  A mesoscopic theory for the primitive model of ionic systems is developed for
arbitrary size, $\lambda=\sigma_+/\sigma_-$, and charge, $Z=e_+/|e_-|$,
asymmetry. Our theory is an extension of the theory we developed earlier for
the restricted primitive model. The case of extreme asymmetries
$\lambda\to\infty$ and $Z \to\infty$ is studied in some detail in a mean-field
approximation. The phase diagram and correlation functions are obtained in the
asymptotic regime $\lambda\to\infty$ and $Z \to\infty$, and for infinite
dilution of the larger ions (volume fraction $n_p\sim 1/Z$ or less). We find a
coexistence between a very dilute 'gas' phase and a crystalline phase in which
the macroions form a bcc structure with the lattice constant $\approx
3.6\sigma_+$. Such coexistence was observed experimentally in deionized aqueous
solutions of highly charged colloidal particles.
