\begin{table}%T7
  \caption{\label{table:radio:den:siii}Electron densities in \cmtrois\ derived using the \SIII~33.4/18.7~\mum\ line ratio.}
    %\centering
\par
       \begin{tabular}[h]{lcr@{\hspace{3pt}}r}
      \hline \hline \\[-5pt]
    \multicolumn{1}{c}{Source} &
    \multicolumn{1}{c}{$\left ( \SIII\ {33.4 \over 18.7} \right )_{\rm o}$} & 
    \multicolumn{2}{c}{\nel (\SIII)} 
\\[5pt] \hline \\[-5pt]
IRAS 01045&             $<$0.38& $>$$2582$\\[0pt]
IRAS 10589&    0.71 $\pm$   0.21&    1038& $(+     748,$  $-365$) \\[0pt]
IRAS 11143&    1.29 $\pm$   0.39&     352& $(+     359,$  $-181$) \\[0pt]
IRAS 12063&    0.67 $\pm$   0.20&    1140& $(+     795,$  $-389$) \\[0pt]
IRAS 12073&    0.64 $\pm$   0.20&    1219& $(+     897,$  $-423$) \\[0pt]
IRAS 12331&    0.99 $\pm$   0.30&     589& $(+     486,$  $-243$) \\[0pt]
IRAS 15384&    0.71 $\pm$   0.21&    1036& $(+     739,$  $-363$) \\[0pt]
IRAS 15502&    1.00 $\pm$   0.31&     583& $(+     499,$  $-245$) \\[0pt]
IRAS 16128&    1.55 $\pm$   0.50&     217& $(+     308,$  $-152$) \\[0pt]
IRAS 17160&    1.16 $\pm$   0.36&     438& $(+     417,$  $-207$) \\[0pt]
IRAS 17221&    1.09 $\pm$   0.36&     496& $(+     495,$  $-234$) \\[0pt]
IRAS 17279&    1.99 $\pm$   0.67& $<$333\\[0pt]
IRAS 18032&    1.19 $\pm$   0.41&     415& $(+     465,$  $-215$) \\[0pt]
IRAS 18479&    0.36 $\pm$   0.18&    2836& $(+    5764,$ $-1259$) \\[0pt]
IRAS 19442&    1.86 $\pm$   0.73& $<$467\\[0pt]
IRAS 19598&    0.44 $\pm$   0.16&    2103& $(+    2137,$  $-786$) \\[0pt]
DR21      &    0.95 $\pm$   0.39&     639& $(+     829,$  $-317$) \\[0pt]
IRAS 23133&    0.44 $\pm$   0.16&    2140& $(+    2152,$  $-796$)
    \\[3pt] \hline
    \end{tabular}
  \end{table}