| Abstract |
Determination of the content of fluoroboric acid occasionally poses difficulties in practice. The method generally used is awkward. The fluoroboric acid (HBF sub 4 ) is hydrolyzed, and the single components fluoric acid (HF) and boric acid (H sub 3 BO sub 3 ) are determined separately. From the results one then calculates the theoretically possible concentration of HBF sub 4 and of excess H sub 3 BO sub 3 or HF. Direct titration of fluoroboric acid is considered impossible, in contrast to the other mineral acids. Concentrations of 110 to 130% are found with this method. It would be of practical significance if step titration could also be applied to the study of metal fluoroborate solutions. Since the equivalence points in this titration are at pH 7 and pH 9, disturbances are to be expected due to the existing heavy metals. The potentiometric titration curves therefore exhibit a shape which differs considerably from that of free HBF sub 4 . The change in the curves leads us to conclude that during titration there is not only precipitation of the metals as hydroxides, but other reactions also occur between the solution partners. The effect of the metals can be eliminated, however, so that direct titration can also be used for the metal fluoroborate solution. It is combined with determination of the metal concentration and thus results in a total analysis of the solution. Potentiometric titration curves are presented for fluoroboric acid, copper fluoroborate, tin fluoroborate, and lead-tin fluoroborate, and results are discussed. 1 reference, 4 figures, 4 tables. (ERA citation 10:013885) |
