Birth of chemistry

1660-the royal society was founded in England

Robert Boyle

1661-Robert Boyle defined element, acid and base. He also discovered the gas law called Boyle.s law.

1666- The French academy of science was founded.

1735-Georg Brandt discovered Cobalt in his Swedish laboratory.

[Miners in the Harz mountains have often been frustrated by a substance which appears to be copper ore but which, when heated, yields none of the expected metal. Even worse, it emits noxious fumes.]

1751- Axel Cronstedt discovered Nickel in Sweden.

A similar demon is blamed by miners in Saxony for another ore which yields a brittle substance instead of copper. The impurity in ore of this type is analyzed in Sweden in 1751 by Axel Cronstedt. He identifies its components as arsenic and a previously unknown hard white metal, quite distinct from copper.

Joseph Black, the Scottish Chemist

1761-Black explored the properties of a gas produced in various reactions. He found that limestone could be heated or treated with acids to yield a gas he called "fixed air." He observed that the fixed air was denser than air and did not support either flame or animal life. Black also found that when bubbled through an aqueous solution of lime (calcium hydroxide), it would precipitate calcium carbonate. He used this phenomenon to illustrate that carbon dioxide is produced by animal respiration and microbial fermentation.

Henry Cavendish

1766-Henry Cavendish had set up a small laboratory in his house. He collected some iron, lead and tin pieces, besides hydrochloric acid. He then put an equal number of iron pieces in both acids. He did the same with the lead and tin piece producing hydrogen. As a result of the chemical process some bubbles surfaced. He collected the gas bubbles in separate balloons. He noticed that all the balloons contained samples of inflammable gases and they all produced similar blue flame. On further observation he found that the gases weighed the same and the volume of inflammable gas produced was proportionate to the metal pieces.

1774- Joseph Priestley and discovery of Oxygen.

On August 1, 1774, he conducted his most famous experiment. Using a 12-inch-wide glass "burning lens," he focused sunlight on a lump of reddish mercuric oxide in an inverted glass container placed in a pool of mercury. The gas emitted, he found, was "five or six times as good as common air." In succeeding tests, it caused a flame to burn intensely and kept a mouse alive about four times as long as a similar quantity of air.

In October 1774, Priestley visiting Paris with his noble patron, he describes his discovery to a gathering of French scientists. Among them is Lavoisier, who develops Priestley's experiments in his own laboratory and realizes that he has the evidence to disprove the phlogiston theory. He named it oxygen [meaning acid maker].

Antoine Lavoisier, the French Chemist.

In 1779 Lavoisier coined the name oxygen for the element released by mercury oxide. He found oxygen made up 20 percent of air and was vital for combustion and respiration. He also concluded that when phosphorus or sulfur are burned in air, the products are formed by the reaction of these elements with oxygen.

In 1777 Lavoisier correctly identified sulfur as an element. He had carried out extensive experiments involving this substance and observed that it could not be broken down into any simpler substances.

In 1778 Lavoisier found that when mercury oxide is heated its weight decreases. The oxygen gas it releases has exactly the same weight as the weight lost by the mercury oxide.

While this may seem obvious to us today, it was less so in those days (hence the general support for the phlogiston theory). After carrying out work with a number of different substances, and recalling earlier work such as his work in 1772 with carbon, Lavoisier announced a new fundamental law of nature:

The law of conservation of mass:

· matter is conserved in chemical reactions

or stated in another way:

· the total mass of a chemical reaction’s products is identical to the total mass of the starting materials

The law of mass conservation only became firmly established after Lavoisier independently discovered it.

In 1783 Lavoisier coined the name ‘hydrogen’ for the gas which Henry Cavendish had recognized as a new element in 1766; Cavendish had called the gas inflammable air.

Working again with Pierre-Simon Laplace, Lavoisier burned hydrogen with oxygen and found that water was produced, establishing that water is not an element, but is actually a compound made from the elements hydrogen and oxygen. This result astonished many people, because at that time ‘everyone knew’ that water was itself one of the ‘indivisible’ element

In1789 Lavoisier published his groundbreaking Elementary Treatise on Chemistry.

Elementary Treatise on Chemistry detailed his oxygen theory of chemistry (banishing phlostigon), made clear the difference between a compound and an element, and contained a list of chemical elements. The list included oxygen, nitrogen, hydrogen, sulfur, phosphorus, carbon, antimony, cobalt, copper, gold, iron, manganese, molybdenum, nickel, platinum, silver, tin, tungsten, and zinc.

Antoine Lavoisier is called the father of modern chemistry.

Experimental science

Van Helmont weighs out 200 lbs of dried earth, 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 169lbs and the earth, when dried, not much less than 200 lbs. Van Helmont concludes, reasonably that the wood, bark and 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 Helmont is unaware of is that the tree has also absorbed carbon and oxygen, as carbon dioxide or CO2, from the air. 

Ironically, Van Helmont 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 Helmont 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 sylvestre (wood gas).

