Historical figure · Pearson Edexcel International GCSE revision on Incandio

Jean-Baptiste Dumas

Who Swapped One Atom for Another · Chemist · 1800–1884

Who established in 1834 that chlorine can take the place of the hydrogen in an organic compound, volume for volume — a fact the reigning theory of chemistry declared impossible.

Defend these ideas against Dumas

Incandio is a free revision platform for the Pearson Edexcel International GCSE, and on it a topic counts as mastered only once you have learned it, proved it in questions, taught it back and defended it against the person with the strongest claim on it. Jean-Baptiste Dumas is that person for 2 topics on the course:

• Alkanes — Chemistry
• Working Out Esters, And What They Are For — Chemistry

Who was Dumas?

Dumas was born at Alais in 1800 and apprenticed to an apothecary, went to Geneva as a young man, and was brought to Paris on Alexander von Humboldt's recommendation. He made his early reputation on the density of vapours, a method for getting at atomic weights that was genuinely his own, and on the analysis of organic substances. The work he is remembered for began, according to the story he told, with a complaint from the Tuileries: candles supplied for a royal ball had filled the room with acid fumes. Dumas found that the wax had been bleached with chlorine, that chlorine had entered the wax, and that hydrogen had left it — the acid smell was hydrogen chloride. From that he drew, through the eighteen-thirties, the law of SUBSTITUTION: an element may be replaced in a compound by another, atom for atom, and what results has the same general character. This was not a small claim. Berzelius's dualistic chemistry, which almost everyone held, said that a compound consists of an electrically positive part joined to an electrically negative part, so that swapping positive hydrogen for negative chlorine ought to destroy the compound rather than modify it. Berzelius said publicly that the idea was absurd, and a famous satire circulated purporting to show that by Dumas's method a substance could have every one of its atoms replaced and remain itself. Dumas was right and dualism did not survive it, though the theory of types he built on the ruins was itself replaced within twenty years by structural formulae — which he never really adopted. He was also, and increasingly, a public man: professor, dean, Master of the Mint, Senator, and briefly minister. His treatment of Auguste Laurent, whose ideas he used and whose career he did not help, is the blot on his record. He taught Pasteur. He died in 1884.

Major achievements

• Established the law of substitution in the 1830s, that one element can replace another atom for atom in an organic compound
• Traced the acid fumes from chlorine-bleached candles to hydrogen driven out of the wax
• Developed the vapour-density method for determining atomic weights
• Built the theory of types, which displaced Berzelius's dualism
• Worked with Boullay on the ethers, taking an ester apart into an acid and a hydrocarbon part

Life in brief

• 1800 — Born at Alais: Apprenticed to an apothecary.
• 1826 — The vapour-density method: Atomic weights from the weight of a vapour.
• 1828 — The ethers, with Boullay: An ester taken apart into a hydrocarbon and an acid.
• 1834 — Substitution: Chlorine takes the place of hydrogen, volume for volume.
• 1839 — The theory of types: Berzelius's dualism publicly broken.
• 1868 — Master of the Mint: A chemist at the head of the coinage.
• 1884 — Dies at Cannes: Senator, and thirty years from the bench.

Explore the life of Dumas — five chapters

1. From an Apothecary's Counter to the Institut — Alais, Geneva, and Humboldt's letter
2. The Candles at the Ball — A complaint from the Tuileries
3. Berzelius Says It Is Absurd — A theory that could not survive a fact
4. Auguste Laurent — The blot on the record
5. A Chemist at the Mint — What happens when a scientist becomes a minister

Read the five-chapter life of Jean-Baptiste Dumas →

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