Larry,
1) You write that "most chemical reactions are driven by vapor pressure". I
disagree. Most chemical reactions do not involve vapor.  All chemical
reactions are driven by enthalphy, entropy and activation energies.
2) "Low partial pressure low reaction rates." Well NH3(g) + HCl(g) ->
NH4Cl(s) has a lower partial pressure on the right side of the reaction, but
you can bet you socks that the reaction rate to form ammonium chloride is
not slow.

Bev
Blackberry



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Larry Dzaugis
Sent: Friday, March 08, 2013 2:45 PM
To: [log in to unmask]
Subject: Re: [TN] Humidity Measurements: Relative or Absolute

Relative humidity, what is measured is the % of water vapor in the air
relative to the amount of water it can hold.

This varies tremendously with temperature.
Just ask the folks in Minnesota how much water must be added to bring that
-40 air at night up to 30% relative humidity when it comes into the
building.
The evaporation of that water consumes a large amount of energy.
Same for drying out the soaking wet air in New Orleans.
A large amount of tonnage required to go from 90%RH to 60%RH over and above
what is required to cool the air.

Most chemical reactions are driven by the vapor pressure. Low partial
pressure low reaction rates.

Absolute humidity would be measured by grams water in cubic meter.
Any change in temperature would influence the number
Watch the drag race when they prep for the 1/4 mile.
Absolute humidity is measured. The water influences the fuel burn and
adjustments are made to fuel and engine settings.


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