Untersuchung des winkler'schen ammoniakmessverfahrens unter anwendung der dampfraumanalyse und glaselektrode

A detailed study of Winkler's method shows that the partial pressure of ammonia in a 0.1 or 0.01 N solution for analysis is significantly lowered only by a boric acid content of 4%; under such conditions there is no danger of loss of ammonia. However, the ammonia can be determined with greater certainty, speed and accuracy by direct titration without addition of boric acid. In the titration of boric acid-free ammonia solutions, the equivalence point lies within the pH range of methyl red; if boric acid (4%) is present, methyl orange should be used. Literature data on the choice of indicator are shown to be false.