Boric acid in aqueous solution

Direction of borate structures by specific cations is also illustrated by the formation of the unusual nonaborate anion in the presence of the imidazo-lium, [C3H7N2], and guanidinium, [C(NH2)3], cations [42]. The reaction of imidazole with three molar equivalents of boric acid in aqueous solution results in the spontaneous formation of the imidazolium salt of the [B90i2(OH)6] anion, shown in Fig. 11, associated with three [C3H7N2] ... 

Diols and polyols can participate in equilibria with boric acid in aqueous solution. The stability of polyolborates is determined by the number of OH groups in cis positions. Complexes with polyols are more stable than with diols, and 1,2-diol complexes are more stable than their 1,3-diol counterparts (Table 10) since the resulting five-membered chelate ring is unstrained.75120 In the case of 1,3,5-triols stable cage-like structures (5) and (6) are favored. Open-chain or five-membered cyclic polyols form more stable chelate complexes than their six-membered counterparts.120 Thus, chelates from alditols and ketohexoses are more stable than the corresponding aldose chelates (Table 10). Many polyols allow quantitative titrimetric determination of boric acid. Of these, mannitol remains the most widely used reagent on the basis of availability, cost and ease of handling.75... 

Ward G.K. and Millero F.J. (1974) The effect of pressure on the ionization of boric acid in aqueous solutions from molal volume data. J. Sol. Chem. 3, 417-430. 

All crystallization reactions were performed at 170°C during 7-14 days, in a stainless steel autoclave equipped with a device for stirring. Hydrogels were obtained by dissolving boric acid in aqueous solution containing tetralkylammonium hydroxides (from Fluka) and RPE grade sodium hydroxide (from Carlo Erba), followed by... 

Solubility OF Boric Acid in Aqueous Solutions of Hydrochloric, Sulphuric, and Nitric Acids at 26°. 

Solubility of Boric Acid in Aqueous Solutions of Urea, Acetone, AND OF Propyl Alcohol at 25°. 

This product is pure enough for use in preparing boron trifluoride. If a clean, pure preparation of ammonium fluoborate is required for another purpose, the best way to make it is to mix the theoretical amounts of ammonium acid fluoride and boric acid in aqueous solution in a plastic dish, and evaporate to crystallization on a steam bath. ... 

Polyborates and pH Behavior. Whereas boric acid is essentially monomeric in dilute aqueous solutions, polymeric species may form at concentrations above 0.1 M. The conjugate base of boric acid in aqueous systems is the tetrahydroxyborate [15390-83-7] anion sometimes called the metaborate anion, B(OH) 4. This species is also the principal anion in solutions of alkali metal (1 1) borates such as sodium metaborate,... 

The parent acid, H3B03, functions as a weak acid in aqueous solution, possessing an ionization constant of about 6 x 10-, at 25°C in dilute solution. As its concentration increases, the ionization constant increases markedly. Kolthoff (220) investigated this effect by electrical conductivity and emf measurements, obtaining values of 4.6 x 1010 and 408 x 10 1 for boric acid concentrations of 0.1 M and 0.75 M respectively at 18°C. These results were attributed to the formation of tetraboric acid. 

Ammonia, alkylamines, and other proton acceptor species can react with boric acid in aqueous or alcoholic solutions to form a wide range of crystalline nomnetal borate salts. Borate salts of aprotic nomnetal cations, such as quaternary ammonium cations, have also been characterized. The ammonium borates are significant commercial products, and the recognition that both protic and aprotic nonmetal cations can stabilize unusual borate anions has led to increased interest in the study of this area. 

The paraffin is oxidized by air between 150 and 200 C in the presence of 0.1 per cent weight potassium permanganate and 5 per cent weight boric add, Hunting the conversion to 15 to 20 per cent. Unconvened paraffins are recovered by distillation and recycled, and the borates are hydrolysed. They are then neutralized with caustic soda to remove acidic compounds and the alcohols are separated by distillation. Boric add in aqueous solution is recovered and recyded in turn. 

A variety of chelates of B-compounds are formed by polyols. For instance, phenyl glycol may be used to extract sodium borate from dilute aqueous solutions. Recently, 2-ethyl-hexanol in kerosene was used to extract boric acid from aqueous solutions (57). 

Boric add acts as a Lewis acid in aqueous solution. 

Boric acid in aqueous or glycerine solutions, and borax (biborate of soda) are sometimes used, but care is necessary in employing these substances, as any excess is liable to decompose the soap. 

Boric acid, B(OH)3, is used as a mild antiseptic. What is the pH of a 0.021 M aqueous solution of boric acid What is the degree of ionization of boric acid in this solution The hy-dronium ion arises principally from the reaction... 

The interactions of boric acid or borate with shikimic and quinic acids in aqueous solutions have been studied by B- and C-n.m.r., with various species in... 

