Dear Frank
"Relative Humidity" is a measure of the actual water content of the air
compared to the water it would contain when saturated.
For example, if it could hold 100 units of water vapour at 40 C, but it only
had 48 units, then it would have a "Relative Humidity" of 48%
In the case of your magnesium Nitrate example, if you started with air
having say 75% RH, or 25% RH, the air and the solution would come into
equilibrium at 48.42 % RH, +/- .37% RH
You can get information on what moisture content air will hold by consulting
a "Psychrometric Chart" or table. See:
http://www.engineeringtoolbox.com/air-psychrometrics-properties-t_8.html
You have heard of "User Friendly"... well, Psychrometric Charts are "User
Hostile" :-( They are complicated, but there is an enormous amount of
helpful information contained within them.
Best wishes,
Kevin
----- Original Message -----
From: "Frank Shields" <[email protected]>
To: "'Discussion of biomass cooking stoves'"
<[email protected]>; <[email protected]>
Sent: Friday, March 22, 2013 5:51 PM
Subject: [Stoves] Relative Humidity question
Dear Stovers,
I have a question regarding Relative Humidity.
A saturated mix of water and magnesium nitrate (for example) at 40c will
produce a 'percent relative humidity' in the air trapped in the container
above of 48.42 +/- 0.37.
What does this mean? Is there a value of grams water per cubic meter of
gas
(or some other unit) that we can use to calibrate instrumentation
measuring
water vapor?
Thanks
Frank
Frank Shields
Control Laboratories, Inc.
42 Hangar Way
Watsonville, CA 95076
(831) 724-5422 tel
(831) 724-3188 fax
www.controllabs.com
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