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Gay-Lussac, Joseph Louis

Gay-Lussac, Joseph Louis

(b. St. Leonard, France, 6 December 1778; d. Paris, France, 9 May 1850)

chemistry, physics.

He was the eldest of five children of Antoine Gay, lawyer and procureur royal at St. Léonard, and Leonarde Bourigner. His father, to distinguish himself from others with the surname Gay in the Limoges region, had begun to call himself Gay-Lussac after the family property near St. Leonard. Joseph Louis, although baptized “Gay,” adopted the same practice.

The comfortable social and economic position of the family was rudely disturbed by the Revolution. In September 1793, when Gay-Lussac was fourteen, his father was arrested as a suspect. The Abbé Bourdeix, who had been giving the son private lessons, fled the country. Joseph Louis was sent to a small private boarding school in Paris, where his lessons included mathematics and science. The opening of the Ecole Polytechnique provided a splendid opportunity for an able boy without fortune. Gay-Lussac was successful in the competitive entrance examination and was admitted on 27 December 1797. Graduating on 22 November 1800, he followed the practice of many of the better students by entering the civil engineering school, the Ecole Nationale des Ponts et Chaussées. In the winter of 1800–1801, the chemist Berthollet, impressed by the ability of the young man, took him to his country house at Arcueil as an assistant. Having already had an excellent mathematical education, Gay-Lussac received training in chemical research from Berthollet, who also played a key role in the professional advancement of his protégé. In 1808 Gay-Lussac married Geneviéve Marie Josephe Rojot; they had five children.

Gay-Lussac was successively adjoint (from 31 December 1802) and repétiteur (from 23 September 1804) at the Ecole Polytechnique. On 31 March 1809 he was given the honorary title of professor of practical chemistry, but upon the death of Fourcroy he was appointed to succeed him as professor of chemistry (17 February 1810). On the creation of the Paris Faculty of Science in 1808, Gay-Lussac was appointed professor of physics; in 1832 he gave up this chair in favor of that of general chemistry at the Museum National d’Histoire Naturelle. On 8 December 1806 Gay-Lussac obtained the coveted place of member of the first class of the Institute (physics section). He was already a member of the Société d’Arcueil and the Societé Philomatique.

Nearly all of Gay-Lussac’s life was devoted to pure and applied science, but he did have a brief political career. He was elected to the Chamber of Deputies in 1831, 1834, and 1837 but resigned on a matter of principle in 1838. On 7 March 1839, having earlier refused a title from Charles X, he was honored by Louis Philippe with nomination to the upper house.

Gay-Lussac’s first major research was on the thermal expansion of gases.1, It was carried out with the encouragement of Berthollet and Laplace in the winter of 1801–1802. There was conflicting evidence about the expansive properties of different gases when heated. Gay-Lussac improved on most earlier work by taking precautions to exclude water vapor from his apparatus and to use dry gases. After examining a variety of gases, including several soluble in water, and repeating each experiment several times, he concluded that equal volumes of all gases expand equally with the same increase of temperature. Over the range of temperature from 0°C, to 100°C. the expansion of gases was 1/266.66 of the volume at 0°C, for each degree rise in temperature. Similar research was carried out independently by Dalton at about the same time. Dalton’s work, however, was considerably less accurate. About 1787 J. A. C. Charles had recognized the equal expansion of several gases but had never bothered to publish his findings. Although the quantitative law of thermal expansion is often called “Charles’s law,” Charles did not measure the coefficient of expansion; moreover, for soluble gases, he had found unequal expansion.

Gay-Lussac made an ascent in a hydrogen balloon with Biot on 24 August 1804. The primary objective of the ascent was to see whether the magnetic intensity at the earth’s surface decreased with an increase in altitude.2 They concluded that it was constant up to 4,000 meters. They also carried long wires to test the electricity of different parts of the atmosphere. Another objective was to collect a sample of air from a high altitude to compare its composition with that of air at ground level. Gay-Lussac made a second ascent, on 16 September 1804, but this time by himself, in order to lessen the weight of the balloon and thus reach a greater height.

He was able to repeat observations of pressure, temperature, and humidity and also make magnetic measurements. He had taken two evacuated flasks, which he opened to collect samples of air when he had attained an altitude of over 6,000 meters. His subsequent analysis of these samples showed that the proportion of oxygen was identical with that in ordinary air. Gay-Lussac reached a calculated height of 7,016 meters above sea level, a record not equaled for another half century.

One of Gay-Lussac’s early collaborators was Alexander von Humboldt. Nearly ten years older than Gay-Lussac, Humboldt already had an international reputation as an explorer; yet he learned something about precision in scientific research from Gay-Lussac, who in turn had his horizons broadened by his German friend. They collaborated in an examination of various methods of estimating the proportion of oxygen in the air, particularly the use of Volta’s eudiometer.3 In this method the gas being, tested (which was required to contain some oxygen) was sparked with hydrogen to form water vapor, which condensed.

The resulting contraction permitted an estimate of the proportion of oxygen in the sample. This method obviously presupposed a knowledge of the relative proportions by volume in which hydrogen and oxygen combine to form water; one of the principal objects of the work of Gay-Lussac and Humboldt was to determine the proportion with the greatest possible accuracy. They also determined the limiting proportions for an explosion to be possible. After carrying out a large number of experiments with an excess of first one gas and then the other, they calculated—making allowance for a slight impurity in the test oxygen—that 100 parts by volume of oxygen combined with 199.89 parts of hydrogen or, they said, in round numbers, 200 parts. Gay-Lussac clearly expressed his preference for volumes, pointing out that the presence of moisture, which would be difficult to estimate gravimetrically, did not alter the volumetric ratio. This memoir made a useful contribution to science not only for its accuracy but as a precursor of Gay-Lussac’s famous research on the combining volumes of gases.

In March 1805 Gay-Lussac embarked on a year of European travel with Humboldt, going first to Rome and ending in Berlin. During this journey Gay-Lussac carried out various chemical analyses. Their principal object, however, was to record the magnetic elemertti at different points along their route.4

To obtain the magnetic intensity, the period of oscillation of a magnetized needle was determined. The magnetic intensity was then found to be proportional to the square of the number of oscillations made by the needle, displaced slightly from the magnetic meridian, in a given time. They did not think that magnetic intensity in any one place changed with time, since on taking readings at Milan on entering and leaving Italy at an interval of six months, they found no difference. A series of prolonged experiments to determine diurnal variation, both on Mount Cenis and in Rome, had not revealed any difference at different hours of the day and night. As regards the general accuracy of their readings, many of which were made under conditions that were far from ideal, they estimated that the greatest discrepancy between their angular readings could not have been more than ten minutes of arc. Their general conclusion was that the horizontal component of the earth’s magnetic intensity increased from north (Berlin) to south (Naples) but that the total intensity decreased on approaching the equator.

