12/26/2018 Boric acid - Wikipedia Boric acid Boric acid, also called hydrogen borate, boracic acid, orthoboric acid and acidum boricum, is a weak, monobasic Lewis acid of boron, which is often used as an antiseptic, insecticide, flame retardant, neutron absorber, or precursor to other chemical Boric acid 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. Contents Occurrence Preparation Properties Reactions Molecular and crystal structure Toxicology Uses Names Industrial Medical IUPAC names Insecticidal Boric acid Preservation Trihydrooxidoboron pH buffer Other names Lubrication Orthoboric acid, Nuclear power Pyrotechnics Boracic acid, Agriculture Sassolite, Recreational Optibor, References Borofax, Trihydroxyborane, Further reading Boron(III) hydroxide, External links Boron Trihydroxide Identifiers Occurrence CAS Number 10043-35-3 (http://w ww.commonchemistr Boric acid, or sassolite, is found mainly in its free state in some volcanic districts, for example, in the Italian region of Tuscany, the y.org/ChemicalDetail. Lipari Islands and the US state of Nevada. In these volcanic settings it issues, mixed with steam, from fissures in the ground. It is aspx?ref=10043-35- also found as a constituent of many naturally occurring minerals – borax, boracite, ulexite (boronatrocalcite) and colemanite. Boric 3) acid and its salts are found in seawater. It is also found in plants, including almost all fruits.[2] 3D model Interactive image (htt Boric acid was first prepared by Wilhelm Homberg (1652–1715) from borax, by the action of mineral acids, and was given the name (JSmol) ps://chemapps.stolaf. sal sedativum Hombergi ("sedative salt of Homberg"). However borates, including boric acid, have been used since the time of the edu/jmol/jmol.php?m ancient Greeks for cleaning, preserving food, and other activities. odel=OB%28O%29 O) Preparation Interactive image (htt Boric acid may be prepared by reacting borax (sodium tetraborate decahydrate) with a mineral acid, such as hydrochloric acid: ps://chemapps.stolaf. edu/jmol/jmol.php?m Na2B4O7·10H2O + 2 HCl → 4 B(OH)3 [or H3BO3] + 2 NaCl + 5 H2O odel=%5BOH%2B% 5D%3D%5BB-%5 [3] It is also formed as a by product of hydrolysis of boron trihalides and diborane: D%28O%29O) B2H6 + 6 H2O → 2 B(OH)3 + 6 H2 ChEBI CHEBI:33118 (http s://www.ebi.ac.uk/ch BX3 + 3 H2O → B(OH)3 + 3 HX (X = Cl, Br, I) ebi/searchId.do?che biId=33118) Properties ChEMBL ChEMBL42403 (http Boric acid is soluble in boiling water. When heated above 170 °C, it dehydrates, forming metaboric acid (HBO2): s://www.ebi.ac.uk/ch embldb/index.php/co H3BO3 → HBO2 + H2O mpound/inspect/ChE MBL42403) Metaboric acid is a white, cubic crystalline solid and is only slightly soluble in water. Metaboric acid melts at about 236 °C, and ChemSpider 7346 (http://www.che when heated above about 300 °C further dehydrates, forming tetraboric acid, also called pyroboric acid (H2B4O7): mspider.com/Chemic 4 HBO2 → H2B4O7 + H2O al-Structure.7346.ht ml) The term boric acid may sometimes refer to any of these compounds. Further heating (to about 330 °C)[4] leads to boron trioxide. ECHA InfoCard 100.030.114 (https:// https://en.wikipedia.org/wiki/Boric_acid 1/5 12/26/2018 Boric acid - Wikipedia H2B4O7 → 2 B2O3 + H2O echa.europa.eu/subs tance-information/-/s There are conflicting interpretations for the origin of the acidity of aqueous boric acid solutions. Raman spectroscopy of strongly ubstanceinfo/100.03 − [5] alkaline solutions has shown the presence of B(OH)4 ion, leading some to conclude that the acidity is exclusively due to the 0.114) abstraction of OH− from water:[5][6][7][8] EC Number 233-139-2 − + −10 E number E284 (preservatives) B(OH)3 + H2O B(OH)4 + H (K = 7.3×10 ; pK = 9.14) KEGG D01089 (http://www.k or more properly expressed in the aqueous solution: egg.jp/entry/D01089) − B(OH) + 2 H O B(OH) + H O+ 3 2 4 3 PubChem CID 7628 (https://pubche This may be characterized[6][7][8] as Lewis acidity of boron toward OH−, rather than as Brønsted acidity. m.ncbi.nlm.nih.gov/c ompound/7628) Polyborate anions are formed at pH 7–10 if the boron concentration is higher than about 0.025 mol/L. The best known of these is UNII R57ZHV85D4 (http the 'tetraborate' ion, found in the mineral borax: s://fdasis.nlm.nih.go − + 2− v/srs/srsdirect.jsp?re 4[B(OH)4] + 2 H [B4O5(OH)4] + 7 H2O gno=R57ZHV85D4) Boric acid makes an important⇌ contribution to the absorption of low frequency sound in seawater.