Evolution of early chemical science

Evolution of early chemical science

During the 19th and 20th century, this transformation was credited to the work of the French chemist Antoine Lavoisier (the "father of modern chemistry"). However, recent work on the history of early modern chemistry considers the chemical revolution to consist of gradual changes in chemical theory and practice that emerged over a period of two centuries. The so-called scientific revolution took place during the sixteenth and seventeenth centuries whereas the chemical revolution took place during the seventeenth and eighteenth centuries.

Several factors led to the first chemical revolution. First, there were the forms of gravimetric analysis that emerged from alchemy and new kinds of instruments that were developed in medical and industrial contexts. In these settings, chemists increasingly challenged hypotheses that had already been presented by the ancient Greeks. For example, chemists began to assert that all structures were composed of more than the four elements of the Greeks or the eight elements of the medieval alchemists. The Irish alchemist, Robert Boyle, laid the foundations for the Chemical Revolution, with his mechanical corpuscular philosophy, which in turn relied heavily on the alchemical corpuscular theory and experimental method dating back to pseudo-Geber.

Earlier works by chemists such as John Baptist van Helmont helped to shift the belief in theory that air existed as a single element to that of one in which air existed as a composition of a mixture of distinct kinds of gasses. John Baptist van Helmont’s data analysis also suggests that he had a general understanding of the law of conservation of mass in the 17 century. Furthermore, work by Jean Rey in the early 17 century with metals like tin and lead and their oxidation in the presence of air and water helped pinpoint the contribution and existence of oxygen in the oxidation process.

Other factors included new experimental techniques and the discovery of 'fixed air' (carbon dioxide) by Joseph Black in the middle of the 18th century. This discovery was particularly important because it empirically proved that 'air' did not consist of only one substance and because it established 'gas' as an important experimental substance. Nearer the end of the 18th century, the experiments by Henry Cavendish. Henry Cavendish was a British scientist noted for his discovery of hydrogen or what he called "inflammable air". He described the density of inflammable air, which formed water on combustion, in a 1766 paper "On Factitious Airs". Antoine Lavoisier later reproduced Cavendish's experiment and gave the element its name.

The latter stages of the revolution was fuelled by the 1789 publication of Lavoisier's Traité Élémentaire de Chimie (Elements of Chemistry). Beginning with this publication and others to follow, Lavoisier synthesised the work of others and coined the term "oxygen". Antoine Lavoisier represented the chemical revolution not only in his publications, but also in the way he practiced chemistry. Lavoisier's work was characterized by his systematic determination of weights and his strong emphasis on precision and accuracy. While it has been postulated that the law of conservation of mass was discovered by Lavoisier, this claim has been refuted by scientist Marcellin Berthelot. Earlier use of the law of conservation of mass has been suggested by Henry Guerlac, noting that scientist Jan Baptist van Helmont had implicitly applied the methodology to his work in the 16th and 17th centuries. Earlier references of the law of conservation of mass and its use were made by Jean Rey in 1630. Although the law of conservation of mass was not explicitly discovered by Lavoisier, his work with a wider array of materials than what most scientists had available at the time allowed his work to greatly expand the boundaries of the principal and its fundamentals.

Lavoisier also contributed to chemistry a method of understanding combustion and respiration and proof of the composition of water by decomposition into its constituent parts. He explained the theory of combustion, and challenged the phlogiston theory with his views on caloric. The Traité incorporates notions of a "new chemistry" and describes the experiments and reasoning that led to his conclusions. Like Newton's Principia, which was the high point of the Scientific Revolution, Lavoisier's Traité can be seen as the culmination of the Chemical Revolution.

Humphry Davy was an English chemist and a professor of chemistry at the London's Royal Institution in the early 1800's. There he performed experiments that cast doubt upon some of Lavoisier's key ideas such as the acidity of oxygen and the idea of a caloric element. Davy was able to show that acidity was not due to the presence of oxygen using muriatic acid (hydrochloric acid) as proof. He also proved that the compound oxymuriatic acid contained no oxygen and was instead an element, which he named chlorine. Through his use of electric batteries at the Royal Institution Davy first isolated chlorine, followed by the isolation of elemental iodine in 1813. Using the batteries Davy was also able to isolate the elements sodium and potassium. From these experiments Davy concluded that the forces that join chemical elements together must be electrical in nature. Davy was also a proponent against the idea that caloric was an immaterial fluid, arguing instead that heat was a type of motion

John Dalton was an English chemist that developed the idea of atomic theory of chemical elements. Dalton's atomic theory of chemical elements assumed that each element had unique atoms associated with and specific to that atom. This was in opposition to Lavoisier's definition of elements which was that elements are substances that chemists could not break down further into simpler parts. Dalton's idea also differed from the idea of corpuscular theory of matter, which believed that all atoms were the same, and had been a supported theory since the 17th century. To help support his idea, Dalton worked on defining the relative weights of atoms in chemicals in his work New System of Chemical Philosophy, published in 1808. His text showed calculations to determine the relative atomic weights of Lavoisier's different elements based on experimental data pertaining to the relative amounts of different elements in chemical combinations. Dalton argued that elements would combine in the simplest form possible. Water was known to be a combination of hydrogen and oxygen, thus Dalton believed water to be a binary compound containing one hydrogen and one oxygen.

Dalton was able to accurately compute the relative quantity of gases in atmospheric air. He used the specific gravity of azotic (nitrogen), oxygenous, carbonic acid (carbon dioxide), and hydrogenous gases as well as aqueous vapor determined by Lavoisier and Davy to determine the proportional weights of each as a percent of a whole volume of atmospheric air. Dalton determined that atmospheric air contains 75.55% azotic gas, 23.32% oxygenous gas, 1.03% aqueous vapor, and 0.10% carbonic acid gas.

Jöns Jacob Berzelius was a Swedish chemist who studied medicine at the Univseristy of Uppsala and was a professor of chemistry in Stockholm. He drew on the ideas of both Davy and Dalton to create an electrochemical view of how elements combined together. Berzelius classified elements into two groups, electronegative and electropositive depending which pole of a galvanic battery they were released from when decomposed. He created a scale of charge with oxygen being the most electronegative element and potassium the most electropositive. This scale signified that some elements had positive and negative charges associated with them and the position of an element on this scale and the element's charge determined how that element combined with others. Berzelius's work on electrochemical atomic theory was published in 1818 as Essai sur la théorie des proportions chimiques et sur l'influence chimique de l'électricité. He also introduced a new chemical nomenclature into chemistry by representing elements with letters and abbreviations, such as O for oxygen and Fe for iron. Combinations of elements were represented as sequences of these symbols and the number of atoms were represented at first by superscripts and then later subscripts.