Discovery of Nitrogen
In 1674 the English physician John Mayow demonstrated that air is not a single element, it is made up of different substances. He did this by showing that only a part of air is combustible. Most of it is not.
Almost a century later, Scottish chemist Joseph Black carried out more detailed work on air. After removing oxygen and carbon dioxide, part of the air remained.
Black used burning phosphorus as the final step in oxygen removal. (Burning phosphorus has a very high affinity for oxygen and is efficient at removing it completely.) Black then assigned further study of the gases in air to his doctoral student, Daniel Rutherford.
Rutherford built on Black’s work and in a series of steps thoroughly removed oxygen and carbon dioxide from air. He showed that, like carbon dioxide, the residual gas could not support combustion or living organisms. Unlike carbon dioxide, however, nitrogen was insoluble in water and alkali solutions. Rutherford reported his discovery in 1772 of ‘noxious air,’ which we now call nitrogen.
Swedish pharmacist Carl Scheele discovered nitrogen independently, calling it spent air.
Scheele absorbed oxygen in a number of ways, including using a mixture of sulfur and iron filings and burning phosphorus. After removing the oxygen, he reported a residual gas which would not support combustion and had between two-thirds and three-quarters of the volume of the original air. Scheele published his results in 1777, although it is thought the work was carried out in 1772.
Although Rutherford and Scheele are now jointly credited with nitrogen’s discovery, it appears to have been discovered earlier by Henry Cavendish, but not published.
Prior to 1772 (the precise date is unknown – Priestley refers to it in his work “Experiments and Observations Made in and Before the Year 1772″) Cavendish wrote to Joseph Priestley describing ‘burnt air’.
The ‘burnt air’ had been prepared by passing air repeatedly over red hot charcoal (removing the oxygen) and then bubbling the remaining gas through a solution of caustic potash (potassium hydroxide) which would have removed the carbon dioxide.
Cavendish wrote: “The specific gravity of this air was found to differ very little from that of common air; of the two, it seemed rather lighter. It extinguished flame, and rendered common air unfit for making bodies burn in the same manner as fixed air, but in a less degree, as a candle which burnt about 80″ in pure common air, and which went out immediately in common air mixed with 6/55 of fixed air, burnt about 26″ in common air mixed with the same portion of this burnt air.”
In 1790 the French chemist Jean-Antoine-Claude Chaptal named the element ‘nitrogen’ after experiments showed it to be a constituent of nitre, as potassium nitrate was called then.
Discovery of Silicon
Quartz (crystalline silicon dioxide) has been known to people for many thousands of years. Flint is a form of quartz, and tools made from flint were in everyday use in the stone age.
In 1789, the French chemist Antoine Lavoisier proposed that a new chemical element could be found in quartz. This new element, he said, must be very abundant. He was right, of course. Silicon accounts for 28% of the weight of Earth’s crust.
It is possible that in England, in 1808, Humphry Davy isolated partly pure silicon for the first time, but he did not realize it.
In 1811, French chemists Joseph L. Gay-Lussac and Louis Jacques Thénard may also have made impure silicon by reacting potassium with silicon tetrafluoride to produce a reddish brown solid which was probably amorphous silicon. They did not, however, attempt to purify this new substance.
In 1824, Swedish chemist Jöns Jakob Berzelius produced a sample of amorphous silicon, a brown solid, by reacting potassium fluorosilicate with potassium and purifying the product with repeated washing. He named the new element silicium.
At that time the concept of semiconductors lay a century in the future. Unaware that such materials existed and that silicon was an excellent example of a semiconductor, scientists debated whether the new element should be classed as a metal or a nonmetal.
Berzelius believed it was a metal, while Humphry Davy thought it was a nonmetal. The problem was that the new element was a better conductor of electricity than nonmetals, but not as good a conductor as a metal.
Silicon was given its name in 1831 by Scottish chemist Thomas Thomson. He retained part of Berzelius’s name, from ‘silicis,’ meaning flint. He changed the element’s ending to on because the element was more similar to nonmetals boron and carbon than it was to metals such as calcium and magnesium. (Silicis, or flint, was probably our first use of silicon dioxide.)
In 1854, Henri Deville produced crystalline silicon for the first time. He did this by electrolyzing an impure melt of sodium aluminum chloride to produce aluminum silicide. The aluminum was removed with water, leaving silicon crystals.
Discovery of Boron
Boron compounds such as borax (sodium tetraborate, Na2B4O7·10H2O) have been known and used by ancient cultures for thousands of years. Borax’s name comes from the Arabic buraq, meaning “white.”
Boron was first partially isolated in 1808 by French chemists Joseph L. Gay-Lussac and L. J. Thénard and independently by Sir Humphry Davy in London. Gay-Lussac & Thénard reacted boric acid with magnesium or sodium to yield boron, a gray solid. They believed it shared characteristics with sulfur and phosphorus and named it bore.
Davy first tried to produce boron by electrolysis of boric acid, but was not satisfied with the results.
