In Fig. 2 the FT-Raman spectra of the four analysed diclofenac sodium commercial solutions are shown. A qualitative analysis of the pharmaceuticals was performed first. All four investigated solutions, beside the active component, contain water, propylene glycol and benzyl alcohol as the main additives. Small amounts of sodium hydroxide, d-mannitol and sodium pyrosulfite or N-acetylcysteine were also detected. They increase the solubility of diclofenac in water or preserve solutions from oxidation. The measured density of the analysed products was found to be 1.0315, 1.0317, 1.0306 and 1.0321 g/mL for D1, D2, D3 and D4 preparations, respectively.