CO2 Bends

To: Plants <Aquatic-Plants at actwin_com>
Subject: CO2 Bends
From: "Olive K. Charlsey" <achaudh at emory_edu>
Date: Sun, 26 May 1996 16:04:56 -0400 (EDT)
If you have read the article at:

http://www.cco.caltech.edu/~aquaria/Krib/Plants/CO2/co2-bends.html

<snip>

I have played with some similar CO2 systems - they are not too efficient
which is good - less chance of overdosing.  Today, I was talking with
John Burleson (with Dupla).  I asked him about his reactors - too
efficient to use without a controller.  When I told him of the filter
idea (I am currently doing it with an eheim), he said there may be some
problem because of the change in partial pressure as the co2 laden
water exits from the filter.  He thought this caused the CO2 to dissolve
instead of converting to carbonic acid.  Neither one of us knew enough
to understand what is really happening, but he assured me that he
discussed this with reliable sources and thought this is discussed in
one of Spotte's books.  The problem is that the dissolved CO2 can cause
an embolism, like the bends for divers.  This may be a good topic for
the net.

<snip>

Then you may be able to answer my question.

CO2 does dissolve in water to form H+HCO3-. There is no other way that it 
dissolves, no matter what pressure, no matter what the concentrations. 

So, what are they talking about in that message?

When the "CO2 laden water" comes out of the filter, it has a higher 
concentration of carbonic acid (H+ HCO3-) since there is no difference 
between dissolved CO2 and carbonic acid.
	
Also, the water is not exactly "laden" compared to the rest of the 
tank water when it exits the filter. Certainly it has a higher CO2 
concentration, but really, not a whole lot more. 

Any thoughts? Am I missing something here?

					Alok