A constant-volume reactor was used for measuring the solidvaporliquid equilibrium conditions of semiclathrates formed in aqueous solutions of tetra-n-butyl ammonium bromide (TBAB) and tetra-n-butyl ammonium chloride (TBAC). The TBAB and TBAC semiclathrates were formed from pure Ar and pure Xe. The experimental temperatures ranged from (284 to 303) K, the experimental pressures ranged from (266 to 6114) kPa, the concentration of TBAB ranged from w(TBAB) = (0.05 to 0.20), and the concentration of TBAC ranged from wTBAC = (0.05 to 0.20). As expected, at a given temperature, the pressure required to form TBAB and TBAC semiclathrates with argon and with xenon was much lower than the pressure that was required to form pure gas hydrates. From the equilibrium data, the enthalpy of formation was estimated to be between (133 and 188) kJ.mol(-1) for semiclathrates formed from argon and (55 and 127) kJ.mol(-1) for semiclathrates formed from xenon.