Acids boric

Boric acid, B(OH)3, is the archetype and primary source of oxo-boron compounds. It is also the normal end product of hydrolysis of most boron compounds. It forms flaky, white and transparent crystals, in which the BO3 units are joined to form planar layers by O-H- O hydrogen bonds, as shown in Fig. 13.5.1. 

Boric acid is a very weak monobasic acid (pA)a = 9.25). It generally behaves not as a Brpnsted acid with the formation of the conjugate-base [BO(OH)2], but rather as a Lewis acid by accepting an electron pair from an OH- anion to 

Thus this reaction is analogous to the acceptor-donor interaction between BF3 and NH3  

In the above two reactions, the hybridization of the B atom changes from sp2(reactant) to sp3(product). 

Partial dehydration of B(OH)3 above 373 K yields metaboric acid, HBO2, which consists of trimeric units B303(0H)3. Orthorhombic metaboric acid is built of discrete molecules B303(0H)3, which are linked into layers by O-H- O bonds, as shown in Fig. 13.5.2. 

Boric acid HgB03 (sasoline) or sodium tetraborate Na2B407.10 H20 are used as row materials for the manufacture of sodium perborate according to the character of the manufacturing process, which ma be chemical or electrochemical. 

Boric acid escapes with jets of steam called soffioni from the ground in central Tuscany in Italy. Steam with a pressure of 3 atm. and 190 °C, whioh contains around 0.1 % of borio acid, is first utilized in a steam turbine and then to concentrate the liquors afterwards it is condensed in water basins to a solu- 

The mineral boronatrocalcite i. e. double borate of sodium and oaloium Na20. 2 CaO. 5 B203.16 H20, is found mainly in Chile and Peru. It is decomposed with diluted hydroohloric acid in wooden vats and boric acid is obtained by crystallizing from dear leach liquor. In a similar way is also treated the mineral boraroite whioh is mainly magnesium borate and chloride MgCl2. 

BP Boric acid JP Boric acid PhEur Acidum boricum USPNF Boric acid 

Boracic acid boraic acid Borofax boron trihydroxide E284 orthoboric acid trihydroxyborene. 

Boric acid is used as an antimicrobial preservative in eye drops,cosmetic products, ointments, and topical creams. It is also used as an antimicrobial preservative in foods. 

Boric acid has also been used therapeutically in the form of suppositories to treat yeast infections, and in dilute concentrations as a mild antiseptic, although it has been superseded by more effective and less toxic disinfectants. See Section 14. 

Boric acid and borate have good buffering capacity and are used to control pH they have been used for this purpose in external preparations such as eye drops.  

In this preparation, borax, the sodium salt of tetraboric acid, is chosen as the source of boron. Although boron is decidedly a non-metal, still its acid-forming characteristics are not highly developed and its acids are readily displaced by strong acids from solutions of their salts. Thus tetraboric acid, H2B4O7, would be set free from borax by hydrochloric acid, but the acid which actually crystallizes is the more highly hydrated orthoboric acid, H3BO3. 

Explain the relations between orthoboric acid, metaboric acid, tetraboric acid, and boric anhydride. Experiment Place a few grams of boric acid on a watch glass upon the steam table (100-110°) and leave for hour. What is formed What would be formed if the acid were heated to 140° Suspend a little of the acid in a loop of platinum wire, and heat in the Bunsen flame. What is formed  

Experiment Place a few crystals of boric acid in a small porcelain dish, cover them with 5 cc. of alcohol, set fire to it. Observe the color of the edges of the flame, especially when stirring and when the alcohol is almost burned out. Repeat, using borax instead of the boric acid, and again, using borax moistened with concentrated sulphuric acid. 

What causes the green color of the flame, and why is it not observed with borax alone  

Repeat if necessary the last part of Experiment 1, noticing the color imparted to the flame while the orthoboric acid is first melting, and again when a clear bead of boric anhydride is obtained. 

Preparation from Borax. Dissolve 12 g of borax in 25 ml of water in a beaker with heating. What is the reaction of the solution to litmus and what is it due to Write the molecular and net-ionic equations of the borax hydrolysis reaction. How can the hydrolysis of borax be facilitated Calculate what amount of a 25% hydrochloric acid solution is needed to prepare boric acid from 12 g of borax. Measure off the calculated amount of acid, and taking a small excess amount, pour the acid into the hot borax solution. Let the solution cool slowly. What substance crystallizes Filter off the crystals on a Buchner funnel, dry them between filter paper sheets, and recrystallize them from hot water, guiding yourself by the table of solubilities. Determine the product yield (in per cent). Keep the prepared boric acid for the following experiments. 

