Joseph Louis Proust, one of the founders of modern chemistry

September 26, 1754, Angers (France) – July 5, 1826, Angers (France)

He combined his studies at the Oratorian College with work at the family pharmacy, where he acquired his first knowledge of chemistry and herbalism, even participating in the creation of a botanical garden in the city.

At the age of 21, he obtained the position of Chief Pharmacist at the Hospital de la Salpétrière in Paris (France) by competitive examination. During his stay in this city, he became friends with the chemist Antoine-Laurent de Lavoisier and with the pharmacist Pilâtre de Rozier (pioneer of ballooning), together with whom he made a balloon ascent on June 23, 1784, in the presence of King Louis XVI of France and King Gustaf III of Sweden.

Between 1778 and 1780, he taught Chemistry and installed the Chemistry and Metallurgy laboratories at the Real Seminario de Vergara (Guipúzcoa, Spain), which was founded by the Real Sociedad Bascongada de Amigos del País.

In 1786, the Spanish government, following a recommendation from Lavoisier and through an agreement between King Carlos III and Louis XVI, hired Proust to teach chemistry in Madrid. After a brief stay, he took charge of the Chemistry and Metallurgy classes at the Royal College of Artillery in Segovia until 1799.

The laboratory of the Royal College was equipped with the best means of the time and in it, Proust carried out numerous experiments on the composition of substances that led him to enunciate and disseminate the Law of Definite Proportions: "Substances are combined in constant proportions and concrete” between 1794 and 1799. This law led him into a public dispute with another French chemist, Claude Louis Berthollet, who defended the variability in the composition of compounds depending on their synthesis method.

During his stay in Segovia, Proust directed and made a great contribution to the publication of the "Annals of the Royal Laboratory of Chemistry of Segovia", whose two complete volumes appeared in 1791 and 1795.

In 1799, the government decided to merge the Chemistry laboratories of the Ministries of State and Finance into what would become the Royal Laboratory of Madrid and appointed Proust director. That same year, Proust participated in the writing and editing of the first Spanish magazine devoted entirely to the natural sciences, "Annals of Natural History" which, in 1801, was renamed "Annals of Natural Sciences". It was a very fruitful time in which he was able to combine research, teaching and in which he published the books "Inquiries on copper tinning, tinware and glaze" (1803) and "Memoire sur le sucre des raisins" (1808). ). His studies on sugar are especially relevant.

Proust enjoys freedom of research and prestige in Spain, he even rejects a substantial offer from a French company in 1806, but at the end of that same year he must travel to France for family reasons and the political situation prevents his return to Madrid, since, between other issues, the abdication of Carlos IV of Spain in 1808 deprives the laboratory of funds.

He settles in Craon (France), where he continues to work and maintain his controversy with Berthollet.

In 1811, Proust got the prestigious Swedish chemist Jöns Jacob Berzelius to recognize his statement, which laid the foundations for the establishment of Dalton's atomic theory.

In 1815, he published "Recueil des memoires relatifs a la poudre a canon", and in 1816 he entered the French Academy of Sciences. Retired by Louis XVIII of France in 1824, he published “Essai sur une des causes qui peuvent amener la formation du calcul”, two years before his death.

Part of Proust's legacy, such as the Artillery Academy Laboratory and Library, was lost during the French invasion.