高等学校化学におけるアンモニアソーダ法の教材開発―イオンの組み替えによる炭酸水素ナトリウムの析出―

抄録

Sodium hydrogen carbonate and sodium carbonate are often used in chemistry experiments at junior and senior high schools. They are also occupying an important position in our daily lives. The ammonia soda method (Solvay process), an industrial process for sodium carbonate, is a subject of study in the “Properties of Inorganic Substances” section of senior high school chemistry. Teaching materials for students to conduct experiments about it have also been developed. However, most of them are demonstration experiments using ammonia solution or dry ice, and it is difficult to get students to make such experiments. In this study, we focused on the phenomenon that when ammonium hydrogen carbonate is added to a sodium chloride solution, precipitation of sodium hydrogen carbonate with low solubility is generated. This kind of phenomenon, in which the combination of ions varies, is called fractional crystallization. First, we explored the solutions and reagents suitable for the students’ experiment, and turned sodium hydrogen carbonate into sodium carbonate. Then, we developed an educational program that included a neutralization titration of sodium carbonate and an investigation of the properties of carbonates.