CO₂ Test #1

Above you see the little test setup. Very low-tech. The cellophane over the bucket is just to maximize CO2 retention. The bubble rate is 82 bubbles per minute. The CO2 line is weighted down in the bottom of the bucket. It took about an hour or so to get to 30 mg/L. Regretfully, I didn't think to time how long it took to reach the various stages until after the fact.

Procedure

1. Prepared an inverted test tube and funnel - making sure there was no trapped air.
2. Placed the narrow end of the funnel into the test tube and proceeded to catch the bubbles as they came up from the end of the CO2 line.
3. Counted the number of bubbles required to fill the test tube to the 5 mL mark.

The above procedures were carried out at several levels of dissolved CO2. The results were as follows:

CO2 Concentration	Bubble Count to 5 mL
<5 mg/L	123
30 mg/L	124
170 mg/L	129
>270 mg/L	122

Conclusion

It does not appear that the amount of dissolved CO2 has any significant effect on the rate at which it dissolves. Had it been the case that the rate at which CO2 dissolved was strongly affected by concentration, the bubble counts should have grown progressively smaller as the CO2 concentration increased. Since they did not, we can conclude that each bubble had approximately the same volume when it reached the top of the water regardless of the concentration of CO2 in the water. In other words, each bubble lost the same amount of CO2 to the water whether the concentration was <5 mg/L or >270 mg/L.