II-3 Group 2: Joseph Louis Proust

Joseph Louis Proust

Born: September 26,1754 in Angers, France

Died: July 5,1826 Paris, France

Occupation: French Chemist

Biography

His Father served as an apthecary in Angers.Joseph studied chemistry in his father's shop and later came to Paris where he gained the appointment of apothecary in chief to the Salpetriere.

Under Carlos IV's influence Proust went to Spain. There he taught at the Chemisrty School in Segovia and at the University of Salamanca. But when Napoleon invaded Spain, they burned Proust's laboratory and forced him back to France.

In 1785 Proust accepted a lucrative teaching position offered by the Spanish government. He spent the next twenty years in Spain at various posts in Madrid and Segovia, thus missing the French Revolution and the rise to power of Napoleon Bonaparte (1769-1821). In addition to teaching chemistry, Proust worked for the Spanish government, frequently conducting geological surveys and analyzing the nation's mineral resources.

Proust’s largest accomplishment into the realm of science was disproving Berthollet with the law of definite proportions, which is sometimes also known as Proust's Law. Proust studied copper carbonate, the two tin oxides,and the two iron sulfides to prove this law. He did this by making artificial copper carbonate and comparing it to natural copper carbonate Between the two types of the other compounds, Proust showed that no intermediate indeterminate compounds exist between them. Proust published this paper in 1794, but the law was not accepted until 1811, when the Swedish chemist Jöns Jacob Berzelius gave him credit for it.

Atomic Theory

The gold foil experiment

Top: Expected results: alpha particles passing through the plum pudding model of the atom with negligible deflection.

Bottom: Observed results: a small portion of the particles were deflected by the concentrated positive charge of the nucleus
 
 
 
 
 
Law of Definite Proportion
In chemistry, the law of definite proportions and also the elements, sometimes called Proust's Law, states that a chemical compound always contains exactly the same proportion of elements by mass. An equivalent statement is the law of constant composition, which states that all samples of a given chemical compound have the same elemental composition.
 
History
This observation was first made by the French chemist Joseph Proust based on several experiments conducted between 1798 and 1804. Based on such observations, Proust made statements like this one, in 1806:
"I shall conclude by deducing from these experiments the principle I have established at the commencement of this memoir, viz. that iron like many other metals is subject to the law of nature which presides at every true combination, that is to say, that it unites with two constant proportions of oxygen. In this respect it does not differ from tin, mercury, and lead, and, in a word, almost every known combustible."
The law of definite proportions might seem obvious to the modern chemist, inherent in the very definition of a chemical compound. At the end of the 18th century. The first proposed, it was a controversial statement and was opposed by other chemists, most notably Proust's fellow Frenchman Claude Louis Berthollet, who argued that the elements could combine in any proportion. The very existence of this debate underscores that at the time, the distinction between pure chemical compounds and mixtures had not yet been fully developed. The law of definite proportions contributed to, and was placed on a firm theoretical basis by, the atomic theory that John Dalton promoted beginning in 1803, which explained matter as consisting of discrete atoms, that there was one type of atom for each element, and that the compounds were made of combinations of different types of atoms in fixed proportions
A related early idea was Prout's hypothesis, which supposed that hydrogen was the only functional unit, and was related to the whole number rule, which was the rule of thumb that atomic masses were whole number multiples of the mass of hydrogen. This was later rejected in the 1820s and 30s following more refined measurements of atomic mass, notably by Jöns Jacob Berzelius, which revealed in particular that the atomic mass of chlorine was 35.45, which was incompatible with the hypothesis.
 
By: Arcilla, Atis, Bongato, Valenzuela