Thermal Lag and Undetermined Premelting

The flow of thermal energy from the sample holder at the programmed temperature, Tp, to the sample at a slightly lower temperature, Ts, is governed by Newton s law of cooling (60). 

The value of R0 is then used graphically to correct the programmed temperature, Tp, to the true sample temperature, Ts. The latter is then plotted against 1 F in the van t Hoff equation. 

Even with correction for thermal lag, the linearity of the plots of Ts against 1/F is not good (60). Melting actually begins at the eutectic temperature which may be far below the range of temperatures being examined. Corrections thus have to be made to the measured areas for melting that has occurred at lower temperatures and that is difficult or impossible to measure. Brown (60) has shown that the correction may l e estimated from 

Another correction in the DSC curve is that of the baseline shift due to 

One of the most serious limitations of the method is the assumption that no solid solutions are formed. For solid solution systems (63, 44) 

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