CO₂ Experiment #2

Background

In CO₂ experiment #1 I tested the hypothesis that the rate at which CO₂ dissolves into water is directly related to the concentration of CO₂ already dissolved in the water. The test was carried out by bubbling CO₂ through the water in a 5-gallon bucket, capturing the bubbles as they reached the top, and counting how many bubbles were required to displace 5 mL — a fancy way of saying that I was measuring the volume of each bubble. Anyway, it turned out that the volume of the bubbles captured did not change significantly regardless of the concentration of CO₂ already dissolved in the water. Each bubble retained a volume of between 0.0388 mL and 0.0407 mL throughout the experiment. Since the bubbles started out the same size, and were the same size when they reached the top, I had to conclude that there was no significant difference in the rate at which CO₂ dissolves in water at concentrations between about 5 mg/L and 270+ mg/L.

The purpose of this experiment will be to confirm or deny the conclusion of experiment #1. I am always reluctant to rely upon one set of measurements. No matter what I am doing, if the consequences of being wrong are anything more than trivial, I prefer to double check. Independent verification is even better. That is why I want to conduct this experiment.

Experimental Design

My current idea is to run the experiment in a somewhat reverse fashion. Instead of capturing gas until it displaces a certain volume, I will start with a known volume and measure the rate at which it dissolves. My proposal is to fill the test tube with 5 mL of CO₂ and then suspend the inverted test tube in a strong water current and measure the time required to dissolve the 5 mL of CO₂. If the results of experiment #1 are indeed correct, the concentration of CO₂ in the water should make no significant difference in the amount of time required to dissolve the 5 mL of CO₂ from the test tube. However, if the results of experiment #1 are not correct, the amount of time required to dissolve the CO₂ from the test tube should increase as the concentration of CO₂ in the water is increased.