In 1807 Gay-Lussac carried out a series of experiments designed principally to see whether there was a general relationship between the specific heats of gases and their densities.5 He measured the change in the temperature of a gas (and thus heat capacity) as a function of density changes produced by the free expansion of the gas. From a modern viewpoint the importance of his work was his establishment of a basic principle of physics, since it follows from his experiments that (in modern terms) the internal energy of an ideal gas depends on the temperature only. He took two twelve-liter, double-neck flasks. To one neck a tap was fitted and to the other a sensitive alcohol thermometer. Each flask contained anhydrous calcium chloride to absorb all moisture. One of the flasks was then evacuated and the other filled with the gas under test. The flasks were then connected with a lead pipe, the taps opened, and the readings of the thermometers carefully noted. It was known that compression of gases was accompanied by evolution of heat and expansion by absorption of heat. Gay-Lussac, however, wished to find the relationship between heat absorbed and heat evolved in the two flasks, and from his experiments he drew the valuable conclusion that these were equal within the limits of experimental error. The change of temperature was, moreover, directly proportional to the change of pressure. This he found by connecting the flasks, equalizing the pressures by opening the tap (that is, reducing the pressure to half, since the volumes were equal), evacuating the second flask, and repeating this process until the temperature change was so slight as to make accurate measurement impossible.

Gay-Lussac’s experiment with two connecting vessels was repeated nearly forty years later by Joule, who apparently knew nothing of the earlier work.

Probably Gay-Lussac’s greatest single achievement is based on the law of combining volumes of gases, which he announced at a meeting of the Société Philpmatique in Paris, on 31 December 1808. For Gay-Lussac himself, the law provided a vindication of his belief in regularities in the physical world, which it was the business of the scientist to discover. Gay-Lussac began his memoir by pointing out the unique character of the gaseous state6 For solids and liquids a particular increase in pressure would produce a change different in each case; it was only matter in the gaseous state that increased equally in volume for a given increase of pressure. His own statement was that “gases combine in very simple proportions…and . . . the apparent contraction in volume which they experience on combination has also a simple relation to the volume of the gases, or at least to one of them.” He gives the following examples of the simple ratios of combining volumes of gases (modern symbols are used for brevity).

These neat ratios do not, however, correspond exactly to his experimental results. He deduced his law from a few fairly clear cases (particularly the first few listed above) and glossed over discrepancies in some of the others. The simple reaction between hydrogen and chlorine, which is often used today as an elementary illustration of the law, was not discovered until 1809 and was included only as a footnote when this memoir was printed.

Gay-Lussac presented his law of combining volumes of gases as a natural consequence of his collaboration with Humboldt, with whom he had found that 100 parts by volume of oxygen combine with almost exactly 200 parts of hydrogen. That his work of January 1805 with Humboldt led naturally to the law of combining volumes may be logically true but historically the connection is less direct. One has to explain the interval of nearly four years between obtaining the first data and the announcement of the law. Probably something had happened earlier in the year 1808 that made Gay-Lussac turn his attention back to his earlier work and realize that the value he had obtained for the combining volumes of hydrogen and oxygen was more than a coincidence and was in fact only one example of a general phenomenon. In the autumn of 1808 Gay-Lussac and Thenard had discovered boron trifluoride. They were particularly impressed by one of the properties of this new gas, the dense fumes produced when it came into contact with the air; they compared these fumes with the fumes produced by the reaction of muriatic-acid gas and ammonia. It seems likely that Gay-Lussac, struck by the reaction of boron trifluoride with moist air, tried its reaction with other gases including ammonia. An obvious reaction for for comparison would be that between hydrochloric-acid gas and ammonia. This reaction was given special prominence in the memoir on combining volumes of gases.

One of the points of strength of the memoir was that it took data from a wide variety of reputable sources. This was no suspect generalization based on the biased experimental work of its author. On the other hand, all the data had not, of course, been conveniently assembled for Gay-Lussac to publish. In many cases the analyses that had appeared in the chemical literature had given only the gravimetric composition, and Gay-Lussac, taking reliable data for the density, had to convert this to a volumetric ratio. A close examination of the provenance of the density data shows that much was derived from his associates in the Société d’Arcueil.

The influence of Berthollet is particularly prominent in Gay-Lussac’s attempt to reconcile the opinions of Dalton, Thomson, and Wollaston on definite and multiple proportions with Berthollet’s known conviction that compounds can always be formed in variable proportions except in special circumstances. It was possible to argue that the gaseous state provided such an exception, and Berthollet accepted Gay-Lussac’s law. Considering the implications of the law for the atomic structure of matter, it would be reasonable to expect Dalton to have welcomed the law of combining volumes as additional evidence for his atomic theory. Dalton, however, refused to accept the accuracy of the results of the French chemist. The Italian physical chemist Avogadro, on the other hand, not only accepted Gay-Lussac’s work but developed its implications for the relationship between the volumes of gases and the number of molecules they contain. His great debt to Gay-Lussac’s memoir was explicit.

Although Berzelius and Gay-Lussac differed in the actual values given to “volume weights” (often by a factor of 2), Berzelius, especially in his earlier work, regarted Gay-Lussac’s method of speaking of volumes as preferable to Dalton’s atoms. It had the advantage of being based on more direct evidence, and there was no absurdity in dealing.with half volumes, whereas there was a contradiction involved in speaking of “half atoms” The obvious disadvantage of translating “atom” as “volume” was that many compounds cannot exist in the gaseous state. Gay-Lussac himself was prepared to estimate the relative vapor density of mercury not by direct means but by calculation based on the weight combining with a given weight of oxygen in the solid state, Gay-Lussac later speculated about the proportion of “carbon vapor” in carbon compounds. His interest in volumes led him to devise an apparatus by which the vapor densities of liquids could be compared.7 The vapor displaced mercury in a graduated glass tube immersed in a glass cylinder containing water which was heated. The apparatus was improved half a century later by A. W. Hofmann, and the method by which the volume of a given weight of a vaporized substance is found is now usually known as Hofmann’s method.

The work of Volta inspired many chemists to investigate the chemical effects of the voltaic pile. Gay-Lussac and Thenard were among this number. They were influenced particularly by the news in the winter of 1807–1808 of Davy’s isolation of potassium and sodium by the use of the giant voltaic pile at the Royal Institution. Napoleon ordered the construction of an even larger pile at the École Polytechnique and Gay-Lussac and Thenard were placed in charge of it. Their research, reported in part 1 of their Recherches physico-chimiques (1811), was basically a repetition of Davy’s experiments. Although Davy seems to have exhausted the most obvious possibilities, Gay-Lussac and Thenard’s report does contain the suggestion that the rate of decomposition of an electrolyte depends only on the strength of the current (and not, for example, on the size of the electrodes), and they used chemical decomposition as a measure of electric current thirty years before Faraday. The Institute’s prize of 3,000 francs for work in the field of galvanism was awarded to Davy in December 1807 and to Gay-Lussac and Thenard in December 1809.

Gay-Lussac and Thenard’s really important contribution stemming from Davy’s work was their preparation (announced to the Institute on 7 March 1808) of potassium and sodium in reasonable quantities and by purely chemical means.8 Davy’s method of electrolysis, although spectacular, had produced only tiny amounts of the new metals. The two young Frenchmen, no doubt under the influence of Berthollet, had reasoned that the action of great heat should change the usual affinities. Thinking that the normal affinities of oxygen for iron and the alkali metals could thus be reversed, they fused the respective alkalies with iron filings subjected to a bright red heat in a bent iron gun barrel. The metal vapor distilled over into a receiver luted to the gun barrel. In this way they prepared samples of about twenty-five grams of each metal at a low cost.

