A new microanalytical system has been developed that employs a rotor containing 15 cuvets spinning past a beam of light. The signal is displayed on an oscilloscope, and a peak is observed continuously for each cuvet. Standards, samples, and reagents are placed in a central loading disc, and all solutions moved out into the cuvets by centrifugal force. Minimum volume to fill the cuvets is 200 λ. By using the Weichselbaum biuret reagent for proteins, 15 analyses may be completed in as little as 30 sec after the rotor is started. The data are obtained photographically. © 1969.