Background: Solid suspension in liquids is an important unit operation generally encountered in the process industry. In the present work solid-liquid suspensions are explored in an agitated vessel with different liquids using two radial impellers namely Rushton turbine and straight blade; two axial impellers namely pitched blade turbine and A320. The critical impeller speed (Njs) at which all solid particles get suspended and the relevant power requirements (Pjs) are evaluated. The effect liquid viscosity on these two parameters is investigated. Conclusion: Results show that critical impeller speed and power consumption decreases as liquid viscosity increases. The critical impeller speed was found to be highest for straight blade impeller and lowest for pitched blade turbine. A320 impeller showed strong dependence of viscosity on critical impeller speed. In addition, the power consumption was found to be least for A320 impeller among the impellers investigated in this study.