[9] InChI Reactions SMILES With polyols such as glycerol and mannitol the acidity of the solution is increased. With mannitol for example the pK decreases to Properties 5.15. This is due to the formation of a chelate, [((OH) C H O ) B]−, and this feature is used in analytical chemistry.[10] 4 6 8 2 2 Chemical BH3O3 formula Boric acid dissolves in anhydrous sulfuric acid:[10] Molar mass 61.83 g·mol−1 + − − B(OH)3 + 6H2SO4 → 3H3O + 2HSO4 + B(HSO4)4 Appearance White crystalline solid Boric acid reacts with alcohols to form borate esters, B(OR) where R is alkyl or aryl. A dehydrating agent, such as concentrated 3 Density 1.435 g/cm3 sulfuric acid is typically added:[11] Melting point 170.9 °C (339.6 °F; B(OH)3 + 3 ROH → B(OR)3 +3 H2O 444.0 K) Boiling point 300 °C (572 °F; Molecular and crystal structure 573 K) Solubility in 2.52 g/100 mL (0 °C) The three oxygen atoms form a trigonal planar geometry around the boron. The B-O bond length is 136 pm and the O-H is 97 pm. water 4.72 g/100 mL The molecular point group is C3h. (20 °C) Crystalline boric acid consists of layers of B(OH)3 molecules held together by hydrogen bonds of length 272 pm. The distance 5.7 g/100 mL (25 °C) between two adjacent layers is 318 pm.[10] 19.10 g/100 mL (80 °C) 27.53 g/100 mL (100 °C) Solubility in Soluble in lower other solvents alcohols moderately soluble in pyridine very slightly soluble in acetone hydrogen bonding (dashed lines) log P -0.29[1] The unit cell of boric acid allows boric acid molecules to form parallel layers in the solid state Acidity (pKa) 9.24, 12.4, 13.3 Conjugate base Borate Toxicology Magnetic -34.1·10−6 cm3/mol susceptibility (χ) Based on mammalian median lethal dose (LD50) rating of 2,660 mg/kg body mass, boric acid is only poisonous if taken internally or Structure inhaled in large quantities. The Fourteenth Edition of the Merck Index indicates that the LD50 of boric acid is 5.14 g/kg for oral Molecular shape Trigonal planar dosages given to rats, and that 5 to 20 g/kg has produced death in adult humans. For comparison's sake, the LD50 of salt is reported to be 3.75 g/kg in rats according to the Merck Index. According to the Agency for Toxic Substances and Disease Registry, "The Dipole moment Zero minimal lethal dose of ingested boron (as boric acid) was reported to be 2–3 g in infants, 5–6 g in children, and 15–20 g in adults. Pharmacology [...] However, a review of 784 human poisonings with boric acid (10–88 g) reported no fatalities, with 88% of cases being ATC code S02AA03 (WHO (htt asymptomatic."[12] ps://www.whocc.no/a Long-term exposure to boric acid may be of more concern, causing kidney damage and eventually kidney failure (see links below). tc_ddd_index/?code Although it does not appear to be carcinogenic, studies in dogs have reported testicular atrophy after exposure to 32 mg/kg bw/day =S02AA03)) D08AD [13] (WHO (https://www.w for 90 days. This level is far lower than the LD50. hocc.no/atc_ddd_ind ex/?code=D08AD)) Hazards https://en.wikipedia.org/wiki/Boric_acid 2/5 12/26/2018 Boric acid - Wikipedia According to the CLH report for boric acid published by the Bureau for Chemical Substances Lodz, Poland, boric acid in high doses Safety data See: data page shows significant developmental toxicity and teratogenicity in rabbit, rat, and mouse fetuses as well as cardiovascular defects, sheet [14] skeletal variations, and mild kidney lesions. As a consequence in the 30th ATP to EU directive 67/548/EEC of August 2008, the EU classification Xn European Commission decided to amend its classification as reprotoxic category 2, and to apply the risk phrases R60 (may impair (DSD) (outdated) fertility) and R61 (may cause harm to the unborn child).[15][16][17][18][19] R-phrases R60 R61 At a 2010 European Diagnostics Manufacturing Association (EDMA) Meeting, several new additions to the Substance of Very High (outdated) Concern (SVHC) candidate list in relation to the Registration, Evaluation, Authorisation and Restriction of Chemicals Regulations S-phrases S53 S45 2007 (REACH) were discussed. Following the registration and review completed as part of REACH, the classification of Boric Acid (outdated) CAS 10043-35-3 / 11113-50-1 is listed from 1 December 2010 is H360FD (May damage fertility. May damage the unborn NFPA 704 child.)[20][21] 0 1 0 Uses Flash point Non-flammable Lethal dose or concentration (LD, LC): Industrial LD50 (median 2660 mg/kg, oral The primary industrial use of boric acid is in the manufacture of monofilament fiberglass usually referred to as textile fiberglass.