Mercury has been applied as a sealing and pressure transmission fluid in many experimental phase equilibrium studies employing the synthetic visual method as well as a moving piston in analytical isobaric and/or isothermal methods. However, mercury is highly toxic and therefore its use is restricted by authorities such as those of the European Union. A new apparatus employing nontoxic GaInSn liquid metal alloy as a sealing, moving piston, and pressure transmission fluid for phase equilibrium measurements with a nonvisual variable volume method is presented. The vapor pressures of toluene, hexylbenzene, and 2-ethylnaphtalene are provided within the applied temperature range of 400-620 K. New values for the parameters of the DIPPR 101 and Wagner equations, and PC-SAFT equation of state were regressed. The results demonstrate that GaInSn can be used in phase equilibrium cells as a very convenient substitute for mercury, especially at high temperatures.