How would I do this experiment?

Question

Assume that the solution in the left beaker contained NaCl in

addition to the urea and albumin. How could you set up an

experiment so that you removed the urea, but left the NaCl

concentration unchanged? Hint: Assume that you also have

control of the contents in the right beaker.

Answer 1

You could use a semi-permeable membrane that allowed diffusion of the ions but not urea or albumin. Or a a semi-permeable membrane that prevented diffusion of ions but allowed neutral molecules to diffuse

Answer 2

Make the solution in the "right" beaker the same NaCl concentration as the one on the left, leaving out the urea.  Set up a dialysis (see the semi-permiable membrane answer above), which will result in diluting your urea until it is of equal concentrations in both beakers.  If you need an even lower concentration than one dialysis will give you, simply repeat.  Eventually the urea will be effectively removed.

To make this work faster, make the "right" beaker much larger and use a relatively large volume in it (i.e. you have 500 uL of urea/albumin/NaCl, so you dialyze it against 4L of NaCl).  This will effectively eliminate the urea from your sample in one step.

Answer 3

You could use a semi-permeable membrane that allowed diffusion of the ions but not urea or albumin.  Or a a semi-permeable membrane that prevented diffusion of ions but allowed neutral molecules to diffuse.