Gerhardt, Charles Frédéric

(b Strasbourg, France, 21 August 1816; d Paris, France, 19 August 1856)

Chemistry.

Gerhardt’s father, Samuel Gerhardt, who came from a family of brewers, was born in Switzerland. As a young man he moved to Strasbourg, where he found employment in a bank and married an outstanding beauty of the town, Charlotte Henriette Weber. Samuel Gerhardt’s position in the banking house of Turkheim gave his family the benefits of a prosperous and cultured home. Like many inhabitants of Strasbourg, the Gerhardts spoke and Wrote French and German with almost equal facility. As was expected of the sons of the bourgeoisie, young Gerhardt attended the lycée where he showed unusual ability. In 1825 Gerhardt pére gave financial backing for the exploitation of a patent for white lead. The partner who was to supply the technical knowledge Withdrew, and Gerhardt was left to run a factory, the scientific aspect of which was quite outside his competence. It was this situation which convinced Gerhardt to provide an eduction for his son Charles which would prepare him for the management of the factory. In 1831 young Gerhardt accordingly entered the newly founded Polytechnicum at Karlsruhe, where he followed intermediate courses in chemistry, physics, and mathematics. In 1833 his father decided to encourage the order aspect of his plan for charles by sending him to a commercial college in Leipzing. Even there, however, he had lodgings in the house of the chemsist Otto Erdmann, who encouraged his scientific interests.

A long paper on the revision of the formulas of natural silicates which Gerhardt wrote in 1834 was accepted for publication by the Journal für Praktische Chemie; and in 1835, before his nineteenth birthday, his further research had won him the honor of election as corresponding member of the Sociétée D’Historie Naturelle de Strasbourg. Having seen the attraction of pure science, he came into open conflict with his father, who wanted him to return to the family chemical factory. After a violent quarrel the son left home to join a regiment of lancers. Here too, he was unhappy and managed to borrow the 2,000 francs necessary to buy himself out. Realizing that his vocation was chemistry, Gerhardt went to Giseen, where Lieberg was beginning to build up a reputation, and was enrolled in Liebig’s course for 1836-1837.

To earn money for his studies, Gerhardt undertook the translation of one of Liebig’s works into French and in so doing helped his own career. In April 1837 he left Liebig to make a final attempt to reconcile himself with his father. Yet he could not settle down to a life of commerce. To make his mark in chemistry he left for Paris. Arriving in October 1838, he enrolled in the course given by Dumas in the Faculty of Sciences. For three years he studied with Dumas and family became his assistant.

Gerhardt’s hard work and brilliant research won him the degress of licentiate and doctor, both in April 1841 (his thesis was on helenin). Within a few days and on the recommedation of Dumas, Gerhardt was nominated to a vacancy in the Faculty of Sciences in Montpellier. In fact Gerhardt was only chargé de cours in 1841 and had to wair three years for nomination to the rank of titular professor. He soon found that the facilities for research were very limited and that it was difficult to settled won so far from Paris and Strasbourg. He went to Paris as often as possible and finally obtained leave of absence to work there, When in 1851 a request for further leave was refused, Gerhardt resigned. He did so the more easily as he was then, with the help of borrowed money, establishing his own private school for practical chemistry. This was not a financial success, but in 1854 he was able to secure a further university appointment. There were two vacancies for chairs of chemistry at Strasboung, in the Faculty of Sciences and the School of Pharmacy, and both were offered to him. Although reluctant to leave Paris, Gerhardt was glad to return to his native city. Above all, his position in French chemistry was now recognized, and his financial problems were at an end. In 1844 Gerhardt had married a Scottish girl, Jane Sanders, whose brother was studying at the University of Montpellier, Gerhardt thus learned to speak and write English as well as French and German.

