¹ Levere, T. L., Affinity and matter. Elements of chemical philosophy 1800–1865, Oxford, 1971Google Scholar. Of relevance to the present subject are also Schelar, V. M., ‘Thermochemistry and the third law of thermodynamics,’ Chymia, 1966, 11, 99–124CrossRefGoogle Scholar, and Raman, V. V., ‘The permeation of thermodynamics into nineteenth century chemistry,’ Indian journal of history of science, 1975, 10, 16–37.Google Scholar

² Leicester, H. M., ‘Germain Henri Hess and the foundation of thermochemistry,’ J. chem. ed., 1951, 28, 581–583CrossRefGoogle Scholar. Hess' papers are reprinted in Ostwald's Klassiker der exakten Wissenschaften, no. 9, Leipzig, 1921.Google Scholar

³ Helmholtz, H., Über die Erhaltung der Kraft, Berlin, 1847, 32.Google Scholar

⁴ Favre, P. A. and Silbermann, J. T., ‘Recherches sur les quantités de chaleur dégagées dans les actions chimiques et moléculaires,’ Ann. chim. phys., 1853, 37, 406–508.Google Scholar

⁵ Levere, , op. cit. (1), 202Google Scholar. Partington, J. R., A history of chemistry, 4 vols., London 1961–1970, IV, 608–612.Google Scholar

⁶ Kragh, H., ‘Julius Thomsen and 19th century speculations on the complexity of atoms,’ Annals of science, 1982, 39, 37–60CrossRefGoogle Scholar. For Colding and his debt to Ørsted, see Dahl, P. F., ‘Ludwig A. Colding and the conservation ot energy,’ Centaurus, 1963, 8, 174–188CrossRefGoogle Scholar. Extracts of Colding's work of 1851 is translated in Lindsay, B. Bruce (ed.), Energy: historical development of the concept, Stroudsburg (Pennsylvania), 1975, 361–364.Google Scholar

⁷ Thomsen, J., ‘Bidrag til et thermochemisk system,’ Kgl. Da. Vid. Selsk. Skr., Mat.-Nat.Afd. (5), 1852, 3, 115–165Google Scholar; ‘Die Grundzüge eines thermochemisches Systems,’ [Poggmdorf's] Annalen, 1853, 88, 349–362Google Scholar; 90, 261–288; 91, 83–104; 92, 34–57.

⁸ Thomsen, J., ‘Om de chemiske processers almindelige character og en på denne bygget affinitetslære,’ Kgl. Da. Vid. Selsk. Oversigter, 1861, 100–134, on 104.Google Scholar

⁹ ‘Grundzüge,’ op. cit. (7), 1854, 92, 34.Google Scholar

¹⁰ Ibid., 36.

¹¹ Ibid.

¹² In the Danish version of 1852 a purely chemical action was stated to be one which is ‘solely caused by the innate forces of the substances’ (p. 157). Thirty years later the criterion read that the process ‘proceeds without the expenditure of external energy and is accomplished only through striving of the atoms towards more stable equilibrium.’ Thomsen, J., Thermochemische Untersuchungen, 4 vols., Leipzig, 1882–1886, I, 16.Google Scholar

¹³ See Kragh, , op. cit. (6).Google Scholar

¹⁴ ‘Grundzüge,’ op. cit. (7), 1853, 90.Google Scholar

¹⁵ Thomsen, J., ‘Thermochemische Untersuchungen. I, Über die Bertholletsche Affinitätstheorie,’ [Poggendorf's] Annalen, 1869, 138, 65–102Google Scholar. Guldberg, C. M. and Waage, P., Études sur les affinités chimique, Christiania (Oslo), 1867Google Scholar. Lund, E. W., ‘Guldberg and Waage and the law of mass action,’ J. chem. ed., 1965, 42, 548–550.CrossRefGoogle Scholar

