Experiments in semi-batch mode are carried out to study the formation kinetics of the mixed hydrate at constant pressure and temperature. After the preparatory steps, the reactor is pressurized to a predefined pressure above the vapor-ice-hydrate (V-I-H) equilibrium curve using the back pressure in the gas cylinder. The crossing of the V-I-H curve marks the start of the capture period which is monitored in intervals ranging from 30 seconds to 2 hours by extracting gas samples via the gas lock. The analysis of the gas samples provides a temporal profile of the mole fraction of CO 2 in the gas phase and allows for the study of induction times and formation kinetics. The gas cylinder remains attached to the reactor and is kept open throughout the experiment to compensate for any gas consumed by the forming hydrate. This continuous supply of gas across the system boundary of the reactor volume ensures a constant pressure and gives the procedure the prefix "semi". Note that the supply of fresh gas at one point of the otherwise closed reactor can be understood as a Dirichlet boundary condition for the mole fraction of CO 2 . As the gas sampling point is far away from that Dirichlet boundary, its effect is negligible for the initial phase of concentration change in that region.