Complete homogenisation of the titrant/analyte mixture was challenging due to their difference in viscosity and the large surface/volume ratio of the small sample containers. To mix aqueous titrant and a viscous reactant, our impeller needed to achieve high shear rates. We first tested a six-bladed Rushton turbine, which performed satisfactorily but was unable to collect viscous material from the sides and bottom of the sample container. This was to be expected since Rushton turbines are characterised by high shear rate and a radial flow pattern. We fabricated a propeller mixer that would also generate an axial flow within the jars due to its ability to move liquid in the z-axis direction. We observed much shorter pH stabilisation times with the propeller mixer, confirming that complete homogenisation had taken place more quickly than with the Rushton turbine despite the lower shear rate. The propeller mixer was coupled to a high-torque DC gearmotor that was controlled with a pulse-width modulation (PWM) driver allowing speed and direction control.