The variation in heat capacity and the thermal shifts which accompany a thermometric determination make the thermogram, even in the case of a very rapid and irreversible reaction, hyperbolic instead of formed of straight segments. These departures from linearity, which are inconvenient in the interpretation and exploitation of the thermograms, can be calculated as a function of the degree of titration. The relation obtained introduces a parameter which the authors call the apparent change of capacity at the equivalence point, and which takes into account the two causes of deviation from linearity. This relationship is confirmed experimentally.