In this study, the effects of impeller rotation speed, off-bottom clearance, blade angle, types of solid and liquid, etc., on the suspension pattern of sedimentary particles and particle rise height in liquid were investigated with a hemispherical vessel without baffles under low particle concentration. The transition conditions of suspension pattern between regimes I and II, and regimes II and III, were observed visually, and their non-dimensional equations were expressed with an acceptable correlation by varying the above operation factors a great deal. Here, regime I is stagnation of particles on a vessel bottom, II is partial suspension, and III is complete suspension in liquid. The non-dimensional equation of the maximum particle rise height was also successfully obtained. The combination of the non-dimensional equations of transition and maximum particle rise height permitted us to determine the adequate solid/liquid mixing operation conditions without collision of particles with device parts.