They were then able to investigate the physical constants of potassium, finding its specific gravity to be 0.874 (modern value, 0.859 at 0°c). Davy had been unable to produce a better result than 0.6. Gay-Lussac and Thenard also discovered the alloy of potassium and sodium that exists as a liquid at room temperature. They then began a program of research in which potassium was not the end product but a reagent used to make further discoveries. In particular, they investigated the reaction between potassium metal and various gases. They found that when potassium is strongly heated in hydrogen, it combines with it to form a gray solid, potassium hydride, which is decomposed by water. They proposed the use of heated potassium as a means of performing an accurate volumetric analysis of nitrous and nitric oxides. The data obtained in this way by Gay-Lussac about the composition of nitric oxide was used by him later as evidence for his law of combining volumes of gases. They found that heated potassium metal decomposed muriatic-acid gas, forming the muriate of potash and hydrogen. Unfortunately they were prevented from reaching the conclusion that the gas was a simple compound of hydrogen and the muriatic radical by the conviction that the reaction was really due to water vapor in the gas.

In a further memoir, Gay-Lussac and Thenard described an experiment in which potassium was heated in dry ammonia, forming a solid (KNH 2)2 and liberating hydrogen. Other related experiments seemed to indicate to them that potassium was not an element at all but a hydride, and they argued this at length with Davy. Despite their mistaken conclusions on this point, the French chemists deserve credit for their discovery of a new class of compounds, the amides of metals.

In their next memoir Gay-Lussac and Thenard made further use of potassium as a reagent, this time to decompose boric acid.9 They were not, however, alone in this field, since in the early summer of 1808 Davy turned his attention to their method of using potassium as a reagent. In a memoir read to the Royal Society on 30 June 1808, Davy described in a footnote how he had ignited boric acid and heated the product with potassium in a gold tube; this process yielded a black substance, which he did not identify but which was later recognized to be boron. It was not until his fourth Bakerian lecture, read on 15 December 1808, that Davy made any claim to the discovery of a new substance. His experimental work was rather poor and hurried. He admitted that he had had a report that Thenard was investigating the decomposition of boric acid by potassium. In December 1808 Davy succeeded in decomposing boric acid. He doubted, however, whether the substance obtained was a “simple body.”

Gay-Lussac and Thenard’s discovery of boron was first announced in November 1808. On 20 June 1808 they had mentioned an olive-gray substance obtained by the action of potassium on fused boric acid, but it was not until 14 November that they claimed to have isolated a new element and discovered its properties. This is one case where the work of Gay-Lussac and Thenard is indubitably prior to that of Davy. Equal weights of potassium metal and fused boric acid were heated together in a copper tube, thus producing a mixture of potassium, potassium borate, and boron, The new element did not dissolve or react chemically with water; this property thus provided a method of separating it. Gay-Lussac and Thenard gave it the name bore (“boron” and noted the similarity of its properties to those of carbon, phosphorus, and sulfur. Boron was found to form borides similar to carbides.

Their success in decomposing boric acid and isolating its “radicals” led Gay-Lussac and Thenard to apply their new reagent, potassium, to the isolation of other radicals. Although the natural limitations of their method prevented them from achieving their immediate objective, they made a number of interesting discoveries.10 In the course of these experiments they tried to prepare pure “fluoric acid” by heating together a mixture of calcium fluoride and vitrified boric acid. Investigating the properties of their fluoric acid, they found it had no effect on glass (a well-known property of hydrofluoric acid), and they reasoned correctly that this must be because it was already combined with an element similar to the basis of silica, namely, the boron from the acid used in its preparation. They therefore named the gas fluoboric gas (boron trifluoride).

They were now ready to prepare true hydrofluoric acid and attempt its decomposition. This difficult feat was not accomplished until 1886, but Gay-Lussac and Thenard managed to prepare nearly anhydrous acid by distilling calcium fluoride with concentrated sulfuric acid in a lead retort.

After an unsuccessful attempt to isolate the muriatic radical by the action of heated potassium on muriates (chlorides) of metals, they turned their attention to oxymuriatic acid (chlorine), hoping to decompose it by removing its supposed oxygen.11 Potassium was useless, but they were even more surprised when they found that even strongly heated carbon would not decompose the gas. This was all the more unexpected since sunlight decomposed it so easily. This led them to carry out further experiments on the effect of light on chemical reactions. They prepared two mixtures of chlorine and hydrogen; one was placed in darkness and the other in feeble sunlight. The first mixture was still greenishyellow in color after several days, but the second had reacted completely by the end of a quarter of an hour, judging by the disappearance of the color of the chlorine. The experiment was repeated with olefiant gas (ethylene) and oxymuriatic-acid gas, which were mixed and left for two days in total darkness. As soon as the mixture was exposed to bright sunlight, there was a violent explosion. This confirmed their hypothesis that the speed of the reaction was proportional to the intensity of the light.

Apart from their early contribution to photochemistry, Gay-Lussac and Thenard made a fundamental contribution to the realization that so-called oxymuriatic acid contained no oxygen and was an element. Their memoir, read at a meeting of the Institute on 27 February 1809, contains the following remark, the wording of which should be carefully noted:

Oxygenated muriatic acid is not decomposed by charcoal, and it might be supposed from this fact and those which are communicated in this memoir, that this gas is a simple body. The phenomena which it presents can be explained well enough on this hypothesis; we shall not seek to defend it, however, as it appears to us that they are still better explained by regarding oxygenated muriatic acid as a compound body.

The explanation of this statement is provided by events at a meeting of the Sociétéd Arcueil. On the previous day, 26 February, Gay-Lussac and Thenard had reading first draft of their memoir In the first reading the authors had suggested unequivocally that oxymuriatic gas was an element. Their patron, Berthollet, unfortunately persuaded them to alter their remarks to make this no more than a possibility—as in the above quotation. Because of .the pressure he exerted on Gay-Lussac and Thenard. Davy is usually credited with the discovery of the elementary nature of chlorine, which he announced in 1810. He had been particularly impressed by the evidence of Gay-Lussac and Thenard that charcoal, even at white heat, could not affect the decomposition of oxymuriatic gas, a result which one would hardly expect in a gaseous oxide.

Another area in which the contributions of Gaylussac were eclipsed by Davy—at least, outside France—was in the understanding of the properties of iodine. We must avoid describing this as the “discovery” of iodine, since it was neither Gay-Lussac nor Davy but Courtois who was the first to study this substance. The details of the story would take considerable space to elaborate; here it is sufficient to do no more than describe the contributions of Gay-Lussac.

Courtois recognized iodine to be a distinctive substance from its purple vapor, but its compound with hydrogen was at first confused with hydrogen chloride. It was Gay-Lussac who gave it the name lode (from the Greek ioeidēs, “violet colored”). On 12 December 1813 an article appeared in Le Moniteur in which Gay-Lussac expressed his view that iodine was probably an element. But he allowed also for the possibility of its being a compound containing oxygen. He stressed the analogy of the properties of iodine with those of chlorine. He was able to prepare the related acid (H I) by the action of iodine on moist phosphorus. He had prepared successively potassium iodate and iodic acid by 20 December 1813; the former was also prepared independently by Davy. A large part of Davy’s claim for the originality of his study of iodine depends on his complete honesty in claiming certain knowledge before that of Gay-Lussac and in particular in dating as II December a paper read to the Institute on 13 December (that is, the day following Gay-Lussac’s publication).

