Evolution of Chemistry to the Periodic Table of the Elements One of the differences between scientists of the 17th and 18th centuries vs. scientists today is that the chemists of times past were often theologians. They studied chemistry and other forms of science because they were incredibly 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

Jean Beguin was a paracelsan iatrochemist who was able to further the techniques necessary which 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 and the way that 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 absolute first chemical textbook, which was known as Tyrocinium Chymicum (Beginner's Chemistry), published in 1610. Beguin was the one who coined the first definition of chemistry, referring to it as the search for medications (Weisstein, 2007): this summarized his viewpoint on chemistry rather aptly. Beguin's take on chemistry was viewing it as a more practical and experimental field with a small usage of theory (Weisstein, 2007).

Robert Boyle

Robert Boyle was a 17th century chemist who had a remarkable impact on the field of chemistry, and is even credited today as a visionary ahead of his time. Alive during The Renaissance, he brought forth great developments in the forward momentum of chemistry and in the evolution of experimental methods and advanced scientific thought (Creighton.edu). "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 aparticle), he was one of the most prominent experimentalists to attack Aristotle's theory of the elements" (Creighton.edu). Boyle's criticism of Aristotle was presented in a book titled The Skeptical Chymist, published in 1661 at the age of 34; within this book, he refuted a major theory of the time which was coined by Aristotle and which posed the notion that everything was composed of earth, air, fire and water and swapped it out 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). Other credits that Boyle gave the world were the fact that he worked on problems concerning elasticity and pressure or gas pressure and volume (Doonan, 1989). Boyle also worked with Robert Hooke who also 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's also important to note that while Boyle was working, few scientists really understood his ideas about atoms and other particles; some of the more bizarre ideas of the period had been accepted by other alchemists without a doubt, though when Boyle presented his atomic theory, some professionals in the field treated it with ridicule (Doonan, 1989). However, the bottom line was that Boyle was able to convince people; he was able to explain that because air can be compressed there must exist rooms between the atoms in the air; since liquids and solids don't often compress, one can infer that they possess atoms which are simply closer together (Doonan, 1989). Once other professionals in the field were able to consider Boyle's idea with a great amount of seriousness and attention, they were then able to see the logic within it, and were able to accept it (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 Boyle was not immediately met with the level of appreciation that he deserved. Another notable addition to science that Boyle was responsible for was the act of collecting hydrogen in a vessel; he also referred to hydrogen as "factitious air" and viewed it to be incredibly flammable (Creighton.edu). Boyle was the first scientist to collect gas...

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).
There was a lot that Boyle did that was ahead of other scientists. In that respect, Boyle was a scientist of firsts. Boyle engaged in his work by conducting experiments; something that we take for granted today, but back then, it is far too easy to forget that the mere idea of an experiment was controversial (bbc.co.uk, 2013). During this period, the main method of discovering something involved arguing it out in connection with the established guidelines that Aristotle was responsible for. Thus, this made Boyle and the way he worked far more cutting edge because he had a greater interest in observing nature and gathering is conclusions from what really happened -- something which is considered standard in this day, but which was seen as radical at the time (bbc.co.uk, 2013). Boyle's sheer working process of systematically engaging in experiments and publishing details on the procedure he used, the apparatus he utilized and the observations he made was innovative for the period.

Notable 18th Century Chemists

Joseph Priestly

Joseph Priestly gained his esteem and fame in the realm of the sciences for he was the one that discovered the existence of a gas referred to 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).

Priestly didn't begin in starting to identify oxygen. The first scientific work he did (The History of Electricity) was supported by Benjamin Franklin; this work helped to motivate him to conduct his own experiments, at first to corroborate those he read about, but also to find answer to questions of his own (Chemheritage.org, 2013). For instance, Priestly in the 1770s "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). It's important to note at this time, that many scientists were still following the teachings of Aristotle, which dictated that there was only one type of air; however, Priestly was able to disprove this by isolating and characterizing eight gases, with oxygen being one of them, s record which was never equaled before that time, and which has never been equaled since that time (Chemheritage.org, 2013). Other experiments of Priestly were able to add to the general knowledge of photosynthesis and respiration (Chemheritage.org, 2013). Another crucial note to bear in mind is that when Priestly was engaging in work which was potentially contradicted the work of Aristotle, was likely to have been met with no small amount of controversy and dissent.

One public battle that Priestley did have to engage in was a long-running one with Antoine-Laurent Lavosier and his supporters about the best way to interpret results of experiments which involve 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 sense, Priestly was able to provide qualitative descriptions about these types of phenomena, discussing for instance, how oxygen was 'dephlogisticated air'" (Chemheritage.org, 2013). In plainer language, it was in the summer of 1774 when Priestly was able to engage in his most famous experiment, one which relied on 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, which was placed within a pool of mercury; a particular gas was emitted and deemed several times better as common air…