The roots of chemistry go back into antiquity with the development of such techniques as metal smelting, textile dyeing, glass making, and butter and cheese preparation. These early chemical techniques were almost all-empirical discoveries. That is, someone either by accident or observation discovered them. They then passed this knowledge down from one generation to the next. For example, because copper is found in its free metallic state, it was first beaten into various implements. Later it was smelted, being perhaps one of the first metals to be separated from its ore.
Empiricism waned with the Greek philosophers who began the first systematic discussions of the nature of matter and its transformations. There were numerous philosophies and schools that grew up around those philosophers. One that is of particular interest to chemists is that of the atomists. Democritus (460-370 B.C.) elaborated much on the idea of atoms. He thought that atoms were solid particles and that atoms existed in a void but could move about and interact with each other; thus, forming the various natural systems of the world. However, Aristotle and Plato rejected the
Empiricism waned with the Greek philosophers who began the first systematic discussions of the nature of matter and its transformations. There were numerous philosophies and schools that grew up around those philosophers. One that is of particular interest to chemists is that of the atomists. Democritus (460-370 B.C.) elaborated much on the idea of atoms. He thought that atoms were solid particles and that atoms existed in a void but could move about and interact with each other; thus, forming the various natural systems of the world. However, Aristotle and Plato rejected the
philosophy of atoms, and it wasn't until the early nineteenth century that Dalton proposed the beginnings of the modern atomic theory.
Socrates, Plato, and Aristotle had the greatest impact on Greek philosophy. Socrates felt that studying the nature of man and his relationships was much more important than studying the science of nature. He did benefit the later development of science by insisting that definitions and classifications be clear, that arguments be logical and ordered, and that there be a rational skepticism. Plato adopted the philosophy that there were four elements: fire, air, water, and earth. Aristotle added to those four elements four associated qualities: hot, cold, wet, and dry. He believed that each element possessed two of these qualities, as illustrated in Figure 0.1.
Socrates, Plato, and Aristotle had the greatest impact on Greek philosophy. Socrates felt that studying the nature of man and his relationships was much more important than studying the science of nature. He did benefit the later development of science by insisting that definitions and classifications be clear, that arguments be logical and ordered, and that there be a rational skepticism. Plato adopted the philosophy that there were four elements: fire, air, water, and earth. Aristotle added to those four elements four associated qualities: hot, cold, wet, and dry. He believed that each element possessed two of these qualities, as illustrated in Figure 0.1.
Figure 0.1. The relationship between the four elements and their associated qualities. This diagram frequently appears in alchemy literature.
According to this philosophy, one element might be changed (transmuted) into another element by changing its qualities. For example, earth was dry and cold, but it could be transmuted into fire by changing its qualities to hot and dry.
These theories remained important for nearly two thousand years. Of greatest significance was the scientific work that took place in Alexandria. Unfortunately, little of it was in the field of chemistry.
It was in Alexandria, toward the end of the first century BC, that western alchemy began growing. Alchemy was a mixture of philosophy, religious, or spiritual, ideas, astrology, and empirical technical skills. Based on the theory that all matter consisted of fire, air, water, and earth with the associated qualities of hot, cold, wet and dry and that by changing the qualities of one form of matter you could change it to another form, the philosophers thought if they systematically changed matter from one form to another in time they could obtain the perfect metal. Not only were they working to form the perfect metal but also to form an elixir of life that would give them spiritual perfection.
According to this philosophy, one element might be changed (transmuted) into another element by changing its qualities. For example, earth was dry and cold, but it could be transmuted into fire by changing its qualities to hot and dry.
These theories remained important for nearly two thousand years. Of greatest significance was the scientific work that took place in Alexandria. Unfortunately, little of it was in the field of chemistry.
It was in Alexandria, toward the end of the first century BC, that western alchemy began growing. Alchemy was a mixture of philosophy, religious, or spiritual, ideas, astrology, and empirical technical skills. Based on the theory that all matter consisted of fire, air, water, and earth with the associated qualities of hot, cold, wet and dry and that by changing the qualities of one form of matter you could change it to another form, the philosophers thought if they systematically changed matter from one form to another in time they could obtain the perfect metal. Not only were they working to form the perfect metal but also to form an elixir of life that would give them spiritual perfection.
Alchemy is the philosophical and primitively empirical study of physical and chemical transformations.
From Alexandria, alchemy quickly spread throughout the Western world. For the next fifteen hundred years, its many practitioners persuaded wealthy patrons to support them in their research with the promise that unlimited wealth was just around the corner—just as soon as they could convert lead or iron into gold or silver.
Don't think that because alchemists promised to convert base materials into precious metals that they were just con-artists promising something for nothing. Many alchemists truly believed that somewhere in nature there existed a procedure that would form precious metals from base materials. As they worked to find this procedure, they learned much about science, although they were not scientists in a modern sense. What alchemy provided to science was the experimental base from which modern chemical theories arose.
