Halogen bonding is a directional intermolecular interaction that occurs between covalently bonded halogens and Lewis bases. It is caused by the anisotropic distribution of charge around the halogen, being distributed radially around the bond axis, with a net positive charge opposite the R-X bond into which a Lewis base can donate its electron density. The past decade has seen an explosion of interest on the topic of halogen bonding, as this important intermolecular interaction is found in a number of applications including porous frameworks, liquid crystals, drug binding and organic catalysis. Measurements of liquid structure on a series of halo-pentafluorobenzene:pyridine mixtures will allow us to understand effect of the halogen substitution (Cl/Br/I) and compare to a similar hydrogen bonding system - pentafluorobenzene:pyridine.