¹⁶ Études, op. cit. (15), 15.Google Scholar

¹⁷ Berthelot, M., ‘Recherches de thermochimie,’ Ann. chim. phys., 1865, 6, 290–464Google Scholar. Crosland, M. P., ‘Berthelot, Pierre Eugène Marcellin,’ in Gillispie, C. C. (ed.), Dictionary of scientific biography, New York, 1970–1980, II, 63–72.Google Scholar

¹⁸ Berthelot, M., ‘Nouvelles recherches de thermochimie,’ Ann. chim. phys., 1869, 18, 5–201Google Scholar; ‘Recherches calorimétrique sur l'etat des corps dans les dissolutions,’ Ann. chim. phys., 1873, 29, 433–514Google Scholar; ‘Sur les principes géneraux de la thermochimie,’ Ann. chim. phys., 1875, 4, 5–131, 141–213.Google Scholar

¹⁹ Berthelot, M., Essai de mécanique chimique fondée sur la thermochimie, 2 vols., Paris, 1879Google Scholar; Thermochimie: données et lois numerique, 2 vols., Paris, 1897.Google Scholar

²⁰ Berthelot, , op. cit. (17).Google Scholar

²¹ Berthelot, M., Lecons sur les méthodes générales de synthèse, Paris, 1864, on 399.Google Scholar

²² Berthelot, , op. cit. (18), 1875, 52.Google Scholar

²³ Ibid., 212.

²⁴ Dumas, M., ‘Remarques sur l'affinité,’ Compte rendu, 1868, 67, 597–614, on 607.Google Scholar

²⁵ Mécanique chimique, op. cit. (19), 1, X.Google Scholar

²⁶ Thomsen, J., ‘Die völlige Ungüldigkeit der von Berthelot … berechneten Zahlenwerte,’ Chem. Ber., 1872, 5, 181–185, on 185.CrossRefGoogle Scholar

²⁷ Thomsen, J., ‘Eine Prioritätsfrage bezüglich einiger Grundsätze der Thermochemie,’ Chem. Ber., 1873, 6, 423–428.CrossRefGoogle Scholar

²⁸ Berthelot, M., ‘Sur la réclamation de priorité élevée par M. J. Thomsen relativement aux principes de la thermochimie,’ Bul. soc. chim. Paris, 1873, 19, 485–489.Google Scholar

²⁹ According to Wurtz, A. (ed.), Dictionnaire de chimie, Paris, 1869–1870, II, 824.Google Scholar

³⁰ See, e.g., the views of Paul Sabatier, Victor Grignard and Pierre Duhem as quoted in Nye, M. J., ‘Berthelot's anti-atomism: a ‘matter of taste’?’ Annals of science, 1981, 38, 585–590CrossRefGoogle Scholar. Also in Metz, A., ‘La notation atomique et la théorie atomique en France a la fin du XIX^e siècle,’ Revue d'historie des sciences, 1963, 16, 233–239, on 236.Google Scholar

³¹ In obituary articles the personality of the deceased is often idealized. In Edward Thorpe's memorial lecture one reads however about Thomsen's ‘cold and unsympathetic nature [which] evoked no warmer feelings.’ Thorpe, E., ‘Thomsen memorial lecture,’ J. Chem. Soc. London, 1910, 97, 161–172, on 165CrossRefGoogle Scholar. Similarly Niels Bjerrum, a student of Thomsen: ‘Thomsen was of a vehement and fiery nature. He could rise against his opponents quite without self-command …,’ Bjerrum, N., ‘Julius Thomsen’ Chem. Ber., 1909, 42, 4971–4988, on 4977.CrossRefGoogle Scholar

³² Experimenticism is the extreme empiricist doctrine that experiments and accurate measurements have absolute priority in the analysis of scientific work. The term was introduced and exemplified by Holton, Gerald in ‘Einstein and the ‘crucial’ experiment,’ Am. j. phys., 1969, 37, 968–982.CrossRefGoogle Scholar

³³ Thomsen, J., ‘Ueber Genauigkeit thermochemischer Zahlenresultate,’ Chem. Ber., 1878, 11, 2183–2188.CrossRefGoogle Scholar

