The congress opened in the assembly hall of the Baden Parliament the 3th September, with Weltzien serving as the general secretary. In his address, he highlighted the international and discipline-specific nature of the meeting. Kekulé delivered an opening address. Wurtz documented the proceedings for future publication. A dinner for 120 people was held in the museum hall.
The next day, the assembly, led by Weltzien, discussed the committee's proposed theme of the day before regarding the disputed meanings of "atom," "molecule," and "equivalence." However, no conclusions were reached, leading the committee to meet twice on the same day. They decided to present three specific nomenclature proposals to the assembly for further consideration.