He enjoyed greater success reacting boric acid with potassium in a hydrogen atmosphere.
The result was a powdery substance.
Davy commented the substance was, “of the darkest shades of olive. It is opake, very friable, and its powder does not scratch glass.” After carrying out a number of chemical reactions to verify the uniqueness of the substance, Davy wrote, “there is strong reason to consider the boracic basis as metallic in nature, and I venture to propose for it the name of boracium.”
Neither party had, in fact, produced pure boron. Their samples were only about 60% pure.
In 1909, American chemist Ezekiel Weintraub was able to produce 99% pure boron, by reducing boron halides with hydrogen.
Almost a century later, in 2004, Jiuhua Chen and Vladimir L. Solozhenko produced a new form of boron, but were uncertain of its structure.
In 2009, a team led by Artem Oganov was able to demonstrate the new form of boron contains two structures, B12 icosohedra and B2 pairs. Gamma-boron, as it has been called, is almost as hard as diamond and more heat-resistant than diamond.
Talking about boron’s part metal, part non-metal properties, Oganov said, “Boron is a truly schizophrenic element. It’s an element of complete frustration. It doesn’t know what it wants to do. The outcome is something horribly complicated.”
Discovery of Aluminum
People have used alum since ancient times for dyeing, tanning and to stop bleeding. Alum is potassium aluminum sulfate.
In the 1750s German chemist Andreas Marggraf found he could use an alkali solution to precipitate a new substance from alum. Marggraf had previously been the first person to isolate zinc in 1746.
The substance Marggraf obtained from alum was named alumina by French chemist Louis de Morveau in 1760. We now know that alumina is aluminum oxide – chemical formula Al2O3.
De Morveau believed alumina contained a new metallic element, but, like Marggraf, he was unable to extract this metal from its oxide.
In 1807 or 1808, English chemist Humphry Davy decomposed alumina in an electric arc to obtain a metal. The metal was not pure aluminum, but an alloy of aluminum and iron.
Davy called the new metal alumium, then renamed it aluminum.
Aluminum was first isolated in 1825 by Hans Christian Ørsted (Oersted) in Copenhagen, Denmark who reported, “a lump of metal which in color and luster somewhat resembles tin.”
Ørsted produced aluminum by reducing aluminum chloride using a potassium-mercury amalgam. The mercury was removed by heating to leave aluminum.
German chemist Friedrich Wöhler (Woehler) repeated Ørsted’s experiment but found it yielded only potassium metal. Wöhler developed the method further two years later, reacting volatalized aluminum trichloride with potassium to produce small amounts of aluminum. In 1856 Berzelius stated that it was Wöhler who had succeeded in 1827. Wöhler is therefore usually given credit for the discovery.
More recently, Fogh repeated the original experiments and has shown that Ørsted’s method can give satisfactory results.
This has strengthened the priority of Ørsted’s original work and his position as discoverer of aluminum.
For almost three decades, aluminum remained a novelty, expensive to produce and more valuable than gold, until in 1854 Henri Saint-Claire Deville in Paris, France found a way of replacing potassium with much cheaper sodium in the reaction to isolate aluminum. Aluminum then became more popular but, because it was still quite expensive, was used in ornamental rather than practical situations.
Finally, in 1886 American chemist Charles Martin Hall and French chemist Paul Héroult independently invented the Hall-Héroult process, which inexpensively isolates aluminum metal from its oxide electrolytically.
Aluminum is still manufactured using the Hall-Héroult process today.
Discovery of Silver
Silver has been in use since prehistoric times. We do not know who its discoverer was, although the discovery would almost certainly have been of native silver.
Nuggets of native silver metal can be found in minerals and sometimes in rivers; but they are rare. Despite native silver’s rarity, very large pieces of it have been found, such as “pieces of native silver as big as stove lids and cannon balls” found in the early 1900s in Northern Ontario, Canada.
Silver has a special place in the history of the elements because it is one of the first five metals discovered and used by humans. The others were gold, copper, lead and iron.
Silver objects dating from before 4000 BC have been found in Greece and from slightly later in Anatolia (in modern Turkey). Silver artifacts have been found in the Sumerian city of Kish dating from about 3000 BC.
Silver and lead often appear together in nature, for example in the mineral galena which is mainly lead sulfide. Galena actually looks metallic (see image) and would have caught the eyes of people looking for metals.
The silver objects found in Greece, Turkey and Kish were made of silver that was refined from lead-containing ores such as galena. (Humans have been successful chemists for a surprisingly long time.)
First the ore was smelted under reducing conditions to obtain a mixture of silver and lead. The metals then went through cupellation: the metals were heated to about 1000 oC in a strong stream of air. Under these conditions lead reacts with oxygen forming lead oxide, leaving liquid silver metal floating on top.
Our name for the element is derived from the Anglo-Saxon for silver, ‘seolfor,’ which itself comes from ancient Germanic ‘silabar.’
Silver’s chemical symbol, Ag, is an abbreviation of the Latin word for silver, ‘argentum.’ The Latin word originates from argunas, a Sanskrit word meaning shining.
