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White crystalline powder or colorless phosphorus flakes with a pearl-luster or hexagonal triclinic crystals. Tasteless, slightly bitter taste. The melting point is about 171ºC. Soluble in water, alcohol, glycerin, ethers and essential oils, the aqueous solution is weakly acidic. The solubility of boric acid in water increases with the increase of temperature, and can volatilize with water vapor. The pH of aqueous solution is 5.1 in Imol/L. 19 can be dissolved in 18mL cold water, 4mL boiling water, 18mL cold alcohol, 6mL boiling alcohol or 4mL glycerin. It has a smooth feeling in contact with the skin and no change in the air. When heated to 100 ~ 105ºC, a molecule of water is lost to form metaboric acid, and when heated for a long time at 104 ~ 160ºC, it is transformed into pyroboric acid, and at higher temperatures, anhydrous matter is formed, and boric anhydride (B2-03) is formed at 300ºC.
| Item | Index | |
| First grade | Second grade | |
| Boric acid(%) | ≥99.5% | ≥96.5% |
| Water insolubles(%) | ≤0.05% | ≤0.15% |
| Sulfate(SO4)(%) | ≤0.10% | ≤0.40% |
| Chloride(CL)(%) | ≤0.01% | ≤0.05% |
| Iron(Fe)(%) | ≤0.003% | ≤0.005% |