In aqueous solution, all the sodium peroxoborates dissociate for the most part into boric acid, or its anion, and hydrogen peroxide. Peroxoborate species are also present in these solutions, depending on the pH and the concentration for the species type. The nature of these species has been extensively examined by classical physicochemical methods (13), by nmr, and by Raman spectroscopy (14—17). Both monomeric and polymeric species are usually present. There is some evidence (18) suggesting that these peroxoborates are more reactive than hydrogen peroxide alone under similar conditions. 

Monobasic aluminum acetate is dispensed as a 7% aqueous solution for the topical treatment of certain dermatological conditions, where a combination of detergent, antiseptic, astringent, and heat-dispersant effects are needed (12). The solution, diluted with 20—40 parts water, is appHed topically to the skin and mucous membranes as a wet dressing (13). Burrow s solution, prepared from aluminum subacetate solution by the addition of a specific amount of acetic acid, is also used as a topical wet dressing. Standards of purity and concentration have been estabHshed for both pharmaceutical aluminum acetate solutions (13). Each 100 mL of aluminum subacetate solution yields 2.30—2.60 g of aluminum oxide and 5.43—6.13 g of acetic acid upon hydrolysis. For the Burow s solution, each 100 mL yields 1.20—1.45 g of aluminum oxide and 4.25—5.12 g of acetic acid. Both solutions may be stabilized to hydrolysis by the addition of boric acid in amounts not to exceed 0.9% and 0.6% for the subacetate and Burow s solutions, respectively (13). 

Determination of borate as nitron tetrafluoroborate Discussion. Boric acid (100-250 mg) in aqueous solution may be determined by conversion into tetrafluoroboric acid and precipitation of the latter with a large excess of nitron [see Section 11.11(E)] as nitron tetrafluoroborate, which is weighed after drying at 110°C. The accuracy is about 1 per cent. 

It may be noted that very weak acids, such as boric acid and phenol, which cannot be titrated potentiometrically in aqueous solution, can be titrated conductimetrically with relative ease. Mixtures of certain acids can be titrated more accurately by conductimetric than by potentiometric (pH) methods. Thus mixtures of hydrochloric acid (or any other strong acid) and acetic (ethanoic) acid (or any other weak acid of comparable strength) can be titrated with a weak base (e.g. aqueous ammonia) or with a strong base (e.g. sodium hydroxide) reasonably satisfactory end points are obtained. 

Aldehydes are obtained in 86% and 75% yields, respectively, from benzoic acid on refluxing for 6 hours and from nicotinic acid on standing at room temperature for 24 hours with bis(N-methylpiperazino)alane in tetrahydro-furan [963]. Reduction of 3-fluorosalicylic acid with 2% sodium amalgam in aqueous solution containing sodium chloride, boric acid and p-toluidine gave, at 13-15°, a Schiff base which on hydrolysis with hydrochloric acid and steam distillation afforded 3-fluorosalicylaldehyde in 57% yield [136. The purpose of p-toluidine is to react with the aldehyde as it is formed and protect it from further reduction. 

Numerous methods for the synthesis of salicyl alcohol exist. These involve the reduction of salicylaldehyde or of salicylic acid and its derivatives. The alcohol can be prepared in almost theoretical yield by the reduction of salicylaldehyde with sodium amalgam, sodium borohydride, or lithium aluminum hydride by catalytic hydrogenation over platinum black or Raney nickel or by hydrogenation over platinum and ferrous chloride in alcohol. The electrolytic reduction of salicylaldehyde in sodium bicarbonate solution at a mercury cathode with carbon dioxide passed into the mixture also yields saligenin. It is formed by the electrolytic reduction at lead electrodes of salicylic acids in aqueous alcoholic solution or sodium salicylate in the presence of boric acid and sodium sulfate. Salicylamide in aqueous alcohol solution acidified with acetic acid is reduced to salicyl alcohol by sodium amalgam in 63% yield. Salicyl alcohol forms along with -hydroxybenzyl alcohol by the action of formaldehyde on phenol in the presence of sodium hydroxide or calcium oxide. High yields of salicyl alcohol from phenol and formaldehyde in the presence of a molar equivalent of ether additives have been reported (60). Phenyl metaborate prepared from phenol and boric acid yields salicyl alcohol after treatment with formaldehyde and hydrolysis (61). 

Very acidic (high valent) cations will readily hydrolyse in aqueous solution, often even at low pH. These cations tend to form the polymeric metal oxide chains mentioned previously. This hydrolysis can be controlled by addition of boric acid (see Sec. 3.2.4.4) and forms the basis of a technique referred to as liquid phase deposition. This method can be reasonably included in the more general term of chemical solution deposition, and is treated, although not comprehensively, in this book. Ref 5 deals more thoroughly with this technique and describes many cases of SiOi as well as some examples of several other oxides not covered in this chapter. 

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