電量滴定法による微量ホウ素の定量法

概要

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Fundamental studies on the coulometric titration method of a small amount of boric acid using mannitol have been carried out. 0.2 M NaBr solution was used as an electrolytic solution and the end point of neutralization was determined with a pH meter having a glass electrode. The results obtained are summerised as follows. (1) It is necessary to add more than 3.5 g of mannitol to 50 ml of the electrolytic solution. (2) In the quantitative determination of boric acid, the electrolytic solution containing a sufficient amount of mannitol was adjusted to a definite pH, and then the sample solution of boric acid was added to it. pH value which decreased was brought back to the initial value by the constant current electrolysis. The time of this electrolysis was measured and the amount of boron was calculated therefrom. The satisfactory results were obtained when the initial and final pH values were in the range of 6.36.8. (3) Under the above conditions, 150 μeq. of boric acid could be determined within an error of several %. (4) Boron (10540 γ) in borax could be determined with several % of error.
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