With the DCATS 33 software module the critical micelle formation concentration (CMC) can be determined automatically with a tensiometer of the DCAT series and a liquid dosing unit LDU 25. The DCATS 33 software module controls the LDU 25 and the DCAT according to individually customisable measuring procedures. The software module can automatically determine the surface tension via the Du Noüy ring or the Wilhelmy plate method, perform the dosing operations with the LDU 25 and mix the solution with the automatic stirrer.