  We consider a model where, for a finite disintegrating system, yields of
composites can be calculated to arbitrary accuracy. An analytic answer for
yields is also known in the thermodynamic limit. In the range of temperature
and density considered in this work, the model has a phase transition. This
phase transition is first order. The analytic expression for yields of
composites, in the thermodynamic limit, does not conform to the expression
$<n_a>=a^{-\tau}f(a^{\sigma} (T-T_c))$ where, the usual identification would be
that $T_c$ is the critical temperature and $\tau,\sigma$ are critical
exponents. Nonetheless, for finite systems, we try to fit the yields with the
above expression. A minimisation procedure is adopted to get the parameters
$T_c,\tau$ and $\sigma$. While deviations from the formula are not negligible,
one might believe that the deviations are consistent with the corrections
attributable to finite particle number effects and might then conclude that one
has deduced at least approximately the values of critical parameters. This
exercise thus points to difficulties of trying to extract critical parameters
from data on nuclear disintegration. An interesting result is that the value of
$T_c$ deduced from the ``best'' fit is very close to the temperature at which
the first order phase transition occurs in the model. The yields calculated in
this model can also be fitted quite well by a parametrisation derived from a
droplet model.
