Surface area of a beaker of water w/ surface tension?

So I'm working on a chemistry lab determining Avogadro's constant with a fatty acid monolayer on a beaker of water, and my calculations are all work out to around 1.3*10^23 (ie a sixth of what they should be). The lab said "fill the beaker with water until it spills over". In doing so, I ended up with a large curve in the surface of the water. However, the lab guidelines don't explain any way to account for that (I assume they wanted the water at 90° to the beaker).

Does anyone know of a formula to find the maximum surface area of water that includes the effects of surface tension? The surface tension is the only error I can think of that can be fixed in my report (other stuff, like adding too many drops stearic acid I'm stuck with...).


No idea about formula, but my guesstimate is that it won't change the surface by more than small single percents (if not even less). No chances for getting your result really closer to NA.

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