Boric acid with ammonia

Boron nitride is an important 13-15 binary compound that exists in a number of different crystal forms. The hexagonal form is similar in structure to graphite (as shown in Figure 3.3) and is thermodynamically the most stable. It s soft and used as a lubricant and as a sheen-producing additive in cosmetics. It s synthesized by heating boron trioxide (BjOg) or boric acid with ammonia at 900 °C ... 

Preparation. Hexagonal boron nitride can be prepared by heating boric oxide with ammonia, or by heating boric oxide, boric acid, or its salts with ammonium chloride, alkaU cyanides, or calcium cyanamide at atmospheric pressure. Elemental nitrogen does not react with boric oxide even in the presence of carbon, though it does react with elemental boron at high temperatures. Boron nitride obtained from the reaction of boron trichloride or boron trifluoride with ammonia is easily purified. 

Alternatively, the compound can be prepared by heating boric oxide or boric acid with ammonium chloride or an alkali metal cyanide. Purified product can be obtained by high temperature reaction of boron halide with ammonia ... 

Kjeldahl nitrogen is the sum of nitrogenous organic compounds, free ammonia, and ammonium. In the presence of H2S04, K2S04, and selenium catalyzer organic nitrogen is converted to ammonium. Free ammonia is also converted to ammonium. After the addition of a base, the ammonia is distilled from an alkaline medium and absorbed in boric acid. The ammonia may be determined colorimetrically at 655 nm or by titration with a standard mineral acid... 

An exhaustive study has been carried out recently on the synthesis of BN nanotubes and nanowires by various CVD techniques.17 The methods examined include heating boric acid with activated carbon, multi-walled carbon nanotubes, catalytic iron particles or a mixture of activated carbon and iron particles, in the presence of ammonia. With activated carbon, BN nanowires are obtained as the primary product. However, with multi-walled carbon tubes, high yields of pure BN nanotubes are obtained as the major product. BN nanotubes with different structures were obtained on heating boric acid and iron particles in the presence of NH3. Aligned BN nanotubes are obtained when aligned multi-walled nanotubes are used as the templates (Fig. 40). Prior to this report, alignment of BN nanotubes was achieved by the synthesis of the BN nanotubule composites in the pores of the anodic alumina oxide, by the decomposition of 2,4,6-trichloroborazine at 750 °C.116 Attempts had been made earlier to align BN nanotubes by... 

Nitrogen is determined by the Kjeldahl method using Devarda s alloy. The complex and the alloy are placed in a standard Kjeldahl apparatus and the ammonia distilled off from a 7.5 M sodium hydroxide solution into 2% boric acid. The ammonia is titrated with standard hydrochloric acid using bromocresol green-methyl red as indicator. 

Boron compounds can be added in combination with other chemicals such as nitrogen and phosphorus. A solution containing sodium tripolyphosphate, boric acid, and ammonia provides a ready-to-use treatment on cellulose products such as plywood, fiberboard, and cardboard (87). The resulting products passed the British Standard 476, Section 6 (Fire Propagation test) Class 0 and Class I requirements of the British Standard Section 7 (Surface Spread of Flame). 

Exhaustive studies have been carried out on the synthesis of BN nanotubes and nanowires by various CVD techniques [225]. The methods examined include heating boric acid with activated carbon, multi-walled carbon nanotubes, catalytic iron particles or a mixture of activated carbon and iron particles, in the presence of ammonia. With activated carbon, BN nanowires are obtained as the primary prod-... 

Mobile liquid mp —58" bp +53". Stable up to 500 when pure and totally anhydrous, dj 0.824 df 0.898. nJJ 1.3821. Critical temp 252". Heat of vaporization 7.0 kcal. Mo) vo) at bp — 99.7 ml. Surface tension at mp — 31.09 dynes/cm. Parachor 207.9. Trouton s constant 21.4. Eotvds constant 2.0. Dipole moment in benzene at 25 — 0.50. Dissolves in water, giving a soln with strong reducing properties. Hydrolyzes slowly in aq soln yielding hydrogen, boric acid, and ammonia. 

