次亜塩素酸ナトリウム
Sodium hypochlorite can also be obtained as a crystalline pentahydrate ·5, which is not explosive and is much more stable than the anhydrous compound. The formula is sometimes given as 2·10. The transparent, light greenish-yellow orthorhombic crystals contain 44% NaOCl by weight and melt at 25–27 °C. The compound decomposes rapidly at room temperature, so it must be kept under refrigeration. At lower temperatures, however, it is quite stable: reportedly only 1% decomposition after 360 days at 7 °C.