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Updated February 20, 2006

ScienceMan Neat Idea - Interface Osmosis Lab

Here's a great idea for the sometimes annoying osmosis lab involving a dialysis baggie and glass tubing;

beaker sensor

Instead of waiting for 20 minutes or longer just to see a small amount of solution movement up the tube, I decided to hook up a low pressure sensor (see above) to the top of the glass tube - this is accomplished with some simple plastic tubing. When you've got the whole thing set up, it should look like this;

setup setup+cpu

The black cable you see in the picture above leads to the science interface, which is connected to the computer (see above). So what is the advantage of this setup? The really big advantage is time. Instead of waiting long periods of time to see a pathetic amount of solution movement in the tube, the low pressure sensor yields readable results in just seconds - if you look at the time scale in the graph below, you'll see the pressure change is stretched out over only 200 seconds. Looking at the graph, you can see even that time interval was unnecessarily long in order to see a pressure change;

graph1

Having this kind of sensitivity makes all sorts of other things possible! What I did is let the experiment run for a while, then I changed the surrounding liquid from distilled water to highly concentrated salt solution. Then for the heck of it, I changed it back again a little while later. Here's the result;

graph2

Pretty cool, eh? Give it a try and let the ScienceMan know how it works out!

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