The gas-solid chemical reactions of pure crystalline alcohol, such as triphenyl carbinol (1) and 1,1-dipbenylethanol-1 (3), with HCl gas and their mechanism are studied using atomic force microscopy (AFM) and known crystal packing data. AFM reveals that the main crystal face (001) of 1 exhibits volcanoes, whereas the long side face (100) gives volcanoes and craters in turn. Both (010) and (100) of 3 exhibit islands. All of those are guided by the crystal structure. Molecular interpretations of the AFM features are given.