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Natural Science - Year II

Unit 37: Lavoisier and Chemical Reactions

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History Weblecture for Unit 37


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History Lecture for Unit 37: Lavoisier and Chemical Reactions

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Outline/Summary

Modern Chemistry: Atomic Theory

Lavoisier and Mdm Lavoisier with lab equipment

Lavoisier

The breakthrough in the definition of chemical elements came through the studies of Antoine-Laurent Lavoisier, a lawyer with a serious hobby in chemical investigations. He was educated at College Mazarin in chemistry, botany, astronomy, and mathematics. Lavoisier, like Tycho Brahe, believed that advances in his field could be made only if he achieved greater precision in his measurements, so when he received an inheritance from his mother, Lavoisier built his own laboratory. He was able to design special equipment for each experiment, so that his containers themselves would not react with the chemicals he was studying. His insistence on experimental accuracy was perhaps even a more enduring legacy to chemistry than his identification of many chemical elements. At the relatively young age of 25, he was elected to the French Academy of Sciences.

Lavoisier was 28 years old when he married the 13-year-old daughter of his co-worker at the Ferme Generale, a private tax collection company. Lavoisier never learned English, but his wife Marie-Anne Pierrette Paulze did, and she translated papers presented to the Royal Society so that her husband could keep up with the new discoveries by the English chemists Joseph Priestley and Henry Cavendish. She also ran a salon, or weekly gathering of intellectuals, for all of Lavoisier's friends, where they could meet and discuss their theories and experiments. Lavoisier was interested in all aspects of chemistry: the nature of acids and bases, the identification of the elements, the composition of compounds and their properties.

Lavoisier Lab Equopment

Like his contemporaries, Lavoisier concentrated on investigation of the nature of air. He performed numerous experiments in which he measured the compounds going into a reaction (the reactants) and the products of the reaction. As a result of his experiments, he decided that phlogiston did not exist, and that in all reactions, the total amount of matter was conserved, even if it changed form. Finally, he published a new list of elements which differed from all his predecessors by its length (loosely grouped by characteristics). Note that the "elements" in boldface are not now considered elements; if you hover your cursor over the name, it should pop up some information about the substance.

Light Suphur Antimony Mercury Lime
  Phosphorus Arsenic Molybdena Magnesia
Caloric Charcoal Bismuth Nickel Barytes
Oxygen Muriatic radical Cobalt Platina Argilla
Azote Fluroic radical Copper Silver Alumina
Hydrogen Boracic radical Gold Tin Silex (Silicon)
    Iron Tungsten Silica
    Lead Zinc  
    Manganese    
Chemistry supplies

A number of Lavoisier's elements are now known to be compounds; for example, lime is a combination of calcium and oxygen, and murietic radical is murietic acid, which we now call hydrochloric acid. Lavoisier's list is important, because he did not confine himself to a few basic elements. His identification of thirty or more elements broke the down the tendency to look for a very few simple elements as the basis for all matter and allowed scientists to perceive patterns across a wider range of fundamental materials.

Unfortunately for the advancement of chemistry, Lavoisier drew some of his income from investments in a company that collected taxes. As a result of his connection with both the aristocracy and a corrupt corporation (which he actually seems to have tried to reform), Lavoisier was guillotined during the French Revolution and all of his chemistry notebooks and equipment were confiscated by the Republic tribunals. After years of diligent efforts, Marie-Anne was able to recover many notebooks and some equipment, most of which is now in the library at Cornell University.

We have now seen how Lavoisier built on the work of Stahl, Priestley, and earlier experimenters in creating his list of chemical elements and their compounds and reactions. Several other important discoveries were also necessary to establish a coherent approach to chemical reactions. One was the realization that compounds had fixed proportions, like a recipe for a cake. Another was the resurgence of the idea that matter could be broken down into discrete particles, or atoms. We've already used this concept in the science section last week; in the next unit we see how it was proposed by John Dalton and gradually accepted during the 19th century.

Read some extracts from the preface to Lavoisier's Traité Elémentaire de Chimie.

  • What was Lavoisier's original purpose in writing his treatise?
  • Why does he think having a precise nomenclature is so important?
  • How does he distinguish between "acidity" and "acids"?
  • Why doesn't Lavoisier start with a history of chemistry?
  • What does he consider the operations of modern chemistry?

Study/Discussion Questions:

Further Study/On Your Own