In 1844 there began a close friendship with Laurent, professor of chemistry at Bordeaux. They had much in common; zeal for a new approach to organic chemistry with poor facilities available for research, and above all, isolation from the center of power in Paris because of the remoteness of their provincial teaching posts. Wurtz justly commented: “In the history of science the great figure of Gerhardt cannot be separated from that of Laurent: their work was done in collaboration, their talent was complementary, their influence was reciprocal,” Most commentators have agreed that Gerhardt had the merit of clarity. Yet he himself remarked how vital an impact was made on him by the profusion of ideas which poured from the pen and the lips of his friend.

Gerhardt was attracted several times in his career to scientific journalism. He was a collaborator in the first issues (1840) of Quesneville’s Revue Scientifique et industrielle, and it is typical of his literary zeal that he should produce a new journal from his association with Laurent. Their Comptes rendus mensuels des travaux chimiques, although a help in publicizing their own work, was not well received and lasted only from 1845 to 1851.

In national and academic poliics Gerhardt was numbered among the radicals. He became bitterly opposed to Dumas, who had come to typify the scientific establishment. Gerhardt’s position was not helped by his readiness to speculate, his lack of tact, and his dogmatism. He was involved in many disputes, even with his protector Liebig. Disputes which began in organic chemistry quickly descended to personalities, and it was characteristic of the organization of French science in the mid-nineteenth century that Gerhardt was not an active member of any important scientific society. On 21 April 1856 he was at last honored by election as a correspondent of the Institute, but within four months he was dead. Gerhardt tragic death in his fortieth year, following a career of banishment to the provinces, did not prevent him from becoming one of the seminal figures in the history of nineteenth-century chemistry.

Gerhardt was sufficiently impressed by the substitution theories of Laurent and Dumas, which had invaded organic chemistry in the late 1830’s that he was prepared to regard each molecule as a unitary structure or “single edifice” within which substitution of different “residues” could occur. He did this in opposition to the more conservative chemists headed by Berzelius, who supported a dualistic theory, according to which all compounds were interpreted as consisting of an electropositive part and an electronegative part. In the case of many organic compounds this interpretation involved the arbitrary grouping of atoms without supporting evidence.

A major problem confronting chemists in the early 1840’s was whether it was possible to ascertain the arrangement of atoms in a compound. Gerhardt reacted violently against the empiricist principle that the arrangement of atoms in a compound. Gerhardt reacted violently against the empiricist principle that the arrangement of the atoms could be inferred from a compound’s more of formation or from its reactions. He maintained that we cannot infer arrangements from reactions; all we can ever know are the reactions. So, whereas the view of Berzelius was that each compound had a rational formula and there remained only the practical difficulty of discovering what it was, Gerhard’ts view became the exact opposite: We could never know the arrangement of atoms but only the reactions of compounds. Any formula must be based on a particular reaction. If an aldehyde behaves in some reactions like an oxide and in others like a hydride, it must be given two different formulas according to the occasion. Gerhardt took his operational definition of a formula to the logical conclusion and stated that a compound has “as many rational formulas as [it has different] reactions,”¹ Consequently his chemistry has a positivist flavor. A chemical formula for Gerhardt was simply equivalent to a particular reaction of a compound and thus had little explanatory value.

A considerable part of Gerhard’t claim to our attention is connected with his use of certain formulas in chemistry. Like Lavoisier, he felt that chemistry could be successfully pursued only if it were based on a rational and systematic language. It was not merely that formulas are a reflection of our basic concepts but, more, that “our formulas are our ideas It is not surprising, therefore, to find Gerhardt insisting on the importance of writing chemical equations: “The only approach which is at the same time rigorous and easy and which can be reconciled with the individual opinions of all chemists is that which consists in expressing reactions by equations from which all purely hypothetical entities are excluded,”² Gerhardt was one of the first to make systematic use of equations in chemistry.

