Proust, Joseph Louis

Proust, Joseph-Louis (1754-1826) French chemist who studied how elements combined to form molecules and formulated the law of definite proportions, which states that regardless of the way a compound is prepared, it always contains the same elements in the same proportions. 

Nickel in Meteorites. Centuries before the discovery of nickel, primitive peoples shaped meteoric iron into implements and swords and appreciated the superiority of this Heaven-sent metal (125). In 1777 J. K. F. Meyer of Stettin noticed that when he added sulfuric acid to some native iron which P. S. Pallas had found in Siberia, he obtained a green solution which became blue when it was treated with ammonium hydroxide. In 1799 Joseph-Louis Proust detected nickel in meteoric iron from Peru (126). This grayish white native iron had been observed by Rubin de Celis. Since it did not rust, it was sometimes mistaken for native silver. 

The trend was definitely toward the principle of fixed composition, but the empirical evidence in its support was still unreliable and allowed room for the doubts of the honest sceptic. Credit is usually given to Joseph-Louis Proust for bringing the law of definite proportions into the continuing consciousness of the chemical community. Proust thought his data justified the assumption of fixed composition and took it as a firm operating principle, very much as Lavoisier had assumed the conservation principle as an axiom. For example, Proust claimed that the quantity of copper oxide prepared from copper carbonate was always the same whatever process used, and that every chemical entity was characterized by a fixed composition. 

The laws of definite and multiple proportions are also associated with Dalton, for they can be explained by his atomic hypothesis. The law of definite proportions or of constant composition had previously been proposed in the work of Jeremias Richter and Joseph-Louis Proust. The law of multiple proportions came to be regarded as an empirical law quite independent of its relation to the atomic hypothesis or perhaps as an empirical law that inspired the atomic hypothesis however, Roscoe and Harden have shown that in Dalton s mind it was a testable prediction which followed from the atomic hypothesis 4). 

By then the French chemist, Joseph Louis Proust, had discovered that whenever elements form compounds these are always of a very definite composition —- the Law of Definite Composition. Water molecules, for example, always contain the same number of hydrogen and oxygen atoms. And Dalton had found that when two elements combine in different ways they do this in simple proportions — the Law of Multiple Proportions. One atom of carbon and one atom of oxygen make carbon monoxide one atom of carbon and two atoms of oxygen make carbon dioxide. 

In the late eighteenth century, Joseph Louis Proust, a French chemist, analyzed many samples of copper(II) carbonate, CuC03. He found that the samples contained the same proportion of copper, carbon, and oxygen, regardless of the source of the copper(II) carbonate. This discovery led Proust to propose the law of definite proportions the elements in a chemical compound are always present in the same proportions by mass. 

The contending scientist, Joseph Louis Proust, was at that time teaching chemistry in Spain. He had made numerous experiments to determine the proportions in which various compounds were formed, and had arrived at the conclusion that Berthollet was entirely mistaken. Proust repeated the experiments of his countryman. He used the purest of chemicals and the most accurate apparatus. He took every precaution to avoid error, and found mistakes in Berthollet s determination. Besides, Berthollet had used substances like glass, alloys, and mixtures of various liquids, all of which were not true compounds. For eight years Proust tried to persuade the scientific world, and especially the followers of Berthollet, that when elements combined to form chemical compounds, the elements united in definite proportions by weight—a theory advanced... 

The law of constant proportions was enunciated by the French chemist Joseph Louis Proust (1754-1826) in 1799. For several years it was attacked vigorously by Claude Louis Bertholet (1748-1822), who contended that the composition of the compound depended on the way in which it was prepared. Proust defended the law by pointing out that the materials described by Bertholet as exceptions were mixtures (of different lead oxides, of mercurous salts and mercuric salts, etc.) or solutions. Accurate data showing constancy of composition of the substances investigated to 1 part in 100,000 were first reported by the Belgian chemist J. S. Stas in 1865. 

Joseph Louis Proust (1754-1826). French chemist. Proust was die first person to isolate sugar from grapes. 

When Joseph Louis Proust (1754-1826) took up pharmaceutical studies, he followed both a natural inclination for analytical chemistry and the family tradition, his father having a pharmacy in Anger where he got his first training. 

The works performed by Antoine Francois de Fourcroy (1755-1809), Louis Nicolas Vauquelin (1763-1829), Joseph Louis Proust (1754-1826) and Jons Jakob Berzelius (1779-1848) introduced new concepts in chemistry. Gay-Lussac published his Law of Combining Volumes in 1809, the year after John Dalton (1766-1844) had proposed his Atomic Theory of Matter around 1803. It was left to Amedeo Avogadro (1776-1856) to take the first major step in rationalizing Gay-Lussac s results two years later. 

The law of definite proportions—The first of these chemical reaction laws, the law of constant or definite proportions, was recognized by Joseph Louis Proust (1754—1826) in 1797, who stated it in 1799 as follows ... 

Opposed to Berthollet s view was the opinion of Joseph Louis Proust (1754-1826), who did his work in Spain, safe (for a time) from the upheavals of the French Revolution. Using painstakingly careful analysis, Proust showed, in 1799, that copper carbonate, for instance, contained definite propor-... 

French chemist Joseph Louis Proust (1754—1826) first stated the law in about 1800. Although this law has been known for 200 years, the belief persists among some people that a fundamental difference exists between compounds prepared in the laboratory and the corresponding compounds found in nature. However, a pure compound has the same composition and properties regardless of its source. Both chemists and nature must use the same elements and operate under the same natural laws. When two materials differ in composition or properties, either they are composed of different compounds or they differ in purity. 

Another chemical law known in Dalton s time had been proposed by Joseph Louis Proust (1754—1826) as a result of his analyses of minerals. Proust found that a particular compound, once purified, always contained the same elements in the same ratio by mass. One such study, which Proust... 

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