Читать книгу The Handy Chemistry Answer Book - Justin P. Lomont - Страница 11

The Philosopher’s Stone was an object of legend among alchemists. It was believed that the Philosopher’s Stone possessed the power to make gold from other cheap metals. It has also been said to serve as the elixir of life, which was sought by many alchemists. Of course, such a stone has never been discovered (at least not outside of Hogwarts).

When did alchemists finally abandon trying to make gold?

In the late 1700s, a scientist named James Price was still hard at work trying to “transmute” metals into gold and silver. In 1782, he claimed he could convert mercury into silver and gold. At first it appeared that his experiments had worked, but conflict rapidly rose. More and more scientists asked to witness the experiments firsthand, and Price eventually lost confidence in the validity of his own work. After disappearing for a few months, in 1783 he invited scientists to his laboratory to witness his experiments in person, but only a few men showed up. In their presence, Price intentionally ingested a poison, killing himself. He was the last of the modern scientists to claim to have achieved the goals of alchemy, and it is no longer believed that anyone will find a simple way to convert inexpensive metals into gold.

How did pharmaceutical science get started?

Paracelsus is credited with being the first person to use chemicals in medicine. Before Paracelsus, people believed that illness and disease were caused by an imbalance in the patient. Hippocrates thought it was an imbalance of the four humours (blood, phlegm, black bile, and yellow bile), and Galen furthered these ideas by assigning a symptom to an imbalance of each of Hippocrates’ humours. These theories supported the use of medical techniques like bloodletting. Paracelsus believed that illness was the result of something from the outside world attacking inside one’s body and that some of the illnesses could be cured by chemicals. He is also known for proposing the basis of toxicology, namely that dosage was critical to whether a substance was poisonous or not.

What was the first chemistry textbook published?

Although numerous chemistry texts exist before it, Alchemia, published by Andreas Libavius in 1597, is considered to be the first organized chemistry textbook. Libavius, born in Halle, Germany, in 1555, was a chemist and a medical doctor, and also served as a schoolmaster at the end of his life. In addition to his noteworthy textbook, Libavius is significant in the history of chemistry for further advancing the discipline away from the realm of magic, the occult, and alchemy toward a teachable, logical, and scientific discipline.

What’s the difference between alchemy and chemistry?

Let’s ask Robert Boyle, who in 1661 published The Sceptical Chymist, arguing that experiments disproved the idea that the universe was composed solely of Aristotle’s four elements. Boyle himself was an alchemist, in that he believed that one metal could be changed into another, but he was a staunch promoter of the scientific method and helped elevate chemistry to a science. So one could simply say that alchemy is a philosophy, while chemistry is a science.

Herbal medications are natural remedies for treating various ailments. Often these are traditional remedies that can date back hundreds of years and are still used today.

How did early chemistry relate to medicine?

Early societies all over the world found that certain types of plants could be used for medicinal purposes. Though only relatively recently have people attempted to gain a detailed understanding of the chemistry behind these methods, the overarching reason why these methods work is because a chemical in the plant interacts with the chemicals in your body in a beneficial way.

What is an herbal medicine?

Herbal medicines are any plants or plant extracts used for treating ailments, aches, pain, or discomfort. They can range from culinary remedies (like chicken soup for the common cold), to calming extracts (like mint tea), to eating whole herbs. Every ancient civilization seems to have discovered the use of plants as medicines in one form or another. Even as far back as five thousand years ago, humans were using herbal medicines, as evidenced by herbs being found alongside well-preserved, mummified humans like Ötzi the Iceman.

How were herbal medicines discovered?

If we had the story of how each and every medicinal herb was discovered, each would likely be an interesting and unique tale. Unfortunately, the use of plants as medicine predates written human history by a few millennia. The earliest written records come from the great ancient civilizations of humankind.

How are herbal medicines prepared?

There are many ways of preparing herbal medicines. Tinctures and elixirs are extractions of herbs using some solvent, usually ethanol. If a plant is extracted with acetic acid, the solution is known as a “vinegar,” even though the solvent is also vinegar. A tisane uses hot water to extract herbs—like tea.

What herbal medicines do people still use today?

