Recently, the icosahedral Al-13-cluster has been shown to possess some unusual characteristics due to its special stability (Bergeron, D. E.; et al. Science 2004, 304, 84-87; 2005, 307, 231-235). Here we present reactions of isolated Al-13-clusters with hydrogen chloride, following their oxidation through the application of Fourier transform ion cyclotron resonance mass spectrometry. Due to the ultra-low-pressure conditions, the reaction time can be expanded to make one intermediate after another come into view. The following intermediates are generated sequentially, releasing AlCl and H-2: Al13HCl-, Al12H-, Al12H2Cl-, Al11H2-, Al12Cl-, and Al-11(-). The resulting reaction scheme proves to be a molecular model for the dissolution of a metal in an acid, revealing the initial steps of a heretofore unknown fundamental heterogeneous reaction.