Joseph Proust
Overview
 
Joseph Louis Proust was a French
French people
The French are a nation that share a common French culture and speak the French language as a mother tongue. Historically, the French population are descended from peoples of Celtic, Latin and Germanic origin, and are today a mixture of several ethnic groups...

 chemist
Chemist
A chemist is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties such as density and acidity. Chemists carefully describe the properties they study in terms of quantities, with detail on the level of molecules and their component atoms...

.
Joseph L. Proust was born on September 26, 1754 in Angers
Angers
Angers is the main city in the Maine-et-Loire department in western France about south-west of Paris. Angers is located in the French region known by its pre-revolutionary, provincial name, Anjou, and its inhabitants are called Angevins....

, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

. His father served as an apothecary 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 http://55.1911encyclopedia.org/P/PR/PROUST_JOSEPH_LOUIS.htm.
Encyclopedia
Joseph Louis Proust was a French
French people
The French are a nation that share a common French culture and speak the French language as a mother tongue. Historically, the French population are descended from peoples of Celtic, Latin and Germanic origin, and are today a mixture of several ethnic groups...

 chemist
Chemist
A chemist is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties such as density and acidity. Chemists carefully describe the properties they study in terms of quantities, with detail on the level of molecules and their component atoms...

.

Life

Joseph L. Proust was born on September 26, 1754 in Angers
Angers
Angers is the main city in the Maine-et-Loire department in western France about south-west of Paris. Angers is located in the French region known by its pre-revolutionary, provincial name, Anjou, and its inhabitants are called Angevins....

, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

. His father served as an apothecary 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 http://55.1911encyclopedia.org/P/PR/PROUST_JOSEPH_LOUIS.htm. He also taught chemistry with Pilâtre de Rozier
Pilâtre de Rozier
Jean-François Pilâtre de Rozier was a French chemistry and physics teacher, and one of the first pioneers of aviation. He and the Marquis d'Arlandes made the first manned free balloon flight on 21 November 1783, in a Montgolfier balloon. He later died when his balloon crashed near Wimereux in...

, a famous aeronaut.

Under Carlos IV's influence Proust went to Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...

. There he taught at the Chemistry School in Segovia
Segovia
Segovia is a city in Spain, the capital of Segovia Province in the autonomous community of Castile and León. It is situated north of Madrid, 30 minutes by high speed train. The municipality counts some 55,500 inhabitants.-Etymology:...

 and at the University of Salamanca
University of Salamanca
The University of Salamanca is a Spanish higher education institution, located in the town of Salamanca, west of Madrid. It was founded in 1134 and given the Royal charter of foundation by King Alfonso IX in 1218. It is the oldest founded university in Spain and the third oldest European...

.
But when Napoleon invaded Spain, they burned Proust's laboratory and forced him back to France. On July 5 1826 he died in Angers, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

.

Proust's best known work was derived from a controversy with chemist C.L. Berthollet. Berthollet did not believe that substances always combine in constant and definite proportions
Law of definite proportions
In chemistry, the law of definite proportions, 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...

 as Proust did. Proust eventually was able to prove Berthollet wrong in 1799 and published his own hypothesis.

Chemistry studies

Proust’s largest accomplishment into the realm of science was disproving Berthollet with the law of definite proportions
Law of definite proportions
In chemistry, the law of definite proportions, 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...

, 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
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 carbonate and comparing it to natural copper carbonate. With this he showed that each had the same proportion of weights between the three elements involved (Cu
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

, C
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

, O
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

). Between the two types of the other compounds
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

, 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.

There are, however, exceptions to the Law of Definite Proportions
Law of definite proportions
In chemistry, the law of definite proportions, 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...

. An entire class of substances does not follow this rule. The compounds are called non-stoichiometric compound
Non-stoichiometric compound
Non-stoichiometric compounds are chemical compounds with an elemental composition that cannot be represented by a ratio of well-defined natural numbers, and therefore violate the law of definite proportions. Often, they are solids that contain crystallographic point defects, such as interstitial...

s, or Berthollides, after Berthollet. The ratio of the elements present in the compound can fluctuate within certain limits, such as in the example of Ferrous oxide. The ideal formula is FeO, but due to crystallographic
Crystallography
Crystallography is the experimental science of the arrangement of atoms in solids. The word "crystallography" derives from the Greek words crystallon = cold drop / frozen drop, with its meaning extending to all solids with some degree of transparency, and grapho = write.Before the development of...

 vacancies it is reduced to about Fe0.95O.

Proust was also interested in studying the sugars that are present in sweet vegetables and fruits. In 1799, Proust demonstrated, to his class in Madrid
Madrid
Madrid is the capital and largest city of Spain. The population of the city is roughly 3.3 million and the entire population of the Madrid metropolitan area is calculated to be 6.271 million. It is the third largest city in the European Union, after London and Berlin, and its metropolitan...

, how the sugar in grapes is identical to that found in honey
Honey
Honey is a sweet food made by bees using nectar from flowers. The variety produced by honey bees is the one most commonly referred to and is the type of honey collected by beekeepers and consumed by humans...

. This later became known as glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

.

External links

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