VOLUME 33, NO. 2, FEBRUARY, 1956
A LABORATORY MIXER J. D. BULTMAN and 1. M. LEONARD Naval Research Laboratory, Washington, D. C.
DURING some recent work on enzymes the authors found it desirable t o subject protein solutions to a mild, reproducible form of agitation. The available mechanical shakers of the reciprocating and "wrist action" type were too violent in their shaking action to be usable. Accordingly, a device was designed that fulfilled the necessary conditions quite well. (See the figure.) The rotating horizontal bar, suspended on its longitudinal axis by sleeve bearings, was made from a piece of fabric-filled phenolic rod, ll/& inches in diameter through which a series of inch holes had been drilled. These holes were drilled in such a fashion that the axis of any given hole was perpendicular to the axes of the adjacent holes. I n order to secure the test tubes in position on the bar, holes were drilled as shown and tapped to receive short '/,-in. X 20 screws. Self-adhesive felt padding can he put on the bottoms of the screws or the screws can he replaced by a flat spring, as shown. The whole assembly is driven by a 60-cycle, 115-volt,
synchronous motor through a 3: 1 ratio reduction gear so that the bar rotates at a steady 20 revolutions per minute. If in each tube is placed a glass ball of slightly smaller diameter than the tube, very good mixing of the contents of the tube can be achieved. This is especially true if it is desired t o keep an insoluble material in a homogeneous suspension. If special temperatures are required, there is no difficulty encountered in operating the mixer in the laboratory refrigerator or incubator.
