A calorimetric method to determine water activity
(2011) In Review of Scientific Instruments 82(11).- Abstract
- A calorimetric method to determine water activity covering the full range of the water activity scale is presented. A dry stream of nitrogen gas is passed either over the solution whose activity should be determined or left dry before it is saturated by bubbling through water in an isothermal calorimeter. The unknown activity is in principle determined by comparing the thermal power of vaporization related to the gas stream with unknown activity to that with zero activity. Except for three minor corrections (for pressure drop, non-perfect humidification, and evaporative cooling) the unknown water activity is calculated solely based on the water activity end-points zero and unity. Thus, there is no need for calibration with references with... (More)
- A calorimetric method to determine water activity covering the full range of the water activity scale is presented. A dry stream of nitrogen gas is passed either over the solution whose activity should be determined or left dry before it is saturated by bubbling through water in an isothermal calorimeter. The unknown activity is in principle determined by comparing the thermal power of vaporization related to the gas stream with unknown activity to that with zero activity. Except for three minor corrections (for pressure drop, non-perfect humidification, and evaporative cooling) the unknown water activity is calculated solely based on the water activity end-points zero and unity. Thus, there is no need for calibration with references with known water activities. The method has been evaluated at 30 °C by measuring the water activity of seven aqueous sodium chloride solutions ranging from 0.1 mol kg−1 to 3 mol kg−1 and seven saturated aqueous salt solutions (LiCl, MgCl2, NaBr, NaCl, KCl, KNO3, and K2SO4) with known water activities. The performance of the method was adequate over the complete water activity scale. At high water activities the performance was excellent, which is encouraging as many other methods used for water activity determination have limited performance at high water activities. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/2222151
- author
- Björklund, Sebastian LU and Wadsö, Lars LU
- organization
- publishing date
- 2011
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- vaporisation, nitrogen, sodium compounds, solutions, thermal variables measurement, calorimetry, chemical variables measurement, calorimeters
- in
- Review of Scientific Instruments
- volume
- 82
- issue
- 11
- article number
- 114903
- publisher
- American Institute of Physics (AIP)
- external identifiers
-
- wos:000297941100043
- scopus:82555173665
- pmid:22129000
- ISSN
- 1089-7623
- DOI
- 10.1063/1.3660815
- language
- English
- LU publication?
- yes
- id
- e7e07377-fc04-4fa9-95eb-a8886e53741b (old id 2222151)
- date added to LUP
- 2016-04-01 12:53:18
- date last changed
- 2022-01-27 08:07:08
@article{e7e07377-fc04-4fa9-95eb-a8886e53741b,
abstract = {{A calorimetric method to determine water activity covering the full range of the water activity scale is presented. A dry stream of nitrogen gas is passed either over the solution whose activity should be determined or left dry before it is saturated by bubbling through water in an isothermal calorimeter. The unknown activity is in principle determined by comparing the thermal power of vaporization related to the gas stream with unknown activity to that with zero activity. Except for three minor corrections (for pressure drop, non-perfect humidification, and evaporative cooling) the unknown water activity is calculated solely based on the water activity end-points zero and unity. Thus, there is no need for calibration with references with known water activities. The method has been evaluated at 30 °C by measuring the water activity of seven aqueous sodium chloride solutions ranging from 0.1 mol kg−1 to 3 mol kg−1 and seven saturated aqueous salt solutions (LiCl, MgCl2, NaBr, NaCl, KCl, KNO3, and K2SO4) with known water activities. The performance of the method was adequate over the complete water activity scale. At high water activities the performance was excellent, which is encouraging as many other methods used for water activity determination have limited performance at high water activities.}},
author = {{Björklund, Sebastian and Wadsö, Lars}},
issn = {{1089-7623}},
keywords = {{vaporisation; nitrogen; sodium compounds; solutions; thermal variables measurement; calorimetry; chemical variables measurement; calorimeters}},
language = {{eng}},
number = {{11}},
publisher = {{American Institute of Physics (AIP)}},
series = {{Review of Scientific Instruments}},
title = {{A calorimetric method to determine water activity}},
url = {{http://dx.doi.org/10.1063/1.3660815}},
doi = {{10.1063/1.3660815}},
volume = {{82}},
year = {{2011}},
}