³⁴ Berthelot, M., ‘Sur la chaleur de dissolution du sulfate de soude,’ Ann. chim. phys., 1878, 14, 445–452.Google Scholar

³⁵ Favre, M. P. A., ‘Réclamation relative a une note de M. J. Thomsen,’ Bul. soc. chim. Paris, 1874, 21, 487.Google Scholar

³⁶ Duhem, P., ‘Thermochimie,’ Revue des questions scientifique, 1897, 12, 361–392, on 363–364 and 368Google Scholar. Reviewing Berthelot's Thermochimie Duhem took the opportunity to launch a strongly worded attack on Berthelot and his position in French chemistry. According to Duhem, Berthelot's principle was a ‘ridiculous tautology’ (370). In 1884 Duhem's doctoral dissertation which contained an attack on the principle of maximum work was rejected as a result of its questioning thermochemical orthodoxy; it was published as a book two years later as Le potentiel thermodynamique (Paris, 1886)Google Scholar. See Miller, D. G., ‘Pierre Duhem’, Physics today, 12 1966, 47–53.CrossRefGoogle Scholar

³⁷ Muir, M. M. Pattison, Principles of chemistry, London, 1884Google Scholar; Ostwald, W., Lehrbuch der allgemeinen Chemie, 2 vols., Leipzig, 1892–1893, 11/1, 64Google Scholar; von Meyer, E., Geschichte der Chemie, Leipzig, 1889, 383.Google Scholar

³⁸ Proc. Roy. Soc. London, 1883, 36, 74.Google Scholar

³⁹ Harry Jones, an American chemist of the Ostwald school, described Thomsen as ‘the type of mind that delights in accurate experimental work’; while Berthelot was ‘not the type of mind to be limited to fine experimental work. … Berthelot made thermochemical measurements for a definite purpose, and that was to see to what far-reaching conclusions they would lead.’ Jones, H. C., A new era in chemistry New York, 1913, 36.Google Scholar

⁴⁰ Paul, H. W., The sorcerer's apprentice. The French scientist's image of German science 1840–1919 Gainesville (Florida), 1972.Google Scholar

⁴¹ Thomsen, J., ‘Thermochemische Untersuchungen über die Theorie der Kohlenstoffverbindungen,’ Chem. Ber., 1880, 13, 1321–1334CrossRefGoogle Scholar; Thermochemische Untersuchungen, op. cit. (12), IV.Google Scholar

⁴² Kekulé, A., Lehrbuch der organischen Chemie, 2 vols., Erlangen, 1866, II, 496.Google Scholar

⁴³ Ladenburg, A., ‘Ueber Benzolformeln,’ Chem. Ber., 1869, 2, 272–274CrossRefGoogle Scholar. A diagonal structure, similar to that proposed by Ladenburg, was forwarded by Claus, A. in his Theoretische Betrachtungen und deren Anwendungen zur Systematik der organischen Chemie, Freiburg, 1867, 207–208Google Scholar. For other candidates and background to the problem of the structure of benzene, see Russell, C. A., The history of valency, Leicester, 1971, ch. 9.Google Scholar

⁴⁴ Thomsen, J., ‘Die Constitution des Benzols,’ Chem. Ber., 1880, 13, 1808–1811CrossRefGoogle Scholar; ‘Zur Benzolformel,’ Chem. Ber., 1880, 13, 2166–2168.Google Scholar

⁴⁵ Ibid., 1810.

⁴⁶ Ibid., 1811.

⁴⁷ Thomsen, J., ‘Om benzolmolekylets konstitution,’ Kgl. Da. Vid. Selsk. Oversigter, 1886, 179–186.Google Scholar

⁴⁸ Armstrong, H. E., ‘The determination of the constitution of carbon compounds from thermochemical data,’ Phil, mag., 1887, 23, 73–109CrossRefGoogle Scholar. Armstrong proposed a ‘centric’ formula which agreed with the nine single bonds suggested by Thomsen.

