Boric Acid

Title: Boric Acid
CAS Registry Number: 10043-35-3
Additional Names: Boracic acid; orthoboric acid
Trademarks: Borofax (Burroughs Wellcome)
Molecular Formula: BH3O3
Molecular Weight: 61.83
Percent Composition: B 17.49%, H 4.89%, O 77.63%
Line Formula: H3BO3
Literature References: Occurs in nature as the mineral sassolite. Manuf: Faith, Keyes & Clark's Industrial Chemicals, F. A. Lowenheim, M. K. Moran, Eds. (Wiley-Interscience, New York, 4th ed., 1975) pp 153-158. Toxicity study: Smyth et al., Am. Ind. Hyg. Assoc. J. 30, 470 (1969). Review of toxicology and human exposure: Toxicological Profile for Boron (PB93-110674, 1992) 110 pp.
Properties: Colorless, odorless, transparent crystals, or white granules or powder; slightly unctuous to the touch. mp ~171°. Phase diagram for the B2O3.H2O system: Kracek et al., Am. J. Sci. 35A, 143 (1938). Volatile with steam. pH: 5.1 (0.1 molar). One gram dissolves in 18 ml cold, 4 ml boiling water, in 18 ml cold, 6 ml boiling alcohol, in 4 ml glycerol; soly in water is increased by HCl, citric or tartaric acids. Soly of boric acid in glycerol solns of various concns: Sciarra, Elliott, J. Am. Pharm. Assoc. Sci. Ed. 49, 116 (1960). LD50 orally in rats: 5.14 g/kg (Smyth).
Melting point: mp ~171°
Toxicity data: LD50 orally in rats: 5.14 g/kg (Smyth).
CAUTION: Potential symptoms of overexposure by ingestion or absorption are vomiting, diarrhea, abdominal cramps, erythematous lesions on skin and mucous membranes, circulatory collapse, tachycardia, cyanosis, delirium, convulsions, coma. Chronic use may cause borism (dry skin, eruptions, gastric disturbances). See E. Browning, Toxicity of Industrial Metals (Appleton-Century-Crofts, New York, 2nd ed., 1969) pp 90-97.
Use: For weatherproofing wood and fireproofing fabrics; as a preservative; manuf cements, crockery, porcelain, enamels, glass, borates, leather, carpets, hats, soaps, artificial gems; in nickeling baths; cosmetics; printing and dyeing, painting; photography; for impregnating wicks; electric condensers; hardening steel. Also used as insecticide for cockroaches and black carpet beetles.
Therap-Cat: Astringent, antiseptic.
Therap-Cat-Vet: Antibacterial and antifungal. Used chiefly in aqueous solution or powders for external use.
Keywords: Antiseptic/Disinfectant; Astringent.
Boric Anhydride Borneol Bornyl Acetate Bornyl Chloride Bornyl Salicylate

Boric acid
Structural formula Space-filling model
Boric acid crystals
CAS number 10043-35-3 YesY
PubChem 7628
ChemSpider 7346 YesY
EC number 233-139-2
KEGG D01089 YesY
ChEBI CHEBI:33118 YesY
ATC code S02AA03,D08AD
Jmol-3D images Image 1
Image 2
Molecular formula H3BO3
Molar mass 61.83 g mol−1
Appearance White crystalline solid
Density 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 (see text)
Molecular shape Trigonal planar
Dipole moment Zero
MSDS External MSDS
EU classification Harmful (Xn)
Repr. Cat. 2
R-phrases R60 R61
S-phrases S53 S45
NFPA 704
NFPA 704.svg
Flash point Non-flammable
LD50 2660 mg/kg, oral (rat)
Related compounds
Related compounds Boron trioxide
Supplementary data page
Structure and
n, εr, etc.
Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Boric acid, also called hydrogen borate, boracic acid, orthoboric acid and acidum boricum, is a weak 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.