Demons in the ore: 1742-1751

Miners in the Harz mountains have often been frustrated by a substance which appears to be copper ore but which, when heated, yields none of the expected metal. Even worse, it emits noxious fumes. In about 1735 Georg Brandt is able to show in his Swedish laboratory that the  previously unknown substance was Cobalt. It has been identified, and Brandt gives its name to the new substance - as cobalt

A similar demon is blamed by miners in Saxony for another ore which yields a brittle substance instead of copper. The impurity in ore of this type is analyzed in Sweden in 1751 by Axel Cronstedt. He identifies its components as arsenic and a previously unknown hard white metal, quite distinct from copper. He honours the new substance and calls it nickel.

Joseph Black and fixed air: 1754-1756
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.

In 1766 Henry Cavendish presents his first paper to the Royal Society. Under the title Factitious 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 by Lavoisier

Hydrogen has been observed as a phenomenon for at least two centuries. The 16th-century alchemist and charlatan Paracelsus 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 specific substance. He believes that he has found the inflammable essence, phlogiston. 

Priestley and oxygen: 1774

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

In October 1774, visiting Paris with his noble patron, he describes his discovery to a gathering of French scientists. Among them is Lavoisier, who develops Priestley's experiments in his own laboratory and realizes that he has the evidence to disprove the phlogiston theory.

Cavendish and water: 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 Boyle's sense of being pure substances unmixed with anything else. Of the four ancient Greek elements, earth is clearly no longer a candidate. Air is separated in 1773 by Scheele into oxygen and nitrogen. Water receives its dismissal from the club at Cavendish's hands in a paper entitled Experiments 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). 

Lavoisier: 1777-1794

Although Antoine Laurent Lavoisier has no single glamorous discovery to add lustre to his name (such as identifying oxygen), he is regarded as the 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's discovery of 'dephlogisticated 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's gas is involved in chemical reactions in the processes 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 sulphur cause him to believe that the new gas is invariably a component of acids. He therefore gives it in 1777 the name oxygen ( 'acid maker'). On a similar principle Lavoisier coins the word hydrogen ('water maker') for the very light gas isolated by Cavendish.

With these two names chemistry takes a clear and decisive step into the modern era. It is an advance which Lavoisier soon consolidates. 

With three other French colleagues Lavoisier publishes in 1787 Méthode de nomenclature chimique (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 Lavoisier is also involved

In 1789 Lavoisier follows this book on chemical methodology with the related fruits of his own researches - Traité élémentaire de chimie (Elementary Treatise of Chemistry). In this he attempts a list of the known elements. 

Lavoisier names more than thirty elements, which he defines - in the tradition begun by Boyle a 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 Lavoisier identifies as elements - oxygen, hydrogen and nitrogen (which he calls azote, 'without life').

Oxygen theory of combustion

The oxygen theory of combustion resulted from a demanding and sustained campaign to construct an experimentally grounded chemical theory of combustion, respiration, and calcination. The theory that emerged was in many respects a mirror image of the phlogiston theory, but gaining evidence to support the new theory involved more than merely demonstrating the errors and inadequacies of the previous theory. From the early 1770s until 1785, when the last important pieces of the theory fell into place, Lavoisier and his collaborators performed a wide range of experiments designed to advance many points on their research frontier.

Lavoisier’s research in the early 1770s focused upon weight gains and losses in calcination. It was known that when metals slowly changed into powders (calxes), as was observed in the rusting of iron, the calx actually weighed more than the original metal, whereas when the calx was “reduced” to a metal, a loss of weight occurred. The phlogiston theory did not account for these weight changes, for fire itself could not be isolated and weighed. Lavoisier hypothesized that it was probably the fixation and release of air, rather than fire, that caused the observed gains and losses in weight. This idea set the course of his research for the next decade.

Along the way, he encountered related phenomena that had to be explained. Mineral acids, for instance, were made by roasting a mineral such as sulfur in fire and then mixing the resultant calx with water. Lavoisier had initially conjectured that the sulfur combined with air in the fire and that the air was the cause of acidity. However, it was not at all obvious just what kind of air made sulfur acidic. The problem was further complicated by the concurrent discovery of new kinds of airs within the atmosphere. British pneumatic chemists made most of these discoveries, with Joseph Priestley leading the effort. And it was Priestley, despite his unrelenting adherence to the phlogiston theory, who ultimately helped Lavoisier unravel the mystery of oxygen. Priestley isolated oxygen in August 1774 after recognizing several properties that distinguished it from atmospheric air. In Paris at the same time, Lavoisier and his colleagues were experimenting with a set of reactions identical to those that Priestley was studying, but they failed to notice the novel properties of the air they collected. Priestley visited Paris later that year and at a dinner held in his honour at the Academy of Sciences informed his French colleagues about the properties of this new air. Lavoisier, who was familiar with Priestley’s research and held him in high regard, hurried back to his laboratory, repeated the experiment, and found that it produced precisely the kind of air he needed to complete his theory. He called the gas that was produced oxygen, the generator of acids. Isolating oxygen allowed him to explain both the quantitative and qualitative changes that occurred in combustion, respiration, and calcination.