The historical association between silver and money is still found in some languages. The French word for silver is argent, and the same word is used for money. The Romans used the word ‘argentarius’ to mean banker (silver trader).
Discovery of Zinc
Zinc ores have been used to make brass (a mixture of copper and zinc) and other alloys since ancient times.
A zinc alloy comprising 87.5% zinc was discovered in an ancient site in Transylvania.
Zinc smelting began in the 12th century in India by reducing calamine (zinc carbonate, ZnCO3) with wool and other organic materials.
The element name is reported to come from the old German word ‘zinke’ meaning pointed; a reference to the sharp pointed crystals formed after smelting.
Credit for isolating the metal is usually given to Andreas Marggraf in 1746, in Berlin. He heated a mixture of calamine ore and carbon in a closed vessel without copper to produce the metal.
Discovery of Nickel
Nickel is present in metallic meteorites and so has been in use since ancient times.
Artifacts made from metallic meteorites have been found dating from as early as 5000 BC – for example beads in graves in Egypt
Iron is the most abundant element in metallic meteorites, followed by nickel.
It was not until the 1750s that nickel was discovered to be an element.
In the 1600s, a dark red ore, often with a green coating, had been a source of irritation for copper miners in Saxony, Germany. They believed the dark red substance was an ore of copper, but they had been unable to extract any copper from it.
In frustration, they had named it ‘kupfernickel’ which could be translated as ‘goblin’s copper’ because clearly, from the miners’ point of view at any rate, there were goblins or little imps at work, preventing them extracting the copper.
Between 1751 and 1754, the Swedish chemist Axel Cronstedt carried out a number of experiments to determine the true nature of kupfernickel. (We now know that kupfernickel is nickel arsenide, NiAs.)
After finding that its chemical reactions were not what he would have expected from a copper compound, he heated kupfernickel with charcoal to yield a hard, white metal, whose color alone showed it could not be copper. Its properties, including its magnetism, led him to conclude that he had isolated a new metallic element.
Cronstedt named the new element nickel, after the kupfernickel from which he had isolated it.
There is a satisfying symmetry in this discovery. Cronstedt was a pupil of George Brandt, who had discovered cobalt, which sits immediately to the left of nickel in the periodic table.
The names of both elements have their origins in the frustrations of miners caused by metal-arsenic ores: nickel arsenide and cobalt arsenide. Cobalt’s name is derived from the German ‘kobold’ meaning ‘goblin’ – a close relative of the creature from which nickel’s name was derived.
In cobalt’s case, miners mistakenly thought the ore contained silver, and called the ore kobold in frustration at the wicked goblins who they believed were preventing them getting silver from the ore.
In the early twentieth century, Ludwig Mond patented a process using nickel carbonyl to purify nickel. This process is still used today.
Discovery of Cobalt
Since ancient times cobalt compounds have been used to produce blue glass and ceramics.
The element was first isolated by Swedish chemist George Brandt in 1735. He showed it was the presence of the element cobalt that caused the blue color in glass, not bismuth as previously thought.
In about 1741 he wrote, “As there are six kinds of metals, so I have also shown with reliable experiments… that there are also six kinds of half-metals: a new half-metal, namely cobalt regulus in addition to mercury, bismuth, zinc, and the reguluses of antimony and arsenic.”
The word cobalt is derived from the German ‘kobold’, meaning goblin or elf.
Discovery of Iron
Iron has been known since ancient times.
The first iron used by humans is likely to have come from meteorites.
Most objects that fall to earth from space are stony, but a small proportion, such as the one pictured, are ‘iron meteorites’ with iron contents of over 90 percent.
Iron corrodes easily, so iron artifacts from ancient times are much rarer that objects made of silver or gold. This makes it harder to trace the history of iron than the less reactive metals.
Artifacts made from meteorite iron have been found dating from about 5000 BC (and so are about 7000 years old) – for example iron beads in graves in Egypt.
In Mesopotamia (Iraq) there is evidence people were smelting iron around 5000 BC.
Artifacts made of smelted iron have been found dating from about 3000 BC in Egypt and Mesopotamia.
In those times, iron was a ceremonial metal; it was too expensive to be used in everyday life. Assyrian writings tell us that iron was eight times more valuable than gold.
The iron age began about 1300-1200 BC when iron became cheap enough to replace bronze.
Adding carbon to iron to make steel was probably accidental at first – a coming together of molten iron and charcoal from the smelting fire. This probably happened about 1000 BC. Until this happened there were few technological reasons for the bronze age to give way to the iron age; the techniques of improving iron by adding carbon (to make steel) and coldworking were needed before iron would be wholly preferred to bronze.
Iron was used commonly in Roman times. In the first century Pliny the Elder said, “It is by the aid of iron that we construct houses, cleave rocks, and perform so many other useful offices in life.”
The origin of the chemical symbol Fe is from the Latin word ‘ferrum’ meaning iron. The word iron itself comes from ‘iren’ in Anglo-Saxon.
