\begin{table}%t4
\caption{\label{tab4}Electron density indicators in NGC~2792.}
\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 & 1.7: & 4500:\\
\ion{[S}{iii}] & 23.3 & 33.5/18.7 & 0.50 & 2300 \\
\ion{[Cl}{iii}] & 23.8 & 5538/5518 & 0.9: & 1500:\\
\ion{[Ar}{iv}] & 40.7 & 4740/4711 & 0.88 & 1500 \\
\ion{[Ar}{v}] & 59.8 & 13.1/7.90 & 1.35 & 4100 \\
\ion{[Ne}{v}] & 97.1 & 24.3/14.3 & 0.70 & 3000 \\  
\hline
\end{tabular}}
\medskip
(:) Indicates uncertain values.
\end{table}