\begin{table}%t5
      \caption{Ratios of column densities, based on Table.~\ref{fa}. Relative
      errors of the ratios are in the range of 5--15\%, for SO, CS, HCO$^+$ and
      HNC. For ratios that include ammonia, errors are in the range 20--25\%.} 
         \label{abratios}          
%\centering
\par
      \[ 
 \begin{array}{lcccccrcccrcrcc} 
   \hline\hline 
   \noalign{\smallskip} 
   & & {\rm \displaystyle\frac{[SO]}{[CS]}} & & 
  {\rm \displaystyle\frac{[HCO^+]}{[CS]}} & &  {\rm \displaystyle\frac{[NH_3]}{[CS]}}  & &
  {\rm \displaystyle\frac{[SO]}{[HNC]}} & & 
  {\rm \displaystyle\frac{[HCO^+]}{[HNC]}} & &  {\rm \displaystyle\frac{[NH_3]}{[HNC]}} \\ 
\par
   \noalign{\smallskip} 
   \hline 
   \noalign{\smallskip} 
    \rm{H1a} && 2.0 && 3.2 &&  186 && 0.6  && 0.9  && 53 \\ 
    \rm{H2a} && 0.5 && 2.6 &&  -   && 0.1  && 0.8  && -  \\ 
    \rm{H2b} && 0.4 && 1.1 &&   39 && 0.2  && 0.6  && 20 \\ 
    \rm{N1a}  && 0.2 && 2.1 &&   -  && 0.2  && 1.6  && -  \\ 
    \rm{T1a} && 0.4 && 1.4 &&  90  && 0.1  && 0.3  && 20 \\ 
  \noalign{\smallskip} 
   \hline 
 \end{array} 
     \] 
\end{table}