Sodium tetrahydroborate

The elements listed in the table of Figure 15.2 are of importance as environmental contaminants, and their analysis in soils, water, seawater, foodstuffs and for forensic purposes is performed routinely. For these reasons, methods have been sought to analyze samples of these elements quickly and easily without significant prepreparation. One way to unlock these elements from their compounds or salts, in which form they are usually found, is to reduce them to their volatile hydrides through the use of acid and sodium tetrahydroborate (sodium borohydride), as shown in Equation 15.1 for sodium arsenite. 

A schematic illustration of a typical inlet apparatus for separating volatile hydrides from the analyte solution, in which they are generated upon reduction with sodium tetrahydroborate. When the mixed analyte solution containing volatile hydrides enters the main part of the gas/liquid separator, the volatiles are released and mix with argon sweep and makeup gas, with which they are transported to the center of the plasma. The unwanted analyte solution drains from the end of the gas/liquid separator. The actual construction details of these gas/liquid separators can vary considerably, but all serve the same purpose. In some of them, there can be an intermediate stage for removal of air and hydrogen from the hydrides before the latter are sent to the plasma. 

Some elements (S, Se, Te, P, As, Sb, Bi, Ge, Sn, Pb) are conveniently converted into their volatile hydrides before passed into the plasma. The formation of the hydrides by use of sodium tetrahydroborate (sodium borohydride) can be batchwise or continuous. 

Sodium tetrahydroborate is quite soluble ia Hquid ammonia and soluble to some extent ia a variety of other solvents. It is appreciably soluble only ia... 

Despite the fact that many boron hydride compounds possess unique chemical and physical properties, very few of these compounds have yet undergone significant commercial exploitation. This is largely owing to the extremely high cost of most boron hydride materials, which has discouraged development of all but the most exotic appHcations. Nevertheless, considerable commercial potential is foreseen for boron hydride materials if and when economical and rehable sources become available. Only the simplest of boron hydride compounds, most notably sodium tetrahydroborate, NajBHJ, diborane(6), B2H, and some of the borane adducts, eg, amine boranes, are now produced in significant commercial quantities. 

Sodium Tetrahydroborate, Na[BH ]. This air-stable white powder, commonly referred to as sodium borohydride, is the most widely commercialized boron hydride material. It is used in a variety of industrial processes including bleaching of paper pulp and clays, preparation and purification of organic chemicals and pharmaceuticals, textile dye reduction, recovery of valuable metals, wastewater treatment, and production of dithionite compounds. Sodium borohydride is produced in the United States by Morton International, Inc., the Alfa Division of Johnson Matthey, Inc., and Covan Limited, with Morton International supplying about 75% of market. More than six million pounds of this material suppHed as powder, pellets, and aqueous solution, were produced in 1990. 

A flow-injection system with electrochemical hydride generation and atomic absorption detection for the determination of arsenic is described. This technique has been developed in order to avoid the use sodium tetrahydroborate, which is capable of introducing contamination. The sodium tetrahydroborate (NaBH ) - acid reduction technique has been widely used for hydride generation (HG) in atomic spectrometric analyses. However, this technique has certain disadvantages. The NaBH is capable of introducing contamination, is expensive and the aqueous solution is unstable and has to be prepared freshly each working day. In addition, the process is sensitive to interferences from coexisting ions. 

Sodium tetrahydroborate (III) (sodium borohydride ), 1 per cent w/v. Dissolve sodium hydroxide pellets (5.0g) in 300 mL of de-ionised water and cool. Add sodium tetrahydroborate(III) (5.0 g) directly to the sodium hydroxide solution and make up the total volume to 500 mL with de-ionised water. Shake the solution thoroughly and filter through a Whatman No. 541 filter paper. (The resulting solution is stable for at least one week.)... 

Little information exists on low-T precipitation of borides from solution. Chromium, cobalt and platinum borides are the only ones claimed to have been obtained from aqueous solution ". Ni2B and C02B are precipitated from a solution of nickel or cobalt acetates by adding a solution of sodium tetrahydroborate ". The formation of these borides at RT gives amorphous products. Hence, heat treatment at 300-700°C leads to crystalline NijB as the main constituent, although the average composition of the precipitate corresponds to NijB . 

In a general method for the selective reduction of ketones in presence of conjugated enones, this is effected by the tetrahydroborate in 1 1 methanol-dichloromethane at 75°C. In favourable cases the reaction is carried out at 20°C in dichloromethane containing a little acetic acid. It should be noted that addition of acetic acid to sodium tetrahydroborate in methanol-dichloromethane leads to vigorous evolution of much hydrogen. 

Contact of a drop of glycerol with a flake of sodium tetrahydroborate leads to ignition, owing to thermal decomposition of the latter at above 200°. Other glycols and methanol also react exothermally, but do not ignite. 

Tetraphosphorus decaoxide Organic liquids Sodium hydride Dimethylformamide Sodium tetrahydroborate Dimethylformamide Sodium Dimethylformamide Sulfinyl chloride Dimethylformamide Triethylaluminium Dimethylformamide... 

To effect reduction to the parent heterocycle, a solution of the dichloro compound in DMF was being added to a hot solution of sodium tetrahydroborate in the same solvent, when a violent explosion occurred [1,2]. This may have arisen either from interaction of the dichloro compound with the solvent, or from the known instability of hot solutions of the tetrahydroborate in DMF. Use of aqueous diglyme as an alternative solvent [3] would only be applicable to this and other hydrolytically stable halides [2],... 

Sodium tetrahydroborate See Sodium tetrahydroborate Acids See other INORGANIC ACIDS... 

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