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. 

Ammonium and Lithium Fluoroborates. Ammonia reacts with fluoroboric acid to produce ammonium fluoroborate (53). An alternative method is the fusion of ammonium bifluoride and boric acid (54) ... 

Gas streams can be analy2ed for ammonia by bubbling a measured quantity of the gas through a boric acid solution to absorb the ammonia. The solution is then titrated against sulfuric acid. This analysis is applicable only if other constituents in the gas stream do not react with boric acid. 

Ammonia and ammonium ions in industrial water streams, including waste-water streams, can be determined by either of two methods (ASTM Procedure D1426). In the first, the sample is buffered to a pH of 7.4 and distilled into a solution of boric acid where the ammonia nitrogen is deterrnined colorimetricaHy with Nessler reagents or titrated using standard sulfuric acid. 

TSR L, TSR L is a color-specified mbber, and the light amber color is produced by selecting clones with a low carotenoid content. After collection, the field latex is preserved with a mixture of ammonia and boric acid and subsequendy treated using 0.05% sodium metabisulfite to inhibit... 

The method may be applied to commercial boric acid, but as this material may contain ammonium salts it is necessary to add a slight excess of sodium carbonate solution and then to boil down to half-bulk to expel ammonia. Any precipitate which separates is filtered off and washed thoroughly, then the filtrate is neutralised to methyl red, and after boiling, mannitol is added, and the solution titrated with standard 0.1M sodium hydroxide solution ... 

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. 

Natural rubber latices in which the customary 0.7% ammonia content has been reduced to 0.2% in conjunction with the addition of a secondary preservative, either sodium pentachlorophenate, zinc diethyl dithiocarbamate or boric acid such latices have the advantage that the deammoniation process before manufacture is unnecessary. 

Ruzhentseva et al (6 +) converted hydralazine to ammonia by heating with zinc in sulfuric acid, forming 3 moles of ammonia per mole of hydralazine. The mixture was made alkaline and the ammonia was distilled into boric acid solution, which was then titrated. 

In the indirect method using boric acid (H3B03), the ammonia reacts with the boric acid, producing a partially neutralized salt of boric acid (H,BOj) ... 

The amount of standardized acid needed is proportional to the amount of ammonia that bubbled through. It is an indirect method because the ammonia is determined but not titrated. It is determined indirectly by titration of H2B03. In a direct titration, the analyte would be reacted directly with the titrant, as per the discussion in Section 4.6. The concentration of the boric acid in the receiving vessel does not enter into the calculation and need not be known. Equation (4.40) is used for the calculation. 

Adsorption of a specific probe molecule on a catalyst induces changes in the vibrational spectra of surface groups and the adsorbed molecules used to characterize the nature and strength of the basic sites. The analysis of IR spectra of surface species formed by adsorption of probe molecules (e.g., CO, CO2, SO2, pyrrole, chloroform, acetonitrile, alcohols, thiols, boric acid trimethyl ether, acetylenes, ammonia, and pyridine) was reviewed critically by Lavalley (50), who concluded that there is no universally suitable probe molecule for the characterization of basic sites. This limitation results because most of the probe molecules interact with surface sites to form strongly bound complexes, which can cause irreversible changes of the surface. In this section, we review work with some of the probe molecules that are commonly used for characterizing alkaline earth metal oxides. 

Procedure. Steam is passed through the steam distillation apparatus for 20-30 min. Check the performance by pipetting 5 ml ammonium-N standard solution into the distillation unit, add 1 drop octan-2-ol, 6 ml magnesium hydroxide suspension and steam distil the released ammonia into 5 ml boric acid solution in a 100-ml conical flask. After approximately 40 ml distillate has been collected over a 5-min period, wash the tip of the condenser into the distillate, add 2-3 drops mixed indicator solution and titrate with 0.005 M H SO until the colour changes from green to purple. A blank distillation/titra-tion is carried out using 5 ml ammonia-free water and subtracted from the standard titre to give a result which should be 5.00 ml. 

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