Manual

User's Guide ______________________________________________________________________
46 __________________________________________________________________ M210934EN-C
3. Define the correlation between aw, T and PPM (w/w) from the
measured values. Calculate A and B according to the following
example.
[ ] [ ]
( ) ( )
1/1-2/1
1(-2(
TT
TPPM LOGTPPMLOG
A
satsat
))
=
[ ]
)(
A/T1 - 1TPPMLOGB
sat
=
Example (measured water content 213 ppm):
T (°C)
aw
ppm
saturation
24.1
0.478
213/0.478 = 445.6067
57.6
0.188
213/0.188 = 1132.979
A = (LOG(1132.98)-LOG(445.607))/(1/(57.6+273.16)-
1/(24.1+273.16)) = -1189.4581
B= LOG(445.607)-(-1189.4581)/(24.1 + 273.16) = 6.6503583
Assumptions:
The isoterm of water activity versus water concentration is linear and the
solubility curve has the form of the given equation.