  The systematic data set on isotopic effects in spectator fragmentation
collected recently at the GSI laboratory permits the investigation of the N/Z
dependence of the nuclear caloric curve which is of interest in several
respects. In particular, new light is shed on the proposed interpretation of
chemical breakup temperatures as a manifestation of the limiting temperatures
predicted by the Hartree-Fock model. The obtained results are discussed within
the general context of temperature measurements in multifragmentation
reactions.
