Jean Baptiste André Dumas (French pronunciation: [ʒɑ̃ batist ɑ̃dʁe dyma]; 14 July 1800 – 10 April 1884) was a French chemist, best known for his works on organic analysis and synthesis, as well as the determination of atomic weights (relative atomic masses) and molecular weights by measuring vapor densities.

[4] In 1822, he moved to Paris, acting on the advice of Alexander von Humboldt, where he became professor of chemistry, initially at the Lyceum, later (1835) at the École polytechnique.

He acted as minister of agriculture and commerce for a few months in 1850–1851, and subsequently became a senator, president of the municipal council of Paris, and master of the French mint, but his official career came to a sudden end with the fall of the Second Empire.

Dumas was one of the first to criticise the electro-chemical doctrines of Jöns Jakob Berzelius, which, at the time his work began, were widely accepted as the true theory of the constitution of compound bodies, and opposed a unitary view to the dualistic conception of the Swedish chemist.

The classification of organic compounds into homologous series was advanced as one consequence of his researches into the acids generated by the oxidation of the alcohols.

[10]: 40 In an 1826 paper, he described his method for ascertaining vapour densities, and the redeterminations which he undertook by its aid of the atomic weights of carbon and oxygen proved the forerunners of a long series which included some thirty of the elements, the results being mostly published in 1858–1860.

[12][10]: 122–124 At the Tuileries palace in Paris, guests at a soirée began reacting adversely to a gas suddenly emitted by the candles.

Dumas extended this to a theory (sometimes considered a law) which states that in an organic compound, a hydrogen atom may be substituted for any halogen.

The basis of this theory rests in the natural history of organism classification, which Dumas learned under the botanist de Candolle.