A completely automated kinetic analyzer particularly suited for performing classical kinetic chemistries on an ultra-micro scale. The analyzer comprises a sample preparation unit and a photometric analytical unit. The preparation unit includes a rotationally indexed tray of sample containers presented in timed sequence to a diluter probe which effects dilution of the samples while transferring them sequentially to respective reaction cups, batches of which are contained in magazines and previously filled, by means of an automatic pipetter, with a first reagent. Conveyors move the magazines in stages through the preparation unit, the sample-reagent mixtures meanwhile undergoing preincubation. A second automatic pipetter thereafter adds a second reagent to each cup, in turn the contents of which are then mixed by an automatic stirrer. The magazines are advanced in stepwise fashion to the analytical unit which includes a photometer having a curvette mounted in a temperature-controlled environment as well as radiometric, computation, and print-out means. A transfer probe picks up the stirred mixture from the reaction cups, in series, and introduces each through a heat exchanger into the curvette where the absorptivity of the mixture is protometrically monitored for a predetermined period and the rate of change in absorbance automatically computed and printed out in standard units representative of the content of the samples of the particular constituent being determined.