Evolution of Chemistry and the Periodic Table of Elements

Introduction: Theology, Philosophy, and the Birth of Modern Chemistry

One of the differences between scientists of the 17th and 18th centuries and scientists today is that the chemists of times past were often theologians. They studied chemistry and other forms of science because they were deeply devout and sought to understand how the world worked; they desired to better understand the hand of the creator (Ihde, 1990).

Notable 17th Century Chemists

Jean Beguin was a Paracelsian iatrochemist who furthered the techniques that developed into the modern science of chemistry (Weisstein, 2007). In that sense, Beguin was in many ways one of the fathers of modern chemistry and was responsible for chemistry being seen as a separate science in the way it is viewed today. "In the preparations of medicines, the iatrochemists experimented extensively in their quest to prepare substances in the simplest way possible. In addition, to ensure that a given substance could be prepared consistently, they developed quantitative methods and accurate systems of record keeping" (Weisstein, 2007). Beguin was responsible for publishing the first chemical textbook, known as Tyrocinium Chymicum (Beginner's Chemistry), in 1610. Beguin was also the one who coined the first definition of chemistry, referring to it as the search for medications (Weisstein, 2007) — a description that summarized his viewpoint rather aptly. Beguin's approach to chemistry viewed it as a practical and experimental field with limited use of theory (Weisstein, 2007).

Robert Boyle was a 17th-century chemist who had a remarkable impact on the field of chemistry and is credited today as a visionary ahead of his time. Active during the Renaissance, he brought forth great developments in chemistry and advanced both experimental methods and scientific thought. "In the 17th century Robert Boyle conducted his now famous experiments on physical properties of gases and combustion. He was outspokenly critical of Aristotle's four-element theory and proposed his own. Although Boyle's theories regarding the nature of substances were vague and not very accurate — for example, he believed that fire was a particle — he was one of the most prominent experimentalists to attack Aristotle's theory of the elements." Boyle's criticism of Aristotle was presented in a book titled The Skeptical Chymist, published in 1661 when Boyle was 34. Within this book he refuted the theory, attributed to Aristotle, that everything was composed of earth, air, fire, and water, and replaced it with the idea that an element "is a substance that cannot be separated into simpler components by chemical methods. The Skeptical Chymist is recognized as the foundation-stone of modern chemistry" (Doonan, 1989). Boyle also worked on problems concerning the elasticity and pressure of gases. He collaborated with Robert Hooke, who invented the precursor to the modern air pump: "While experimenting with air, Boyle began to promote his atomic theory, which is the foundation for our modern understanding of matter" (Doonan, 1989).

It is also important to note that while Boyle was working, few scientists fully understood his ideas about atoms and other particles. Some of the more unusual ideas of the period had been accepted by other alchemists without question, yet when Boyle presented his atomic theory, some professionals in the field met it with ridicule (Doonan, 1989). However, Boyle was able to persuade others by explaining that because air can be compressed there must be spaces between its atoms; and since liquids and solids do not readily compress, one can infer that their atoms are simply closer together (Doonan, 1989). Once other professionals were able to consider Boyle's ideas seriously, they could see the logic within them and accept them (Doonan, 1989). Thus, while Boyle was responsible for some of the most brilliant ideas regarding the nature of gases, they were not well received at the time, and he was not immediately met with the appreciation he deserved. Another notable contribution Boyle made was collecting hydrogen in a vessel; he referred to hydrogen as "factitious air" and observed it to be highly flammable. Boyle was the first scientist to collect any gas in a vessel at all.

During the time Boyle was active, he created one of the foremost contributions to science — an idea meant to illustrate how gases behave under pressure: "This is now known as Boyle's Law. Stated simply, Boyle's Law is that the volume of a given quantity of gas varies inversely with the pressure when the temperature is constant" (Doonan, 1989).

In many respects, Boyle was a scientist of firsts. He conducted experiments — something taken for granted today, but back then the mere idea of an experiment was controversial. During this period, the prevailing method of acquiring knowledge involved argumentation grounded in the established framework that Aristotle had set down. This made Boyle's approach far more cutting-edge, because he had a greater interest in observing nature and drawing conclusions from what actually happened — something considered standard practice today but regarded as radical at the time. Boyle's systematic process of conducting experiments and publishing detailed accounts of his procedures, apparatus, and observations was itself innovative for the period.

Joseph Priestley gained his fame in the sciences for discovering the existence of a gas known as oxygen (Chemheritage.org, 2013). "When Joseph Priestley discovered oxygen in 1774, he answered age-old questions of why and how things burn" (acs.org, 2013).

Priestley did not begin his career investigating oxygen. His first scientific work, The History of Electricity, was supported by Benjamin Franklin and motivated him to conduct his own experiments — at first to corroborate those he had read about, but also to answer his own questions (Chemheritage.org, 2013). In the 1770s he "began his most famous scientific research on the nature and properties of gases. At that time he was living next to a brewery, which provided him an ample supply of carbon dioxide. His first chemical publication was a description of how to carbonate water, in imitation of some naturally occurring bubbly mineral waters. Inspired by Stephen Hales's Vegetable Staticks (first edition, 1727), which described the pneumatic trough for gathering gases over water, Priestley began examining all the 'airs' that might be released from different substances" (Chemheritage.org, 2013). At this time, many scientists still followed the Aristotelian teaching that there was only one type of air. Priestley disproved this by isolating and characterizing eight gases — with oxygen being one of them — a record never equaled before or since (Chemheritage.org, 2013). Other experiments by Priestley added to the general knowledge of photosynthesis and respiration (Chemheritage.org, 2013). It should be noted that work potentially contradicting Aristotle would have met with no small amount of controversy and dissent.

One public dispute that Priestley engaged in was a long-running disagreement with Antoine-Laurent Lavoisier and his supporters about the best way to interpret results of experiments involving gases (Chemheritage.org, 2013). "Priestley interpreted them in terms of phlogiston — the hypothetical principle of flammability that was thought to give metals their luster and ductility and was widely used in the early 18th century to explain combustion, calcination, smelting, respiration, and other chemical processes. Proponents of phlogiston did not consider it to be a material substance, so it was therefore unweighable" (Chemheritage.org, 2013). In this framework, Priestley provided qualitative descriptions of such phenomena — describing oxygen, for instance, as "dephlogisticated air" (Chemheritage.org, 2013). His most famous experiment came in the summer of 1774, when he used a 12-inch-wide glass burning lens (acs.org, 2013). He trained the lens and sunlight on a lump of mercuric oxide in an inverted glass container placed within a pool of mercury; the gas emitted was found to be several times better than common air (acs.org, 2013). Subsequent tests showed it caused flames to burn more intensely and kept a mouse alive longer (acs.org, 2013).