\begin{table}%t5
\caption{\label{tab5}Electron density indicators in NGC~6210.}
\small%\centerline
 {
\begin{tabular}{lcccc}
\hline
\hline
Ion &Ioniz. & Lines& Observed &$N_{{\rm e}}$ \\
&Pot.(eV) & used  & ratio & (cm$^{-3}$)\\
\hline
\ion{[S}{ii]} & 10.4 & 6731/6716 & 1.66  & 3600\\
\ion{[O}{ii]} & 13.6 & 3626/3729 & 1.99 & 3800\\
\ion{[S}{iii]} & 23.3 & 33.5/18.7 & 0.487 & 2700 \\
\ion{[Cl}{iii]} & 23.8 & 5538/5518 & 1.17 & 3400\\
\ion{C}{iii]} & 24.4 & 1906/1909 & 1.40 & 2000:\\ 
\ion{[A}{iv]} & 40.7 & 4740/4711 & 1.30 & 6800\\
\hline
\end{tabular}}
\medskip
: Indicates uncertain value.
\end{table}