Chemistry (History) Essay Example

scientific theory. Forecastles that the difference in material substances is a matter of balance, then that balance might be changed. Copper might become gold. Among the practical scientists of Alexandria are men who can be seen as the first alchemists and the first experimental chemists. Their trade, as workers in precious metals, involves melting gold and silver, mixing alloys, changing the color of metals by mysterious process. These are the activities of chemistry.

The everyday items of a chemical laboratory - stills, furnaces, flasks - are all in use in Alexandria.

There are strong mystical influences in Egypt, some of them deriving from Bibliographically, and this tradition too encourages experiment. Astrologers believe in many hierarchies, among the planets in the heavens but also among metals in the earth. Lead is the lowest of the metals, gold the highest. Left to itself, out of sight in the earth, lead may slowly be transformed up the scale to achieve ultimate perfection as gold. If this process could be accelerated, in the back of a Jeweler's shop, there would be certain immediate advantages.

In the early centuries, the experiments of chemistry and alchemy go hand in hand. Beginning of the Christian Era - End of 17th Century (Alchemy) The Advent of the Alchemists Influenced greatly by Aristotle ideas, alchemists attempted to transmute cheap metals to gold. The substance used for this conversion was called the Philosopher's Stone. 30th Century (sass's) - 1 5th Century (sass's) Failure of the Goldenness Although Pope John XII issued an edict against gold-making, the gold business continued.

Despite the alchemists' efforts, transmutation of cheap metals to gold never happened within this time period.

1520 Elixir of Life Alchemists not only wanted to convert metals to gold, but they also wanted to find a chemical concoction that would enable people to live longer and cure all ailments. This elixir of life never happened either. Alchemy in Asia: 8th - 10th century AD There are two important centers of alchemical experiment in medieval Asia. One safeguarding the caliphate, where from the 8th century there is enthusiastic translation and study of Certifications texts.

Arab alchemists, in their pursuit of synthesized gold, make practical advances in techniques of distillation. And they identify several chemical substances.

The other great centre is China, where alchemical experiments nave a slightly different purpose. The quarry is still gold, but as an elixir of eternal life. This is the pursuit of the Dadaists(one of whom describes, with gentle irony, inexperience which goes wrong in the 9th century). It is Dadaists who make the most startling chemical coverer of the period -gunpowder.

Gunpowder: 10th century In about 1040 a Chinese manual on warfare is issued under the telecommuting of Military Technology. It is the first document to describe gunpowder.

This black powder, formed by pounding a mixture of saltwater, charcoal and sulfur (a dangerous process if the pounding is overdone), seems to have been developed in the small chemical laboratories attached to the temples of Dishwasher research is conducted mainly on the secret of eternal life. At this early stage in China the military use of gunpowder is limited to grenades and mobs lobbed at the enemy from catapults.

Its real destructive force will only emerge when the explosion is confined, in the development of artillery. Science's siesta:

8th - 15th century AD In the profoundly Christian centuries of the European Middle Ages the prevailing mood is not conducive to scientific enquiry. God knows best, and so He should - since He created everything.

Where practical knowledge is required, there are ancient authorities whose conclusions are accepted without question -Ptolemy in the field of astronomy,Galen on matters anatomical. A few untypical scholars show an interest in scientific research.

The 13th-century Franciscan friar Roger Bacon is the most often quoted example, but his studies include alchemy and astrology as well as optics and astronomy. The practical skepticism required for science must await the Renaissance. Van Hellion: AD 1648 A book is published in Amsterdam in 1648 which can be seen as a definitive turning point between alchemy and chemistry.

Entitled Rotors Medicine(Origin of Medicine), it is the collected papers of Jan Baptists van Hellion, an aristocrat who has lived quietly on his estate near Brussels conducting scientific experiments. Van Hellion is inclined to mysticism.

He believes in alchemy and in the philosopher's stone which, if found, could turn base metals into gold. But he also conducts experiments on entirely scientific principles.

Some, like his famous five-year project with a willow tree, lead him to the wrong conclusion. But the method is valid. Van Hellion weighs out 200 lbs to dried earth n, places it in an earthenware container and plants a willow tree weighing 5 lbs. For five years he waters the plant daily. At the end of the experiment the willow tree weighs bases and the earth, when dried, not much less than 200 lbs.

Van Hellion concludes, reasonably that the wood, bark

ND leaves of the tree must be composed of water, which he therefore considers to be the chief constituent of all matter.

He is half right - any willow tree is about 50% water. What van Hellion is unaware of is that the tree has also absorbed carbon and oxygen, as carbon dioxide or CA, from the air. Ironically, Van Hellion himself becomes the first scientist to postulate the existence of carbon dioxide. He burns 62 lbs of charcoal and finds that he is left with only 1 lb of ash.

What has happened to the rest? Van Hellion is convinced, ahead of his time, of the indestructibility of matter. Indeed he is able to demonstrate that metal dissolved in acid can be recovered without loss of weight.

So he now reasons that the missing 61 lbs have escaped in the form of an airy substance to which he gives the name gas Sylvester(wood gas). The identity of this wood gas is not discovered until a century later (bypasses Black), but van Hellion is the first to have suggested the existence of gaseous substances other than air.

