Heat of titration reaction:

Typical shapes of enthalpogram are shown in Figure a and b. On both enthalpograms, the base line represents temperature-time blanks recorded prior to the start of the actual titration, B corresponds to the beginning of addition of titrant, and C is the end point and CD the excess reagent line. Thus BC is the titration branch proper of the enthalpograms. In cases where ?H <0, it has an ascending slope shown in as Figure a whereas for  ?H >0, it has a descending slope as showing Figure both cases the excess reagent branches of the enthalpograms (CD) are drawn with ascending slope because the dilution of most titrants is an exothermic process. In sequence to minimize variations within heat capacity during titration, that is customary to use titrants 50-100 times more concentrated than the unknown titrated. Therefore the volume of titrate solution is maintained virtually constant, but the titrants are diluted appreciably. The heat of dilution can be corrected for conveniently by the linear back extrapolation CB´. Under these conditions, the extrapolated ordinate height BB´ represents a measure of the change of temperature. ?T, due to the titration reaction, as well as of integral heat, Q, evolved or absorbed viz.

BB´ ∝ ?T

                                                                  ?T =Q/K = - N.?H/K

where K denotes the effective heat capacity and N is the number of moles reacted in the titration. By Eq., it is evident in which the quantity BB' can be used for obtaining the following informations;

• Heat of titration reaction, ?H, whenever a known amount of titrate is used.
• Concentration of an unknown 'titration', while ?H is known (?T is proportional to concentration and independent of tirate sample size).
• Amount of an unknown in a known volume of titrate.