Water Activity Measurements by the Isopiestic Method for the MCl–CaCl2–H2O (M = Na, K) Systems at 323.15 K

2015 ◽  
Vol 60 (8) ◽  
pp. 2285-2290 ◽  
Author(s):  
Haijun Han ◽  
Lijiang Guo ◽  
Dongdong Li ◽  
Ouyang Dong ◽  
Yan Yao ◽  
...  
Keyword(s):  
Water Activity ◽  
Isopiestic Method ◽  
Activity Measurements

Determination of fictive binary data for plutonium(IV) nitrate

2000 ◽  
Vol 88 (1) ◽  
Author(s):  
N. Charrin ◽  
Philippe Moisy ◽  
P. Blanc
Keyword(s):  
Water Activity ◽  
Ternary Mixture ◽  
Binary Data ◽  
Activity Measurements

A method is described for determining binary data for electrolytes from a study of a ternary mixture. The method is based on the concept of thermodynamically simple solutions and on water activity measurements. An application is described in which binary data for plutonium(IV) nitrate are determined from a ternary mixture of Pu(NO

Statistical Evaluation of Water Activity Measurements Obtained with the Vaisala Humicap Humidity Meter

1983 ◽  
Vol 48 (2) ◽  
pp. 534-538 ◽  
Author(s):  
GUILLERMO FAVETTO ◽  
SILVIA RESNIK ◽  
JORGE CHIRIFE ◽  
CONSTANTINO FERRO FONTAN
Keyword(s):  
Water Activity ◽  
Statistical Evaluation ◽  
Activity Measurements

scholarly journals Evaluation of free water and water activity measurements as functional alternatives to total moisture content in broiler excreta and litter samples

2014 ◽  
Vol 93 (7) ◽  
pp. 1782-1792 ◽  
Author(s):  
E. van der Hoeven-Hangoor ◽  
C.J. Rademaker ◽  
N.D. Paton ◽  
M.W.A. Verstegen ◽  
W.H. Hendriks
Keyword(s):  
Moisture Content ◽  
Water Activity ◽  
Free Water ◽  
Activity Measurements ◽  
Total Moisture Content

scholarly journals Using water activity measurements to evaluate rheological consistency and structure strength of sludge

2013 ◽  
Vol 228 ◽  
pp. 799-805 ◽  
Author(s):  
G. Agoda-Tandjawa ◽  
E. Dieudé-Fauvel ◽  
R. Girault ◽  
J.-C. Baudez
Keyword(s):  
Water Activity ◽  
Activity Measurements ◽  
Structure Strength

A theoretical treatment of cation exchangers - III. The hydration of cations in polystyrene sulphonates

1955 ◽  
Vol 228 (1174) ◽  
pp. 322-341 ◽  
Keyword(s):  
Water Molecule ◽  
Water Activity ◽  
Adsorption Isotherms ◽  
Liquid Water ◽  
Adsorbed Water ◽  
Isopiestic Method ◽  
Water Molecules ◽  
Hydration Water ◽  
Monovalent Cations ◽  
Free Energies

The adsorption of water by the polystyrene sulphonates of cations has been investigated at 0 and 25° C, using an isopiestic method. The adsorption isotherm and the heats (enthalpies) and entropies of hydration have been obtained for the monovalent cations H, Li, Na, K, Cs, NH4, Ag and for the divalent cations Be, Mg, Ca, Sr, Ba, Hg. With the exception of H, which gives a smooth enthalpy-water-content curve, all monovalent cations show a more or less marked step in the differential enthalpy of adsorbed water between the first and second water molecule adsorbed per ion, thereafter the steps are less clearly defined. The differential entropies show similarities to those calculated for a B. E. T. isotherm, except that the curves show two minima which correspond to approximately 0.15 and 1.5 molecules of water/ion. The adsorption isotherms follow more or less the model of the B. E. T. isotherm, with several significant differences: ( a ) the volatility of the second and further water molecule/ion is not that of liquid water, but only tends to reach this value after several molecules/ion are adsorbed, and the energy levels of the first successive water molecules, though rising rapidly, differ substantially from that of liquid water; ( b ) the adsorption process of the first water molecule is significantly different from a Langmuir mechanism, and varies approximately as the one-half power of the water activity. The knowledge of the free energies, enthalpies and entropies permits a fair analysis of the hydration mechanism into its individual steps, which then permits a calculation of the standard state enthalpies and entropies of the first hydration steps. Both functions show a markedly linear relationship with the ionic radius of the unhydrated ion when summed up for the first two water molecules adsorbed. The knowledge of the adsorption isotherms permits one to differentiate between water adsorbed with zero free energy (swelling water) and the excess adsorbed water (cationic and anionic hydration water). The amount of hydration water associated with the cations has been obtained in this way both for mono- and divalent ions. The amount varies both with the water activity and with temperature. It is clear from the small free energies of hydration of all monovalent ions that the association of almost all water molecules is very loose, and is not related to the co-ordination number of the ions.

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