Neuere Beiträge zur katalytischen Bestimmung von Vanadinspuren mit Hilfe eines Landolt-Systems

Summary

The inhibition period of the bromate-bromide-ascorbic acid system is shortened by the catalytic action of vanadium. The bromine set free at the endpoint and which is scarcely visible to the unaided eye, is indicated at p_H = 5 by rhodamine B, cresyl violett or trypaflavine, whose fluorescence is extinguished by traces of bromine. An excellent indication is obtained with a mixture of rhodamine B and trypan red, whose fluorescence color is changed. Acridine red, that indicates the endpoint with a quenching effect, can be employed not only at p_H 5 but also at p_H 2. Traces of vanadium in a concentration range of 0.1–100μg/5 ml can be determined with analytical precision by means of the simultaneous comparation method when the above fluorescence indicators are employed. This paper also contains statements regarding the effect of foreign ions on the catalyzed reaction.