The Karlsruhe Congress was called so that European chemists could discuss matters of chemical nomenclature, notation, and atomic weights. The organization, invitation, and sponsorship of the conference were handled by Kekulé, Wurtz, and Karl Weltzien. As an example of the problems facing the delegates, Kekulé's Lehrbuch der Organischen Chemie gave nineteen different formulas used by chemists for acetic acid, as shown in the figure on this page.
The Karlsruhe meeting ended with no firm agreement on the vexing problem of atomic and molecular weights. However, on the meeting's last day reprints of Cannizzaro's 1858 paper on atomic weights, in which he utilized earlier work by Avogadro, were distributed. Cannizzaro's efforts exerted a heavy and, in some cases, an almost immediate influence on the delegates. Lothar Meyer later wrote that on reading Cannizzaro's paper, "The scales seemed to fall from my eyes."
An important long-term result of the Karlsruhe Congress was the adoption of the now-familiar atomic weights (actually, atomic masses) of approximately 1 for hydrogen, 12 for carbon, 16 for oxygen, and so forth. There was also a recognition that certain elements, such as hydrogen, nitrogen, and oxygen, were composed of diatomic molecules and not individual atoms. Ihde has argued that the Karlsruhe meeting was the first international meeting of chemists and that it led to the eventual founding of the International Union of Pure and Applied Chemistry.
According to Wurtz's list, the congress was attended by the scientists listed below.
Germany. Berlin: Ad. Baeyer, G. Quinke; Bonn: Landolt; Breslau: Lothar Meyer; Kassel: Guckelberger; Klausthal: Streng; Darmstadt: E. Winkler; Erlangen: v. Gorup-Besanez; Freiburg i. B.: v. Babo, Schneyder; Giessen: Boeckmann, H. Kopp, H. Will; Göttingen: F. Beilstein; Halle a. S.: W. Heintz; Hanover: Heeren; Heidelberg: Becker, O. Braun, R. Bunsen, L. Carius, E. Erlenmeyer, O. Mendius, Schiel; Jena: Lehmann, H. Ludwig; Karlsruhe: A. Klemm, R. Muller, J. Nessler, Petersen, K. Seubert, Weltzien; Leipzig: O. L. Erdmann, Hirzel, Knop, Kuhn; Mannheim: Gundelach, Schroeder; Marburg a. L.: R. Schmidt, Zwenger; Munich: Geiger; Nuremberg: v. Bibra; Offenbach: Grimm; Rappenau: Finck; Schönberg: R. Hoffmann; Speyer: Keller, Mühlhaüser; Stuttgart: v. Fehling, W. Hallwachs; Tübingen: Finckh, A. Naumann, A. Strecker; Wiesbaden: Kasselmann, R. Fresenius, C. Neubauer; Würzburg: Scherer, v. Schwarzenbach
United Kingdom. Dublin: Apjohn; Edinburgh: Al. Crum Brown, Wanklyn, F. Guthrie; Glasgow: Anderson; London: B. J. Duppa, G. C. Foster, Gladstone, Müller, Noad, A. Normandy, Odling; Manchester: Roscoe; Oxford: Daubeny, G. Griffeth, F. Schickendantz; Woolwich: Abel
France. Montpellier: A. Béchamp, A. Gautier, C. G. Reichauer; Mülhousen i. E.: Th. Schneider; Nancy: J. Nicklès; Paris: Boussingault, Dumas, C. Friedel, L. Grandeau, Le Canu, Persoz, Alf. Riche, P. Thénard, Verdét, C.-A. Wurtz; Strasbourg i. E.: Jacquemin, Oppermann, F. Schlagdenhaussen, P. Schützenberger; Tann: Ch. Kestner, Scheurer-Kestner