Chemical Revolution

Chemical revolution involved the conceptual change which followed the development of the oxygen theory by Lavoisier that replaced the then popular phlogiston theory. Several factors contributed to this revolution including Priestley and Cavendish experiments, which proved that air is a mixture of gases rather than a single element as the then conventional understanding.

The improvement in communication of scientific findings increased public interest in chemistry and contributed to the replacement of the old concepts with new concepts.

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This paper will examine the traditional scientific concepts including the much celebrated phlogiston theory of early 18th century and relate it with Lavoisier’s new approach. Initially, Lavoisier’s aim was to seek new interpretation of the existing concepts but his discovery led to replacement of the phlogiston theory.

The phlogiston theory was popular and universal in the 18th century and this limited the development of new concepts. However, Perrin notes that, “Lavoisier’s quest for reinterpretation of ideas built on concepts of earlier investigators; Boyle and Mayow, led to the oxygen theory” (54).

Phlogiston theory was a major achievement from the traditional theoretical principles since the phlogiston could be chemically established.

The starting point of chemical revolution involved the phlogiston theory, which held that combustion of substances released a phlogiston. This theory also explained the converse process of calcinations. The fact that the concepts of this theory were not a mere speculation but had experimental evidence, made the theory popular and universally accepted in early 18th century.

Even Lavoisier submitted to the universality of this theory before his experiments led to a new discovery. Towards the end of the 18th century, many substances were identifiable in laboratory and the new Lavoisier concepts led to the replacement of the phlogiston theory.

Many factors contributed to the popularity of the phlogiston theory in the early 18th century. Before the phlogiston theory, it was believed that substances released the principle of inflammability when undergoing combustion and metals lost a metallic principle when undergoing calcinations.

Stahl experimentally identified the metallic principle and inflammability principles making his phlogiston theory popular. He was also able to make sulfur from its combustion products hence reversing the combustion process. Other concepts popular in the 18th century included the Etienne-Francois concepts regarding the reactivity of substances with each other and the rate of reactions.

Stahl developed the affinity tables where elements were arranged based on their reactivity which allowed a systematic study of reactions and identification of new elements.

However, some “British investigators led by Henry Cavendish and Joseph Priestley followed the isolation, identification of the properties and effects of the various components of air” (Perrin 71).

The major debate during this period especially in France revolved around the composition of air contained within bodies and its role. Some researchers believed that air was physically trapped within bodies while others argued that air is chemically combined in bodies like Gabriele-Francoise Venel.

Still others like Johann Theodor Eller held the view that decomposition produced the air trapped in the bodies. Nevertheless, in the midst of all these debates and ‘confusions’, Lavoisier’s experiments avoided the concepts of phlogiston theory and the affinity concepts laid down by earlier scientists.

Several factors contributed to Lavoisier’s success in coming up with new concepts to rival the phlogiston theory. His extensive reading of other scientists work coupled with inquisitiveness enabled him to note the differences between the findings and to design new experiments. He was also keen on the use of instruments to increase the accuracy of the results obtained from physical experiments.

He was able to dispute the conventional hypothesis held by chemists that solutions of air made up vapor and instead proposed that an igneous fluid was responsible for turning water into steam. He opposed Stahl’s view that air cannot be compressed to fit into a specific body, by proposing that compressed air occupies less space.

Lavoisier used quantitative physical methods that were not employed by researchers of the time, which allowed him to obtain reliable and accurate results. He kept records and data collected from scientific experiments such as thermometer and barometer readings. In addition, he used quantitative methods involving weight measurements that allowed him to relate the weight of reactants and products in his experiments.

From earlier Lavoisier’s experiments, it is evident that use of quantitative methods and the earlier concepts concerning air allowed Lavoisier to develop the oxygen theory that immensely contributed to chemical revolution. However, his efforts at the start of his experiments were primarily to increase the understanding of the existing concepts rather than to replace them. Later, after more discovery and innovations he disputed the phlogiston theory causing a major conceptual change.

In 1774, Lavoisier studied the residue formed after combustion of mercury called the ‘red precipitate’. According McEnvoy, the phlogiston theory postulated that metals emitted a phlogiston during combustion leaving behind a residue (calx) (311). Lavoisier established that the red precipitate when heated decomposed into metallic mercury without the addition of charcoal as earlier suggested by Stahl.

This presented a serious limitation of the phlogiston theory since the phlogistons were not involved in the calcinations process. The developments in Lavoisier’s experiments presented many anomalies regarding the concepts of the phlogiston theory. In the beginning, the weight increase though experimentally established, could not be attributed to addition of air during combustion and calcinations.

Still, the phlogiston theory was still relevant since there were no alternative concepts to explain these observations. The emergence of many alternative concepts by Lavoisier that produced anomalous results to the phlogiston theory led to the development of an alternative theory to replace the phlogiston theory.

In producing the new theory, Lavoisier established experimental evidence in support of his new concepts, which at the same time attacked the older doctrines of Stahl. This phenomenon comes out clearly in the late 1770s when Lavoisier produced experimental evidence that disputed the concepts of phlogiston theory while increasing strength of his oxygen theory.

During the same period, Lavoisier and Laplace innovated methods of quantitative measurement of heat, which allowed them to estimate the specific heats released by substances undergoing combustion. Lavoisier was now able to include these findings into his oxygen theory making it more understood.

An important discovery by Lavoisier that triggered the chemical revolution was the discovery of oxygen gas. Other researchers like Pierre Bayen in 1774, were able to isolate oxygen by heating mercury oxide but identified it as carbon dioxide. Joseph Priestley also managed to isolate the same gas but identified it as nitrogen (Perrin 67).

However, in 1775, Lavoisier, isolated and identified oxygen gas. He further noted that the gas was one of the components of atmospheric air thus contradicting the earlier concepts that the atmospheric air is homogeneous. This among other discoveries was revolutionary in chemistry.

Works Cited

McEnvoy, John. The Revolutionary Identity and the Chemical Revolution, 1993. Web. 6 April 2011.

Perrin, Chris. “Research Traditions, Lavoisier and the Chemical Revolution.” Osiris 2.4 (1988): 53-81.


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