Abstract: A chemical analyzer in which the measurement of the change in attenuation of RF radiation propagated through a sample is used as the basis for calculating the change in concentration of a given chemical in the sample. Also disclosed are various probe and system designs which facilitate the use of RF attenuation as a basis for measurement of certain chemical characteristics of a sample.

Abstract: Efficient mixing is promoted in a turbulent stirring unit by providing an agitator with flexible finger-like appendages and by varying the rate of rotation of a rotating magnetic field such that the fingers execute an undulatory motion, disrupting laminar flow and tending to collapse the liquid vortex. Motor control for controlling the fluctuation of the rotating magnetic field may provided by simple and economical electronic or electromechanical means. The control unit may be separately configured to control a number of other pieces of equipment, either in common or independently. The controller also may be integrated into stirrers, vortexers or shaker tables or externally provided to control existing units.

Abstract: A ladder with retractable rungs is disclosed herein. The ladder includes an elongated housing having alternating apertures on opposite sides. A stem is carried in the housing. The stem can be manually reciprocated longitudinally and has a series of rungs hingedly attached to it. The rungs engage the apertures and extend outward to provide a step when the stem is moved upward. A supporting rod is pivotally connected inside the housing at its base so as to be swingable from a position to one side of the housing to a center position. The stem must be lifted when the supporting rod is moved to the center position, where the supporting rod then supports the stem with the rungs in the open position. A retaining rod is mounted pivotally inside the housing at the top of the stem. It is also swingable from one side to a center position where it prevents the stem from moving upward.