Thermodynamic data from DTA

By rules of simple accounting, changes in the enthalpy of the sample at any point in time will either be manifested by a temperature change in the sample or heat flow in or out of it  

If the test tubes are identical and we carefully match the total7 heat capacities of the sample and reference fluids, then it can be assumed that heat capacities as well as the thermal conductivities on both sides are equal. By subtracting the time rate of change in enthalpy of the reference from that of the sample, all enthalpy changes in the sample due merely to temperature change are eliminated. What is left must be enthalpy changes due strictly to transformations occurring within the sample  

7The total heat capacity refers to the heat capacity of the entire mass, that is the molar heat capacity multiplied by the mass, divided by the molecular weight. This is also referred to as the thermal mass . 

If the thermal conductivity of the test tube is high, then the second term dominates  

the area under a DTA trace is proportional to the change in enthalpy of the sample (under conditions of constant pressure), as long as the following assumptions axe valid  

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