Abstract: An apparatus for determining the volume fractions of the phases in a suspension includes a body, a channel structure, which is formed in the body, and an inlet area and a blind channel, which is fluidically connected to and capable of being filled via the same. Furthermore, a drive for imparting the body with rotation, so that phase separation of the suspension in the blind channel takes place, is provided. The blind channel includes such a channel cross-section and/or such wetting properties that, when filling same via the inlet area, higher capillary forces act in a first cross-sectional area than in a second cross-sectional area, so that at first the first cross-sectional area fills in the direction from the inlet area toward the blind end of the blind channel and then the second cross-sectional area fills in the direction from the blind end toward the inlet area.