\begin{table}%t1
\caption{Description of the sample. The neutral and molecular hydrogen column 
densities were taken from Ledoux et~al. (2003). Both [Fe/H] and metallicity values
  were from this work and correspond to the values integrated over the 
  systems. Metallicity was derived in all cases from [S/H], 
  except for $Q~1157+014$ for which [S/H] determination was uncertain,
  so we  used [Zn/H] instead.  \label{tab:obs}}
%\centerline
{  \begin{tabular}{lcccccc}\hline\hline
    Quasar & $z_{\rm em}$ & $z_{\rm abs}$ & log$N$(H~{\sc i})$^{a}$ & log$N$(H$_{2}$) &
    [Fe/H] &   Metallicity      \\\hline
    $0013-004$ & 2.09 & 1.973 & 20.83 & 17.72 & $-1.46\pm0.01$ & $-0.68\pm0.03$\\
    $0405-443$ & 3.00 & 2.595 & 20.90 & 18.16 & $-1.30\pm0.10$ & $-0.93\pm0.02$\\
    $0405-443$ & 3.00 & 2.549 & 21.00 & $<$$13.9$ & $-1.49\pm0.01$ & $-0.96\pm0.04$\\
    $0528-250$ & 2.80 & 2.811 & 21.35 & 18.22 & $-1.44\pm0.01$ & $-1.07\pm0.01$\\
    $1037-270$ & 2.31 & 2.139 & 19.70 & $<$$13.7$ & $-0.51\pm0.03$ & $-0.19\pm0.02$ \\
    $1157+014$ & 1.99 & 1.944 & 21.80 & $<$$14.5$ & $-1.84\pm0.03$ & $-1.41\pm0.02$\\
    \hline
  \end{tabular}}
  \end{table}