Gerhardt’s most conspicuous contribution to the developemfent of organic chemistry was his homologous series. His earliest publications were characterized by attempts to arrange organic compounds in series of increasing complexity: his “ladder of combustion,” rising from water and carbon dioxide at the foot to albumin and fibrin at the summit, was analogue of the biologists’ ladder of nature, another biological analogy was to underlie the application of his homologous series when they were refined in 1843: Gerhardt presupposed a principle of plenitude in organic chemistry which dictated that hitherto undocumented members of any series must exist. In addition, the concept of homology itself was of biological origin, deriving from Cuvier. For Gerhardt, however, it did not carry that structural connotation which it had for Cuvier. On this subject Gerhardt, simply asserted: “We call substances homologues when they exhibit the same chemical properties and when there are analogies in the relative proportions of their elements.”³

Drawing on the work of Dumas—who, in 1842, had observed that a whole series of acids could be generated by the formula (C⁴ H⁴)_n O⁴ [(CH₂)_n O₂ in modern notation]—and also of Kopp, who had investigated “a great regularity in the physical properties of analogous organic compounds.” Gerhardt generalized the concept of homologous series and introduced it into his Précis de chimie organique of 1844. He did so with particular reference “to the four known alcohols, since he could demonstrate a significant numerical relation between their empirical formulas: They could be written in the forms [(CH²) + H² O]; [(CH²)² + H² O}: [(CH²)¹⁶ + H² O]. Furthermore, their respective oxidation, sulfonation, and halogenation products could all be denoted by formulas in which: the characteristic (CH₂) unit recurred. The solution which Gerhardt found to the problem of prediction was then explicit in his enthusiastic conclusion: provided one knew how properties varied regularly along a series, “it would suffice to know the composition, the properties and the mode of formation of a single product obtained [from one of the above compounds] in order to be able to predict the composition, properties and mode of formation of all substances similar to this first product.”⁴

Gerhardt systematically showed how one could argue from the reactions of one compound to those of another on the basis of a formal numerical analogy displayed by their respective empirical formulas. His enthusiasm for this system of classification led to his being accused, of doing algebra rather than chemistry. Nevertheless, on this basis Gerhard not only forecast the existence of many new compounds, such as those required to complete the alcohol series, [(CH²)ⁿ + H² O], but also predicted the properties of many others, such as, the boiling point (140°C.) of propionic acid. Within the space of twenty years organic compounds had been removed from what Wöhler had described, as a primeval forest and had been transplanted in decorous straight lines. Within the next few years the carbon-carbon bonds of Kekulé were to explain the significance of the recurrent CH₂ unit; and in retrospect the only serious shortcoming of Gerhardt’s understanding of homology was its failure to do justice to structural isomerism.

If the concept of homology was Gerhardt’s most notable contribution, his most notorious was a reform of the presuppositions then underlying the determination. of chemical equivalents. As a consequence of the prevalent disregard for Avogadro’s hypothesis, current equivalents were not based on equal volumes of vapor. Accordingly, Berzelius saw nothing wrong in writing water as H² O and acetic acid as C⁴ H⁸ O⁴, in order that the later might be considered the hydrate of an oxide (C⁴ H⁶ O³ +H² O) analogous to an inorganic acid; compare sulfuric acid (SO³+H² O). Similarly, (Gmelin’s alternative system allowed an organic acid to be envisaged as an anhydride plus water (C⁴ H³ O³ + HO). But in both cases there was an inconsistency, and it was Gerhardt who faced the consequences of removing it. The inconsistency was this: if H² O represented an equivalent of water corresponding, to two volumes of vapor; how could the same equivalent of water be preformed within an organic acid if the overall equivalent of the acid corresponded to four volumes of vapor? To eliminate the inconsistency, it would be necessary to represent the water participating in organic reactions by H⁴ O² (Berzelius’ system) or by H² O² (Gmelin).

