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Re: What is in all those bubbles?
>From: olga at arts_ubc.ca
>Date: Mon, 12 Feb 1996 14:42:14 -0700
>Subject: What is in those bubbles?
Olga asked Mon. 12 Feb why all the CO2 in the bubbles just under the
surface and coming out of the power head didn't lower the pH more.
It is likely that those bubbles don't have very much CO2 in them. A bubble
can start out with a lot of CO2 in it, but as the CO2 diffuses out, other
gasses diffuse in. Since your tank water is pretty much in equilibrium with
the atmosphere, the nitrogen will diffuse out of the water into the bubble
until the partial pressure of the nitrogen in the bubble equals that of the
water. At that time, the bubble will be about 79% nitrogen. The same sort
of thing happens with a bell. You can start with 100% CO2 in it, and you
would think that it would all dissolve in the water, leaving no gas in the
bell, but nitrogen and some oxygen are diffusing from the water into the
bell as the CO2 is diffusing out, and eventually you wind up with a smaller
volume of gas in the bell that is about 79% nitrogen and 21% oxygen. You
really did get almost all the CO2 in the water; it just doesn't look like
it.
Paul Krombholz Tougaloo College, Tougaloo, MS 39174
Where we had some snow flurries, but I want more!