LATENT-HEAT MEASUREMENTS OF THE SMECTIC A-CHOLESTERIC TRANSITION ON BINARY-MIXTURES

New differential scanning calorimetry measurements of the smectic A-ch olesteric latent heat of transition for binary mixtures of cholesteryl nonanoate (C-9) and cholesteryl heptanoate (C-7), cholesteryl nonanoa te and cholesteryl caproate (C6) are reported for cooling cycles. Thes e measurements give evidence of a tricritical point at approximately t he reduced temperature T(SACh)/T(ChI) is-approximately-equal-to 0.92 f or 63.1 mol per cent C-9 in the mixture of C6 and C-9. This tricritica l point occurs at reduced temperatures and concentrations different fr om those already obtained for heating cycles for the same mixture.