Consequently, in his famous paper read before the Paris Academy of Science in September 1842, Gerhardt enumerated a host of organic reactions in order to demonstrate that when water was produced or utilized in such reactions, it was in quantities which could, be represented, only by H⁴ O², on a four-volume system. From similar considerations with respect to the participation of carbon dioxide in organic reactions, Gerhardt argued that the only way to achieve consistency was either to double all two-volume inorganic formulas or to halve all four-volume organic formulas. But this was a particularly drastic measure—since it destroyed almost all the current constitutional analogies between inorganic and organic compounds—and such was the dogmatic and precocious tone of its advocate that Gerhardt’s revision met constant hostility.

It was not until February 1845 that even the sympathetic Laurent finally agreed to the innovation, one corollary, of which merits special, attention. If all organic formulas corresponding to four volumes of vapor really had to be divided by two, then no four-volume formula could be tolerated if it included an add number of atoms. Both Laurent and Gerhardt were therefore obliged to instigate a program of reanalysis in cases, where four-volume formulas failed to conform to their scheme; and the implication that their contemporaries, particularly Liebig, had been incompetent did much more to increase their professional alienation during the 1840’s. It has often been said that Gerhardt’s standardization constituted a revival of Avogadro’s hypothesis, but this is not strictly true. Nothing could be further from Avogadro’s hypothesis than Gerhardt’s conclusion that “atmos, equivalents, and volumes are synonymous. …” Certainly it was a corollary of Avogadro’s hypothesis that molecular formulas should be standardized in the way Gerhardt had chosen, but Gerhardt himself was preoccupied with the corollary Simplification, and the elimination of the internal inconsistency had been ends in themselves, and it was left to Laurent and others to clarify further the relationship between atoms, equivalents, and molecules.

Another notable, althought less well-known, contribution of Gerhardt’s was his redefinition of acids. Since the standardization of inorganic and organic formulas, effected by Gerhardt” strictly precluded the preexistence, of water in, the molecule of a monobasic acid, some alternative convention for the formulation of acids was required. During the 1830’s Liebig had become dissatisfied with the (anhydride + water) model but) had not been prepared to introduce the alternative hydrogen theory in inorganic chemistry, even though he had commended it for the organic domain. Gerhardt’s view of chemistry, however, was dominated by the attempt to introduce organic concepts into inorganic chemistry and he felt no compunction in introducing a universal definition of acidity based on hydrogen. The idea that an acid could be defined with reference to its displaceable hydrogen appealed to Gerhardt for the additional reasons that salt formation could then be construed as a displacement reaction rather than as an addition reaction.

In this way one of the prevalent electrochemical theory was removed. Hitherto, acid, base, and salt had often been defined in terms of each other, so it was an obvious merit of Gerhardt’s definition that it broke the circle. The essential conceptual advance consisted, in the obliteration of the artificial distinction between “oxacids” and “hydracids,” In deference to their heritage from Lavoisier, chemists had been obliged to create a special class for acids, such as hydrochloric, which contained no oxygen. These were the “hydracids.” Long after Lavoisier’s Erroneous explanation of acidic properties was obsolete the classification of acids still paid lip service to it. A conceptual switch was necessary to recognize hydracids as the rule and to transpose the oxacids accordingly. Pursuing this transposition to its conclusion, Gerhardt was able to refine Liebig’s criteria for the establisblishment of acid basicity: the diagnostic value of acid and double salts assisted in the determination of the number of replaceble hydrogen atmos in a given acid. The dibasicity of sulfuric acid was at last publicized; and when, in 1856, Alexander Williamson expressed the respective basicities of nitric, sulfuric, and, phosphoric acids as NO₃ H SO₄ H₂;PO₄ H₃, he added that the “labors of Messers. Laurent and Gerhardt greatly contributed to the establishments of these results which are uncontroverted.”

