Boric acid fluorides

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 ... 

Manufacture. Fluoroborate salts are prepared commercially by several different combinations of boric acid and 70% hydrofluoric acid with oxides, hydroxides, carbonates, bicarbonates, fluorides, and bifluorides. Fluoroborate salts are substantially less corrosive than fluoroboric acid but the possible presence of HF or free fluorides cannot be overlooked. Glass vessels and equipment should not be used. 

Eluorspar assay may be completed by fluoride determination alone, because the mineralogical grouping rarely iacludes fluorine minerals other than fluorite. Calcium can be determined as oxalate or by ion-selective electrodes (67). SiUca can be determined ia the residue from solution ia perchloric acid—boric acid mixture by measuriag the loss ia weight on Aiming off with hydrofluoric acid. Another method for determining siUca ia fluorspar is the ASTM Standard Test Method E463-72. 

Various other soft materials without the layer—lattice stmcture are used as soHd lubricants (58), eg, basic white lead or lead carbonate [598-63-0] used in thread compounds, lime [1305-78-8] as a carrier in wire drawing, talc [14807-96-6] and bentonite [1302-78-9] as fillers for grease for cable pulling, and zinc oxide [1314-13-2] in high load capacity greases. Graphite fluoride is effective as a thin-film lubricant up to 400°C and is especially useful with a suitable binder such as polyimide varnish (59). Boric acid has been shown to have promise as a self-replenishing soHd composite (60). 

Diphenylamine can also be produced by passing the vapors of aniline over a catalyst such as alumina, or alumina impregnated with ammonium fluoride (17). The reaction is carried out at 480°C and about 700 kPa (7 atm). Conversion per pass, expressed as parts diphenylamine per 100 parts of reactor effluent, is low (18—22%), and the unconverted aniline must be recycled. Other catalysts disclosed for the vapor-phase process are alumina modified with boron trifluoride (18), and alumina activated with boric acid or boric anhydride (19). 

The presence of inorganic salts may enhance or depress the aqueous solubiUty of boric acid it is increased by potassium chloride as well as by potassium or sodium sulfate but decreased by lithium and sodium chlorides. Basic anions and other nucleophiles, notably borates and fluoride, greatly increase boric acid solubihty by forrning polyions (44). 

Boric acid and fluoride ion react to form a series of fluroborates where OH is displaced by (see Fluorine compounds, inorganic—Boron, FLUOROBORic acid). Stepwise formation of the ions fluorotrihydroxyborate [32554-53-3] BF(OH) 3, difluorodihydroxyborate [32554-52-2] BF2(OH) 2 trifluorotrihydroxyborate [18953-00-9] BF3(OH) 3, proceeds rapidly in acidic solutions, but tetrafluoroborate [14874-70-5], forms slowly (56). A... 

The sulfide ions in Ln S, LnSF were detenuined after sample s treatment by titrated solution in a week-acid media. Excess iodine was titrated with Na S Oj solution. Fluoride ions in LnF, LnSF were detenuined after sample s treatment by H BO titrated solution. After the removal of BF excess boric acid was converted into the stronger mannitoboric acid, which was titrated potentiometrically with NaOFI solution. 

Fluor-, of or combined with fluorine, fluoro-, fluo-, fluoride of (see instances following),. ammonium, n. ammonium fluoride, -an-thenchinon, n. fluoranthenequinone. -anti-mon, n. antimony fluoride, -arson, n. arsenic fluoride, -baryum, n. barium fluoride, -benzol, n. fluorobensene, fluobenaene. -bor, n. boron fluoride. -borsMure, /. fluo-boric acid. -brom, n. bromine fluoride, -chrom, n. chromium fluoride, -eisen, n. iron fluoride. 

Fluoride ion, and weak acids and bases do not interfere, but nitrate, nitrite, perchlorate, thiocyanate, chromate, chlorate, iodide, and bromide do. Since analysis of almost all boron-containing compounds requires a preliminary treatment which ultimately results in an aqueous boric acid sample, this procedure may be regarded as a gravimetric determination of boron. 

In 1888, Turpin prepd a series of cool expls which were permissable, by incorporating materials such as alkali chlorides, Na or K bicarbonate (up to 50% content), fluorides, acetates, oxalates, Ba carbonate. 10H2O, chromates, hyposulfites, stannic acid, boric acid, borates, etc, in the expls listed above eg, a) K chiorate 45, double salt of Ca and K acetochlorate 35, tar 18, charcoal 5, and alkali bicarbonate or oxalate I5ps b) K chlorate 15, double salt of K and Amm chlorobichromate 35 K or Na nitrate 10, tar 18, charcoal 5, and K or Na bicarbonate 15ps... 