Aspirin and quinine are probably the most famous herbal medicines that have made the transition to mainstream medicine. Many modern medicines were originally isolated from plants, however, but the commercial sources are now usually man-made. For example, Taxol® (paclitaxel) was originally isolated from the Pacific yew tree. In 1967 this compound was found to be useful as a treatment for various types of cancer. For almost thirty years, most of the paclitaxel that was given to patients was obtained from the yew tree. Alternate supplies of this drug were developed in the 1990s, moving this natural drug into the realm of modern synthetic medicines.

How do herbal medicines differ from modern medicine?

Modern pharmaceutical medicines usually contain only one active ingredient, or a few at most. The rest of the ingredients in a pill are there to aid in its delivery in one way or another. Herbal medicines, because they are made from plants that were once living, can contain many more chemicals, though only one may be the active ingredient in this case as well.

How did chemistry affect trade in ancient times?

Ancient chemistry was involved in the production of many goods that were important to trade. These included salt, silk, linen dyes, precious metals, wine, and pottery.

What is fire?

The chemical description of fire is a combustion reaction. It involves the reaction of oxygen with molecules in some combustible material. The fire itself is caused by energy released by this reaction in the form of heat and light. The fire you see is not only the light that’s being released, but also glowing hot gases.

Before matches and butane lighters were invented, people could use flint to start fires for heat and cooking. Striking a hard piece of metal against flint causes a spark, which can in turn catch tinder on fire.

How can a fire be started with a piece of flint?

Almost everyone has seen a movie character start a fire using a piece of flint, but you may wonder how this is possible. Flint is a hard stone that can produce sparks when it is struck against a metal, such as steel. The sharp edge of the flint breaks off a small splinter of steel, which is heated significantly by the friction from the strike of the flint. As this splinter of hot steel reacts with oxygen in the air, a spark is produced. The sparks generated in this way can then ignite a piece of dry wood, paper, or other fuel.

Who first realized that air has weight?

It was actually a mathematician named Evangelista Torricelli who is the first on record to demonstrate that air has weight. His experiment to prove this fact was prompted by the observation that water from a mineshaft could only be pumped upward to reach a certain height. Torricelli thought that the air pushing down on the surface of the water must play a role. To test this theory, in 1643 he placed a sealed tube of mercury upside down in a bowl of mercury. He observed that the weight of the air would keep the mercury in the tube at a certain level, and on different days he observed that the mercury would rise to different levels. We now know this is because the air pressure varies from day to day, and Torricelli’s experiment was the first barometer.

Who first realized that oxygen gas (O₂) was required for fire?

Philo of Byzantium in the second century B.C.E. was the first to observe (or at least the first to record such an observation) that if you placed a jar on top of a candle with water around its base, some water would be drawn up into the jar as the candle burned and eventually went out once all the oxygen was consumed. Although the experiment was well-designed, he ended up with an incorrect conclusion about the process. Robert Boyle repeated the experiment but replaced the candle with a mouse (seriously), and noticed the water also rose up the container. From this experiment he correctly inferred that whatever the component in air was (he called it nitroaerues), it was needed for both combustion and respiration. Robert Hooke, and others, likely produced oxygen gas in the seventeenth century, but didn’t realize it was an element as the phlogiston theory (see below) was in vogue at the time. So to really realize that oxygen gas was required for fire, it first had to be, well, discovered.

What is the theory of phlogiston?

In 1667, a scientist named Johann Joachim Becher introduced the theory of phlogiston as an explanation for the various observations scientists had made regarding combustion. These observations include the fact that some objects can burn while others cannot, and that a flame in a sealed container can go out before the combustible material is consumed. Becher proposed that a weightless (or almost weightless) substance called phlogiston was present in all materials that could burn and that this phlogiston was the substance being given off during combustion. If a candle placed in a closed container went out, Becher said this was because the phlogiston from the candle was moving into the air and that the air could only absorb a certain concentration of phlogiston before it became saturated and could no longer absorb more phlogiston from the candle. Another tenet of this theory was that the purpose of breathing was to remove phlogiston from the body. Air that had been used for combustion couldn’t be used to breathe then because it was already saturated with phlogiston.

How was the theory of phlogiston disproved?

Antoine Lavoisier, an eighteenth-century French chemist, disproved the theory of phlogiston by showing that combustion required a gas (oxygen) and that that gas has weight. Lavoisier did this by burning elements in closed containers. These solids gained mass, but the total weight of the containers did not change—what did change was the pressure inside the vessel. When Lavoisier opened the vessel up, air rushed in, and the total weight of the vessel increased. So Becher had it backward: oxygen was being used up by the candle instead of phlogiston being given off by the flame.

