The Birth of Chemistry

Demons in Ore: 1742-1751

 Miners in the Harz mountains have often been frustrated by a substance that appears to be a copper ore but which, when heated, yields none of the expected metal. Even worse, it emits noxious fumes. In about 1735 Georg Brandt was 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 - cobalt

 A similar demon is blamed by miners in Saxony for another ore that 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

1754 Joseph Black heated limestone and produced his fixed air.

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.

The classic experiments of Joseph Black on magnesia alba (basic magnesium carbonate) in the 1750s; by extensive and careful use of the chemical balance, showed that an air with specific properties could combine with solid substances like quicklime and could be recovered from them.

1766-Henry Cavendish discovered inflammable gas, hydrogen.

1773-Sheele isolated oxygen using silver carbonate.

1774-Priestly discovered Oxygen by heating HgO.

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.

1775-Micro-Organisms observed using Microscope.

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.

Lavoisier is most noted for his discovery of the role oxygen plays in combustion. He recognized and named oxygen (1778) and hydrogen (1783) and opposed the phlogiston theory. Lavoisier helped construct the metric system, wrote the first extensive list of elements, and helped to reform chemical nomenclature.

1778-Lavoisier named the elements, hydrogen, Oxygen, and Nitrogen. He announced that air is composed of two gases, oxygen, and nitrogen.

He explained the combustion. He concluded that during calcination, metals absorb oxygen and increase their weight.

He was 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 research with phosphorus and sulphur caused 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 that Lavoisier soon consolidates.

1781-Cavendish synthesized water by burning Hydrogen in Oxygen. 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).

1782-Lavoisier established the law of conservation of mass.

He said,” In a chemical  change nothing is lost and nothing is created and everything is transformed.”  He was considered the father of modern chemistry.

1789-For the first time, He Made a list of 23 known elements. He wrote the elementary treatise on chemistry. This text clarified the concept of an element as a substance that could not be broken down by any known method of chemical analysis.

1793-Alessandro Volta, an Italian Physicist, and chemist discovered the Principle of the primary battery.

In 1800, Volta invented the voltaic pile, an early electric battery, which produced a steady electric current. Volta had determined that the most effective pair of dissimilar metals to produce electricity was zinc and copper. Volta's method of stacking round plates of copper and zinc separated by disks of cardboard moistened with a salt solution was termed a voltaic pile. 

 Volta's invention was built on Luigi Galvani's 1780s discovery of how a circuit of two metals and a frog's leg can cause the frog's leg to respond. Volta demonstrated in 1794 that when two metals and brine-soaked cloth or cardboard are arranged in a circuit they produce an electric current. In 1800, Volta stacked several pairs of alternating copper (or silver) and zinc discs (electrodes) separated by cloth or cardboard soaked in brine (electrolyte) to increase the electrolyte conductivity. When the top and bottom contacts were connected by a wire, an electric current flowed through the voltaic pile and the connecting wire.

Thus, Volta is considered to be the founder of the discipline of electrochemistry.

 A Galvanic cell (or voltaic cell) is an electrochemical cell that derives electrical energy from spontaneous redox reactions taking place within the cell. It generally consists of two different metals connected by a salt bridge, or individual half-cells separated by a porous membrane.

 A voltaic cell is an electrochemical cell that uses a chemical reaction to produce electrical energy. The important parts of a voltaic cell: The anode is an electrode where oxidation occurs. The cathode is an electrode where reduction occurs.

 In redox reactions, electrons are transferred from one species to another. If the reaction is spontaneous, energy is released, which can then be used to do useful work. To harness this energy, the reaction must be split into two separate half-reactions: the oxidation and reduction reactions. The reactants are put into two different containers and a wire is used to drive the electrons from one side to the other. In doing so, a Voltaic/ Galvanic Cell is created.

1794- The great chemist, Lavoisier was executed in the French Revolution.

1803-Dalton's atomic theory.

Dalton proposed a modern atomic theory in 1803 which stated that all matter was composed of small indivisible particles termed atoms, atoms of a given element possess unique characteristics and weight, and three types of atoms exist; simple (elements), compound (simple molecules), and complex (complex molecules).

1803-The law of multiple proportions by Dalton.

The law of multiple proportions is one of the basic laws of stoichiometry used to establish the atomic theory.

In 1803, an English meteorologist began to speculate on the phenomenon of water vapor. John Dalton (1766-1844) was aware that water vapor is part of the atmosphere, but experiments showed that water vapor would not form in certain other gases. He speculated that this had something to do with the number of particles present in those gases. Perhaps there was no room in those gases for particles of water vapor to penetrate. There were either more particles in the “heavier” gases or those particles were larger. Using his own data and the Law of Definite Proportions, he determined the relative masses of particles for six of the known elements: hydrogen (the lightest and assigned a mass of 1), oxygen, nitrogen, carbon, sulfur, and phosphorous. Dalton explained his findings by stating the principles of the first atomic theory of matter.