⁴⁹ Quoted from Bjerrum, , op. cit. (31), 4983Google Scholar. This letter, as well as most other letters and unpublished materials which Thomsen left at his death, seems to have been lost. The archive of the Royal Library in Copenhagen includes eight boxes with source materials on Thomsen but nothing of particular interest to the history of chemistry. The Wilhelm-Ostwald-Archiv in Berlin (GDR) owns a small number of letters from Thomsen to Ostwald.

⁵⁰ Jahn, H., Die Grundsätze der Thermochemie, Vienna, 1882, 147.Google Scholar

⁵¹ Cooke, J. P., ‘Notice of Julius Thomsen's thermochemical investigation of the molecular structure of the hydrocarbon compounds,’ Am. j. sci., 1881, 21, 87–98, on 98.CrossRefGoogle Scholar

⁵² Muir, Pattison, op. cit. (37), 174f and 303fGoogle Scholar; Mendeléev, D. I., ‘Ueber die Verbrennungswärme der Kohlenwasserstoffe,’ Chem. Ber., 1882, 15, 1555–1559.Google Scholar

⁵³ Armstrong, , op. cit. (48)Google Scholar; Pickering, S. U., ‘Note on the foregoing communication,’ Phil, mag., 1887, 23, 109–112CrossRefGoogle Scholar; ‘On thermochemical constants,’ Phil, mag., 1888, 26, 53–62.Google Scholar

⁵⁴ Stohmann, F., Rodatz, P. and Herzberg, H., ‘Ueber den Wärmewerthe des Benzols,’ J. prakt. Chemie, 1886, 33, 241–260CrossRefGoogle Scholar. Stohmann adopted the calorimetric technique developed by Berthelot and his pupils; in 1887 he worked in Berthelot's laboratory where he was introduced to the bomb calorimeter.

⁵⁵ Thomsen, J., ‘Ueber die Verbrennungswärme des Benzols,’ J. prakt. Chemie, 1886, 33, 564–567CrossRefGoogle Scholar; Stohmann, F., ‘Entgegnung zu vorstehender Abhandlung des Herrn Thomsen,’Google Scholaribid., 568–576; ‘Zur weiteren Beleuchtung der Untersuchungen des Herrn Julius Thomsen,’ J. prakt. Chemie, 1887, 35, 136–141Google Scholar. Exchange of views between Thomsen, and Stohmann, in J. prakt. Chemie, 1886, 34, 55–56.CrossRefGoogle Scholar

⁵⁶ Brühl, J. W., ‘Kritik der Grundlagen und Resultate der sogenannten Theorie der Bildungswärme organischer Körper,’ J. prakt. Chemie, 1887, 35, 181–204, 209–236.CrossRefGoogle Scholar

⁵⁷ Ostwald, W., Zs. phys. Chemie, 1887, 1, 201Google Scholar. Most of Ostwald's early contributions to chemistry were in the tradition of Thomsen whose approach to the problem of affinity inspired him much. For Ostwald's indebtedness to Thomsen, see Ostwald, W., Lebenslinien. Eine Selbstbiographie, 3 vols., Berlin, 1926.Google Scholar

⁵⁸ Thomsen sought, apparently in vain, to convince Ostwald that his thermochemical data on organic substances were superior to those of Berthelot and Stohmann and ought to be republished in Zeitschrift für physikalische Chemie. Referring to the omission of his organic data in the third edition of Landolt's physikalisch-chemischen Tabellen Thomsen protested against ‘such an outrageous treatment from the side of one of the main works in German literature.’ Letter from Thomsen, to Ostwald, , 01 27, 1905Google Scholar. I am grateful to the Wilhelm-Ostwald-Archiv for sending me copies of the Thomsen-Ostwald correspondence.