How was oxygen gas first discovered?

Well, to answer that question, you would first want to know who first discovered oxygen, and there is no simple answer to that question! There are three people to whom discovery of this can be ascribed: Carl Wilhelm Scheel, Joseph Priestley, and Antoine Lavoisier. Scheele produced O₂ (he called it “fire aire”) from mercuric oxide (HgO) in 1772, but the result wasn’t published until 1777. Meanwhile, in 1774 Priestley produced O₂ (he called it “dephlogisticated air”) using a similar experiment, which was published in 1775. Lavoisier claimed to have independently discovered the gas, and was in fact the first to explain how combustion worked via quantitative experiments, leading to the principle of Conservation of Mass, and ultimately disproving the entire idea of phlogiston. Whew. So Scheel found it first, but didn’t report it; Priestley reported it first, but didn’t have the explanation correct; and Lavoisier was last, but nailed it. Who would you give credit to?

What is electrochemistry and how was it discovered?

Modern electrochemistry studies reactions that take place at the interface of an electronic conductor and a source of charged ions (possibly a liquid). The development of electrochemistry began with studies on magnetism, electric charge, and conductivity. The earliest experiments typically focused on questions surrounding properties of materials; for example, which materials can be magnetized and which materials can be charged? As early as the 1750s scientists had discovered that electrical signals were important to human life and were using them to treat medical issues such as muscle spasms. In the late 1700s, Charles Coulomb developed laws describing the interactions of charged bodies, which are still used widely today and taught in any introductory course on electricity and magnetism.

The first electrochemical cells were developed during the 1800s. Electrochemical cells are arrangements of electrodes and sources of ions that either generate electric current from a chemical reaction, or alternatively, use electricity to drive a chemical reaction. Today these cells find applications in daily life, such as in the batteries that power your car or cell phone. Today electrochemistry still constitutes an important field of research and is one that will likely continue to lead to the development of new products and technologies.

What is the law of definite proportions?

The law of definite proportions says that a substance always contains the same proportions of each element of which it’s composed. For example, a molecule of water (H₂O) always contains two hydrogen atoms for every oxygen atom. This is commonly understood among modern chemists, but it was an important step in working toward a microscopic understanding of the composition of matter. The first to make such claims, in the early 1800s, was the French chemist Joseph Proust. It was a controversial idea at that time, and other chemists believed that elements could be combined in any proportion.

What is Avogadro’s constant?

Avogadro’s constant is a large number used to discuss large quantities of atoms or molecules, usually when chemists talk about quantities they can actually see or measure out. The number itself (rounded at three decimal places) is 6.022 × 10²³. It’s just a big number that relates an atomic or molecular mass to the mass of a collection of many atoms or molecules. Avogadro’s number of atoms of an element is called a mole of that element, and, similarly, Avogadro’s number of molecules of a compound is a mole of that compound. For example, the atomic mass of oxygen is about 16 grams per mole, and 6.022 × 10²³ atoms (1 mole) of oxygen weigh(s) about 16 grams. The most recent (and accurate) definition of this constant was 6.02214078(18) × 10²³, which was calculated by careful measurements of the mass and volume of 1-kilogram (about 2.2 lbs.) spheres of silicon-28, a particular isotope of silicon (see next chapter concerning isotopes).

When was Avogadro’s constant discovered?

Amedeo Carlo Avogadro published a paper in 1811 describing his theory that a volume of gas (at a given temperature and pressure) contains a certain number of atoms or molecules regardless of what gas it is. Avogadro didn’t actually determine what that number was, however. It took just over fifty years for someone to make progress on that: Johann Josef Loschmidt, in 1865, estimated the average size of molecules in air. It’s nothing short of amazing that he ended up being off by only a factor of two. Jean Perrin, a French physicist, accurately determined the constant using a few different techniques. He was awarded the Nobel Prize in Physics in 1926 for the work, but Perrin proposed that the constant be named for Avogadro—and the name stuck. (For more on the use of the constant, see “Atoms and Molecules.”)

Why is chemistry “the central science”?

Chemistry is called the central science because it’s related to everything! It connects and draws from topics in biology, physics, materials science, mathematics, engineering, and other fields. Chemistry is important to how our body functions, to the food we eat, to how our medicines work, and to pretty much everything else in our lives. After reading this book, we hope you’ll agree!