Abstract: To enable the storage and retrieval of a plurality of different aliquot valves of blanking standards or serums for photometric comparison with plural test sample aliquots processed in a colorimeter of an automated chemistry system that does not contain a computer memory for its various operations, a blanking solution is fed into the system as if it was a test sample, plural aliquots of the blanking solution are taken and processed each with different reagents, the transmission of each processed blanking aliquot is converted to an analog measurement of absorbance and then converted into an equivalent digital value that is stored in a simple memory until subsequently needed. Thereafter, by an addressing of specific colorimetric measurements on then present test sample aliquots in the colorimeter, the blanking values are called from memory and converted back to their analog values for photometric comparison with the test sample aliquots.