Pure Boric Acid Crystals , Best Boric Acid For Ramming Mass / Glass Ceramics

Powder orthoboric acid H3BO3 used in manufacturing of ramming

mass and glass ceramics

►Specification

►Origin of 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 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.

► Molecular and crystal structure

  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. The molecular point group is C3h.

Crystalline boric acid consists of layers of B(OH)3 molecules held together by

hydrogen bonds of length 272 pm. The distance between two adjacent layers is

318 pm.

    Based on mammalian median lethal dose (LD50) rating of 2,660 mg/kg body

mass, boric acid is only poisonous if taken internally or 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 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 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. However, a review of 784 human poisonings with boric acid (10–88 g)

reported no fatalities, with 88% of cases being asymptomatic."Toxicology

Long-term exposure to boric acid may be of more concern, causing kidney damage

and eventually kidney failure (see links below). Although it does not appear to be

carcinogenic, studies in dogs have reported testicular atrophy after exposure to 32

mg/kg bw/day for 90 days. This level is far lower than the LD50.

    According to the boric acid IUCLID Dataset published by the European

Commission, boric acid in high doses shows significant developmental toxicity and

teratogenicity in rabbit, rat, and mouse fetuses as well as cardiovascular defects,

skeletal variations, and mild kidney lesions. As a consequence in the 30th ATP to

EU directive 67/548/EEC of August 2008, the European Commission decided to

amend its classification as reprotoxic category 2, and to apply the risk phrases R60

(may impair fertility) and R61 (may cause harm to the unborn child).

      At a 2010 European Diagnostics Manufacturing Association (EDMA) Meeting,

several new additions to the Substance of Very High Concern (SVHC) candidate

list in relation to the Registration, Evaluation, Authorisation and Restriction of

Chemicals Regulations 2007 (REACH) were discussed. Following the registration

and review completed as part of REACH, the classification of Boric Acid CAS

10043-35-3 / 11113-50-1 is listed from 1 December 2010 is H360FD (May damage

fertility. May damage the unborn child.)

 ►Preparation

     Boric acid may be prepared by reacting borax (sodium tetraborate

decahydrate) with a mineral acid, such as hydrochloric acid:

Na2B4O7·10H2O + 2 HCl → 4 B(OH)3 [or H3BO3] + 2 NaCl + 5 H2O

It is also formed as a by product of hydrolysis of boron trihalides and

diborane

B2H6 + 6 H2O → 2 B(OH)3 + 6 H2

BX3 + 3 H2O → B(OH)3 + 3 HX (X = Cl, Br, I)

 ►Application in Industry

1. As part of some proprietary formulas

   In electroplating, boric acid is used as part of some proprietary formulas. One suc

h known formula calls for about a 1 to 10 ratio of H3BO3 to NiSO4, a very small por

tion of sodium lauryl sulfate and a small portion of H2SO4.

2. Manufacturing of ramming mass

   It is also used in the manufacturing of ramming mass, a fine silica-

containing powder used for producing induction furnace linings and ceramics.