When carrying out the enthalpy change of a reaction between two aqueous solutions, the immediate surrounding is the solution itself, so a thermometer can be placed in the solution to record the temperature change. 
To correct for heat loss a cooling curve can be used. The temperature is measured every 30s until it stays constant. The reactants are mixed and the temperature is taken every 30s until the temperature has fallen for several minutes. A temperature-time graph is plotted. To find the correct temperature, you can extrapolate back to the time when the reactants were mixed.
To correct for heat loss a cooling curve can be used. The temperature is measured every 30s until it stays constant. The reactants are mixed and the temperature is taken every 30s until the temperature has fallen for several minutes. A temperature-time graph is plotted. To find the correct temperature, you can extrapolate back to the time when the reactants were mixed.