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热力学分析是分析化工实际问题的有力工具,本文阐述了它在沉淀转化反应中的应用。绘制的碳酸铵溶液中包括 NH_2COO~-在内的各组分的平衡分布图表明,图中存在 NH_2COO~-的稳定区;在相同 pH 值条件下,碳酸铵溶液中由于 NH_2COO~-的存在,使 CO_3~(2-)的分布系数 aco_3~(2-)比纯碳酸溶液为小.解释了硝酸磷肥碳化法将CaHPO_4转化为 CaCO_3时需要过多(NH_4)_2CO_3的原因.进一步绘制的 log[Ca2~+]对 pH 的活度一活度图及由它导出的图能很好地预测各变量对沉淀转化条件的作用。
Thermodynamic analysis is a powerful tool to analyze the practical problems of chemical industry. This paper describes its application in precipitation conversion reaction. The equilibrium distribution of each component including NH_2COO ~ - in the drawn ammonium carbonate solution shows that there is a stable region of NH_2COO_-- in the sample. Due to the presence of NH_2COO - in the ammonium carbonate solution at the same pH, So that the distribution coefficient aco_3 ~ (2-) of CO_3 ~ (2-) is smaller than that of pure carbonic acid solution.The reason why too much (NH_4) _2CO_3 is needed to convert CaHPO_4 to CaCO_3 is explained.Correlation log [ Ca2 ~ +] activity on pH activity diagram and the map derived from it can well predict the role of variables on the conditions of precipitation.