Question

During solvent extraction, how do you know which is the aqueous layer?

Answer 1

Well, it should be pretty obvious.......

Explanation:

For a start, the ethereal layer, even laden with organic solute, should be less dense than the aqueous layer, and thus should be floating on top. Sometimes you can even tell by rubbing the solvent with your fingers.

There are some organic solvents, for instance `"methylene chloride"`, which are denser than the aqueous solvent. `CH_2Cl_2` has a density of `1.33*g*cm^3`, and thus will normally be the bottom layer in the separating funnel (caution, if you get this solvent in the webbing between your fingers, it WILL sting!).

If all else fails, take a Pasteur pipette full of the top layer, and add it successively to approx. `1-2*mL` volumes of water, and then ether. After you make your determination return the water/ether to the separating funnel - yield is always to be maximized. So if in doubt, verify.