The application of multimodal tomographic techniques to the in situ study of the semibatch precipitation of aluminum hydroxide, an industrially important alumina precursor, has been developed. For the first time Electrical Resistance Tomography (ERT) and Positron Emission Particle Tracking (PEPT) have been used concomitantly to study precipitation and hydrodynamics. This combination of techniques allows a step change in our ability to understand industrial precipitation processes. The semibatch precipitation of aluminum hydroxide was investigated in a stirred vessel operated with different configurations. Mixing conditions during semi batch precipitation have been shown to determine particle properties. Variables such as impeller design, power input, and feed location were used to provide different mixing conditions at the feed point where the reagents contact and precipitation takes place. The mixing performance during precipitation can be analyzed using ERT, with information of how the feed plume is dispersed under different mixing conditions. The flow conditions in the feed region can be characterized using PEPT. Together, the techniques can establish how the feed plume is dissipated into the bulk fluid.