Heat of combustion of appropriate quantitative sample can bring a temperature rise of the system by 1.5 ～ 2.0℃.Plot the recorded value of the water temperature against time， the curve ABCD can be obtained， as shown in Fig.2—3 and Fig.2—4.In the graphics，point A is the temperature of record beginning， point B stands for the starting of the burning and the heat of reaction is conducted to the water， point C stands for the stopping of burning.The change in temperature between point B and point C must be corrected.To plot the point O at the portion BC of curve ABCD，draw vertical line ab through the point O， extend the line AB and line DC to line ab，point H and point G can be obtained.Determining the location of point O is very important， adjust carefully the position of point O so that the areas shaded by BGO equals to the areas shaded by CHO.The temperature difference between point H and point G is the calibrated change in temperature.
If the outer jacket contains the water that preadjusted the temperature to about 1℃ lower than room temperature.We may locate the point O at the temperature of jacket water of calorimeter directly.Then draw the vertical line ab through point O，point G and point H can be obtained by extending AB and DC to line ab.The value of the change in temperature is the same by above—mentioned two ways.
