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CO2 dissolution

     A while back there was a discussion of the speed and volume of a 
captured quantity of CO2 as it dissolved into the water mass. I paid 
little attention to the string other than to think it was interesting but 
I don't use that method to inject the CO2 in my tank. Recently I decided 
to supplement a trickle of CO2 by way of an air stone from a yeast 
generator in hopes of lowering the pH a bit more. When it began to bubble 
I noticed an interesting thing. The bubbles are medium sized as you would 
guess from a low volume source and they race for the surface in the 
normal way until they get about halfway up where they very rapidly lose 
volume and speed and by the time they reach the surface they are indeed 
microscopic. At first I thought it was an optical illusion or my eyes 
playing tricks on me. Evidently the CO2 dissolves rather rapidly into the 
water mass and you can trace its rate by the deflating of the bubbles as 
they travel through the water column. Is the rate of dissolving of CO2 
the same despite the previous quantities that have already been 
dissolved? I realize there is a chemical reaction that removes the gas 
molecules from the water thereby, I suppose, preventing the saturation 
point from being reached. Still it's weird watching fast moving gas 
bubbles slow down on their way to the surface and decrease in size to a 
vanishingly small speck.
      Thanks for listening... Lyle Babberl