balance is important; he believed that the mass of materials had to be accounted for in chemical processes. Van Helmont was the first to recognize that many reactions produce substances that are, in his words, “far more subtle or fine…than a vapor, mist, or distilled oiliness, although…many times thicker than air.” To describe these substances, he invented the word gas (from “chaos”) and identified a number of gases, including carbon dioxide. (Ironically, carbon dioxide was the major substance overlooked in his willow tree experiment.) His work on gases was taken up by the British natural philosopher Robert Boyle, among others, and the word gas, after being reintroduced by the 18th-century French chemist Antoine-Laurent Lavoisier, became a standard chemical term.