By: Karen Koyko
Phlogiston was described as a “chemical of an earthy nature, dry and adapted to combination with solids.1” It was originally thought that when a substance burned, it’s phlogiston was violently given off through a flame, so that the product of burned materials would weigh less once burned. The ironic part was that when the substance was weighed after it was burned, it weighed more than it initially had. Although Johann Beecher (1635-1682) introduced the theory and Georg Stahl (1659-1743) furthered and elaborated on what he thought was the key theory of combustion, this type of mental theorizing stalled the development of more scientific thinking4, primarily because the scientists of the times ignored experimental evidence that disproved a popular philosophical theory.
In the late 1700’s, it was Joseph Priestley’s curiosity that sparked a change in experimental thinking. Priestley had been brought up his entire life believing in the phlogiston theory. However, while frequenting a public brewery near his home, he noticed that gas continually bubbled from the huge vats of beer. He was fascinated by this, and soon discovered that this gas had the property of extinguishing burning chips of wood.
Priestley’s
curiosity and scientific mind took over, and he succeeded in “making”
(isolating) the gas. When he tried to
mix it with water, it fizzed. He had
created soda water, and was given a gold medal by the Royal Society. The College of Physicians were hopeful that
this might be some sort of cure for scurvy, which it wasn’t. Priestley continued his testing, using
various types of experimentation, and succeeded in obtaining a gas (oxygen)
from mercury monoxide. He tried
breathing this gas (oxygen) and discovered that his breath felt light and easy,
and suggested that it might be good for the lungs in cases of illness1. However, having been raised on phlogiston
theories, his conclusions were philosophical and based on vague connections he
tried to build between his solid experimental data, and what he believed to be
truth of those philosophies.
About the time
that Priestley’s revolutionary political thinking was forcing him to give up
science and flee to America from an angry religiously motivated mob, Antione
Lavoisier (1743-1794) was fascinated by Priestley’s work, and could not give up
studying Priesteley’s ideas until he discovered the truth behind
combustion. He, unlike Priestley, did
not believe the phlogiston theories, as the experimental data suggested that
more was occurring than the theory could explain.
Through
repeating thousands of unoriginal experiments, Lavoisier eventually used his
great skill in analytical reasoning and synthesis to explain his observations
by stating that burning was the union of the burning substance with
oxygen. He is considered the father of
modern chemistry based upon his statement, “One may take it for granted that in
every reaction there is an equal quantity of matter before and after the operation.1” This is the basis for the Law of
Conservation of Mass, which is still held to be a key foundation in
science.
In 1780
Lavoisier collaborated with Pierre Laplace to forever unite chemistry and
biology. They designed experiments that
explained the process of respiration in animals, thus showing one of the many
ways in which the sciences are interrelated.
Lavoisier was also instrumental in his contributions to methods of
chemical nomenclature and theories on the states of matter.
Questions for Discussion:
1. Based on the information given about Antoine Lavoisier, do you think he deserves the title of “The Father of Modern Chemistry?” Why, or why not?
2. What do you think the key shift was in the processes of scientific inquiry or scientific thinking from the Beecher and Stahl, to Priestley and Lavoisier? How did the scientists approach their work and analyze their findings differently?
3. How do your experiences, beliefs, and interests affect what you choose to study?
4. It took thousands of years to arrive at the theories we now accept as commonplace. What misconceptions, biases or beliefs do you have that might influence your interpretation of results, as occurred with Priestley?
5. Could Priestley’s views been altered with more information or more instruction? How?
6. Can you think of any misconceptions that you have had that have been altered? What occurred to cause you to change or modify your views?
7. Do misconceptions help you to understand ideas more clearly? Explain your reasoning.
References:
1. Hays, H.R. (1973). Birds, beasts, and men: a humanist history of zoology. Baltimore. Penguin Books, Inc.
2. http://library.thinkquest.org/2690/hist/traditional.html?tqskip1=1&tqtime=0128
3. http://cti.itc.virginia.edu/~meg3c/classes/tcc313/200Rprojs/lavoisier2/home.html
4. http://www.scs.uiuc.edu/~mainzv/exhibit/stahl.htm
Curriculum Fit: Bio 20, Unit 2: Energy Flows and Cellular Matter. Chem 20 or 30. Virtually any Science curriculum, since it’s dealing with
scientific methodology and misconceptions as a whole.