Because alchemists promised impossible chemical feats and did not follow modern scientific methods, historians often call this time period the “dark age” of science. However, their logic was quite sound. Their goal to change matter from one form to another was the result of looking at the many dramatic changes they could see in nature. For example, in a fire, wood simply “disappeared” leaving a small amount of ashes. Thus, as the alchemists observed dramatic changes such as this, they reasoned that it should be as easy to make other sorts of changes—such as changing lead into gold. They had no way of knowing that converting lead to gold involved a totally different type of change than that of using fire to turn wood into ashes.
The move toward modern chemistry took a long time. Physics
Don't think that because alchemists promised to convert base materials into precious metals that they were just con-artists promising something for nothing. Many alchemists truly believed that somewhere in nature there existed a procedure that would form precious metals from base materials. As they worked to find this procedure, they learned much about science, although they were not scientists in a modern sense. What alchemy provided to science was the experimental base from which modern chemical theories arose.
Because alchemists promised impossible chemical feats and did not follow modern scientific methods, historians often call this time period the “dark age” of science. However, their logic was quite sound. Their goal to change matter from one form to another was the result of looking at the many dramatic changes they could see in nature. For example, in a fire, wood simply “disappeared” leaving a small amount of ashes. Thus, as the alchemists observed dramatic changes such as this, they reasoned that it should be as easy to make other sorts of changes—such as changing lead into gold. They had no way of knowing that converting lead to gold involved a totally different type of change than that of using fire to turn wood into ashes.
The move toward modern chemistry took a long time. Physics
and medicine had provided an experimental base, but first the philosopher’s attitude toward nature had to change to a more inductive approach. That is, as René Descartes advocated, accept only those things that you can prove. Perhaps the biggest obstacle to modern chemistry was that of chemical identity. There was the need to replace the alchemist’s four elements with the understanding of atoms. Scientists needed to understand that the identity of a substance stayed the same even when that substance became a part of another substance. For example, copper is always copper even when mixed with zinc to form bronze, an alloy of copper. Robert Boyle (1627-1691) did much to do away with the view of the four elements, as well as to begin the study of gases (or air). Many scientists studied gases and isolated a number of pure gaseous compounds, but they all thought that these gases were either very pure air or very impure air. Antoine Lavoisier (1743-1794) finally moved chemistry into its own as a modern science with his recognition that oxygen was not just very pure air, it was a completely separate element.
Early in the nineteenth century, as modern chemistry began developing, chemists mostly ignored organic chemistry, viewing it as either medically or biologically related because nearly all the known
Early in the nineteenth century, as modern chemistry began developing, chemists mostly ignored organic chemistry, viewing it as either medically or biologically related because nearly all the known
organic compounds were derived from living organisms, both plant and animal. An exception to this was Lavoisier, who was very interested in organic chemistry and considered it to be a part of chemistry. He looked at some organic compounds and found that they all contained carbon.
Because organic compounds were much more complex and unstable than the inorganic compounds being synthesized at the time, chemists had not knowingly prepared any and, in fact, thought that they were impossible to prepare. They believed that these compounds came only from living organisms. That is, the formation of the known organic compounds, such as urea, starches, oils, and sugar, required some “vital force” possessed by living organisms. Thus, organic chemistry became the study of compounds having a vital force, or vitalism. Some chemists felt that, because of the “vital force,” organic compounds did not follow the same rules that other compounds did.
Because organic compounds were much more complex and unstable than the inorganic compounds being synthesized at the time, chemists had not knowingly prepared any and, in fact, thought that they were impossible to prepare. They believed that these compounds came only from living organisms. That is, the formation of the known organic compounds, such as urea, starches, oils, and sugar, required some “vital force” possessed by living organisms. Thus, organic chemistry became the study of compounds having a vital force, or vitalism. Some chemists felt that, because of the “vital force,” organic compounds did not follow the same rules that other compounds did.
Unaffected by the attitudes concerning organic chemistry, Michel Chevreul set out to study the composition of fats using the process of saponification, or soap making. In 1816, Chevreul separated soap into several pure organic compounds and found that these compounds were very different from the fat that he had started with. He had unwittingly dealt vitalism a major blow.
To do his work, Chevreul first made soap. He repeated the process many times making the soap from several sources of fat and alkali. Then, after he separated the soap from the glycerin, he separated the soap into its various fatty acids. He called these compounds fatty acids because he had isolated them from the soap, which he had prepared from animal fat. Previously people had not understood that a chemical reaction took place during the soap making process. They thought that soap was simply a combination of the fat and alkali. Unfortunately, other chemists took a long time to recognize the significance of Chevreul's work.
Another chemist that brought vitalism to its end was Friedrich Wöhler with his synthesis of urea in 1828—as he said, “without the use of a kidney”. The following reaction is the synthesis of urea using the starting material aqueous ammonium hydroxide and cyanogen.