During the 1830’s the attempt to model the structure of organic compounds on the dualistic structure of inorganic compounds led to the postulation of a large, number of hypothetical redicals, supposedly analogues of the inorganic elements. According to Liebig’s famous definition, organic chemistry differed from inorganic chemistry in that it dealt with compound rather than simple radicals. Ethyl choloride, for example, could be envisaged as a salt in which the composite ethyl redical played a role analogous to the potassium of potassium chloride. As complex a Bunsen: as(C⁴ H¹² As²) Cl with the implication that the complex radical.(C⁴ H¹² As²) should be as, capable of isolation as me inorganic elements, Bunsen was convinced that the he had isolated the free cacodyls radical.

In the 1840’s Kolbe and Frankland isolated what they thought were the methyl and ethyl radicals and thus appeared to corroborate the analogy between metal and redical, but there was a disconcerting feature of this corroboration. If one bowed before Gerhardt’s insistence that molecular formulas should all refer to the same volume of vapor, it was impossible to equate what Bunsen had isolated with the hypothetical constituent of the cacodyls compounds, just as it was also impossible to equate Kolbe’s species with the hypothetical methyl. The equivalent vapor densities of the isolated with the hypothetical constituent of the cacodyls compounds, just as it was also impossible to equate Kolbe’s species with the hypothetical methyl. The equivalent vapor densities of the isolated species corresponded to the dimers (C⁸ H²⁴ As⁴) and dimethyl, respectively. How were these results to be interpreted? It was a clear case of circular verification: if one accepted the dualistic approach to organic chemistry, then Kolbe’s work confirmed it; if one accepted Gerhardt’s presuppositions, it did not. Eventually the inert character of the Kolbe-Frankland hydrocarbons, together with their respective boiling points, testified in Gerhardt’s favour; and by 1851 Frankland himself was admitting that what he had taken to be methyl and ethyl were in reality stable dimmers. Gerhardt’s ideas were, therefore, instrumental in preventing a serious misinterpretation of hydrocarbon chemistry, as they were also in drawing attention to the legitimacy of postulating diatomic molecules X₂ (compara (CH³)₂) in contradistinction to the tenets of electrochemical theories.

One of Gerhardt’s principle claims to fame was his “type” theory. The concept of a chemical “type” has a long and intricate history, Chemists had long given similar compounds similar names (compare the “pyrites” of iron and copper), and when Berzelius had eventually represented the sulfates, selenates, and chromates by the formulas MO.SO³, MO. SeO³, and MO. CrO³, he had recongnized more than a superficial resemblance. The discovery of isomorphism by Mitscherlich and of chlorine substitution within organic compounds by Laurent and Dumas culminated in Dumas’s “type theory” (1838-1840), which purported to explain the common properties of parent and chlorine derivative with reference to a common spatial arrangement of their constituents: acetic and trichloracetic acids, for example, belonged to the same “chemical” type. Impressive as Dumas’s theory was, it had at least two outstanding defects. First, since there turned out to be no rigid distinction between substitutions with and without retention of properties, Dumas’s division between “chemical” and “mechanical” Types—which had been designed to cater to such a distinction—began to appear arbitary. Second, during the 1840’s, when the central problem became one of classification, his types proved to be too specific. They might illuminate the relation between any one acid and its chlorine derivatives, but there was no obvious way of correlating the types of different parent acids. It seemed that what was required was to expand the concept of “type” for an economic classification and for an understanding of all substitution reactions (irrespective of a change in properties), and yet escape the problems associated with the ever-increasing number of conflicting opinions about the precise arrangement of atoms within a given compound.

It was Gerhardt who provided a solutions to this problem when, in his definitive exposition of a “new type theory” (1853-1856), he illustrated how one could envisage organic compounds as substitutionary derivatives of a minimal number of inorganic compounds: water, ammonia, hydrogen, and hydrogen chloride. Several chemists contributed the empirical foundation for this new theory. Williamson, for example, was able to prepare mixed ethers which admirably conformed to the water type—compare

while Hofmann showed that the amines could be subsumed under ammonia as an all-embracing type— compare.