 Elements are composed of extremely small particles called atoms. Atoms of the same element are identical in size, mass, and other properties. Atoms of different elements have different properties. Atoms cannot be created, subdivided, or destroyed. Atoms of different elements combine in simple whole-number ratios to form chemical compounds. In chemical reactions, atoms are combined, separated, or rearranged to form new compounds

1804-French chemist Joseph Proust proposed the law of definite proportions, which states that elements always combine in small, whole-number ratios to form compounds, based on several experiments conducted between 1797 and 1804.

 In chemistry, the law of definite proportion, sometimes called Proust's law or the law of definite composition, or the law of constant composition states that a given chemical compound always contains its component elements in a fixed ratio (by mass) and does not depend on its source and method of preparation.

1808- Law of combining volumes by Gay-Lussac. Gay-Lussac announced what was probably his single greatest achievement: from his own and others' experiments he deduced that gases at constant temperature and pressure; combine in simple numerical proportions by volume, and the resulting product or products—if gases—also bear a simple proportion by volume to the volumes of the reactants. In other words, gases under equal conditions of temperature and pressure react with one another in volume ratios of small whole numbers. This conclusion subsequently became known as "Gay-Lussac's law" or the "Law of Combining Volumes".

1811-Avogadro's law, which states that equal volumes of different gases at the same temperature and pressure must contain the same number of particles. 

Amedeo Avogadro (1776-1856), hypothesized that equal volumes of gases at the same temperature  and pressure contain equal numbers of molecules, from which it followed that relative molecular weights of any two gases are the same as the ratio of the densities of the two gases under the same conditions of temperature and pressure.

 

1812-using Volta's battery, Humphry Davy isolated new elements like, potassium, Sodium, Magnesium, Calcium, Strontium, Barium, and Boron. He went on to electrolyse molten salts and discovered several new metals, including sodium and potassium, highly reactive elements known as alkali metals. During the first half of 1808, Davy conducted a series of further electrolysis experiments on alkaline earths including lime, magnesia, strontites, and barytes.

1814-On 30 June 1808, Davy reported to the Royal Society that he had successfully isolated four new metals which he named barium, calcium, strontium, and magnesium. The observations gathered from these experiments also led to Davy isolating boron in 1809

1817-Jacob Berzelius was a Swedish Chemist.

Berzelius, [disciple of Dalton], named the elements and used symbols to represent elements in a chemical formula. He also calculated the atomic weights of different elements.

Berzelius began his career as a physician but his researches in physical chemistry were of lasting significance in the development of the subject. He is especially noted for his determination of atomic weights; his experiments led to a more complete depiction of the principles of stoichiometry, or the field of chemical combining proportions. In 1803 Berzelius demonstrated the power of an electrochemical cell to decompose chemicals into pairs of electrically opposite constituents.

Berzelius's work with atomic weights and his theory of electrochemical dualism led to his development of a modern system of chemical formula notation that could portray the composition of any compound both qualitatively (by showing its electrochemically opposing ingredients) and quantitatively (by showing the proportions in which the ingredients were united). His system abbreviated the Latin names of the elements with one or two letters and applied subscripts to designate the number of atoms of each element present in both the acidic and basic ingredients

1834-Michael Faraday

Faraday discovered that when electricity is passed through ionic solutions, the amount of chemical change produced was proportional to the quantity of electricity passed through it.

Electrochemistry is a branch of chemistry concerned with the relation between electricity and chemical change. Many spontaneously occurring chemical reactions liberate electrical energy, and some of these reactions are used in batteries and fuel cells to produce electric power. Conversely, electric current can be utilized to bring about many chemical reactions that do not occur spontaneously. In the process called electrolysis, electrical energy is converted directly into chemical energy, which is stored in the products of the reaction. This process is applied in refining metals, electroplating, and in producing hydrogen and oxygen from water.

An electrolytic cell is an electrochemical cell that drives a non-spontaneous redox reaction through the application of electrical energy. They are often used to decompose chemical compounds, in a process called electrolysis—the Greek word lysis means to break up.

An electrolytic cell has three component parts: an electrolyte and two electrodes (a cathode and an anode). The electrolyte is usually a solution of water or other solvents in which ions are dissolved.

 

Faraday's law states that “the amount of any substance deposited or liberated during electrolysis is proportional to the quantity of electric charge passed and to the equivalent weight of the substance.” 

Faraday's First Law of Electrolysis. The mass of the substance (m) deposited or liberated at any electrode is directly proportional to the quantity of electricity or charge (Q) passed. Faraday further observed that 1 Faraday (96,485C) of charge liberates 1 gram equivalent of the substance at the electrodes.

Faraday’s First Law of Electrolysis states that the chemical deposition due to the flow of current through an electrolyte is directly proportional to the quantity of electricity (coulombs) passed through it.