Gay-Lussac’s major publication on iodine was not ready to be read to the Institute until 1 August 1814,12 by which time not only Davy but Vauquelin had explored the subject fairly extensively. Gay-Lussac, however, deserves full credit for his detailed study of hydrogen iodide, which he found to have a 50 percent hydrogen content by volume. He contrasted its thermal decomposition with the stability of hydrogen chloride. By the action of chlorine on iodine, he prepared, independently of Davy and at about the same time, iodine monochloride and trichloride. After further careful study of the properties of iodine, he prepared and examined a number of iodides and iodates. He prepared for the first time ethyl iodide by distilling together concentrated hydriodic acid with absolute alcohol.

The close analogy that he emphasized between chlorine and iodine led him to a further investigation of the former, and he discovered chloric acid by the action of sulfuric acid on a solution of barium chlorate. Later, in collaboration with Welter, he discovered dithionic acid (H2S2O6)13. He also showed that aqua regia contains chlorine (which attacks gold) and nitrosyl chloride (NOCI) and that both gase are evolved on heating 14

In 1809 Gay-Lussac established by purely empirical means the general principle that the weight of acid in salts is proportional to the oxygen in the corresponding oxide15 (Salts were then consider to be compounds of metallic oxides with “acids,” that is, acid anhydrides.) Gay-Lussac used this principle (occasionally referred to as a law) to determine the composition of some soluble salts. The analysis of insoluble salts was comparatively straightforward, but there was little agreement about the composition of the majority of salts, those which were soluble and could not therefore be weighed as precipitates. For example, insoluble lead sulfate had been found by analysis to consist of lead, 100.00; oxygen, 7.29; and acid, 37.71. Knowing the proportions of oxygen in the corresponding oxides of lead and copper, soluble copper sulfate must therefore contain oxygen and acid in the same proportions as lead sulfate: copper, 100.00; oxygen, 24.57; acid, 127.09. This was in fairly close agreement with the value obtained experimentally by L. J. Proust.

An extension of Gay-Lussac’s principle could be used to determine the composition of sulfites indirectly. Direct determination presented practical difficulties, because sulfites are easily oxidized by the atmosphere to sulfates. The principle could be used in reverse if the composition of the salt were known and if the weight of oxygen that would combine with a given weight of the metal were required. This was applicable to the newly isolated barium.

Among his other work in inorganic chemistry Gay-Lussac investigated the thermal decomposition of sulfates16 Under suitable oxidizing conditions, he was able to convert the sulfides of zinc and iron to the sulfates. His thermal decomposition of sulfuric acid in a porcelain tube showed the volumetric composition of sulfur trioxide to be 100 parts sulfur dioxide and 47.79 parts oxygen. In 1808 Gay-Lussac was able to use this data to help establish his law of combining volumes of gases.

Gay-Lussac carried out research on sulfides. The most important part of this work for the subsequent history of qualitative analysis was his investigation of the precipitation of metal sulfides. It was generally considered that such metals as zinc, manganese, cobalt, and nickel could not be precipitated by passing hydrogen sulfide through solutions of their respective salts. Gay-Lussac successfully demonstrated that the sulfides of these metals could be precipitated if they were present as salts of acetic, tartaric, or oxalic acids (that is, weak acids) or, better, in the presence of an alkali, such as ammonia.17

In 1809 Gay-Lussac carried out a study of the combining volumes of nitric oxide and oxygen.18 This was a more complex problem than he then realized, but he returned to it in 1816 after criticism of his earlier work by Dalton; this time his results were of permanent value.19 He recognized five oxides of nitrogen. which he listed as follows:

 Vols. of NitrogenVol 5.of OxygenModern Formula
Oxide d’azote10050N2O
Gaz nitreux100100NO
Acide pemitreux100150N2O3
Acide nitreux100200NO2
Acide nitrique100250N2O5

Lavoisier’s oxygen theory of acids had been questioned by Berthollet, who had failed to find oxygen either in hydrogen sulfide or in prussic acid. Although both gave acid reactions, Berthollet was not fully satisfied that Lavoisier’s theory was erroneous; it was therefore left to his pupil Gay-Lussac to demonstrate conclusively that there was a definite class of acids that, instead of containing oxygen, contained hydrogen. Gay-Lussac introduced the term “hydracid” to denote this class, which included hydrochloric acid, hydriodic acid, and hydrogen sulfide.20 Gay-Lussac thus introduced the name hydrochloric acid (acid, hydrochlorique) for what had been called muriatic acid. Yet, so firmly accepted was Lavoisier’s idea of oxygen as an acidifying principle that Gay-Lussac was convinced that hydrogen had no connection with the acidic properties and was in fact a principle of alkalinity.21 If, for example, a solution of hydrogen sulfide showed acidic properties, it would have to be attributed to the sulfur that it contained.

Gay-Lussac’s important research on prussic acid began with his successful preparation in 1811 of the anhydrous acid by the action of hydrochloric acid on mercuric cyanide.22 In 1815 he determined the physical constants of the acid, including its vapor density.23 He expressed its composition as follows: one volume of carbon vapor, one-half volume hydrogen, one-half volume nitrogen. He also expressed this in gravimetric terms, his figures being reasonably accurate. When he heated mercuric cyanide, he found that it decomposed into mercury and an inflammable gas composed of carbon and nitrogen. He proposed for this gas the name cyanogéne (from the Greek kyanos, “dark blue”). He carefully examined the new compound, establishing its composition and showing that it combined with alkalies to form salts (cyanides). He investigated the properties and composition of cyanogen chloride, previously discovered by Berthollet. He examined several compounds derived from cyanogen, including ferrocyanate, which he clearly recognized as a compound radical and which he would have written as Fe(CN)6 with modern atomic weights.24 He later analyzed Prussian blue and made suggestions about its composition.25

Gay-Lussac demonstrated the growth of crystals of ammonia alum over those of potash alum and suggested that “the molecules of the two alums have the same form,”26 This has sometimes been incorrectly interpreted as an anticipation of Mitscherlich’s law of isomorphism.

Gay-Lussac’s study of the solubility of salts is of considerable importance, since he was the first to construct a solubility curve showing the variation of solubility of various salts in water at different temperatures.27. He recognized that the amount of solid has no influence on the ultimate solubility. He understood that the solubility of a salt in water at a given temperature is a constant in the presence of excess solute. He noticed the break in the solubility curve of hydrated sodium sulfate and that this occurs at the point of maximum solubility.

Gay-Lussac studied the effect of the material and form of different vessels on the constancy of boiling points of liquids.28 He found that the vapor pressure of a solution is lower than that of the pure solvent, for example, a solution of sodium chloride with a specific gravity of 1.096 was 0.9 that of the vapor pressure of water.

Gay-Lussac, in considering the action of chlorine on alkalies, stated, “There is a general rule that in every case where the same elements can form compounds of different stability (but capable of existing simultaneously under the same given conditions), the first to be formed is the least stable.”29 This is a remarkably perceptive statement and is almost the “law of successive reactions” proposed by Ostwald in 1897.

