Isothermal heat flow calorimetry data measures the sum of all ongoing chemical reactions in a cement paste. A conventional way to analyze this data is to qualitatively compare the heat flow curves of chemically different samples, e.g., containing different retarders or different dosages of the same retarder. Our dataset comprises heat flow data on the influence of equally increasing amounts of etidronic acid, sucrose, and racemic tartaric acid on the hydration of a CEM I at a w/c ratio of 0.5. We begin by graphically comparing the heat flow curves (Figure ). To make retarder comparison as simple as possible, all retarder dosages are given in µmol g -1 . As an example, the molecular weight of etidronic acid is 206 g mol -1 , therefore a dosage of 5 µmol g -1 corresponds to a dosage of 0.103 % by weight of cement. The qualitative analysis reveals that the retardation caused by tartaric acid is significantly smaller than the retardation due to etidronic acid or sucrose at the same concentration. In fact, in the dosage range studied, tartaric acid hardly retards at all. Tartaric acid has been reported to be a strong retarder at a concentration of 20 mmol L -1 , which corresponds to a dosage of 10 µmol g -1 .