\begin{table}%t7
%\centering
\par
\caption {\label{cold}H$_2$ densities and molecular column densities of 
H$^{13}$CO$^+$ and HN$^{13}$C derived assuming extended emission and a temperature of 21~K for all molecules, for the precursor component of L1448-mm. }
\begin{tabular}{lcc}
\hline \hline
\noalign{\smallskip}
&  H$_2$ density (cm$^{-3}$)& Column density (cm$^{-2}$) \\ \cline{2-3} 
Molecule &  & \\
\hline
\multicolumn{3}{c}{(0,~0)}\\  
H$^{13}$CO$^+$   & $5.0\times10^6$ & $9.3\times10^{11}$ \\
SiO & $1.6\times10^6$ & $1.2\times10^{11}$ \\
HN$^{13}$C   & $\la$$ 1.3\times10^6$ & $3.7\times10^{11}$\\ 
H$^{13}$CN & $\la$$4.8\times10^6$ & $3.3\times10^{11}$  \\ \hline
\multicolumn{3}{c}{(0,~--10)}\\  
H$^{13}$CO$^+$   & $3.7\times10^7$ & $2.6\times10^{11}$ \\
SiO & $3.5\times10^6$ & $1.4\times10^{11}$ \\
HN$^{13}$C   & $\la$$ 7.1\times10^5$ & $6.8\times10^{11}$\\ 
H$^{13}$CN & $\la$$3.6\times10^6$ & $4.2\times10^{11}$  \\ \hline
\end{tabular}
\end{table}