boric acid


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boric acid,

any one of the three chemical compounds, orthoboric (or boracic) acid, metaboric acid, and tetraboric (or pyroboric) acid; the term often refers simply to orthoboric acid. The acids may be thought of as hydrates of boric oxide, B2O3. Orthoboric acid, H3BO3 or B2O3·3H2O, is colorless, weakly acidic, and forms triclinic crystals. It is fairly soluble in boiling water (about 27% by weight) but less so in cold water (about 6% by weight at room temperature). When orthoboric acid is heated above 170°C; it dehydrates, forming metaboric acid, HBO2 or B2O3·H2O. Metaboric acid is a white, cubic crystalline solid and is only slightly soluble in water. It melts at about 236°C;, and when heated above about 300°C; further dehydrates, forming tetraboric acid, H4B4O7 or B2O3·H2O. Tetraboric acid is either a vitreous solid or a white powder and is water soluble. When tetraboric or metaboric acid is dissolved it reverts largely to orthoboric acid. The major uses of the boric acids are in forming other boron compounds and in borate salts, e.g., boraxborax
or sodium tetraborate decahydrate
, chemical compound, Na2B4O7·10H2O; sp. gr. 1.73; slightly soluble in cold water; very soluble in hot water; insoluble in acids.
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. A dilute water solution of boric acid is commonly used as a mild antiseptic and eyewash. Boric acid is also used in leather manufacture, electroplating, and cosmetics. Boric acid can be crystallized from an acidified borax solution. It occurs as the mineral sassolite in the Tuscan region of Italy, where it is also recovered from hot springs and vapors. In the United States boric acid is recovered from brines from Searles Lake in California.

Boric Acid

 

(also orthoboric acid), H3BO3, a weak inorganic tribasic acid; colorless crystals in the form of flakes. Density, 1.48 g/cm3. Moderately soluble in cold water and more soluble in hot water, which is used to purify it (solubility per 100 g H2O: 2.66 g at 0° C; 39.7 g at 100° C). Boric acid is soluble in alcohol and other organic substances. When heated it loses water, turning first into metaboric acid, HBO2, and then into boric anhydride, B2O3. The salts of boric acid—borates—are derived mainly from various polyboric acids with the general formula nB2O3 · mH2O. When boric acid reacts with alcohols in the presence of concentrated H2SO4 (for bonding water), esters—for example, boric methyl ester—are formed:

3CH3OH + H3BO3 = B(OCH3)3 + 3H2O

When ignited, the esters of boric acid burn with a green flame, which is a qualitative reaction for boron. Boric acid is found in nature in hot springs as a dissolved form and as vapor. It evolves in the form of the mineral sassolite from hot springs and excrustations in volcanic craters. The industrial significance of natural boric acid is relatively small; it is usually obtained during the processing of borates.

Large quantities of boric acid are used to produce enamel wares. In laboratory practice boric acid is used in the preparation of buffer systems. In medicine it is used as an antiseptic. Aqueous solutions of boric acid serve as mouth and throat rinses and eyewashes. Ointments, pastes, and powders with boric acid and boric alcohol (boric acid dissolved in alcohol) are administered for some skin diseases (boric alcohol is also prescribed as ear drops). Boric acid is an ingredient in contraceptives.

V. L. VASILEVSKII

boric acid

[¦bȯr·ik ′as·əd]
(inorganic chemistry)
H3BO3 An acid derived from boric oxide in the form of white, triclinic crystals, melting at 185°C, soluble in water. Also known as boracic acid; orthoboric acid.

boric acid

1. a white soluble weakly acid crystalline solid used in the manufacture of heat-resistant glass and porcelain enamels, as a fireproofing material, and as a mild antiseptic. Formula: H3BO3
2. any other acid containing boron
References in periodicals archive ?
The selectivity value of the reverse osmosis membrane according to borate and polyborate ions is significantly higher than for boric acid, since the dimensions of the latter are close to the dimensions of water molecules (Fig.
Microwave carbothermal reduction is fast and effective for synthesizing well crystallized nanostructured equiaxial boron carbide, starting with inexpensive and simple precursors such as boric acid and carbon black, without any reaction agent as magnesium or aluminum, or cobalt as catalyst.
(2006, 2008), who found > 80% mortality in the application of boric acid to vegetation against a laboratory-reared population of Ae.
The ototoxic effect of boric acid solutions applied into the middle ear of guinea pigs.
Out of five different compositions, we have found three glass samples composed of 80% boric acid and 20% potassium carbonate; 75% boric acid and 25% potassium carbonate; 70% boric acid and 30% potassium carbonate by XRD technique.
Also it has been proposed [10, 23] that the formation of oxides of Ce(III) and Ce(IV) occurs using boric acid as accelerator; this formation could be due to the reduction of boric acid resulting in local alkalinization.
Boric acid for recurrent vulvovaginal candidiasis: the clinical evidence.
Boric acid varied from 40% to 100% N statin 50% Terconazole 70% Flurytosme 90% Itraconazole 90.9% Clotrimazole 36% Ketnconazole 50% Fluconazole 28.6%-92.3% Buconazole 100% Miconazole 100% by Tori Hudson, ND
Thus only an impression is left on the starch structure indicating presence of boric acid which will further be confirmed using other techniques in the paper.
In different experiments one litre liming float was taken in a beaker, stirred and treated by weak acids namely; phosphoric acid, oxalic acid, acetic acid, boric acid and formic acid to achieve pH between 6.2-6.6 and then passed through the absorbent prepared from the raw trimmings of cattle hides keeping the quantity of absorbent constant i.e 500 g in each experiment.