To determine the change in enthalpy in a neutralization reaction (ΔH), a known amount of basic solution may be placed in a calorimeter, and the temperature of this solution alone recorded.  Then, a known amount of acidic solution may be added and the change in temperature measured using a thermometer.  The difference in temperature (ΔT, in units K or °C) may be calculated by subtracting the initial temperature from the final temperature.  The enthalpy of neutralization ΔH may then be calculated according to the following equation:
Regardless of the specific chemical process, with a known calorimeter constant and a known change in temperature the heat added to the system may be calculated by multiplying the calorimeter constant by that change in temperature.