Zapins

Does anyone know if Kordon breather bags are permeable to chemicals other than gases?

Like if I had a Kordon bag of distilled water in the tank, would the distilled water absorb minerals/chemicals through the plastic?

 

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Bert H

Interesting question. I don't know. Are you thinking of using it as a dialysis bag?

hoppycalif

As I understand how the breather bags work, they are just gas permeable membrane bags. So, if any ions were to make it through the bags I would expect them to do so only very, very slowly. When I was experimenting with gas permeable membranes for making drop checkers the liquids remained separated for many days. But, that was with different membrane materials.

KnaveTO

My understanding of the Kordon Bags is they are gas permeable but not water permeable.

Zapins

Hehe, actually I asked this as I was reading hoppy's drop checker thread, then I read ahead like 25 posts and found that people already thought of it... I thought I was the first one to think of using the bag for the pH meter xD

By the way, since it won't transfer ions across the membrane the bag won't work for a drop checker because most CO2 is not in gas form in the water, its in acid form with dissociated H ions. Only about 10% is in gas form which explains why it takes so long for measurements to register.

Did you ever find a good membrane hoppy?

hoppycalif

The membrane made for DO probes works well for a drop checker, and with great effort can be used to make a quick responding drop checker. But, that quick response comes at the price of difficulty in making it, difficulty in reading the color, and short life for it.

CO2 in water is in a constant state of changing between carbonic acid, carbonate and carbon dioxide. It will leave the water as easily as it enters the water, so having to change back to carbon dioxide doesn't slow it down much at all. The reason for this is.....uh.....beyond the scope of this forum. (I refuse to admit a lack of knowledge about this, I just don't want to talk about it.)

Zapins

Why would you need to know the color, if you have a digital pH probe like the one used for solenoid CO2 regulators then you can use the pH to find the CO2 chart since we already know the kH of the solution that its in.

Well the reason the CO2 doesn't go through the kordon bag is because its liquid to liquid the partial pressure hasn't really changed much.

hoppycalif

If anything the CO2 seems to go through the membrane faster than through the air gap, since all of the membrand drop checkers I made had a faster, or at least as fast, response time to the regular ones. I didn't try this with a pH probe, just water with pH reagent, so I had to see the color. My pH probe isn't suitable for use as a CO2 probe - too big, no way to hold it in the water, and the sensor end isn't easily adapted to a little balloon of 4 dKH water.

 

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