高純度炭酸ナトリウムの乾燥条件の検討

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Sodium carbonate, a primary standard of volumetric analysis, is used as a standard of hydrochloric acid and sulfuric acid in Japan, and is certified in different countries by using different drying conditions. The drying conditions for reference materials have a significant effect on the titration results due to changes in the acidimetric factor. The drying conditions for sodium carbonate were investigated by thermogravimetry-mass spectrometry (TG-MS), gravimetric titration, mass and pH measurements. In TG-MS analysis, about 29mg of sodium carbonate was heated from room temperature to 700℃. The loss through heat was 2.1%, and the amount of water content detected was 1.8%. Most of the weight lost through heat was caused by releasing water, which was produced at about 100℃, and carbon dioxide was released at about 100℃ and 600℃. The weight of sodium carbonate dried at different temperatures was decreased, which also indicates the decomposition of sodium carbonate under high-temperature conditions. Sodium carbonate samples dried at 100℃ to 700℃ for 1h were gravimetrically cross-titrated with each other using 1.5mol/L hydrochloric acid as an intermediate titrant. The effective purity of sodium carbonate was significantly increased at over 400℃. In addition, the pH value of carbonate-free solutions of sodium carbonate dried at different temperatures prepared by precipitation as a barium carbonate was increased, especially at over 500℃. It was concluded that suitable drying conditions were 200℃〜400℃, and the optimum condition was approximately 300℃ for 2h.
社団法人日本分析化学会の論文
2008-01-05

高純度炭酸ナトリウムの乾燥条件の検討

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