Boric Acid

Boric acid, also called hydrogen borate, boracic acid, orthoboric acid and acidum boricum, is a weak, monobasic Lewis acid of boron often used as an antiseptic, insecticide, flame retardant, neutron absorber, or precursor to other chemical compounds. It has the chemical formula H3BO3 (sometimes written B(OH)3), and exists in the form of colorless crystals or a white powder that dissolves in water. When occurring as a mineral, it is called sassolite.

Parameter Value

CAS Number


Chemical formula


Molar mass

61.83 g·mol−1


White crystalline solid


1.435 g/cm3

Melting point

170.9 °C (339.6 °F; 444.0 K)

Boiling point

300 °C (572 °F; 573 K)

Solubility in water

2.52 g/100 mL (0 °C)
4.72 g/100 mL (20 °C)
5.7 g/100 mL (25 °C)
19.10 g/100 mL (80 °C)
27.53 g/100 mL (100 °C)

Solubility in other solvents

Soluble in lower alcohols
moderately soluble in pyridine
very slightly soluble in acetone

Acidity (pKa)

9.24, 12.4, 13.3

Magnetic susceptibility (χ)

-34.1·10−6 cm3/mol

Website Designed and managed by MK Web Solutions