# Fraction of solute in two layers

Derive the following equation for the fraction of a solute in layer 1 of the 2 layers formed by two immiscible liquids;

Fraction of solute in layer 1 = (KD*V1)/((KD*V1)+V2)

where KD=Distribution coefficient for the solute between chemical in V1 and chemical in V2
V1=Volume of liquid in layer 1
V2=Volume of liquid in layer 2

I understand that to find the fraction of A in the total A+B you simply divide A by A+B. But how does the distribution coefficient fit into this?

## Answers and Replies

Borek
Mentor
Distribution coefficient is a ratio of concentrations.

yes i have that information, im having trouble understanding how to incorporate it into the expression for the fraction of solute in each of the layers of liquid at equilibrium. Essentially i want to know where this equation comes from. Any ideas/ answers would be greatly appreciated Borek
Mentor
Write equations describing your system. Definitions of fractions won't hurt either.

Using the definition of KD being ratio of concentrations in the 2 layers, try writing KD in terms of solute present in the 2 layers, A & B and the volumes V1 & V2

With the equation that you've made and A/(A+B) you should be able to slove this quite neatly