A method for measuring the solid fraction of tetra-n-butyl ammonium bromide (TBAB) semi-clathrate hydrates slurries based on electrical conductivity was developed. The method was used to study CO<sub>2</sub> absorption by TBAB hydrate slurries. The solid fraction of the hydrate slurries increased through CO<sub>2</sub> absorption. The CO<sub>2</sub> absorption in the hydrate slurries increased by 71% relative to that in the TBAB solution. This change in ratio was higher for a bubble column reactor than that for a stirred-tank batch reactor. Fluctuations at the interface of the hydrate slurries through flow mixing were found to be especially important for improving gas-hydrate contact.