Methyl borate, volatilization

Gas Fluxing. The methyl borate azeotrope is used as a gaseous flux for welding and brazing. The Gas Flux Co., Elyria, Ohio, manufactures the methyl borate azeotrope for their own use. The azeotrope acts as a volatile source of boric oxide and is introduced directly into the gas stream as a flux for the surfaces to be joined in the welding process. The European automobile industry is the primary user of this process, though there may be some usage for this purpose in the United States. 

B203 Pt Useful for oxides and silicates. Principal advantage is that flux can be completely removed as volatile methyl borate ( CH30]3B) by several treatments with HC1 in methanol. 

Boric acid alone is more rapidly eliminated as the volatile methyl borate, B(OCH3)3, (highly poisonous). If much boric acid is present, two treatments with CH3OH and HC1 may be required. 

If borate is present and fluoride is absent, the former may be removed by repeated evaporation to dryness on a water bath with a mixture of 5 ml methanol (inflammable ) and 10 ml concentrated HC1. The borate slowly volatilizes as methyl borate, (CH3)3B03 (POISONOUS). 

If borate is found to be present, transfer the centrifugate from Group II to a small crucible, heat to expel hydrogen sulphide (do not evaporate to dryness), and allow to cool. Add 2-3 drops concentrated hydrochloric acid and 5-6 drops methanol, and heat on a water bath until the solution is almost evaporated to dryness. Repeat the addition of hydrochloric acid and methanol, and evaporate to dryness on the water bath. If borate is the only interfering ion, dissolve the residue in 2 ml of 2m hydrochloric acid, and continue the analysis for cations. The borate is volatilized as methyl borate (poisonous). 

The conversion of boron compounds to trialkoxyboranes is the basis for a widely used historic prospecting procedure for identification of borate minerals. By adding a mineral acid and methanol to a ground mineral sample and then igmting the mixture, one can observe whether it bums with the green flame of volatile methyl borate. 

Volatilization is usually utilized for separating individual trace elements from the sample before the determination. The methods based on volatilization are concerned mainly with non-metallic and amphoteric elements which have high vapour pressure in the elemental form (e.g., chlorine, bromine, sulphur), or in compounds with halogen, hydrogen, or oxygen. Other volatilization methods exist for the separation of certain elements, such as the distillation of boron as methyl borate. 

This reagent, stable in water in slightly alkaline conditions, is ideal for reducing sugars. The aldehyde function is reduced to a primary alcohol and the ketone function to a mixture of secondary alcohol epimers. The simplest treatment after reduction consists in eliminating the sodium on a cation exchanger column, then reaction with boric acid in the form of volatile methyl borate by co-evaporation with methanol. The alditol is recovered by evaporation of the solvent to dryness or lyophilization. 

Another approach proposed for proteetion of eomposites is a vapour phase treatment (Murphy et al., 2002 Vinden et ai, 1990). Certain esters of boron have high vapour pressures making them readily volatile and suitable for vapour phase treatment. For example trimethyl borate boils at 65°C so the treatment requires both timber and pressure vessel to be heated to at least this temperature. Trimethyl borate will reaet with the adsorbed moisture in the wood to yield methyl aleohol (whieh is reeovered) and borie acid that remains in the wood ... 

As catalysts for this reaction, inorganic acids having low volatility and high stability at the temperatures necessary may be used. Phosphoric acid or phosphates, boric acid, boric anhydride or borates may be used either in the molten state, supported on inert carriers, or as the solid salts.108 The use of excess amounts of carbon monoxide and high pressure are specified. Thus, when one volume of methyl chloride and 8 volumes of carbon monoxide are passed, as a mixture, over sodium metaphosphate on pumice at 700° to 800° C. a conversion to 10 or 15 per cent of acetyl chloride is obtained. The use of pressure enables much higher yields to be obtained. 

PHN, ACE, PYR, CHY, B[a]P, and benzo[e]pyrene were separated in a 50 mM borate buffer (pH 9) containing a mixture of 20 mM neutral methyl-(3-cyclodextrin (M(3CD) and 25 mM anionic sulfobutylether-(3-cyclodextrin (SB(3CD) at 30 kV and 30°C. " B[a]P and benzo[e]pyrene were successfully resolved with the other compounds in under 11 min in a 50-cm effective length of capillary without micelles in the mobile phase. The system was also less sensitive to temperature and separation potential. LIE detection with excitation at 325 nm at 2.5 mW from a He/Cd laser coupled to an optical fiber allowed for detection limits in the sub ppb range. The method described above was applied to the analysis of contaminated soil that had been extracted by supercritical CO2 for 20 min at 120°C and collected in methanol/DCM. ° Of the 16 EPA PAH mixtures, eleven compounds were detectable in the low ppb range. Ten of the eleven detectable compounds were measured in the soil extract. When compared to RP-HPLC, CE values were slightly lower but only six compounds were detected by HPLC-FLD. No direct relationship between PAH molecular size, polarity, or volatility with migration order was observed and B[b]F/B[k]F isomers were readily separated. 

Acid or alkaline solutions of borates are most commonly to be tested. Consequently the boric acid should be converted beforehand to its volatile methyl ester, b.p. 65° C, which is distilled into the fluoride-containing reagent solution. The ester is then saponified ... 

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