GE PM880 - Page 214

4/9/98
A-32 Application of the Hygrometer (900-901D1)
B: SPECIAL CASE (cont.)
Note: If the saturation concentration at the desired ambient
temperature can not be found for any of these special case
hydrocarbons, the value at any other temperature may be
used, because K is constant over a large temperature
range.
3. Find the moisture content in hexane, at an ambient
temperature of 10°C, if a dew point of 0°C is measured with
the GE Panametrics hygrometer.
a. From the literature, it is found that C
S
for hexane at a
temperature of 20°C is 101 PPM
W
.
b. Using a straightedge on Figure A-2, connect the 101
PPM
W
saturation concentration with the 20°C ambient
temperature and read the Henry’s Law Constant of 5.75 on
the center scale.
c. Using the straightedge, connect the above K value of 5.75
with the measured dew point of 0°C, and read the correct
moisture content of 26 PPM
W
where the straightedge
crosses the moisture content scale.
4. Find the moisture content in an unknown organic liquid, at an
ambient temperature of 50°C, if a dew point of 10°C is
measured with the GE Panametrics hygrometer.
a. Either perform a Karl Fischer analysis on a sample of the
liquid or obtain a dry sample of the liquid.
b. Either use the PPM
W
determined by the Karl Fischer
analysis or add a known amount of water (i.e. 10 PPM
W
)
to the dry sample.