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Old 03-20-2009, 02:50 AM
Devataa Devataa is offline
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Default HELP! Diffusion rate in and out of a cell membrane proof wet cell battery apparatus.

So based on the concept of a wet cell battery, I set up a apparatus for a school project to see if the diffusion rate of a solution will increase form high concentration side of the membrane to the low concentration side and by how much by the influence of ultrasound. So the way I decided I’d go about this is with a PVC pipe, cut in the middle so I have two PVC sections, in-between the sections I have a high protein semi-permeable membrane that reacts to bleach. So the top section of the PVC will have a diluted concentration of Bleach and the bottom half will have de-ionized solution of water. The top will have a copper cathode (just a thick copper wire sticking out the side near the top opening of the tube) and the bottom (below the membrane) will have an anode (thick aluminum wire coming out the side near the bottom end of the tube). The bottom end of the tube is plunged. So in theory, as I pour in a diluted bleach solution (full of Na+ ions and OH- or ClO- ions, unsure, if anyone has the answer to that, the disassociation of bleach in water would be GREATLY appreciated), the potential difference should decrease relative to the top cell and bottom cell (divided by the membrane) as the bleach solution leaks through the membrane creating one solution the potential difference should decrease to a time where voltage is 0 (ideally). This way I can calculate the diffusion of Bleach in respect to time in relation to the membrane. So what I am asking is: is anything missing? Do I need to Bridge the two halves with a bridge (if so what material/metal?) so there is a flow of electrons across the wire from the bleach solution (basic, ph of around red 7sih)?

I have tried an instance where there was a bridge present and one void of a copper bridge, I am getting inconsistent results and the membrane is not rupturing, maybe that might be due to very low concentrations (.0001 , .001, and .01 % by volume have been attempted). None the less, the graphs of the experiment show a sharp increase of voltage (when I introduce the solution) then a stabilized voltage, why is it stable? The experiment was run for 7 hours strait. Should voltage not decrease with time? What am I doing wrong or am I missing the concept totally? I know that the membrane reacts with the bleach because at 6% concentration it dissolves (looks like it) within minutes. At home I did a quick experiment to see if bleach will even work as a solution for potential difference, compared to a table spoon full of salt and a tall glass of water, bleach Potential difference with respect to tap water was greater (some 500 something mV) verse salt’s (400 something mV)

Basically what I want to see is the slow and steady decrease (or sharp if the membrane ruptures fully diluting the solution dramatically and quickly) in the voltage as a measurement of potential difference form the top cell from the membrane and the bottom. Why is this not working? Please help. Thank you. Collecting data by Logger Pro, a Verneir product. And a back up of Fluke Multimeter.

The reason behind the experiment is to help support claim of my previous study that Ultrasound enhances the efficiency of antibiotics on bacterium viability solely due to diffusion rate enhancements in and out of the membrane. So with the above apparatus, there will be 2-3 control trials and 2-3 respectivly variable trials in which the surface of the tube of the variable trials will be exposed to 90* sinusodal 20Khz Frequenzy wave of .08 mW/cm^2 intensity.

This is an Extension is on a Project that has been selected to go to 2009 ISEF, Intel's International Science and Engineering Fair. I just need a suggestion. anyone? anything?!

Last edited by Devataa; 03-20-2009 at 07:09 PM.. Reason: need a quicker response.
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