Question

How would you determine the relative density of two solvents that are not miscible?

Answer 1

Which is the solvent that ends up as the bottom layer when you mix the solvents in a separating funnel?

Explanation:

The bottom layer is the solvent with greater density.

Typically, when you do a solvent extraction, the organic layer floats ON TOP of the water (because, typically, organic solvents have densities `<1*g*mL^-1`).

Of course (i), methylene chloride, `CH_2Cl_2`, which is a commonly used organic solvent, has a density of `1.33*g*mL^-1`. Would the pure solvent float or sink in a separating funnel when layered with water?

Of course (ii), when you do solvent extractions, because the solute might be partitiioned across the phases and cause density to alter, sometimes you do not know which layer is which.