Question

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

Answer 1

Hint : We know that by the use of the definition of relative density and Archimedes principle to deduce the expression. Balance the forces on the body which is immersed in water to find the buoyant force. Relative density of a substance is equal to the ratio of density of the substance and the density of water at $4{}^\circ C$

Complete Step By Step Answer:
Archimedes' principle states that the upward buoyant force that is exerted on a body immersed in a fluid whether fully or partially submerged is equal to the weight of the fluid that the body displaces and acts in the upward direction at the center of mass of the displaced fluid. Archimedes' principle is a law of physics fundamental to fluid mechanics.
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 $<1\cdot g\cdot m{{L}^{-1}}$ Of course (i), methylene chloride, $C{{H}_{2}}C{{l}_{2}}$, which is a commonly used organic solvent, has a density of $1.33\cdot g\cdot m{{L}^{-1}}$. 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 partitioned across the phases and cause density to alter, sometimes you do not know which layer is which.
Relative density is a comparison of the density of the substance with that of water. Relative density is a pure density with no unit because it is a ratio of densities of different substances. Density of water being one gm. per cc the numerical value of density and relative density is the same. The numerical value of relative density is the same in all systems.

Note :
Remember that the values of relative densities of different substances are only calculated with respect to the density of water at four degree Celsius only. This is because the density of water increases up to four degree Celsius and decreases above this temperature.