| 摘要 |
PURPOSE:To prevent effectively the coloring of condensed phosphoric acid, by adding hydrogen peroxide to a reaction system for dissolving phosphoric acid anhydride in phosphoric acid manufactured by the wet process to produce the condensed phosphoric acid. CONSTITUTION:Phosphoric acid manufactured by the wet process is introduced into a reaction tank, and phosphoric acid anhydride is then mixed therewith. The temperature is increased by the heat of reaction, but kept at 120 deg.C or below in a water bath. Condensed phosphoric acid is produced while adding 0.005- 0.05pts.wt., expressed in terms of hydrogen peroxide based on 100pts.wt. H3PO4, hydrogen peroxide to the resultant mixture at the same time. Thus, colored materials due to a very small amount of organic materials in the phosphoric acid manufactured by the wet process and lower phosphoric acid in the phosphoric acid anhydride are decomposed by the hydrogen peroxide.
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