It is he who coins the word 'gas' - deriving it from Chaos(sounding similar in Flemish), which is used in Greek mythology to mean the original emptiness before creation. The principles of experiment enter chemistry in the work of van Hellion, and are developed by another aristocrat fascinated by the puzzles of science - Robert Bobble. Robert Bowie: AD 1661-1666 The experimental methods of modern science are considerably advanced by the work of Robert Bobble during the sass.

He is skilful at devising experiments to test theories, though

an early success is merely a matter of using von Curricle's air pump to create a vacuum in which he can observe the behavior of falling bodies. He is able to demonstrate the truth officinal's proposition that all objects will fall at the name speed in a vacuum. But Bobble also uses the air pump to make significant discoveries of his own - most notably that reduction in pressure reduces the boiling temperature of a liquid (water boils at 1000 at normal air pressure, but at only ICC if the pressure is reduced to one tenth).

Bole's best-known experiment involves a U-shaped glass tube open at one end.

Air is trapped in the closed end by a column to mercury. Bobble can snow that it TN weight of mercury is doubled, the volume of air is halved. The conclusion is the principle known still in Britain and the USA as Bole's Law - that pressure and volume re inversely proportional for a fixed mass of gas at a constant temperature. Bole's most famous work has a title perfectly expressing a correct scientific attitude. The Skeptical Sympathizers in 1661.

Bobble is properly skeptical about contemporary theories on the nature of matter, which still derive mainly from the Greek theory four elements.

His own notions are much closer to the truth. Indeed it is he who introduces the concept of the element in its modern sense, suggesting that such entities are 'primitive and simple, or perfectly mingled bodies'. Elements, as he imagines them, re 'corpuscles' of different sorts and sizes which arrange themselves into compounds - the chemical substances familiar to our senses. Compounds, he argues, can

be broken down into their constituent elements.

Bole's ideas in this field are further developed in his Origin of Forms and Qualities (1666). Chemistry is Bole's prime interest, but he also makes intelligent contributions in the field of pure physics.

In an important work of 1663,Experiments and Considerations Touching Colors, Bobble argues that colors have no intrinsic identity but are modifications in light fleeted from different surfaces. (This is demonstrated within a few years Boonton in his work on the spectrum. ) As a man of his time, Bobble is as much interested in theology as science.

It comes as a shock to read his requirements for the annual Bobble lecture which he founds in his will. Instead of discussing science, the lecturers are to prove the truth of Christianity against 'notorious infidels, biz. , atheists, theists, pagans, Jews and Mohammedan'.

The rules specifically forbid any mention of disagreement among Christian sects. Joseph Black and fixed air: AD 1754-1756 Joseph Black presents his doctoral thesis to the university of Edinburgh in 1754 and publishes it in expanded form two years later as Experiments upon Magnesia Alba, Quicklime, and Some Other Alkaline Substances.

The experiments which he describes are a classically complete series of compound transformations of calcium, carbon and oxygen - though it is not as yet possible to express his results in these terms. Black has observed that if he heats chalk (calcium carbonate), he gets quicklime (calcium oxide) and a gas, the presence of which he can identify by its weight. Unwilling as yet to speculate on its identity, he calls it fixed air - because it exists in solid form until released.

As a next stage, Black demonstrates that en can reverse the process.

Mixing water with the quicklime, he gets a substance (slaked lime) which will take up the fixed air again - leaving him with his original amount of chalk and the water. In other experiments Black is able to show that this same unknown gas, his fixed air, is produced as a result of burning charcoal, of fermentation and of breathing. He demonstrates this last point to his students by breathing through a tube into a Jar of intimate (a clear solution of slaked lime). The liquid turns cloudy as grains of chalk form in it.

Blacks fixed air is the gas Sylvester which the existence has been postulated by van Hellmann century earlier. Its composition as carbon dioxide is not discovered until the sass, when Laboriousness's it by burning carbon in oxygen. Blacks proof that such a gas exists prompts an energetic search for others. Hydrogen is identified backhanders in 1766, and oxygen almost simultaneously by Schlep and Priestley in the sass. Meanwhile Black has observed another important scientific principle, latent heat. Cavendish and hydrogen: AD 1766 In 1766 Henry Cavendish presents his first paper to the Royal Society.

Under the delectation's Airs he describes his experiments with two gases. One is the 'fixed air' identified by Joseph Black. The other is a gas which Cavendish calls 'inflammable air', soon to be given the name hydrogen billionaires. Hydrogen has been observed as a phenomenon for at least two centuries. The 16th- century alchemist and charlatan Paralegals finds that the dissolving of a metal in acid releases a form of air which will burn.

But Cavendish is the first to identify it as pacific substance. He believes that he has found the inflammable essence,phlogiston.

The study of gases in the laboratory is by now a standard chemical process thanks to the pneumatic trough developed in the early part of the 18th century by Stephen Hales. An upturned vessel, full of water, stands in a shallow trough of water. Gas is collected in the top of the vessel, displacing water and being sealed in by it.

