The Ostwald coefficients L2,1 of He, Ne, Ar, Kr, N2, O2 , CH4, CF4, and SF6 dissolved in 2,2,4-trimethylpentane (isooctane) have been measured at the temperature 298.15 K and the pressure 101325 Pa with a modified Ben-Naim/Baer-type apparatus. Subsequently, the L2,1 values are converted to Henry fugacities (Henry’s law constants) at the vapour pressure of the solvent, and mole fraction solubilities at a partial gas pressure p2 = 101325 Pa by using the thermodynamically rigorous methods previously given. This improved, medium-precision apparatus (the imprecision is about ± 0.5 per cent) combines easy handling with automated data retrieval and is totally mercury-free.