High-precision titrimetry of boric acid: Some calculations and measurements of inflection points

High-precision coulometric titrations of boric acid

“…The precision of the me th od , expressed as a s tandard deviation of a s in gle de te rmination is 0.0033 perce nt. It can therefore be infe rred t.hat th e di scre pan cy found by Le Duigou and Lau er be twee n co ulo metric and co nve ntional acidimetry of boric acid does not have its origin in coulometric titration, and is apparently not inh erent to thi s syste m, since our in vestigations were condu c ted under conditions which were similar to those us ed by these authors [7].…”

“…The effect of mannitol on the strength of boric acid has been investigated quite extensively [15][16][17][18][19][20][21][22]. Much of this work can be summarized from the analytical standpoint as follows: (a) boric acid becomes stronger as the mannitol concentration increases; (b) in concentrated solutions, anomalous conductance values indicate association; (c) electrolytes in solution affect the boric acid hydrolytic equilibrium.…”

“…Howe ver, thi s method is somewhat empirical in nature , partic ularly with re s pect to the amount of polyol required for titration and moreo ver, is generally precise to only a fe w parts p e r th ousand. Le Duigou and Lauer recently re ported a procedure for the coulome tric de te rmination of boron [7]. Th eir precision for l50-mg samples of boric acid was on th e orde r of 0.02 pe rce nt.…”

Potentiometric Titrations

“…Finally, the authors (139) demonstrate that an inflection point of minimum slope might be observed in strong acid-base titration if the titrant is very dilute. Le Duigon and Lauer (54) have applied Meites and Goldmann's results to the determination of pKa for the boric acid-mannitol complex. Conventional calculations resulted in a concentration-dependent constant, but the inclusion of the dilution effect gave a true pKa = 5.…”