ABSTRACT
If the total heat capacities of the empty sample and reference containers were perfectly matched, then the empty sample container versus empty reference container trace should appear as a flat baseline of zero value during the entire scan. This is rarely the case (due to asymmetries in instrument construction) and is actually not necessary for this calculation. The temperature deviation from this, line for the other traces is a result of the extra thermal mass on the sample side, causing it to lag the reference in temperature during the heating ramp. Defining Cp as the specific heat (J/g·K), the sample specific heat is determined by the ratio:
where M is mass as determined from an analytical balance, and D.T's are measured at the same temperature. For reproducibility, the standard and reference granules should be of the same size and the sample container should be placed in the same position in the DSC cell. Alternatively, a single-scan DSC design has also been recently described (25]. If the heat capacity of the unknown varies measurably with temperature, this variation is determined by taking sequential measurements of D.T over the tested temperature range.
