# Biographies of Scientific Men/Gay-Lussac

Gay-Lussac
GAY-LUSSAC
1778-1850
LUIS JOSEPH GAY-LUSSAC, the brilliant chemist and physicist, was born at St Léonard-le-Noblat (Haute-Vienne), France, on 6th December 1778.
The same year (1793) that witnessed the execution of Louis XVI. and Marie Antoinette, Gay-Lussac came to Paris and entered the École Polytechnique. Although so young, it was his delight and ambition to be in Paris. "Paris," said Heinrich Heine, "is not simply the capital of France, but of the whole civilized world, and the rendezvous of its most brilliant intellects." Gay-Lussac studied for three years at the École Polytechnique, after which he was promoted to the Département des Ponts et Chaussées (a Government department including everything connected with the making and repairing of roads, bridges, canals, etc.). His next position was as an assistant to C. L. Berthollet—a celebrated chemist—and in 1801, a year after the terrible and decisive Battle of Marengo, Gay-Lussac published his first paper on "La Dilatation des Gaz et Vapeurs," which was ​followed by "Le Perfectionnement des Thermomeètres et Baromètres," "L'Action Capillaire," "La Fusion des Vapeurs," etc.
In 1804 Gay-Lussac, in conjunction with Alexander von Humboldt, published an important memoir on the chemical and physical properties of air taken at an altitude of 23,000 feet. Ballooning in the early part of the nineteenth century was attended with the greatest risks; but he and Humboldt were intrepid naturalists, and undertook the investigation of the atmosphere at great heights—hygrometry, atmospheric electricity, aqueous tension, atmospheric pressure, etc., were some of the subjects investigated. Their memoir was published by the Académie des Sciences, and contained the announcement that hydrogen and oxygen combine to form water in the proportion of two hundred volumes of hydrogen to one hundred volumes of oxygen. It was from this discovery that Gay-Lussac was led to the most important law of volumes, which he discovered in 1809. This was his chef d'œuvre; but more anon.
Gay-Lassac investigated the nature of volcanic gases—more particularly hydrochloric acid gas—and "the vapours that rise from the fumarolles cause the sublimation of the chlorides of iron, copper, lead, and ammonium; iron glance and chloride of sodium (the latter often in large quantities) fill the cavities of recent lava streams and the fissures of the margin of the crater." In the Annales de ​Chimie, tome xxii., p. 415, he gave the chemical process in the formation of specular iron.
In 1809, the same year that he discovered the law of volumes, Gay-Lussac was elected Professor of Chemistry at his alma mater—the École Polytechnique, Paris—and remained at the great military school for twenty-three years. In 1832 he transferred to the same chair in the Jardin des Plantes.
In 1823 he published a memoir on the dynamics of earthquakes, in which he says that "the earth, so many centuries old, still preserves an internal force, which raises mountains, overturns cities, and agitates the entire mass. Most mountains, in issuing from the bosom of the earth, must have left vast cavities, which have remained empty, at least unless they have been filled with water and gases."
The existence of alkaline metals was prophesied by Lavoisier in 1793; and potassium and sodium were discovered by Davy in 1807, by means of the voltaic pile; and in the following year Gay-Lussac discovered a new process which yielded both potassium and sodium more abundantly than the voltaic pile. This was by the action of white-hot iron on the hydroxides of potassium and sodium. No doubt the brilliant researches of Davy stimulated Gay-Lussac and his collaborates Thénard, and in their Recherches Physico-Chimiques (1811) are to be found many remarkable observations on the action of the voltaic pile which Napoleon had constructed for ​the École Polytechnique. Much to his credit, the greatest military genius the world has ever seen was always interested in the work of men of science, and greatly esteemed their talents. It was through the influence of Napoleon (then First Consul) that Alexander Volta was awarded a gold medal, a prize of 6000 francs (both of the Académie des Sciences), and the Cross of the Légion d'Honneur, for his electrical researches.
