We report measurements of the equilibrium pressure of single guest clathrate hydrates of C2H6, C2H2, and Kr at low temperatures (mainly in the range (150 to 230) K). The results are compared with other data reported in the literature and used to determine new empirical correlation laws allowing to calculate the equilibrium pressure of clathrates of these species at any temperature below the freezing point of water. Enthalpies of clathrate formation/dissociation for these molecules are estimated using the Clausius-Clapeyron equation and show good agreement with previous reported calorimetric measurements. These results are of particular interest for studies of extraterrestrial ice-rich environments such as comets and icy moons in the solar system.