Recent advances in homeopathic medicines have improved diagnosis and treatment of various diseases. Using UV-Vis spectroscopy, the absorption of light by Arsenicum album was measured to obtain qualitative information about the medicinal solute species. Different potencies from three manufacturers were analyzed using a UV-Visible 2600 spectrometer. Results showed that arsenic trioxide solute species exist as quantum-sized nanoclusters regardless of potency, with dilution reducing specific interactions. The dilution series followed homeopathic principles. The study indicates that qualitative analysis of homeopathic medicines using UV-Visible spectroscopy is feasible.