In the year (1809) that Napoleon defeated the Austrians at Wagram, and annexed Tuscany and the Papal States, Gay-Lussac announced his discovery of the law of volume. This all-important law is generally stated, in these days, in the following words: When gases or vapours, either elementary or compound, unite together to form a new product, the resulting product always occupies two volumes. Occasionally the resulting volume is the sum of the constituent volumes, but usually there is condensation. The following examples illustrate the law of Gay-Lussac:—
* H + Cl = HCl
* Volumes 1 + 1 = 2
* 2H + O = H$_2$O (steam)
* Volumes 2 + 1 = 2
* N + 3H = HN$_3$
* Volumes 1 + 3 = 2
* NH + HCl = N$_4$Cl (vapour)
* Volumes 2 + 2 = 2
The resulting volume is always two.
​Gay-Lussac stated in the Mémoires de la Société d'Arcueil, tome ii., p. 207, that "lorsque deux gaz se combinent, leurs volumes mesurés a la même température et à la même pression sont dans des rapports simples." It will be seen that Gay-Lussac anticipated the great law of Avogadro, although it was left to the Italian physicist to distinguish between the ultimate particles of compounds and elements—between molecule and atom. As Roscoe and Schorlemmer say: "The discovery by Gay-Lussac of the law of volume—combination, together with Avogadro's explanation of the law—served no doubt as most valuable supports of Dalton's atomic theory; but the truth of this latter theory was still further asserted by a discovery made by Dulong and Petit in 1819. These French chemists determined the specific heat of thirteen elementary bodies, and found that the numbers thus obtained, when compared with the atomic weights of the same bodies, showed that the specific heats of the several elements are inversely proportional to their atomic weights; or, in other words, the atom of each of these elements possesses the same capacity for heat. Although subsequent research has shown that this law does not apply in every case, it still remains a valuable means of controlling the atomic-weight determinations of many elements."
Gay-Lussac was the inventor of the tower, known by his name, in the manufacture of sulphuric acid. Formerly the nitrous fumes were allowed to escape into the air, but ​now they are utilized according to Gay-Lussac's method. This consists in absorbing the vapours by means of sulphuric acid of a specific gravity—1·76. On treating this nitrous sulphuric acid with steam, nitrous fumes are evolved and passed again into the chamber, while the diluted sulphuric acid is again concentrated.
In 1808 Gay-Lussac and Thénard prepared boron by decomposing boron trioxide with potassium. They also prepared boron fluoride by heating together boron trioxide and calcium fluoride; and they determined the composition of boric acid both synthetically and analytically. In 1809 Gay-Lussac discovered the chemical action of light on a mixture of hydrogen and chlorine; and in 1810, he and Thénard examined hydrofluoric acid, which had been discovered by Scheele in 1772. In the same year (1810) they established the elementary nature of phosphorus, an important investigation which led to the discovery of the element's various allotropes.
In 1814, the year that Napoleon defeated the Prussians and signed his abdication of the throne of France, Gay-Lussac and Davy discovered hydriodic acid, and examined the element iodine which had been previously isolated by Courtois (1811). Gay-Lussac also examined bromine, and demonstrated the compound nature of fluor spar.
In 1815 Gay-Lussac made a most important discovery, namely, that of cyanogen gas; and proved that this gas habitually imitated the element chlorine in its ​combinations; that it is the radicle of hydrocyanic acid and cyanic acid; and that prussic acid is a compound of carbon, hydrogen, and nitrogen. Cyanogen, it may be mentioned, plays an important part in many organic reactions and compounds.
Gay-Lussac observed that the action of chlorine on hydrocyanic acid replaced the hydrogen forming cyanogen chloride, or acide chlorcyanique of his day; and he found that when beeswax was bleached by means of chlorine, it lost hydrogen and took up an equal volume of chlorine. At a royal ball at the Tuileries, in the reign of Charles X. (brother of Louis XVI.), the guests were "much annoyed by the irritating vapours which came from the wax candles to illuminate the apartments." This was due to the fact that the manufacturer had used chlorine to bleach the wax, and the irritating vapours contained hydrochloric acid.
