Products Description of Orthoboric acidCAS#10043-35-3
Boric acid is an inorganic compound generated when boron trioxide dissolves in water. It exists in multiple forms including tetraboric acid H₂B₄O₇ (pyroboric acid), polymeric metaboric acid (HBO₂)ₙ, and orthoboric acid H₃BO₃. Of these variants, orthoboric acid contains the highest proportion of combined water and demonstrates the best stability.
Ortho‑boric acid, generally referred to simply as boric acid, appears as lustrous white powdery or triclinic flaky crystals. It delivers a faintly bitter taste and produces a greasy sensation upon skin contact, and is odorless. It is soluble in alcohols, glycerol, ethers and essential oils. Its aqueous solution shows weak acidity and it is classified as a typical Lewis acid.
Upon heating, orthoboric acid undergoes step‑wise dehydration: it converts to metaboric acid at 70‑100 °C, pyroboric acid at 150‑160 °C, and finally boric anhydride (B₂O₃) at 300 °C.
Boric acid is toxic to humans. Its water‑solubility varies with temperature: 2.77 g/100 mL at 0 °C, 3.65 g/100 mL at 10 °C, 4.87 g/100 mL at 20 °C, 5.74 g/100 mL at 25 °C, 6.77 g/100 mL at 30 °C, 8.90 g/100 mL at 40 °C, 11.39 g/100 mL at 50 °C, 14.89 g/100 mL at 60 °C, 23.54 g/100 mL at 80 °C and 38.00 g/100 mL at 100 °C. The addition of hydrochloric acid, citric acid or tartaric acid can improve its aqueous solubility, which enables purification via recrystallization.
Orthoboric acid Chemical Properties
| Melting point | 160 °C (dec.) (lit.) |
| Boiling point | 219-220 °C (9.7513 mmHg) |
| density | 1.440 g/cm3 |
| vapor pressure | 2.6 mm Hg ( 20 °C) |
| storage temp. | Store at +5°C to +30°C. |
| solubility | H2O: soluble |
| form | working solution |
| pka | 8.91±0.43(Predicted) |
| Specific Gravity | 1.435 |
| color | ≤10(APHA) |
| Odor | Odorless |
| PH Range | 3.8 - 4.8 |
| PH | 3.6-4.4 (25℃, saturated solution in H2O) |
| Water Solubility | 49.5 g/L (20 ºC) |
| Sensitive | Hygroscopic |
| λmax | λ: 260 nm Amax: 0.05 λ: 280 nm Amax: 0.05 |
| Merck | 14,1336 |
| BRN | 1697939 |
| Exposure limits | ACGIH: TWA 2 mg/m3; STEL 6 mg/m3 |
| InChIKey | KGBXLFKZBHKPEV-UHFFFAOYSA-N |
| LogP | -1.09 at 22℃ |
| CAS DataBase Reference | 10043-35-3(CAS DataBase Reference) |
| NIST Chemistry Reference | B(OH)3(10043-35-3) |
| EPA Substance Registry System | Orthoboric acid (10043-35-3) |
