84:. The vessel is then heated to a known temperature, such as in a boiling water bath, causing the entire sample to vaporize and completely displace the air from the vessel. The vessel is then sealed, such as with a flame to melt the neck of a glass flask, dried, and re-weighed. By subtracting the tare of the vessel, the actual mass of the unknown vapor within the vessel can be calculated.
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Either the volume of the vessel does not vary significantly between room temperature and the working temperature, or the volume of the vessel may be accurately determined at the working temperature
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Grider, Douglas J.; Tobiason, Joseph D.; Tobiason, Fred L. (1988). "Molecular weight determination by an improved temperature monitored vapor density method".
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The molecular weight of the chemical is then simply the mass in grams of the vapor within the vessel divided by the calculated number of mole.
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Kaya, Julie J.; Campbell, J. Arthur (1967). "Molecular weights from Dumas bulb experiments".
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For the method for quantitative determination of nitrogen, see
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Darrell Ebbing; Steven D. Gammon (12 January 2007).
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