A sample of 12 Abell clusters of galaxies has been studied in the opti
cal and X-ray bands. The optical data are derived from automatic photo
metry based on microdensitometric scans of Palomar Schmidt F-band plat
es. ROSAT PSPC data were obtained from the public archive. Galaxy dens
ity and X-ray luminosity profiles have been constructed and deprojecte
d by parametric and nonparametric techniques to obtain volume density
profiles. We find a relation between the gas density rho(gas) and the
galaxy density rho(gal) consistent with the prediction of the hydrosta
tic isothermal model. We confirm that more than 70% of the cluster mas
s is dark within 1.5 Mpc h(50)(-1) from the cluster center. Outside 25
0 kpc we find a nearly constant MIL, ratio, which on average is 137 M.
/L., implying that the galaxy mass traces the total matter distributio
n. The dark mass-to-light ratio has a similar behavior. We also find a
baryonic fraction f(b) approximate to 0.2, which, assumed as represen
tative of the cosmic value and compared with nucleosynthesis calculati
ons, constrains the cosmological parameter Omega(0), to be smaller tha
n 0.25.