The difference between spin only magnetic moment values of $\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_3\right]_{\mathrm{Cl}}$ and $\left[\mathrm{Cr}_2\left(\mathrm{H}_2 \mathrm{O}\right)_3\right]_{\mathrm{l}} \mathrm{Cl}_3$ is $\_\_\_\_$ .
