Unit mass balances with negligible

Unit Mass Balances with Negligible Contaminant Mass in the Wastewater... 

As with the mass balances over a unit, contaminant balances around a storage vessel are not required due to the contaminant mass being negligible at this stage. 

For liquids stored at their saturation vapor pressure, P = Ps, and Equation 4-91 is no longer valid. A much more detailed approach is required. Consider a fluid that is initially quiescent and is accelerated through the leak. Assume that kinetic energy is dominant and that potential energy effects are negligible. Then, from a mechanical energy balance (Equation 4-1), and realizing that the specific volume (with units of volume/mass) v = 1/p, we can write... 

Unusual are measurements for which a direct link to the mole is useful. We should probably not talk about traceability in that connection, because that term is defined as a relation between measured values. An acceptable chain of measurements for compound X of established purity, containing element E that has isotope E and that would establish a link to the mole, then would take one of the following general routes the amount of substance (X)->n(E)->n( E)-> (12C) or n(X)->n(E)-> (C)-> (12C). The ratio of atomic masses m( E)lm( 12C) is also involved in the definition, but that ratio is known with a negligible uncertainty compared with the other links in the chain. Clearly, only in a few instances will laboratories attempt to execute such a chain of measurements for a link to the SI unit. Is it fear that such a difficult process is involved in every chemical analysis that has kept so many chemists from using the mole as the way to express chemical measurement values Or is it just habit and the convenience of a balance that subconsciously links amount of substance to amount of mass ... 

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