⁵⁹ Clarke, F. W., ‘A new law in thermochemistry,’ Proc. Washington Acad. sci., 1903, 5, 1–37Google Scholar; Thomsen, J., ‘F. W. Clarkes neues thermochemisches Gesetz,’ Zs. phys. Chemie, 1903, 43, 487–493.Google Scholar

⁶⁰ Thomsen, J., ‘Thermochemische Untersuchungen, XVII,’ J. prakt. Chemie, 1874, 11, 261–283Google Scholar; Nernst, W., ‘Über die Bildungswärme der Quecksilberverbindungen,’ Zs. phys. Chemie, 1888, 2, 23–28.Google Scholar

⁶¹ Thomsen, , Zs. phys. Chemie, 1888, 2, 21–22Google Scholar; letter from Thomsen, to Ostwald, , 12 12, 1887 (Wilhelm-Ostwald-Archiv).Google Scholar

⁶² Körber, H-G. (ed), Aus dem wissenschaftlichen Briefwechsel Wilhelm Ostwald, 2 vols., Berlin(GDR), 1961, II, 41.Google Scholar

⁶³ Meyer, L., ‘Die bisherigen Entwickelung der Affinitätslehre,’ Zs. phys. Chemie, 1, 1887, 134–144, on 140 and 143.Google Scholar

⁶⁴ Naumann, A., Grundriss der Thermochemie, Braunschweig, 1869, 2Google Scholar. An extended and updated version of Naumann's work, much in use in Germany, appeared in 1882 as Lehr- und Handbuch der Thermochemie. Friedrich Mohr wrote on chemical affinity in the same vein, see his Mechanische Theorie der chemischen Affinität, Braunschweig, 1868.Google Scholar

⁶⁵ Jahn, , op. cit. (50), 205.Google Scholar

⁶⁶ Berthelot, M., ‘Atomes et équivalents,’ Comptes rendus, 1877, 84, 1269–1276Google Scholar. Nye, M. J., Molecular reality, London, 1972, 7Google Scholar. See also Levere, , op. cit. (1), 207–211Google Scholar and Nye, , op. cit. (30).Google Scholar

⁶⁷ Deville, H. Sainte-Claire, Lecons sur la dissociation, Paris, 1866.Google Scholar

⁶⁸ van der Kolk, H. W. Schröder, ‘Ueber die mechanische Energie der chemischen Wirkungen,’ [Poggendorf's] Annalen, 1864, 122, 439–454, on 452.Google Scholar

⁶⁹ Rayleigh, Lord, ‘On the dissipation of energy,’ Nature, 1875, 11, 454–455 (Royal Institution lecture).Google Scholar

⁷⁰ Potilitzin, A., Chem. Ber., 1879, 12, 2369–2374.Google Scholar

⁷¹ Muir, Pattison, op. cit. (37), 446Google Scholar. For other contemporary criticism, see Rathke, B., ‘Ueber die Principien der Thermochemie,’ Abhandl. d. Naturf. Ges. zu Halle, 1882, 15, 197–227Google Scholar; Meyer, L., Die modernen Theorien der Chemie, 4th edn., Breslau, 1883Google Scholar; Duhem, P., Le potentiel thermodynamique, Paris, 1886.Google Scholar

⁷² Thomsen, , op. cit. (27), 428.Google Scholar

⁷³ In particular through the works of Helmholtz, and Helmholtz, van't Hoff. H., ‘Zur Thermodynamik chemischer Vorgänge,’ Sitzungsber. Akad. Wiss. Berlin, 1882, 1, 21–39, 825–836Google Scholar. van't Hoff, J. H., Études de dynamique chimique, Amsterdam, 1884.Google Scholar

⁷⁴ Thermochemische Untersuchungen, op. cit. (12), II, 1883, 428.Google Scholar

⁷⁵ In 1894 Berthelot admitted that the principle of maximum work has no general validity; he argued that it was a primitive version of the law of entropy. Berthelot, M., ‘Le principe du travail maximum et l'entropie,’ Comptes rendus, 1894, 118, 1378–1392.Google Scholar

⁷⁶ The controversy between thermochemistry and thermodynamically based physical chemistry will be the subject of a forthcoming paper of R. G. A. Dolby. I am grateful to Dr. Dolby for his critical remarks to earlier versions of the present paper.

⁷⁷ Clarke, , op. cit. (59), 2.Google Scholar

⁷⁸ Nye, , op. cit. (30).Google Scholar