Some 2,500 years ago, the Greek philosopher Aristotle postulated that all matter is comprised of four basic elements: earth, water, air and fire. The idea dominated science until the late 18th century, when revolutionaries from rival nations transformed chemistry from a jumble of medieval alchemy into a true science. The pace of discovery accelerated rapidly as chemists on the frontiers of knowledge established the theories and methodologies of modern science.
When Unitarian minister Joseph Priestley discovered oxygen in 1774, he answered age-old questions of why and how things burn. Born in England in 1733, Priestley was a passionate champion of the ideals articulated in the American Declaration of Independence. Like his friend Benjamin Franklin, he was deeply involved in politics as well as science.
Priestley isolated several gases, including what was later called oxygen. He accurately documented its properties but explained what he observed in terms of then-prevailing theory, which held that when things burned they lost "phlogiston," an inflammable substance. (In actuality, just the opposite happens: substances combine with oxygen when they burn.)
When Priestley's vocal support for the American and French revolutions made staying in England untenable, he immigrated to America in 1794 and settled in Northumberland, Pennsylvania. Priestley continued investigating gases, isolating carbon monoxide in 1799 and building a 1,600-volume library and state-of-the art laboratory. Read more »
Antoine Lavoisier explained the principles of modern chemistry. Born into the French aristocracy in 1743, he studied law but distinguished himself in science, earning election to the French Academy of Sciences at age 25.
Duplicating Priestley's experiments, he challenged prevailing “phlogistic” theory and demonstrated the true role of oxygen in combustion. Lavoisier also described the role of oxygen in respiration, and showed that water is not an element but a compound comprised of hydrogen and oxygen. In 1789, the year the French stormed the Bastille and America ratified its Constitution, Lavoisier published Traite Elementaire de Chimie (Elements of Chemistry), the first cohesive presentation of the principles of modern chemistry: the law of the conservation of matter, how heat affects chemical reactions, the nature of gases, and how acids and bases react to form salts. It also listed all the then-known elements.
Lavoisier's insights quickly gained widespread acceptance, although a few chemists, including Priestley, clung to the discredited notion of phlogiston. Put to death by guillotine in 1794 through an excess of revolutionary fervor, Lavoisier never saw the dawn of the new century that recognized his work as the foundation of modern chemistry. Read more »
In 1895, Edward Morley calculated the relative atomic weight of oxygen (on the scale hydrogen – 1 exactly) as 15.879, setting an important new standard of accuracy. Nineteenth-century chemists used oxides to calculate the atomic weights of other elements, so this finding made their calculations more accurate as well.
Born in 1838, Morley was trained to follow in his father's footsteps as a minister. But his love of science and mathematics won out, and he became an instructor at the school today known as Case Western Reserve University in Cleveland, Ohio. There, his analytical techniques earned him national renown. Morley went to elaborate lengths to ensure that his calculations were accurate. Indeed, they were so accurate they agree with the measurements of today's sophisticated equipment. Read more »
In 1900, University of Michigan chemist Moses Gomberg achieved what chemists had long believed impossible: he isolated an organic free radical (a carbon compound with an unpaired electron). The accomplishment paved the way for development of polyethylene, Plexiglas®, and other polymers used by the plastics industry.
Today, organic free radicals are involved in producing nearly half of the polymers we use, from plastic bottles to latex paint. Gomberg's discovery also advanced biochemistry, biology and medicine. Organic free radicals are crucial to our understanding of many natural phenomena, including how our bodies synthesize DNA and why some oxidative processes support life while others cause disease. Read more »
In 1906, Charles James, a University of New Hampshire chemist, developed a method of separating the rare earth elements that prevailed for the next 40 years. These elements provide the color red in color television picture tubes and are used in glass polishes, ceramic glazes, lasers, superconductors and diagnostic imaging in medicine.
