Sodium borohydride stabilised solution

A study showed that 0.05 M solutions stored in a open bottle and in the presence of sodium borohydride (used as a stabiliser) were the only ones that could be stored. 

Stabilised sodium borohydride solutions, (a) 1.00 m Aqueous solution dissolve 0.8 g of sodium hydroxide in 150 ml of water, add 7.71 g of sodium borohydride (assuming 98% purity) and stir to dissolve. Dilute the solution to 200 ml and filter. (b) 2.50 m Aqueous solution repeat the procedure under (a) exactly but increasing the amount of sodium borohydride to 19.25g. (c) 1.00 m Ethanol solution dissolve 0.8 g of sodium hydroxide in 10 ml of water, dilute to 200 ml with absolute ethanol and add 7.71 g of sodium borohydride. Stir until solution is effected and filter. 

A stabilised solution suitable for catalytic reduction was prepared by dissolving 4.0 g of sodium borohydride powder in a mixture of 95 ml of absolute ethanol and 5 ml of 2 m sodium hydroxide and filtering the resulting solution. This solution is best prepared freshly the day of use for maximum catalyst reproducibility but may be utilised satisfactorily for up to 5 days if kept refrigerated. Formation of small amounts of sediment under refrigeration is not harmful. 

Sodium borohydride Solid pellets or preferably an aqueous solution, stabilised with NaOH, of concentration geared to the hydride generator. 

This solid, which is stable in dry air up to 300°, is a less powerful reducing agent than lithium aluminium hydride, from which it differs also by being soluble in hydroxylic solvents and to a lesser extent in ether-type solvents. Sodium borohydride forms a dihydrate melting at 36-37°, and its aqueous solutions decompose slowly unless stabilised to above pH 9 by alkali. (For example, a useful sodium borohydride solution is one that is nearly saturated at 30-40° and containing 0.2% sodium hydroxide.) Its solubility in water is 25, 55 and 88g per lOOmL... 

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