\begin{table}%t4
\caption{Electron density indicators in \object{NGC~6826}.}\label{tab4}
%\centering
\small
\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 & 1.37 & 1900\\
$[$\ion{O}{ii}$]$ & 13.6 & 3626/3729 & 1.50 & 2200\\
$[$\ion{S}{iii}$]$ & 23.3 & 33.5/18.7 & 0.70 & 1400 \\
$[$\ion{Cl}{iii}$]$ & 23.8 & 5538/5518 & 0.91 & 1600\\
$[$\ion{C}{iii}$]$ & 24.4 & 1906/1909 & 1.47 & 1600 \\
$[$\ion{O}{iii}$]$ & 35.1 & 51.8/88.4 & 2.87 & 1350 \\
$[$\ion{Ar}{iv}$]$ & 40.7 & 4740/4711 & 0.93 & 2200\\
\hline
\end{tabular}
\end{table}