Properties. 1. Prepare 2-3 ml of a saturated boric acid solution and test it with litmus and curcuma paper. 

Evaporate the boric acid solution in a porcelain bowl until almost dry, add a little methanol, and light the evolving vapour. What is the flame colour due to  

Pour a drop of concentrated sulphuric acid and a drop of glycerin onto a watch glass and add a small amount of borax. Carefully stir the mixture with the eye of a platinum wire and introduce it into the flame of a burner. How is the flame coloured Write the equation of the reaction. 

Hydrogen orthoborate. Red atoms are oxygen white atoms are hydrogen and yellow atom is boron. PUBLISHERS RESOURCE CROUP 

The most common method of producing boric acid is by treating the relatively abundant borax with hydrochloric or sulfuric acid and crystallizing out the boric acid that forms in the reaction. A less common method of preparation involves the treatment of borax brine solutions with a chelating agent that binds to the borates present in the brine, which can then be converted to boric acid. 

The most common sources of boric acid are hot springs and volcanic sites such as the mineral springs at Vichy and Aix-la-Chapelle in France and Wiesbaden in Germany, around the volcanic regions of Tuscany in Italy, and in dry lakes of California and Nevada, such as California s Borax Lake. 

Boric acid was once used as an ingredient in talcum and diaper powders and in salves for diaper rashes because of its antiseptic properties. The compound was eventually banned for such uses, however, when regulators decided that it was too toxic if it accidentally entered the body through an open wound or by being swallowed. 

Some other important applications of boric acid include the following  

Rio Tinto Borax at Boron, California, is perhaps the single largest producer of borate chemicals in the world with a capacity of over 1.6 billion pounds per year. This company was formed from a merger of Luzenac (French) with Dampier (Australian) and US Borax (USA). Other borate-producing companies are American Borate (in Nevada) and Searles Valley Mineral (California). 

The US borate capacity is about 2.6 billion pounds per year while Turkey has a capacity of about 3.5 billion pounds annually. The United States exports about half of its production. 

Borax is used to make glass fibers for tire cord. 

Borax is used to produce boric acid, which is used to make zinc borate hydrate (a flame-retardant additive used in rubber compounding). 

Boric acid is reacted directly with zinc oxide to produce zinc borate hydrate, a commonly used flame retardant. 

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Boron trichloride, BCI3. Colourless mobile liquid, m.p. — 107°C, b.p. 12-5°C. Obtained directly from the elements or by heating B2O3 with pels in a sealed tube. The product may be purified by distillation in vacuo. It is extremely readily hydrolysed by water to boric acid. TetrachJoroborates containing the BCJ4 " ion are prepared by addition of BCI3 to metal chlorides. 

Boron III) oxide, B2O3, is obtained by ignition of boric acid. Combines with water to reform B(0H)3. The fused oxide dissolves metal oxides to give borates. 

Prepared by condensing p-chlorophenol with phlhalic anhydride in sulphuric acid solution in the presence of boric acid. The chlorine atom is replaced by hydroxyl during the condensation. It can also be prepared by oxidation of anthraquinone or 1-hydroxyanthraquinone by means of sulphuric acid in the presence of mercury(ll) sulphate and boric acid. 

Strong oxidising acids, for example hot concentrated sulphuric acid and nitric acid, attack finely divided boron to give boric acid H3CO3. The metallic elements behave much as expected, the metal being oxidised whilst the acid is reduced. Bulk aluminium, however, is rendered passive by both dilute and concentrated nitric acid and no action occurs the passivity is due to the formation of an impervious oxide layer. Finely divided aluminium does dissolve slowly when heated in concentrated nitric acid. 

Boron trioxide, B2O3 is the anhydride of boric acid, H3BO3 and can be prepared by heating the acid ... 

Boron trioxide is not particularly soluble in water but it slowly dissolves to form both dioxo(HB02)(meta) and trioxo(H3B03) (ortho) boric acids. It is a dimorphous oxide and exists as either a glassy or a crystalline solid. Boron trioxide is an acidic oxide and combines with metal oxides and hydroxides to form borates, some of which have characteristic colours—a fact utilised in analysis as the "borax bead test , cf alumina p. 150. Boric acid. H3BO3. properly called trioxoboric acid, may be prepared by adding excess hydrochloric or sulphuric acid to a hot saturated solution of borax, sodium heptaoxotetraborate, Na2B407, when the only moderately soluble boric acid separates as white flaky crystals on cooling. Boric acid is a very weak monobasic acid it is, in fact, a Lewis acid since its acidity is due to an initial acceptance of a lone pair of electrons from water rather than direct proton donation as in the case of Lowry-Bronsted acids, i.e. 

