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I How osmotic membranes function

  1. Nov 26, 2016 #1
    I've been doing some experiments with dialysis tubing I purchased online and just have some general questions.

    Firstly how does osmosis work exactly? I read that because there are less free molecules of the solvent on one side that the solvent on the other side flows in but there were lots of other explanations online as well.

    Secondly everything I've found for using dialysis tubing suggests sucrose (table sugar) but after a few hours or so I notice that there is some sugar that has gotten out of the container, I've tried tying knots, rubber bands, super glue, etc to close the ends so it must be leaking out of the pores in the membrane itself. Is there anyway to prevent this? Or will some of the solute always leak out of the membrane over time?

    Finally is there anyway to calculate how fast the solvent flows through the membrane? I was able to find equations for determining the pressure but nothing related to how quickly the solvent will pass through to equalize the pressure
  2. jcsd
  3. Nov 26, 2016 #2


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    Osmotic pressure can be explained with thermodynamical arguments, namely by the maximization of total entropy of the system and surroundings when the solutions on both sides of the membrane are equally concentrated. Unfortunately, thermodynamics can only tell us the direction of some spontaneus process, not its rate - therefore no easy formula for the flow rate through the membrane exists.
  4. Nov 26, 2016 #3
    Ok, thanks ^-^
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