Phase diagrams and water activities of aqueous ammonium salts of malonic acid.
Phase diagrams and water activities of aqueous ammonium salts of malonic acid.
复制标题
丙二酸铵盐水溶液的相图和水活度。
DOI：
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发表时间：
2011
影响因子：
2.9
通讯作者：
Breanna Reusch
中科院分区：
文献类型：
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作者：
K. Beyer;M. Richardson;Breanna Reusch
在自由对流层中观察到丙二酸，在其他二元酸中，丙二酸是对流层气溶胶的一种成分。这些气雾剂可以吸收氨，从而部分或完全中和酸。因此，需要研究氨化的二元酸对大气温度下气溶胶中可能存在的物相的影响。为此，用薄膜的差示扫描量热法和红外光谱研究了丙二酸氢铵/水、丙二酸铵/水和丙二酸三铵/水的低温固液相图。结果表明，溶解度由大到小的顺序为丙二酸三铵>丙二酸氢铵>丙二酸>丙二酸铵。我们还确定了在丙二酸铵体系中可能会形成水合物，并在240 K以下分解。我们报告了每个体系在冰熔点的水的活度，直到各自的共晶浓度，并且发现对于给定的水的摩尔分数，铵含量的增加导致水活度系数的降低。
Malonic acid has been observed in the free troposphere and as a component of tropospheric aerosol, among other dicarboxylic acids. These aerosols can uptake ammonia, which partially or completely neutralizes the acids. Therefore, the impact of ammoniated dicarboxylic acids on the phases that can exist in aerosols at atmospheric temperatures needs investigation. To that end, the low temperature, solid/liquid phase diagrams of ammonium hydrogen malonate/water, ammonium malonate/water, and triammonium hydrogen malonate/water have been investigated with differential scanning calorimetry and infrared spectroscopy of thin films. Results show that the order of increasing solubility is triammonium hydrogen malonate, ammonium hydrogen malonate, malonic acid, and ammonium malonate. We have also determined a hydrate may form in the ammonium malonate system and decompose below 240 K. We report water activities at the ice melting points for each system up to the respective eutectic concentrations, and find for a given mole fraction of water, increasing ammonium content leads to decreasing water activity coefficients.