The 17 rare earth elements, often found together in the mineral monazite, are metals with similar characteristics. In the periodic table, they include number 21 (scandium), number 39 (yttrium), and numbers 57 (lanthanum) through 71 (lutetium). Read more »
The discovery that earned C. V. Raman the 1930 Nobel Prize in physics was born of an investigation of light sparked by a question a child might ask. Returning to his native India by way of the Mediterranean Sea, Raman wondered at the sea's deep blue color. Dissatisfied with the prevailing explanation — that it reflected the sky — he delved further and demonstrated a universal truth about the behavior of light.
In 1928, Raman discovered that when a beam of colored light enters a liquid, it scatters and some of it emerges as a different color. This deceptively simple observation had profound implications. As Raman said, "The character of the scattered radiations enable us to obtain an insight into the ultimate structure of the scattering substance."
Physicists welcomed Raman's finding as proof of quantum theory. Chemists found it an invaluable tool for analyzing the composition of liquids, gases, and solids. The introduction of lasers in the 1960s made it even more useful. Today, the Raman Effect is used to monitor everything from manufacturing processes to the onset of life-threatening illnesses. Read more »
Chemist Hermann Staudinger helped lay the foundation that made the modern plastics industry possible. Early 20th century chemists believed that the remarkable physical properties of materials like rubber and cellulose were the result of small molecules aggregated into large units by forces weaker than chemical bonds. In 1920, Staudinger published a paper challenging that view. He postulated that rubber and similar materials are composed of very large molecules, called macromolecules, that are held together by chemical bonds—the same forces that hold smaller, lighter molecules together.
Although other chemists ridiculed his idea, Staudinger articulated theories that formed the basis for countless industrial developments from nylon to plastic. He received the 1953 Nobel Prize in chemistry for his work with polymers.
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In a famously simple but elegant experiment conducted in 1962, Neil Bartlett, a young chemist at the University of British Columbia, changed the face of chemistry. Before Bartlett's experiment chemists had believed that the noble gases were inert, that is unable to react. But Bartlett proved this wrong by combining xenon with a platinum fluoride to form the world's first noble gas compound. Today, only neon and helium of the six known noble gases remain unable to react. Compounds of the other four noble gases—xenon, radon, krypton and argon—are used in a variety of applications, including in lasers and to create anti-tumor agents. Read more »
Marshall Nirenberg electrified the scientific world in August 1961 when he announced the deciphering of the genetic code. Nirenberg, assisted by Heinrich Matthaei, a postdoctoral fellow, had performed experiments at the National Institutes of Health showing that messenger RNA transcribes genetic information from DNA, which it then uses to assemble amino acids into complex proteins, the very stuff of life.
The initial experiment revealed the first word of the genetic code. In the next few years, Nirenberg’s laboratory discovered the codes for all possible combinations of the twenty amino acids. Nirenberg’s work helped pave the way for the mapping of the human genome and for much of recent understanding of the correlations of genetics and disease. Read more »
In 1985 Richard Smalley and Robert Curl of Rice University and Harry Kroto of the University of Sussex discovered the first known molecular form of carbon, C60. At first, the structure of these clusters stumped the team. After much discussion and trial and error in trying to construct a 60-carbon atom structure, the team realized the form was a closed sphere. They named it buckminsterfullerene (often shortened to fullerenes or buckyballs), after architect Buckminster Fuller, whose geodesic domes suggested a structure of 12 pentagons and 20 hexagons.
Research on fullerenes has led to the synthesis of more than one thousand new compounds, and to advances in the development of carbon nanotubes, which have uses in tiny motors and as ball bearings and lubricants. Fullerenes continue to provide abundant research opportunities in pure chemistry, materials science, pharmaceutical chemistry, and nanotechnology. Read more »
MRI (magnetic resonance imaging) has become a staple of medical diagnostics. Millions of Americans have had an MRI; it is a useful non-invasive and non-destructive diagnostic tool for imaging soft tissues such as the brain, heart and muscles, and for discovering tumors in many organs. MRI is an application of NMR (nuclear magnetic resonance), an analytical tool of chemists found in laboratories worldwide.
Together, NMR and MRI revolutionized the practice of chemistry and medicine by providing fast, non-destructive, and non-invasive means for the observation of matter from the atomic to the macroscopic scale. Read more »
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