Abstract: Apparatus for processing materials including a receptacle for containing and processing fluid materials such as animal feed. A frame supports the receptacle on a base surface. A weighing mechanism supports the frame and includes at least one member yieldable proportionally in response to the weight of materials contained in the receptacle. An arm connected to the yieldable member is movable in response to its movement. An enclosed collapsible container or bellows having circumferentially corrugated cylindrically-shaped sidewalls and first and second closed ends has a first end being supported by a fixed support. The second end is aligned with, and movable in response to, movement of the arm. A conduit in fluid flow communication with the interior of the collapsible container is at its other end visually transparent, vertically aligned, open to the atmosphere, and contains a liquid.