Nonadiabatic scanning calorimetry

Here, we will focus on a specific high-resolution calorimetric technique, i.e. nonadiabatic scanning calorimetry. This technique implies a calorimeter apparatus capable of operating in the ac as well as in the relaxation mode. The combination of these modes makes it possible to distinguish between the continuous and discontinuous transitions. 

More evidence for a critical point comes from adiabatic and nonadiabatic scanning calorimetry measurements [138], [139], a comparison of which yields the latent heat effects associated with a first-order phase transition. Figure 7.19 shows data from both techniques for two chiralities of a CE2 sample. The sharp peaks, which are due to the nonabiatic technique only, represent first-order helical-BPI and BPI-BPIII transitions the BPIII-isotropic peak only shows first-order behavior for X = 0.40. Repeated runs for various chiralities establishes that, for this system, Xc x 0.45. A complete experimental analysis of the rotatory power and calorimetric experiments has been performed by Kutnjak et al. [139], who conclude that the data is consistent with mean field behavior. Since that time, however, new theory has appeared which allows different conclusions. 

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