It was, in fact, in the context of establishing the utility of the water type that Gerhard himself made what was his most prestigious contribution to practical chemistry. According to the water type theory, acetic acid could be written as and by a further substitution of an acyl group for a hydrogen atom there should result a compound Gerhardt’s triumph was to prepare acetic anhydride by the reaction of acetyl chloride with sodium acetate. Furthermore, by producing mixed anhydrides, he established—against contemporary opinion—that two equivalents of a monobasic acid were involved in the process; compare

Gerhardt’s type theory dominated the organic chemistry of the late 1850’s, not simply because of its comprehensiveness but also because it could be extended in a number of profitable directions. The introduction of the methane type completed a series which was highly suggestive in the context of emerging ideas on valency:

Moreover, this theory was highly flexible, since types could be conjugated, condensed, or multiplied in order to accommodate more elusive species, such as ammonium hydroxide:

Although the purely formal nature of Gerhardt’s types prevented their earning a permanent place in the body of chemical theory, at the time of their inception they exerted a powerful unifying influence on the development of chemistry. In two quite different senses Gerhardt had contributed to the unification of chemical theory. In the first place, by introducing the radicals, such as ethyl, into types such as water, Gerhardt was able to achieve some kind of rapprochement between radical and type concepts which had hitherto been in opposition. Second, by subsuming all organic compounds under four inorganic types, he was advocating analogies of unprecedented generality between organic and inorganic compounds. Gerhardt, like Laurent, was convinced of the unity of chemical theory; and when Wurtz (1862) sought a proof of the artificiality of the inorganic-organic dichotomy, it was to Gerhardt’s theory of types that he appealed.

Gerhardt will occupy a permanent position in the history of chemistry for his services to organic classification, for his concept of homology, for his preparation of acid anhydrides, and for his reform of equivalents. His unitary emphasis, while remaining indispensable for the comprehension of organic compounds, was eventually superseded in inorganic compounds, was eventually superseded in inorganic chemistry as ionic concepts marked the culmination of a return to a more mechanistic apprcoah. Indeed, shortly after the death or Gerhardt chemistry was to change its sights. A new program, explicitly hostile to Gerhardt’s positivist construction of chemistry, was promulgated by Kekulé and Scott-Couper. Reductionist in intent, it focused attention once more on the elements themselves and on the individual atoms, with the object of so elucidation the nature of chemical bonding that the properties of any compound could be demonstrated to follow from those of its constituent elements. Questions concerned with the real demonstrate of atoms in a molecule and with what held them together could not be bypassed for long, and with the resuscitation of these questions certain features of Gerhardt’s unitary chemistry were quietly forgotten; no longer was it reasonable to regard all reactions as double decompositions, and no longer could all the metals be regarded as diatomic M₂. Nevertheless, whenever chemical philosophers have gathered together, there have been those, like Benjamin Brodie, who have expressed their gratitude to those “great chemists, Laurent and Gerhardt who implanted in the science the germ of a more abstract philosophy, which it has ever since retained.”

NOTES

1. Grimaux and Gerhardt, Charles Gerhardt, sa vie…, p. 490.

2.Précis de chimie organique, I viii-ix.

3.Annales de chimie et de physique, 3rd ser., 8 (1843), 245.

4.Revue scientifique er industrielle, 14 (1843), 588

BIBLIOGRAPHY

I. Original Works. Gerhart’s books are Précis de chimie organique, 2 vols. (Paris, 1844-1845); Introduction à l’étude de la chimie par le système unitaire (Paris, 1853-1856).

