Prehistoric men made use of air as an aid for driving windmills and sailing boats. The Romans used warm air systems for heating their villas and palaces. In the year 210 BC, Archimedes discovered that a body is proportionately lighter, the more liquid, gas or respectively air, this body displaces. Centuries passed without noteworthy progress being made in natural science with regard to gases. Up to the 17th century, one still regarded air as a uniform substance.
Carbon dioxide was discovered by J.B. van Helmont (1577-1644) as a product of combustion and fermentation. Carbon dioxide occurs in volcanic gases and many minerals, and reaches air through combustion of carbonates (salt of carbonic acid) but also respiration by humans and animals.
Evangelista Torricelli (1608-1647) was the first to recognise that the weight of air pressed against the earth's surface. In the year 1644, Torricelli first succeeded in measuring air pressure. Torricelli filled a thin 1 m long tube with mercury and placed this tube, with the opening downwards, vertically into an open dish which had been filled with mercury. The mercury column inside the tube shrank from 1000 mm to 760 mm. Otto von Guericke (1602-1686) pumped the air out of two hemispheres. Even 24 horses were unable to separate the hemispheres which were void of air (evacuated). Guericke also constructed the first pressure gauge. A copper sphere was evacuated. The difference in weight between the copper sphere filled with air and the evacuated one corresponded to the weight of the air. Edme Mariotte (1620-1684) carried out the same experiments with enclosed gas volumes independently of Robert Boyle and found the same interrelationships. This led posterity to deduce Boyle-Mariotte's law : The volume of gas is inversely proportional to the pressure Blaise Pascal (1623-1662) established the proof of the correctness of Torricelli's declaration.
On the 19th September 1648, a barometer accompanied an ascent of the 1465 m high Puy de Dome. The difference in level of 85 mm water column (WC) provided the final proof of the existence of air. Robert Boyle (1627-1691) used a bent glass tube which was sealed at one end. The air volume enclosed in this glass tube was subjected to the pressure of a mercury column of variable height. By this means, the relationship between volume and pressure in an enclosed quantity of air was established. This simple law consists of the fact that the product of the volume of an enclosed quantity of gas, multiplied by the pressure, always remains the same. Gabriel D. Fahrenheit (1686-1736) made the first mercury thermometer, that is valid to this day in the English speaking world with its freezing point at 32°F and boiling point at 212°F.
Anders Celsius (1701-1744) proposed the introduction of the 100° temperature scale in the "Proceedings of the Royal Swedish Academy". Henry Cavendish (1731-1810) discovered hydrogen when dissolving metals in acid and also discovered that the combustion of hydrogen leads to the formation of water.
In 1783 Lavoisier found that hot iron and water vapour generate iron oxide and hydrogen. He called the element Hydrogène, or hydrogen in English. Because of its reactive inertia, nitrogen was recognised as an element relatively late in time. K.W. Scheele showed in his "Treatise on Air and Fire" that air contains a component which permits neither respiration nor combustion. He called this component "spoilt air". Antoine Lavoisier (1743-1794) determined this element, which can neither sustain combustion nor life, and called it Azote. J.A.C. Chaptal introduced the designation Nitrogenium for this element.
The utilisation on a large scale of nitrogen from air followed only in the 20th century. K.W. Scheele (1742-1786) obtained oxygen for the first time by heating silver carbonate and mercury oxide and called this fire gas in contrast to inert gas (nitrogen). Lavoisier is said to have given the former the name Oxygenium having recognised the correct explanation of the combustion processes.
Oxygen is emitted by plants through the assimilation of carbon dioxide by a process known as photosynthesis.
Air pollution considerably weakens solar radiation which is a precondition of assimilation. Deforestation of the earth's surface has already reduced the generation of oxygen to two thirds of previous values. John Dalton (1776-1844) established the theory that every element is composed of several atoms and that one or several atoms of the one element always combine with one or several atoms of another. Joseph Gay-Lussac (1778-1850) transferred Dalton's theory of atoms to the chemistry of gases and formulated the general gas law as a combination of the laws of Boyle-Mariotte and Celsius. The relationship between pressure, temperature and volume of an enclosed quantity of gas was thus defined.
Formula 1.3.1
Lord Kelvin (1824-1907) succeeded in abstracting objective temperature from the subjective feeling of warmth and thus created the technically correct scale division which starts at the point of absolute zero.
The existence of argon or other rare gases was suspected by Cavendish because there always remained a reaction-wise inert residue when he transmuted the components of air into chemical compounds. Argon was discovered in 1894 as a component of atmospheric air by the Englishmen Ramsay and Rayleigh, after these had been struck by the divergence in density between the residual gas, believed to be nitrogen (after extracting the oxygen from air) and that of chemically pure nitrogen obtained by decomposition. The rare gas helium was discovered in the atmosphere of the sun by P. Jansen in 1868, in 1882 Palmieri found it in the course of the spectral analysis of Vesuvius lava. In 1895 Ramsay succeeded in producing pure helium in larger quantities from the mineral cleveite. Later, proof of the presence of helium in air was also established by Kayser. In 1897 neon was discovered by Ramsay due to its scarlet red spectral light and called it neon (from the Greek word "new"). The natural neon isotopes were already discovered by 1912 in the mass spectroscope by Thomson. Krypton was produced for the first time by Ramsay in 1898, obtaining it from air by using Linde's process for air liquefaction. It was again Ramsay who discovered and produced xenon in the year 1898 when he subjected the coarse argon obtained from air to a closer investigation and gave the name of Xenon (Greek word xenos = guest, foreigner) to this element.