Barker and Kahn have made a detailed study of the exchange in carbon tetrachloride media using the isotope " Sb to label the Sb(III) species. The reaction was carried out in sealed ampoules covered with A1 foil in the presence of an atmosphere of He or Ar gas. The separation method used involved complexing the Sb(V) with fluoride (brought about by addition of ethanol, HCl and HF) followed by precipitation of the Sb(III) with H2S and finally addition of boric acid and HCl, removal of the CCI4, and treatment with H2S to remove the Sb(V). Zero-time exchange was 5 %. 

About 0.1-2.0g of wet sediment was placed into a Teflon vessel and 3mL of concentrated nitric acid, 0.5mL concentrated perchloric acid, and 4mL concentrated hydrofluoric acid were added. The closed vessels were kept at room temperature for lh. The samples were then placed in a pressure cooker and heated for lh on a hot plate at a temperature of 300°C. After cooling, the vessels were uncapped and the samples evaporated to 2mL on a hot plate at 250°C. After cooling, 3mL concentrated nitric acid was added. To complex the fluorides, lg boric acid was added to each sample. The solutions were transferred to lOOmT volumetric flasks and adjusted to volume with deionized water. Inorganic arsenic standards, having the same acid content as the samples, were used for calibration. 

The crude product contains hydrogen fluoride which is removed by the addition of boric acid to the wash water (H3BO3 -f-4HF — HBF4 + 3H2O). The sodium fluoride disposes of... 

In dilute aqueous solutions, the boric acid molecule remains undissociated B(0H)3 but in concentrated solutions, B(OH)4 and complex polyborate anions, such as B303(0H)4 are formed. Reactions with fluoride ion produce fluoroborates, BF(OH)3, BF2(OH)2, BFsCOH), BF4, and B3O3F63 in stepwise sequence. It forms similar polyions with amides and borates. 

Silicate analysis is not without problems. If measurement of silicon is not required, it may be volatilized off as silicon tetrafluoride, using hydrofluoric acid, although some calcium may be lost as calcium fluoride. Alternatively, sodium carbonate-boric acid fusions may be employed. Where possible, final solutions are made up in hydrochloric acid. 

Alkali tetrafluoroborates are stable white salts which can easily be prepared starting from boric acid and alkali fluoride in concentrated hydrochloric acid.63... 

The alkali niobates are most conveniently prepared by the action of caustic alkalis on niobic acid or on solutions of niobium oxytri-fluoride. Other compounds of niobic acid and bases are generally prepared by fusing niobic add with the oxide, hydroxide, carbonate, or other salt of the metal. Occasionally double decomposition of a soluble alkali niobate and a soluble salt of the metal has been employed. Larsson s method1 consists in predpitating a solution of potassium niobate with a salt of a metal the dried predpitate is fused for thirty-six hours at a high temperature with boric acid, and the melt is boiled with water to which hydrochloric acid has been added. The residue consists of crystals of the insoluble niobate of the metal, usually the metaniobate. 

Mercury(II) is also a very effective masking agent for Cl-, Br- and I- as well as S03 . Masking of fluoride ions is important analytically and this can be done effectively by transforming it into a variety of stable coordination compounds, e.g. boric acid yields BF4-, beryllium gives BeF42-and a number of stable octahedral complexes are formed with Al, Fe, Ti, Zr, Nb and Ta. 

The term demasking is used rather broadly to describe any process which reverses the process of masking. Control of the pH can be used to mask calcium ions in admixture with copper(II) whereby, in sufficiently acid solution, the latter is precipitated by oxine whereas the concentration of Ox- is reduced sufficiently by protonation to prevent the precipitation of calcium oxinate. Raising the pH will increase [Ox-] and both metals can now be precipitated. A more obvious example is the addition of fluoride ions to form the very stable complex anion SnF62- and so to mask tin(IV) against its precipitation as SnS2- Addition of boric acid will give BF4- and so demask the tin. 

Enamels - [BARIUMCOMPOUNDS] (Vol3) - [ALUMINUMCOMPOUNDS - ALUMINIUMOXIDE(ALUMINA) - CALCINED,TABULAR, AND ALUMINATE CEMENTS] (Vol2) - [TIN COMPOUNDS] (Vol 24) -aluminum fluoride in [FLUORINE COMPOUNDS,INORGANIC - ALUMINUM](Vol 11) -antimony compds in [ANTIMONY COMPOUNDS] (Vol 3) -borate in [BORON COMPOUNDS - BORON OXIDES, BORIC ACID AND BORATES] (Vol 4) -boric oxide in prepn of [BORON COMPOUNDS - BORON OXIDES, BORIC ACID AND BORATES] (Vo 14) -lithium for [LITHIUM AND LITHIUM COMPOUNDS] (Vol 15)... 

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