As might be expected from a pupil of Berthollet, Gay-Lussac made several contributions to an understanding of chemical equilibrium and the realization of the relevance to a reaction of the mass of the reactants. He showed, for example, that the action of steam on heated iron is a reversible action.30 Following Berthollet’s ideas, Gay-Lussac considered that when sulfuric acid is added to a solution of borax, “the base is partitioned between the two acids . . . in proportion to the numbers of their atoms.”31 Toward the end of his career, Gay-Lussac wrote a long historical article on affinity. He considered the particles in a solution of different salts to be in state of random motion (Pêle-mêle) at the moment of mixture. Eventually a situation of equilibrium was obtained, but any slight alteration of conditions could bring about a further exchange of the acid and basic parts of the salts in solution. He introduced the concept of permutation of the constituent part of salts (équipollence):

At the moment of mixture of two neutral salts, two new salts are formed in certain ratios with the two original salts: and then according to whether one of the properties of insolubility, density, fusibility, volatility, etc. is greater for the new salts than for the original salts, there will be a disturbance of equilibrium and the separation of one or even several salts.32

Although Gay-Lussac is probably best known for his work in physical and inorganic chemistry, he also made a number of important contributions to organic chemistry. In January 1810 Gay-Lussac and Thenard developed the pioneer work of Lavoisier on the quantitative combustion analysis of organic compounds. Whereas Lavoisier had burned a few inflammable substances in oxygen gas, Gay-Lussac and Thenard greatly extended the generality of the method by the use of an oxidizing agent:33 They at first proposed potassium chlorate, but as this was found to act too powerfully, Gay-Lussac suggested in 1815 that copper oxide was preferable and thereby established its use. They applied their method in 1810 to the analysis of twenty vegetable and animal substances. On the basis of these analyses, they divided vegetable substances into three classes according to the proportion of hydrogen and oxygen contained in them. One of these classes included compounds—such as starch, gum, and sugar—in which the proportion of oxygen to hydrogen was the same as in water. This classification was accepted by William Prout, who referred to this group as the saccharine class, later called carbohydrates.

Gay-Lussac’s analysis of prussic acid in 1815 is particularly important because he drew attention to the existence of a radical (—CN) that is fully analogous to the chlorine in hydrochloric acid and the iodine in iodic acid, the essential difference being that “this radical is compound.”34 This was the first example of the analysis of a carbon-containing radical. If this had been generally considered as an organic radical, it might have anticipated the radical theory of organic chemistry of the 1830’s.

In 1815 Gay-Lussac referred to prussic acid as a “true hydracid in which carbon and nitrogen replace[author’s italics] chlorine in hydrochloric acid . . .35 He later took the idea of replacement beyond the theoretical plane when he considered actual reactions in organic chemistry. When discussing the action of chlorine on oils and waxes, he observed that the chlorine removes part of the hydrogen from the oilforming hydrochloric acid and also “part of the chlorine combines with the oil and takes the place of the hydrogen removed.36 In 1834 Dumas began to develop the principle adumbrated by Gay-Lussac into a general theory of substitution in organic chemistry.

One of the consequences of Gay-Lussac’s volumetric approach to chemistry was his conversion in 1815 of the gravimetric analysis of alcohol by Theodore de Saussure in terms of olefiant gas and water into a volumetric analysis.37 This gave approximately equal volumes. Gay-Lussac confirmed that the sum of the vapor densities of olefiant gas and water is equal to the vapor density of absolute alcohol within the limits of experimental error. He therefore, concluded that alcohol is composed of one volume of olefiant gas and one volume of water. By similar reasoning he concluded that “sulfuric ether” (diethyl ether) is composed of two volumes of olefiant gas and one volume of water. Gay-Lussac’s work was the inspiration of the etherin theory of Dumas and Boullay in 1827.

Gay-Lussac also contributed to the early history of isomerism. In 1814 he remarked that acetic acid and matière ligneuse (“cellulose”) have the same composition and concluded that it is the arrangement of the constituent particles of a compound which determines whether a substance has a neutral, acidic, or alkaline character.38 In 1824, in his capacity as chemical editor of the Annales de chimie et de physique, he remarked that if Wöhler’s analysis of silver cyanate was correct, it was identical with that of silver fulminate and that the explanation must lie in the different arrangement of the elements within the two compounds. 39 Later he showed experimentally that racemic acid (a name introduced by him) has the same composition as tartaric acid.40

We have left until now Gay-Lussac’s vital work on volumetric analysis, since this belongs to the later part of his life, when he was largely occupied with applied science. French chemists made most of the basic contributions to the history of volumetric analysis. Some pioneer work was carried out by Henri Descroizilles, but the subsequent work of Gay-Lussac was even more influential. Although the French term litre was used about 1800, the concept of titration passed into general chemical practice from the method proposed by Gay-Lussac for estimating the purity of silver.

In 1824 Gay-Lussac extended earlier methods for the estimation of hypochlorite or chlorinated lime solution using indigo solution.41 He later improved on the method by the use of standard solutions of certain reducing agents: arsenious oxide, mercurous nitrate, and potassium ferrocyanide.42 His 1824 paper is important, as it contains the first use of the terms pipette and burette for the respective pieces of apparatus that have since become standard. Gay-Lussac’s apparatus was an improvement on that used earlier by Descroizilles and Welter. Gay-Lussac’s pipette had essentially the form of its modern counterpart, but his burette was more like a graduated cylinder with a connecting side arm. In a paper published in 1828 Gay-Lussac also used a one-liter volumetric flask.43 In this paper he described acide normale (“normal acid”) as a standard solution of l00 grams of sulfuric acid diluted to one liter. Gay-Lussac used litmus as an indicator and described accurately the color transition in different reactions. In 1829 he published a method for the determination of borax.44 Sulfuric acid was added to a solution of the borax. The turning of the litmus present to the “color of onion skin” indicated the neutralization of the soda present in the borax. He even carried out an indicator correction, measuring the amount of acid required to change the color of the same amount of indicator as had been used in the titration.

Gay-Lussac made a major contribution to chemical analysis in 1832 when he introduced a volumetric method of estimating silver, which he justly claimed was much more accurate than the centuries-old method of cupellation.45 He proposed two parallel procedures for this method, one gravimetric, which he said was the more accurate, and one volumetric, which had the advantage of simplicity. The principle of both methods was the precipitation of silver chloride. He prepared a standard solution of sodium chloride of such concentration that 100 milliliters precipitated rather less than one gram of silver. Another standard solution of sodium chloride one-tenth of the concentration of the first was also prepared. One gram of silver was accurately weighed and then dissolved in nitric acid; 100 milliliters of the concentrated sodium chloride solution was added, and the precipitate of silver chloride was allowed to settle. The dilute sodium chloride solution was then added in one-milliliter portions; after each addition, the flask was shaken and the precipitate allowed to settle. The procedure was continued until further addition caused no precipitation. This final excess of sodium chloride was found exactly by back-titrating with standard silver nitrate solution. It was characteristic of Gay-Lussac’s standard solutions that they could be used only for specific analyses and for given weights of a sample, since the concentration of his solutions had no chemical basis related to equivalent weights. While, therefore, Gay-Lussac must be given credit for showing volumetric analysis to be convenient, rapid, and accurate, the establishment of a general system of volumetric analysis had to wait until the achievements of Fredrik Mohr in the next generation of chemists.