His major research papers are the following: “Sur la constitution des sels organiques à acids complexes,. et leurs rapports avec les sels ammoniacaux,” in Annales de chimie, 2nd ser., 72 (1839), 184-215; “Recharches chimiques sur les hules essentielles,” ibid., 3rd ser., 1 (1841), 60-111; “On the chemical Classification of Organic Substances,” in Revue scientifique er industrielle, 7 (1841), 104, 8 (1842), 300; 10 (1842), 145; 12 (1843), 592; 14 (1843), 580; “Consideéations sur les équivalents de quelques corps simples et composés,” in Annales de chimie,7 (1843), 129-143, and 8 (1843), 238-245; “Recherches sur la salicine,” ibid., 8 (1843), 215-229; “Recherches chimiques sur l’essence de valéeriane et l’essence d’estragon,” ibid., pp. 275-295, also in Annalen der Chemie, 45 (1843), 29-41; “Action de l’acide sulfurique sur les matiéres,” in Comptes rendus hebdomadaires des séances de l’Académie des sciences, 16 (1843), 458-460; “Sur les combinaisons de l’acide sulfurique acec les matières organiques,” ibid :ibid., 17 (1843), 312-317; “Recherches concernant les alcalis organiques,” ibid., 19 (1844), 1105-1107; “Sur la généation de l’éther,” in Revue scientificque, 2nd sed., 3 (1844), 304-310; “Sur le point d’ébullition des hydrogénes carbonés,” in Annales de chimie, 14 (1845), 107-114, also in Journal für praktische Chemie, 35 (1845), 300-305; “Sur une nouvelle classe de composés organiques,” in Annales de chimie, 14 (1845), 117-125, and 15 (1845), 88-96; “Observations sur la formation des formules chimiques,” in Journal de pharmacie, 8 (1845), i-viii; “Sur l’identité de l’essence d’estragon et de l’essence d’anis,” in Comptes rendus hebdomadaires des séances de l’Académie des sciences, 20 (1845), 1440-1444; “Sur la loi de saturation des corps copulés,” ibid., pp. 1648-1657; “Sur les mellonures,” ibid., 21 (1845), 679-681; “Introduction à l’étude de la chimie,” in Journal de pharmacie, 145 (1848), 63-67; “Recherches sur les anilides,: in Annales de chimie, 24 (1848), 163-207; “Remarques sur les combintaitons des acides avec les alcalis organiquies,” in Comptes rendus mensuels des travaux chimiques, 5 (1849), 160-170; “Recherches sur les phénidesm nouvelle classed de composés organiques,: ibid., pp. 429-437; “Sur la composition des mellonures et de leurs dérivés”, ibid., 6 (1850), 233-236; “Remarques sur un travail de M. Williamson relatif aux éthers,” ibid., pp. 361-364; “Sur la constitution des composés organiques,” ibid., 7 (1851), 65-84; “Sur la basicité des acides,” ibid., pp.129-156, also in Journal für praktische Cheimie, 53 (1851), 460-488; “Recherches sur les acides organiques anhydres,” in Annales de chimie, 37 (1853), 285; “Note sur la théorie des amides,” in Comptesrendus hebdomadaires des séances de l’Académie des sciences37 (1853), 280-284; “Addition aux recherches sur les amides,” in Annales de chimie, 46 (1856), 129-172; and “Recherches sur les amides,” ibid., 53 (1858), 302-313.

Many of Gerhardt’s most revealing articules were published in Comptes rendus mensuels des travaux chimiques between 1846 and 1852. For his correspondence, see M. Tiffenaeau, ed., Correspondance de C. Gerhardt (Paris, 1918).

II. Secondary Literature. On Gerhardt or his work, see E. Grimaux and C. Gerhardt, Charles Gerhardt, sa vie, son veuvre, sa correspondance (Paris, 1900); J. Jacques, “Onze lettres inédites de Charles Gerhardt à J. B. Dumas,” in Bulletin de la Société chimique de France, 156 (1856), 1315-1324; C. de Milt, “Auguste Laurent. Guide and Inspiration of Gerhardt,” in Journal of Chemical Education, 28 (1951), 198-204; J. F. H. Papillon, La vie et l’oeuvre de C. F. Gerhardt (Paris, 1863); and J. R. Partington, History of Chemistry, IV (London, 1964), 405-424 and passim.

M. P. Crosland

J. H. Brooke