In the past decade, research on Room Temperature Ionic Liquids (RTILs) for chemical separations has been tremendously accelerated due to their exceptional properties of negligible vapor pressure, high thermal stability, high ionic conductivity and non-flammability. However, application of RTILs in the separation science and technology is significantly hindered without a complete scientific data on physical and transport properties of these liquids. In this study, we extend the studied transport phenomena beyond the widely studied imidazolium-cation based RTILs with the evaluation of phosphonium- and newly synthesized ammonium-based RTILs. We will contribute property measurements of density, surface tension, viscosity, gas solubility and diffusivity in various phosphonium- and ammonium-based RTILs. We will discuss temperature dependence and property changes due to increasing carbon number of the alkyl chains in the cations.