To do his work, Chevreul first made soap. He repeated the process many times making the soap from several sources of fat and alkali. Then, after he separated the soap from the glycerin, he separated the soap into its various fatty acids. He called these compounds fatty acids because he had isolated them from the soap, which he had prepared from animal fat. Previously people had not understood that a chemical reaction took place during the soap making process. They thought that soap was simply a combination of the fat and alkali. Unfortunately, other chemists took a long time to recognize the significance of Chevreul's work.
Another chemist that brought vitalism to its end was Friedrich Wöhler with his synthesis of urea in 1828—as he said, “without the use of a kidney”. The following reaction is the synthesis of urea using the starting material aqueous ammonium hydroxide and cyanogen.
NH4OH + (CN)2 = NH2CONH2
Ammonium Hydoxide + Cyanogen = Urea
Wöhler’s goal was not to synthesize urea; he was trying to make ammonium cyanate (NH4OCN), a compound he needed for his research. In fact, he may have become frustrated because he tried to
make ammonium cyanate by several different routes. He tried reacting silver cyanate with ammonium chloride, reasoning that silver chloride is insoluble and would precipitate from solution. He tried reacting lead cyanate with ammonium hydroxide. Finally, he tried aqueous ammonium hydroxide and cyanogen. But, every attempt led to the same white crystalline substance that was not the desired product.
Wöhler made his mark in the annals of chemistry by deciding to identify this unknown substance. Once he identified it as urea, he also recognized the importance of his discovery. As he wrote in 1828 “[The] research gave the unexpected result . . . that is the more noteworthy inasmuch as it furnishes an example of the artificial production of an organic, indeed a so-called animal substance from inorganic materials.”
Chevreul and Wöhler had forever altered the study of organic chemistry. As other chemists looked at the work that Chevreul and Wöhler had done, they saw that chemists could indeed synthesize compounds of carbon without a living organism. They then began making carbon compounds and studying them. Soon many chemists were achieving remarkable successes in the new art of the synthesis of organic compounds. Thus began the study of organic compounds.
Inevitably, someone would take these new developments from the organic chemistry research laboratory and find ways to market them. William Henry Perkin was the first to do so. In 1856, at the age of 18, while on vacation from London’s Royal College of Chemistry,
Wöhler made his mark in the annals of chemistry by deciding to identify this unknown substance. Once he identified it as urea, he also recognized the importance of his discovery. As he wrote in 1828 “[The] research gave the unexpected result . . . that is the more noteworthy inasmuch as it furnishes an example of the artificial production of an organic, indeed a so-called animal substance from inorganic materials.”
Chevreul and Wöhler had forever altered the study of organic chemistry. As other chemists looked at the work that Chevreul and Wöhler had done, they saw that chemists could indeed synthesize compounds of carbon without a living organism. They then began making carbon compounds and studying them. Soon many chemists were achieving remarkable successes in the new art of the synthesis of organic compounds. Thus began the study of organic compounds.
Inevitably, someone would take these new developments from the organic chemistry research laboratory and find ways to market them. William Henry Perkin was the first to do so. In 1856, at the age of 18, while on vacation from London’s Royal College of Chemistry,
Perkin was working in his home laboratory. While naively attempting to make quinine, a task not accomplished until 1944, he accidentally synthesized the dye now called Perkin’s mauve. The next year, using money borrowed from his father, he built a factory and marketed the new dye. From there, he worked with coal tar and found that coal tar was a rich source of starting materials for a variety of new dyes.
Another step in the progress of organic chemistry was the drilling of the first oil wells in Pennsylvania in 1859. The oil pumped from those wells provided a new, cheap, and abundant source of carbon compounds. Today the petrochemical industry supplies the raw materials for thousands of different products including a variety of things from explosives and fuels to pharmaceuticals and agricultural chemicals.
In 1895, the Bayer Company of Germany established the pharmaceutical industry. Then in 1899, the company began marketing aspirin, as a result of the work of Felix Hoffmann. Hoffmann learned how to prepare aspirin from natural salicylic acid. For hundreds of years, people had chewed the bark of the willow tree to relieve minor pain. Willow tree bark contains the analgesic salicylic acid. Aspirin is superior to salicylic acid as an analgesic because it produces less irritation to the stomach and effectively treats the pain.
In 1895, the Bayer Company of Germany established the pharmaceutical industry. Then in 1899, the company began marketing aspirin, as a result of the work of Felix Hoffmann. Hoffmann learned how to prepare aspirin from natural salicylic acid. For hundreds of years, people had chewed the bark of the willow tree to relieve minor pain. Willow tree bark contains the analgesic salicylic acid. Aspirin is superior to salicylic acid as an analgesic because it produces less irritation to the stomach and effectively treats the pain.
In the early days of chemistry, chemists learned a great deal about the simple compounds not usually found in living systems, but they learned very little about the organic compounds that are found in living systems. They were far too complex for the simple analytical tools available in the nineteenth century and the early twentieth century. Thus, progress was slow in understanding the chemistry of living systems. The subsequent development of powerful analytical tools allowed many insights into biologically important molecules and opened up new areas for scientific study.
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