  Faraday’s second law of electrolysis states that, when the same quantity of electricity is passed through several electrolytes, the mass of the substances deposited are proportional to their respective chemical equivalent or equivalent weight.

Chemical Equivalent or Equivalent Weight

The chemical equivalent or equivalent weight of a substance can be determined by Faraday’s laws of electrolysis, and it is defined as the weight of that substance which will combine with or displace the unit weight of hydrogen.
The chemical equivalent of hydrogen is, thus, unity. Since the valency of a substance is equal to the number of hydrogen atoms, which it can replace or with which it can combine, the chemical equivalent of a substance, therefore may be defined as the ratio of its atomic weight to its valency.

In 1841, the chemical society of London was founded in England by 77 scientists as a result of increased interest in scientific matters. Chemist Robert Warrington was the driving force behind its creation. The Chemical Society of London is a "fruitful amalgamation of the technological and academic chemists". 1845-the Royal College of Chemistry was founded.

1851-The Royal School of Mines was established in London

 

1852-concept of valency by Edward Frankland.

Research beginning about 1850 led him to the idea that an atom of an element can combine only with a certain limited number of atoms of other elements. He thus established a theory of valency (1852), which became the basis of modern structural chemistry.

In 1866 he published an influential textbook, Lecture Notes, in which he adopted Crum Brown’s graphic (structural) formulas and argued (against Kekulé) that elements could exhibit more than one valence below a fixed upper maximum. 

 From 1863 to 1870 he and Baldwin Duppa exploited zinc ethyl and other organic reagents, including ethyl acetate, in the synthesis of ethers, dicarboxylic acids, unsaturated monocarboxylic acids, and hydroxy acids. This meticulous work revealed clearly the structure and relationship of these compounds, and of course, its methodology had a great bearing on the growth of the chemical industry.

Reagents are "substances or compounds that are added to a system in order to bring about a chemical reaction or are added to see if a reaction occurs. 

In1860-world's first chemical conference was held in Europe [Karlsruhe Congress] by Kekule.140 delegates participated in it. The young Siberian Mendeleyev was also present in the meeting.

 An important long-term result of the Karlsruhe Congress was the adoption of the now-familiar atomic weights.

Prior to the Karlsruhe meeting, and going back to Dalton's work in 1803, several systems of atomic weights were in use. In one case, a value of 1 was adopted as the weight of hydrogen (the base unit), with 6 for carbon and 8 for oxygen. As long as there were uncertainties over atomic weights then the compositions of many compounds remained in doubt. Following the Karlsruhe meeting, values of about 1 for hydrogen, 12 for carbon, 16 for oxygen, and so forth were adopted. This was based on the recognition that certain elements, such as hydrogen,  nitrogen, and oxygen, were composed of diatomic molecules and not individual atoms.

Rocke says. “If you believed Avogadro’s theory, then you could get the correct molecular formula for molecules, as well as the correct atomic weights, which was the groundwork required to construct the periodic table,“ he says.

When the 1860 conference began, the chemistry was in a total state of disarray.

Participants broke into groups to discuss contentious issues, such as stoichiometry or representation of molecular formulas, and then they would return to the plenary hall to share their deliberations, Podlech says. However, sometimes a group’s consensus was undermined by the presenter’s personal opinions

In fact, the conference was mostly dominated by voices from the old guard—so much so that the organizers began to fear their efforts were in vain and that the conference was going to be a complete failure. But just before the meeting’s close, a relatively unknown Italian chemist named Stanislao Cannizzaro gave a long, impassioned, and eloquent lecture that argued for Avogadro’s perspective on molecules. After Cannizzaro’s lecture, one of his friends handed out a paper that effectively reiterated his speech and that several important delegates read on their trips home.

“It was as though the scales fell from my eyes; doubt vanished, and it was replaced by a feeling of peaceful certainty,“ wrote Meyer, who would later go on to construct a correct periodic table around the same time as Mendeleev put his together. Mendeleev wrote that the meeting “produced such a remarkable effect on the history of our science that I consider it a duty ... to describe all the sessions ... and the results.“

But Cannizzaro’s plea needed some time to sink in, and it took about a decade before scientists hashed out the correct molecular weights that enabled the periodic table to emerge. “On that last day in Karlsruhe, there were no cheers, no sudden enlightenment, no ovation,” Rocke notes. “The assembled chemists simply quietly filed out of the hall and went home.

The Karlsruhe meeting was the first international meeting of chemists and it led to the eventual founding of the International Union of Pure and Applied Chemistry (IUPAC).

Later, German chemist Lothar Meyer, and the Russian chemist Dmitri Mendeleev, who had both been in attendance at Karlsruhe, constructed element arrangements using the Cannizzaro numbers - on tables: with the elements arranged in rows and columns - for schoolbooks. 

In1869-Mendeleyev constructed the periodic table of elements, based on increasing atomic weights of elements.

1898-discovery of Nobel gases by William Ramsay.