In 1816 "Gay-Lussac made the remarkable observation that when a crystal of common potash alum is hung up in a saturated solution of ammonia alum it grows exactly as if it had been placed in the solution from which it was originally obtained. From this fact he drew the conclusion that the molecules of these two alums possess the same form." This was the beginning of Mitscherlich's law of isomorphism, which was discovered in 1810.
Gay-Lussac, by igniting potassium carbonate in iodine vapour, or chlorine gas, obtained an evolution of oxygen ​and carbon dioxide. His chemical and physical researches were incessant, and most important discoveries were made by this indefatigable genius.
Gay-Lussac discovered the monochloride and trichloride of iodine, and dithionic acid; and "by heating sodium in dry ammonia, Gay-Lussac and Thénard obtained an olive-green, easily-fusible mass, sodamide, hydrogen being separated. This substance with water forms sodium hydroxide and ammonia; with carbon monoxide, it forms sodium cyanide and water; and with dry hydrochloric acid it forms sodium and ammonium chlorides."
Gay-Lussac also worked on the products of the explosion of gunpowder in both confined and open spaces. This was the beginning of the vast province of artillery science; and his elaborate and beautiful researches on the fulminates of silver and mercury were of the highest order. Mercury fulminate is prepared by warming alcohol with nitric acid and mercuric nitrate. It forms silky, lustrous prisms, which explode with the utmost violence upon being heated or struck; hence it is extensively used for percussion caps, dynamite cartridges, etc. The analogous silver fulminate is still more explosive.
In 1831 Gay-Lussac was elected a member of the Chamber of Deputies; and in 1839 he was created a peer of France by King Louis Philippe. The latter's education, it may be remarked, was entrusted to the ​celebrated Madame de Genlis, and her teaching was planned on the principles of Rousseau.
In addition to his discoveries and researches in chemistry, Gay-Lussac was a brilliant physicist. The law of the expansion of gases was discovered by him and Charles: a gas expands 1273rd of its volume for each degree of temperature (Centigrade) above 0° C; or, in other words, the law of Gay-Lussac states that all gases in all conditions present one coefficient of expansion —0·00367; that is, when heated from 0° to 100° they expand like air, namely, a thousand volumes of a gas measured at will occupy 1367 volumes at 100°. Regnault, in the year that Gay-Lussac died (1850), showed that Gay-Lussac's law is not entirely correct.
Gay-Lussac invented an alcoholmeter. It is used to determine the strength of spirituous liquors; that is, the proportion of pure alcohol which they contain. He also invented the syphon barometer. In this barometer both the longer and shorter limbs are closed, but the shorter one contains a capillary aperture through which the atmospheric pressure is transmitted.
Gay-Lussac invented an apparatus for ascertaining vapour densities. It involved the determination of the volume of a given weight of vapour; but this method and those of Dumas, Bunsen, and Hofmann have been superseded by that of Victor Meyer, or the air-displacement method.
​Gay-Lussac did valuable work on vapour densities, vapour tensions, and solubilities. The effect of variation of temperature on the solubility of different salts was very clearly demonstrated by him; and he was the first to have recourse to the graphic method of expressing solubilities.
In addition to numerous memoirs, Gay-Lussac wrote a Cours de Physique, Cours de Chimie, Leçons de Chimie, etc.
His work was a brilliant conglomerate of faits accomplis in the earliest days of modern chemistry and physics. He was a man of extensive learning—homo multarum scientiarum—and was always ready to give the best advice to students and others.
Gay-Lussac received most of the honours that fall to the lot of men of science. He died on 9th May 1850, a hundred and nine days before the death of the "bourgeois king," Louis Philippe, and a year before the coup d'état of Napoleon III.
Among posthumous honours, there is the Lycée Gay-Lussac at Limoges, and the Rue Gay-Lussac, Paris, near the Panthéon and Luxembourg.
In conclusion, "the alchemists were right. There is a philosopher's stone; but the stone is itself a compound of labour, perseverance, and genius, and the gold which it produces is the gold of true knowledge, which shall never grow dim or fade away."