Laurent , Auguste

(1807–1853) French chemist

The son of a mining engineer, Laurent was born at La Folie in France. He was educated at the mining school in Paris and worked for some time as a mining engineer before becoming an assistant to Jean Dumas in Paris. He was appointed professor of chemistry at Bordeaux in 1838. He returned to Paris in 1846 but he found it difficult to find employment, largely, it is thought, because of his unpopular chemical views. He worked for a short time as an assayer in the Mint in 1848 and later at Sèvres. Laurent worked closely with Charles Gerhardt, so that it is not always possible to separate their ideas very precisely. His collected papers were published posthumously in his Methode de Chimie(1854; Method of Chemistry).

Dumas had formulated his theory of substitution in 1834. According to this theory hydrogen can be actually removed from certain substances and replaced by other substances. Laurent used this to demolish Berzelius's electrochemical theory, pointing out that in the synthesis of trichloroacetic acid the electronegative chlorine replaces the electropositive hydrogen. Laurent's powerful arguments against the orthodox chemistry won him little support and less popularity.

With Gerhardt, he introduced type theory, in which organic compounds are recognized as having common structural features by which they can be assigned to various types. Thus alcohol, water, ammonia, ether, and numerous other types were distinguished. Type theory, soon to be superseded by the chemistry of Stanislao Cannizzaro and August Kekulé;, was valuable in that it provided a tolerable basis of classification and some understanding of the chemistry of organic compounds.

It was Laurent who saw that chemists must distinguish clearly between atoms, molecules, and equivalents. He regarded the molecules of hydrogen, oxygen, and others as consisting of two atoms, forming what he called an ‘homogeneous compound’, which, by double decomposition, could form ‘heterogeneous compounds’. This provided a sound base for the accurate determination of atomic weights. Unfortunately, Laurent did not have the funds, facilities, or time to provide the necessary experimental support for his theories, and without the essential laboratory work his views were ignored.