As early as 1807 Gay-Lussac had discussed the optimum temperature for the production of sulfuric acid in the lead chamber process.46 His main contribution to this industry, however, was his suggestion of 1827 dealing with the spent gases discharged into the atmosphere at the end of the lead chamber process containing the expensive and noxious oxides of nitrogen. The latter were to be absorbed by passing them up a tower packed with coke over which trickled concentrated sulfuric acid. The adoption of this method had to wait until John Glover showed in 1859 that the oxides of nitrogen absorbed in the Gay-Lussac tower could be used again in the chamber if the acid, containing oxides of nitrogen, were passed through a second tower in which it could come into contact with water and sulfur dioxide. This released the oxides of nitrogen and simultaneously produced acid of the right concentration for use in the Gay-Lussac tower.


1. “Sur la dilatation des gaz et des vapeurs,” in Annales de chimie, 43 (1802), 137–175.

2. “Relation d’un voyage aérostatique,” in Journal de Physique, 59 (1804), 314–320, 454–461, written with J. B. Biot.

3. “Expériences sur les moyens eudiométriques et sur la proportion des principes constituants de l’atmosphère,” ibid., 60 (1805), 129–168.

4. “Observation sur l’inclinaison des forces magnétiques . . .,” in Mémories de physique et de chimie de la société d’Arcueil, 1 (1807), 1–22, written with Humboldt.

5. “Premier essai pour déterminer les variations de température qu’éprouvent les gaz en changeant de densite . . .,” ibid., pp. 180–203.

6. “Mémorie sur la combinaison des substances gazeuses, les unes avec les autres,” ibid., 2 (1809), 207–234; translated in Alembic Club Reprint no. 4. pp. 8–24.

7. Annonce d’un travail sur la densité des vapeurs dde divers liquides,” in Annales de chimie, 80 (1811), 218.

8. “sur la décomposition de la potasse et de la soude,” ibid., 65 (1808), 325–326, written with Thenard; “Extrait de plusieurs notes sur les métaux de la potasse et de la soude,” ibid., 66 (1808), 205–217, written with Thenard.

9. “Sur la décomposition et la recomposition de l’acide boracique,” ibid., 68 (1808), 169–174, written with Thenard.

10. “Sur l’acide fluorique,” ibid., 69 (1809), 204–220, written with Thenard; “Des propriétés de l’acide fluorique et surtout de son action sur le métal de la potasse,” in Mémories de physique et de chimie de la Société d’Arcueil, 2 (1809), 317–331, written with Thenard.

11. “De la nature et des propriétés de l’acide muriatique et de l’acide muriatique oxigéné,” ibid., pp. 339–358, written with Thenard; translated in Alembic Club Reprint no. 13. pp. 34–48.

12. “Mémoire sur l’iode,” in Annales de chimie, 91 (1814), 5–121.

13. “Sur un acide nonveau formé par le souufre et l’oxigéne,” in Annales de chimie et de physique. 2nd ser., 10 (1819), 312, written with Welter.

14. “Mémorie sur l’eau régale,” ibid., 3rd ser., 23 (1848), 203.

15. “Sur le rapport qui existe entre l’oxidation des métaux et leur capacité de saturation pour les acides,” in Mémories de physique et de chimie de la Société d’Arcueil, 2 (1809), 159–175.

16. “sur la décomposition des sulfates par la chaleur,” ibid., 1 (1807), 215–251.

17. “Sur la précipitation des métaux par l’hydrogéne sulfuré,” in Annales de chimie, 80 (1811), 205–208.

18. “Sur la vapeur nitreuse, et sur le gaz nitreux considéré comme moyen eudiométrique,” in Mémoires de physique et de chimie de la Société d’Arcueil, 2 (1809), 235–253.

19. “Sur les combinaisons de l’azote avec l’oxigène,” in Annales de chimie et de physique, 2nd ser., 1 (1816), 394–410.

20. “Mémorie sur l’iode,” ibid., 91 (1814), 9, 148–149.

21. “Recherches sur l’acide prussique,’ ibid., 95 (1815), 155.

22. “Note sur l’acide prussique,” ibid., 77 (1811), 128.

23. “Recherches sur l’acide prussique,” ibid., 95 (1815), 136–231.

24. “Sur l’acide des prussiates triples,” ibid., 2nd ser., 22 (1823), 320–323.,

25. “Faits pour servir àl’historie du bleu de Prusse,” ibid., 46 (1831), 73–80.

26. C. F. Bucholz and Meissner, “Expériences pour déterminer la quantité de strontiane contenue dans plusieurs espèces d’arragonite,” ibid., 2 (1816), 176.

27. “Premier mémoire sur la dissolubilité des sels dans l’eau,” ibid., 11 (1819), 296–315.

28. “Note sur la fixité du degré d’ébullition des liquides,” ibid., 7 (1817), 307–313.

29. “Sur les combibaisons du chlore avec les bases,” ibid., 3rd ser., 5 (1842), 302–303.

30. “Observations sur l’oxidation de quelques métaux,” ibid., 2nd ser., 1 (1816), 36–37.

31. “sur la décomposition réciproque des corps,” ibid., 30 (1825), 291.

32. “Considérations sur les forces chimiques,” ibid., 70 (1839), 431.

33. “Sur l’analyse végétale et animale,” in Journal de physique, 70 (1810), 257–266.

34. “Recherches sur l’acide prussique,” in Annales de chimie, 95 (1815), 161.

35.ibid., 155 (my italies).

36.Cours de chimie,, II, Leçon 28 (16 July 1828).

37. “Sur l’analyse de l’alcool et de l’ether sulfurique,” in Annales de chimie, 95 (1815), 311–318.

38. “Mémorie sur l’iode,” ibid., 91 (1814), 149 n.

39. F. Wöhler, “Recherches analytiques sur l’acide cyanique,” ibid., 2nd ser., 27 (1824), 199–200 n.

40.Cours de chimie, II, Leçon 24, 1, 23

41. “Instruction sur l’essai du cholrure de chaux,” in Annales de chimie et de physique, 2nd ser., 26 (1824), 162–175.

42. “Nouvelle instruction sur la chlorométrie,” ibid., 60 (1835), 225–261.

43. “Essai des potasses du commerce,” ibid., 39 (1828), 337–368.

44. “Sur l’analyse du borax,” ibid., 40 (1829), 398.

45.Instruction sur l’essai matières d’argent par la voie humide (Paris, 1832), passim.

46. “Sur la décomposition des sulfates par la chaleur,” in Mémories de physique et de chimie de la Société d’Arcueil, 1 (1807), 246.


I. Original Works. Gay-Lussac was the author of Recherches physico-chimiques, faites sur la pile, sur la préparation chimique et les propriété du potassium et dusodium . . . 2 vols. (Paris, 1811), written with Thenard; and Instruction sur l’essai des matières d’argent par la voie humide . . . publiée par la Commission des monnaies et médailles (Paris, 1832). Although he himself never compiled elementary textbooks, the following, based on his lectures, were published: Cours de chimie par M. Gay-Lussac, comprenant l’historie des sels, la chimie végétale et animale . . . 2vols. (paris, 1828); and Leçons de physique de la Faculté des seciences se Paries, recueillies et rédigées par M. Grosselin, 2 vols. (Paris, 1828).

