On Fri, Sep 5, 2008 at 2:50 PM,
<jonw@psubs.org> wrote:
>A gallon of air, which contains exactly 231 cubic inches,
>exerts 11 lbs. 10 ounces
That should be 8.34 pounds. You sound like you are mixing theoretical calculations with practical applications. It's impossible to measure "a gallon of air" in a practical setting and attempt to associate the results with theoretical calculations without taking into account the other factors associated with your test. The air you captured for testing had to be contained in something. That "something" also displaces water. When you did your measurements, you needed to calculate the displacement for all the various parts that were contributing to the test. The air pressure when you "captured" the air for your test would have affected the outcome of the test as would the displacements associated with the container, weights, and rope or string that I'm assuming you used to pull the container under water.
If you required 83.119 pounds of weight to make a cubic foot of air neutrally buoyant, then you had 20.719 pounds of buoyancy associated with the material you were using to conduct the test.