The molecular structure of sodium ethylmercury thiosalicylate (also known as thimerosal and Merthiolate) and related arylthiolate mercury alkyl compounds, namely PhSHgMe and PhSHgEt, have been determined by single crystal X-ray diffraction. H-1 NMR spectroscopic studies indicate that the appearance of the Hg-119 mercury satellites of the ethyl group of thimerosal is highly dependent on the magnetic field and the viscosity of the solvent as a consequence of relaxation due to chemical shift anisotropy.