Abstract: A process for the purpose of the thermostatic control of a sample fluid to be analyzed, as well as reagents and optionally the solvents necessary for performing analyses in an automatically functioning analyzer, wherein the sample container containing the sample fluid as well as the cells containing the reagents are placed in a rack made from good thermally conducting material. The rack is fixed in the analyzer at the individual processing stations between two side walls. At least one of the side walls is heated, so that the rack is thermostatically controlled and, consequently, so is the sample fluid and the reagents.