Volkova Natalia, Hansson Henri, Ljunggren Lennart
Department of Biomedical Science, Malmö University, SE-205 06, Malmö, Sweden.
Department of Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
J Pharm Anal. 2013 Jun;3(3):193-199. doi: 10.1016/j.jpha.2012.12.003. Epub 2012 Dec 20.
Isothermal titration calorimetry (ITC) was used to study interactions between water vapour and the surface of thermally converted sodium bicarbonate (NaHCO). The decarboxylation degree of the samples was varied from 3% to 35% and the humidity range was 54-100%. The obtained enthalpy values were all exothermic and showed a positive linear correlation with decarboxylation degrees for each humidity studied. The critical humidity, 75% (RH), was determined as the inflection point on a plot of the mean-ΔH kJ/mole NaCO against RH. Humidities above the critical humidity lead to complete surface dissolution. The water uptake () was determined after each calorimetric experiment, complementing the enthalpy data. A mechanism of water vapour interaction with decarboxylated samples, including the formation of trona and Wegscheider's salt on the bicarbonate surface is proposed for humidities below RH.
采用等温滴定量热法（ITC）研究了水蒸气与热转化碳酸氢钠（NaHCO₃）表面之间的相互作用。样品的脱羧程度在3%至35%之间变化，湿度范围为54 - 100%。所获得的焓值均为放热，并且在所研究的每种湿度下，与脱羧程度呈正线性相关。临界湿度75%（相对湿度）被确定为平均ΔH（kJ/摩尔Na₂CO₃）对相对湿度的曲线图上的拐点。高于临界湿度的湿度会导致表面完全溶解。在每次量热实验后测定吸水量（），以补充焓数据。对于相对湿度以下的湿度，提出了水蒸气与脱羧样品相互作用的机制，包括在碳酸氢盐表面形成天然碱和韦氏盐。
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