Abstract: The invention concerns a filtering unit comprising a filter diaphragm (11), a backing surface (12) disposed against the diaphragm, and passages through which the liquid to be filtered can be supplied on one side of the diaphragm and the liquid that has drained through the diaphragm can be removed from the opposite side of the diaphragm. As taught by the invention, the backing surface (12) is provided with ridges (13) lying side by side and with grooves (14), moving liquid in the direction parallel to the diaphragm (11), between them and which start in the central part of the surface in different directions and lead to the periphery of the surface, curving in such manner that the spacing of mutually adjacent ridges is substantially constant on the entire area of the backing surface. The backing surface (12) will then to the filter diaphragm (11) lend throughout uniform support.

Abstract: The invention concerns a centrifuge intended for use in mainpulating liquid batches on an analytical scale. The centrifuge consists of a body (2) rotatable about its axis (1) provided with input and output conduits (8,9,11) and presenting the essential feature that therein are contained two parallel, circular arc-shaped volumes (3,4) located at different distances from the axis (1) of the body (2) constituting the center of curvature, and communicating with each other through a narrow gap (7) so that when the body is rotating, the heavier components of the liquid accumulate in the volume (4) further away from the axis, and the lighter components accumulate in the volume (3) closer to the axis, whereafter one of these two volumes can be emptied through a conduit (12), while the surface tension acting in the gap between the volumes keeps the liquid in the other volume in its place. The centrifuge of this invention is particularly appropriate for separating blood plasma from the red and white cells in the blood.