Gay-Lussac’s most important research papers include “Sur la dilatation des gaz et des vapeurs,” in Annales de chimie, 43 (1802), 137–175; “Relation d’un voyage aérostatique,” in Journal de physique, 59 (1804), 314–320, 454–461, written with J. B. Biot; “Expériences sur les moyens eudiométriques et sur la proportion des principes constituants de l’atmosphere,” ibid., 60 (1805), 129–168, written with Humboldt; “Observations sur l’intensité et l’inclinaison des forces magnétiques, faites en France, en Suisse, en Italie, etc.,” in, Mémoires de physique et de chimie de la Société d’Arcueil, I (1807), 1–22, written with Humboldt; “Premier essai pour determiner les variations de température qu’éprouvent les gaz en changeant de densité, et considérations sur leur capacité pour le calorique,” ibid., pp. 180–203; “Extrait de plusieurs notes sur les métaux de la potasse et de la soude,” in Annales de chimie, 66 (1808), 205–217, written with Thenard; “Mémoire sur la combinaison des substances gazeuses, les unes avec les autres,” in Mémoires de physique et de chimie de la Société d’Aruceil, 2 (1809), 207–234; “Sur l’acide fluorique,” in Annales de chimie, 69 (1809), 204–220, written with Thenard; “De la nature et des propriétés de l’acide muriatique et de l’acide muriatique oxigéné,” in Mémoires de physique et de chimie, 74 (1810), 47–64, written with Thenard; “Mémoire sur l’iode,” ibid., 91 (1814), 5–121; “Recherches sur l’acide prussique,” ibid., 95 (1815), 136–231; “Sur l’analyse de l’alcool et de l’ether sulfurique,” ibid., pp. 311–410; “Sur les combinaisons de l’azote avec l’oxigéne,” in Annales de chimie et de physique, 2nd ser., I (1816), 394–410; “Premier mémoire sur la dissolubilité des sels dans l’eau,” ibid., II (1819), 296–315; “Instruction sur l’essai du chlorure de chaux,;ibid., 26 (1824), 162–176; “Essai des potasses du commerce,” ibid., 39 (1828), 337- 368; “Considerations sur les forces chimiques,” ibid., 70 (1839), 407–434; and “Mémoire sur l’eau régale,” ibid., 3rd ser., 23 (1848), 203–229.

II. Secondary Literature. On Gay-Lussac and his work, see D. F. J. Arago, “Biographie lue en séance de l’Académie des sciences le 20 décembre 1852,” in Oeuvres de François Arago, Notices biographiques, 2nd ed., III (Paris, 1865), 1–112; E. Blanc and L. Delhoume, La vie émouvante et noble de Gay-Lussac (Paris, 1950); M. P. Crosland, “The Origins of Gay-Lussac’s Law of Combining Volumes of Gases,” in Annals of Science, 17 (1961), 1–26; and The Society of Arcueil. A view of French Science at the Time of Napoleon I (Cambridge, Mass., 1967); J. R. Partington, A History of Chemistry, IV (London, 1964), pp.77–90; and F. Szabavary, History of Analytical Chemistry (Oxford, 1966).

M. P. Crosland

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Gay-Lussac, Joseph-Louis

Gay-Lussac, Joseph-Louis


Joseph-Louis Gay-Lussac was one of the great scientists of the industrial age. Born on December 6, 1778, in St. Léonard in central France, he was the eldest of five children. His father was a public prosecutor and judge advocate, and the political unrest surrounding the French Revolution played an early role in young Joseph's development. When his father was arrested in 1794 (he was later released) as a member of the bourgeois establishment, Gay-Lussac was sent to a boarding school in Paris.

Three years later Gay-Lussac was accepted to the newly founded and elite École Polytechnique in Paris, where he initially studied mathematics and engineering. However, he soon fell in love with science and especially chemistry. This was in no small part due to the influence of the renowned scientist Claude-Louis Berthollet (17481822), a lecturer at the École who was also a contemporary of Antoine Lavoisier. It was Berthollet who took Gay-Lussac under his wing as his student and laboratory assistant.

The research for which Gay-Lussac is perhaps most famous involves the experiments with gases he completed early in his scientific career. Upon graduation from the École in 1800, he remained Berthollet's assistant and a frequent guest at his country house at Arcueil, near Paris. With the encouragement of Berthollet, mathematician Pierre-Simon de Laplace, and others, Gay-Lussac began his own research in the winter of 1801 and 1802.

Among Gay-Lussac's early work was an extensive investigation of how the volume of various gases changes with temperature. The English scientist John Dalton was independently studying the same phenomenon. Both found that the volume V of all gases studied increased similarly with higher temperature T when pressure P was held constant (VαT at constant P ). Each published his results around 1802, with Gay-Lussac's experimental work being both more thorough and more precise than that of Dalton. However, the credit for this discovery typically goes to neither Dalton nor Gay Lussac, but instead to Jacques Charles. Charles had done some initial work on the thermal expansion of gases in 1787. Although Charles never published the results of his experiments, in his own scientific memoirs Gay-Lussac acknowledged hearing of Charles's work. Thus, the law governing the thermal expansion of gases, while sometimes called Gay-Lussac's law, has come to be known largely as Charles's law.

Gay-Lussac's studies were not limited to the physical properties of gases. In 1804 Gay-Lussac took advantage of the world's growing interest in ballooning and made multiple flights to study both Earth's magnetic field and how the temperature and composition of the atmosphere changed with increasing altitude. On his second flight, he took samples of air while reaching an altitude of 23,018 feet in a hydrogen balloon, a record that lasted for almost fifty years. Upon his return to Earth, he compared the gas samples to those taken at ground level and concluded that they were essentially identicalthis despite making note of a headache during the flight that very possibly resulted from the decreased oxygen levels at high altitude.

In 1808 Gay-Lussac published his "Law of Combining Volumes of Gases." He determined that when different gases reacted, they would always do so in small whole number ratios (e.g., two volumes of hydrogen would react with one volume of oxygen in forming H2O). This was one of the greatest advancements of its time and helped form the basis for later atomic theory and how chemical reactions occur.

With his colleague Louis-Jacques Thénard (17771857), Gay-Lussac did considerable work with electrochemistry to produce significant amounts of elemental sodium and potassium, highly reactive and useful substances that were used to isolate and discover the element boron. Gay-Lussac also completed extensive studies of acids and bases and was the first to deduce that there were binary (two element) acids such as hydrochloric acid (HCl) in addition to the known oxygen-containing acids like sulfuric acid (H2SO4). Additionally, he was able to determine the chemical composition of prussic acid to be hydrocyanic acid (HCN) and was considered the foremost practitioner of organic analysis.

