Abstract: A ball valve is provided which has a ball stem machined to have a through hole connecting the inlet and outlet port of the valve body when the stem is in a first rotational position. The valve body has a drain port which is aligned with the axis of the stem. When the stem is rotated 90.degree. the drain is connected to both the inlet and outlet ports. This connection is provided by a slot extending over 180.degree. of the periphery of the ball end of the stem in a plane normal to the axis of the through hole.

Abstract: The small volume recirculator includes a mixing chamber for receiving recirculated slurry from an inlet arranged to carry the slurry on its return path from the analyzer. An impeller is provided in a housing which is connected to the mixing chamber by way of an opening such that the housing receives the slurry from the reservoir through the opening and provides passage by way of an output tube to the analyzer. The connection between the housing and the chamber is sufficiently direct so that a vortex is set up in the mixing chamber. This provides the mixing. The impeller is rotatably mounted by shaft means which extends above the level of the slurry to a power drive train in avoidance of any shaft seals in the slurry path.