The H-1 NMR spectra of binary mixtures of 4-methylpyridinium chloride and 4-methylpyridinium iodide were measured as a function of temperature and composition over the entire composition range. Correlations were made between these spectra and thermodynamic and transport properties of the melts. The effect of hydrogen bonding on the melt’s properties was assessed and a four "component" model was proposed to account for these properties. A pronounced "mixed ion" effect was observed in the NMR spectra, but was barely discernible in the transport properties and completely absent in the thermodynamic properties.