ABSTRACT
Every chemical transformation is accompanied by changes in enthalpy and under adiabatic conditions by changes in temperature. This well-known phenomenon is the basis of thermometry. The solutions used for the measurements and the instrument must be of the same temperature. Three parallel measurements are carried out in each case with different amounts of chlorine water. Because of the volatility of chlorine water, the amount of the chlorine present in the reaction space is determined during the reaction by the measurement of the equivalent amount of elementary iodine liberated from the reagent. For this purpose, the plastic beaker is taken out of the instrument and put upon a magnetic stirrer motor, then the iodine is titrated with 0.1 N sodium thiosulfate solution. The deflection is plotted as the function of the chlorine in milligrams determined in the 200-cm3 test solution.
