But then what should we make of this conclusion if we consider other properties of gases? In particular, since small volumes of gas (smaller than the atmosphere)
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ll their container, the gas interacts with both the upper and lower walls of any measuring container. Both forces affect the scale, and so weighing a gas is not just measuring the force required to balance the downward force of gravity in any direct mechanical sense. Operationally how- ever, weighing a gas is just like weighing any other
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uid. Methods dating back to Galileo [2]