The dissolution method was used predominantly at atmospheric conditions to measure the liquid-solid mass-transfer coefficient in two-phase flow packed-bed reactors. In an attempt to investigate the effect of reactor pressure and gas flow rate on the liquid-solid mass-transfer coefficient in a trickle-bed reactor using the dissolution method, difficulties were encountered in implementing this method at low- to high-pressure operation. Noticeable losses in the dissolved material were observed as a result of flashing/stripping from the liquid phase to the atmosphere and the effluent gas stream. This leads to misinterpretation of the effect of reactor pressure and to improper conclusions, In this note, we intend to alert researchers about such drawbacks, which would be encountered at atmospheric to low pressures and to provide suggestions to overcome such problems.