With this device Cavendish is able to calculate the specific gravity of hydrogen. He finds that it is one fourteenth that of common air (it is the lightest substance known). Within less than two decades of his observation, a dramatic use is found for this very light new gas - invigilation.

Priestley and oxygen: AD 1774 Joseph Priestley, a misinterpretations, is employed as IL brain trot about 1 in an English nobleman's house, Bowdon in Wiltshire. He is provided with a laboratory to carry out his chemical researches. And he has recently acquired a large 12-inch lens, with which he can focus intense heat on chemical substances.

In August 1774 he directs his lens at some mercury oxide. He discovers that it gives off a colorless gas in which a candle burns with an unusually brilliant light.

Experimenting further with this gas, he records a few months later that 'two mice and myself have had the privilege of breathing it'. The mice were presumably offered the privilege first. Priestley has isolated oxygen. He foresees a medical use for it (it may be peculiarly salutary for the lungs in certain cases'), but he does not

fully appreciate its chemical significance - largely because he believes in the phlogiston theory.

He calls the new gas 'depreciatively air', on the assumption that the phlogiston has been removed from it.

In October 1774, visiting Paris with his noble patron, he describes his discovery to a adhering of French scientists. Among them slaveries, who develops Priestley experiments in his own laboratory and realizes that he has the evidence to disprove the phlogiston theory. Priestley meanwhile isolates a great many other gases.

Though he is the first to publish his discovery of oxygen, he has in fact been preceded in the identification of both oxygen and nitrogen by the Swedish chemist Carl Wilhelm Schlep. Schlep separates air in 1773 into two gases which he calls 'fire air' (oxygen) and 'foul air (nitrogen).

His findings only become known with the publication of his book Air ND Fibrin 1777, but it is established that the experiments date from four years earlier. Like Priestley, Schlep is handicapped by his belief in topologist's theory. When isolating hydrogen, he concludes - as has Cavendish - that it is pure phlogiston. Cavendish and water: AD 1784 During the last three decades of the 18th century, with more and more chemical substances becoming identified, there is great interest in which of them may be elements - in Bole's sense of being pure substances unmixed with anything else.

Of the four incinerating elements, earth is clearly no longer a candidate. Air is separated in 1773 by Selections oxygen and nitrogen. Water receives its dismissal from the club at Cavendish hands in a paper indeterminateness in Air(1784). Cavendish mixes hydrogen and oxygen, in the

proportion 2:1, in a glass globe through which he passes an electric spark. The resulting chemical reaction leaves him with water, which stands revealed as a compound (H2O).

Lavisher: A Although Antoine Laurent Lavisher has no single glamorous discovery to add luster to his name (such as postulating thefts gas, or identifying oxygen), he is regarded as he father of modern chemistry. The reason is that during the last two decades of the 18th century he interprets the findings of his colleagues with more scientific clarity than they have mustered, and creates the rational framework within which chemistry can develop. He gives evidence of this in his response to Priestley discovery of 'depreciatively air'.

He undertakes a series of experiments which reveal the involvement of this new gas in the processes where phlogiston has been assumed to play a key role.

He is able to show that Priestley gas is involved in chemical reactions in the recesses of burning and rusting, and that it is transformed in both burning and breathing into the 'fixed air' discovered by Joseph Black. His researches with phosphorus and sulfur cause him to believe that the new gas is invariably a component of acids. He therefore gives it in 1777 the name oxygen (from the Greek for 'acid maker').

On a similar principle Lavisher coins the word hydrogen (eater maker') for the very light gas isolated backhanders. With these two names chemistry takes a clear and decisive step into the modern era.

It is an advance which Lavisher soon consolidates. With three other French colleagues Lavisher publishes in MMГ©toothed De nomenclature chime (Method of Chemical Nomenclature). Their scheme, soon universally

accepted, sweeps away the muddled naming of substances which has descended from alchemy and replaces it with a logical system of classification.

This is an achievement of French rationalism comparable to the metric system, in the planning of which Lavisher is also involved.

In 1789 Lavisher follows this book on chemical methodology with the related fruits of his own researches -TraitГ© Г©lГ©maintainer De chime(Elementary Treatise of Chemistry). In this he attempts a list of the known elements. Lavisher names more than thirty elements, which he defines - in the tradition begun by Bayle century earlier - as substances which can be broken down no further by any known method of analysis.

The majority are metals, but there are by now three gases which Lavisher identifies as elements - oxygen, hydrogen and nitrogen (which he calls azotes, 'without life'). Lavisher is immensely active in public affairs, in addition to his scientific work.

Unfortunately his tasks have included, under the ancient rГ©gimp, membership of the former gГ©nГ©role or tax authority. By the time to the Terror, in 1794, it makes little deterrence that Lavisher NAS been on the liberal and reformist side on contemporary issues.

An order is given for the arrest of all the former members of the former gГ©nГ©role. In May 1794, in a trial lasting only part of a day, twenty-eight of them including Lavisher appear before a revolutionary tribunal. Condemned to death, they are guillotined that same afternoon. A colleague of Lavisher, who has worked with him on the commission to introduce the metric system, comments: 'It took only a moment to cut off that head; a century may not be enough to

produce another like it.

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