In later years, Gay-Lussac continued to advance science. He developed a precise method for analyzing the alcoholic content of liquors and patented a method for the manufacture of sulfuric acid. His last publication on aqua regia (a mixture of nitric and hydrochloric acids that dissolves gold or platinum) came out the year before his death in 1850. Gay-Lussac was a topnotch experimentalist and theoretician. More than twenty-five years after Gay-Lussac died, the prominent chemist Marcellin Bertholet (18271907) once said, "We all teachthe chemistry of Lavoisier and Gay-Lussac" (Crosland, p. 248), a fitting tribute to two outstanding scientists of the era.

see also Acid-Base Chemistry; Berthollet, Claude-Louis; Charles, Jacques; Dalton, John; Davy, Humphry; Lavoisier, Antoine.

David A. Dobberpuhl


Arago, François (1855). "Oeuvres Complètes de François Arago." In Great Chemists, tr. and ed. Eduard Farber (1961). New York: Wiley-Interscience.

Crosland, Maurice P. (1978). Gay-Lussac, Scientist and Bourgeois. Bristol, U.K.: Western Printing Services.

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Joseph Louis Gay-Lussac

Joseph Louis Gay-Lussac

The French chemist and physicist Joseph Louis Gay-Lussac (1778-1850) is distinguished for his work on gas laws and for his studies of the properties of cyanogen and iodine.

Born at Saint-Léonard in the department of Vienne, Joseph Gay-Lussac came from a solidly bourgeois family. The storms of the French Revolution delayed his education, but largely by his own disciplined self-teaching, he passed the examinations and was admitted to the prestigious École Polytechnique in 1797. Here he became the protégé of Claude Louis Berthollet.

In these early years Gay-Lussac's skill as an experimenter and scientific instrument maker was well developed. In 1802 he published a law of the expansion of gases by heat, which became known as Charles' law. In 1804 he made an ascent of 23,000 feet in a balloon to collect samples of the atmosphere for chemical analyses and to measure the dependence of the earth's magnetic field on elevation. In 1806 Gay-Lussac was elected to the Institut de France, and in 1809 he became a professor of chemistry at the École Polytechnique and professor of physics at the Sorbonne. He invented the portable barometer, steam injector pump, and air thermometer and improved the spirit lamp and the chemist's furnace. In addition to his work on these laboratory devices, he contributed to the production and improvement of industrial chemical machinery and processes, above all in the important sulfuric acid tower which bears his name.

In 1805-1806, through the intervention of Berthollet, Gay-Lussac accompanied the scientific explorer Alexander von Humboldt on his expedition through Italy and Germany making measurements of terrestrial magnetism. While in Rome, the young chemist was able to use the laboratory of Wilhelm von Humboldt, on which occasion he discovered the presence of fluorides and phosphates in the bones of fish. Not long after this, Gay-Lussac met a beautiful girl in a Paris draper's shop, soon became engaged, and then sent his fiancée to school to complete her chemistry education. In 1808 he married her. The marriage lasted for 40 years and was marked by the closest collaboration of hearts and minds.

In addition to his well-known work on the combining properties of gases, Gay-Lussac also worked on the determination of vapor densities, and the coefficients of expansion of gases, in which he pioneered the procedures, and contributed to the careful quantitative measurements that in later years were so useful for grounding the kinetic theory of gases and thermal physics. He published his most influential work in 1808, the law of combining volumes of gases.

Electrolysis and Iodine

Some of Gay-Lussac's best work, however, was done in close collaboration with Louis Jacques Thénard, the chemist who created the foundations of organic analysis. Together they produced the alkali metals in quantity by reacting fused alkalis with red-hot iron. Napoleon made considerable sums available to the École Polytechnique to support their work on electrolysis. However, though aware of the theoretical importance of the electrolytic process, they elaborated a more efficient method of producing the alkali metals.

Gay-Lussac investigated (1813-1814) the chemical properties of iodine and described his findings in a number of papers presented to the Institut de France. However, Sir Humphry Davy, visiting in Paris at the time, wrote a particularly insulting note to the scientific world claiming priority for the discovery of the elemental nature of iodine, asserting that Gay-Lussac had learned the fundamental properties of iodine from him. In yet another controversy Gay-Lussac and Thénard claimed a priority of 36 hours for their isolation of boron. They claimed that the experiment was completed on June 21, 1800, and the results sent to Geneva for publication, whereas Davy's announcement was supposedly dated June 30. It should be noted that the potassium that Davy used to treat borax was produced by using the Thénard-Gay-Lussac method.

Other Achievements

The French partners also carried out extensive investigations on the composition of hydrochloric acid. Individual work by Gay-Lussac on the properties of the sulfates and sulfides, as well as other salts, was an important step in the perfection of what later became known as volumetric analysis. He compiled extensive solubility charts for numerous compounds. Classic work on cyanogen compounds was carried out by him largely on his own. He was also the first to recognize that the CN combination was stable and behaved as a radical in the various combinations into which it entered.

Gay-Lussac served in 1818 as superintendent of the government gunpowder plant and as chief assayer of the national mint in 1829. King Louis Philippe raised him to the peerage in 1839. The honor had been delayed for 17 years, for, argued the old aristocracy, Gay-Lussac worked with his hands. He died on May 9, 1850.

Further Reading

Gay-Lussac is discussed in Sir William A. Tilden, Famous Chemists: The Men and Their Work (1921); Edward Farber, ed., Great Chemists (1961); and Maurice Crosland, The Society of Arcueil: A View of French Science at the Time of Napoleon I (1967). □

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Gay-Lussac, Joseph Louis

Joseph Louis Gay-Lussac (zhôzĕf´ lwē gā-lüsäk´), 1778–1850, French chemist and physicist. He was professor in Paris at the Sorbonne, at the Polytechnic School, and at the Jardin des Plantes. Gay-Lussac made two balloon ascensions in 1804, attaining on the second a height of about 7,016 m (23,000 ft), to test the variation of the earth's magnetic field and the composition of the atmosphere at varying altitudes. He made advances in industrial chemistry; in the field of analytical chemistry he improved the methods of analyzing gas mixtures, studied prussic acid and iodine, and isolated cyanogen. With L. J. Thénard he improved Davy's method of isolating alkali metals, showed chlorine to be an element, and isolated boron. In physics he is known especially for his work on gases. In 1802 he discovered independently that a gas at constant pressure expands, for each degree of temperature, by a constant fraction of its volume at 0°C. This law, first discovered (1787) by J. A. C. Charles, is known as Charles's law or as Gay-Lussac's law (see gas laws). However, Gay-Lussac's name is more commonly associated with another law of gases, the law of combining volumes, which Gay-Lussac was the first to formulate (c.1808). This law states that the volumes of gases that interact to give a gaseous product are in the ratio of small whole numbers to each other and that each bears a similar relation to the volume of the product.

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Gay-Lussac, Joseph Louis

Gay-Lussac, Joseph Louis (1778–1850) French chemist and physicist. He discovered (1808) the law that gases combine in a simple ratio by volume (Gay-Lussac's law). Gay-Lussac also discovered the law of gas expansion, often attributed to J. A. C. Charles.

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"Gay-Lussac, Joseph Louis." World Encyclopedia. . 27 Apr. 2017 <>.

"Gay-Lussac, Joseph Louis." World Encyclopedia. . (April 27, 2017).

"Gay-Lussac, Joseph Louis." World Encyclopedia. . Retrieved April 27, 2017 from