In the presence of glycerol or mannitol (polyhydroxo compounds) boric acid behaves as a much stronger acid the reaction can be represented as ... 

Titration. The solution of ammonia absorbed in saturated boric acid may now be titrated as an alkali directly with 0 025 A.HCl (best obtained by dilution of commercially available standard A.HCl in a graduated flask). Three drops of indicator (mixed methyl-red/methyl-ene-blue being most satisfactory) are added to the liquid in the receiver and the 0 025 A.HCl run in from an accurate burette. 

Alkyl borates. By heating boric acid with excess of the alcohol the water formed in the reaction is removed by fractional distillation as an azeo tropic mixture with the alcohoi, for example ... 

This reaction is due to the combination of two da hydroxyl groups of the compound with the boric acid to form a much stronger monobasic acid ... 

If it is desired to employ fluoboric acid HBF4, it can be prepared by adding 100 g. of A.R. boric acid in small proportions to 325 g. of A.R. hydrofluoric acid (40 p>er cent. HF) cooled in ice the hydrofluoric acid is contained in a Bakelite beaker, a beaker coated with wax or in a lead vessel. A simple container may also be prepared by cutting of the neck of the wax bottle (in which the hydrofluoric acid is supplied) with a large e.g., a butcher s ) knife which has been slightly warmed. One-third of the above solution should be employed in the preparation. Handle unth great care. 

The fluoboric acid may be prepared by adding 92 g. of A.R. boric acid slowly and with constant stirring to 250 g. of hydrofluoric acid (40-48 per cent.) in a copjier, lead or a waxed-lined beaker. A lead rod may be used for stirring. All operations should be carried out in a fume cupboard. 

Caustic alkali in the eye. Proceed as for acid in the eye, but wash with 1 per cent, boric acid solution in place of bicarbonate solution. 

Boric acid is also an important boron compound with major markets in textile products. Use of borax as a mild antiseptic is minor in terms of dollars and tons. Boron compounds are also extensively used in the manufacture of borosilicate glasses. Other boron compounds show promise in treating arthritis. 

With sodium hydroxide as the base boron of the alkylborane is converted to the water soluble and easily removed sodium salt of boric acid... 

H3B03 orthoboric acid (or boric acid) H4P2O3 peroxodiphosphoric acid... 

X mL of 0.2M NaOH Added to 100 mL of Stock Solution (0.04M Acetic Acid, 0.04M H3PO4, and 0.04M Boric Acid)... 

Another type of demasking involves formation of new complexes or other compounds that are more stable than the masked species. For example, boric acid is used to demask fluoride complexes of tin(IV) and molybdenum(VI). Formaldehyde is often used to remove the masking action of cyanide ions by converting the masking agent to a nonreacting species through the reaction ... 

Boric acid F, glycol, mannitol, tartrate, and other hydroxy acids... 

Turmeric paper (gives a rose-brown coloration with boric acid) wash tbe ground root of turmeric with water and discard tbe washings. Digest with alcohol and filter, using the clear filtrate to impregnate white, unsized paper, which is then dried. 

Alkali metals Moisture, acetylene, metal halides, ammonium salts, oxygen and oxidizing agents, halogens, carbon tetrachloride, carbon, carbon dioxide, carbon disul-flde, chloroform, chlorinated hydrocarbons, ethylene oxide, boric acid, sulfur, tellurium... 

Although not commonly used, thermometric titrations have one distinct advantage over methods based on the direct or indirect monitoring of plT. As discussed earlier, visual indicators and potentiometric titration curves are limited by the magnitude of the relevant equilibrium constants. For example, the titration of boric acid, ITaBOa, for which is 5.8 X 10 °, yields a poorly defined equivalence point (Figure 9.15a). The enthalpy of neutralization for boric acid with NaOlT, however, is only 23% less than that for a strong acid (-42.7 kj/mol... 

In this experiment phosphate is determined by singlecolumn, or nonsuppressed, ion chromatography using an anionic column and a conductivity detector. The mobile phase is a mixture of n-butanol, acetonitrile, and water (containing sodium gluconate, boric acid, and sodium tetraborate). 

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