Test for Magnesium with p-Nitrobenzeneazoresorcinol The Effect of Diverse Ions

Abstract

HE qualitative test for magnesium employing the reagent T p-nitrobenzeneazoresorcinol, commonly called S. and 0. reagent, which produces a sky-blue lake in a magnesium solution made alkaline with sodium hydroxide, was first proposed by Suitsu and Okuma (6) who claimed that 0.002 mg. of magnesium can be thereby detected.Ruigh (4) found that excess of ammonium salts destroys the sensitivity of the reagent and that nickel and cobalt interfere by givin somewhat similar blue lakes, and stated that after the rernova? of the heavy metals by precipitation as sulfides the test is absolutely characteristic. Eegriwe (1) corroborated the interference of nickel and cobalt and added chromic ion to the list. Stone ( 5 ) stated that ammonium salts and organic matter d e crease the sensitivity. Newell, Pike, and Ficklen (3) claimed that the test is not so specific as might be desired and that the sensitivity is only 2 parts per million. They stated that most of the cations of group I1 and all those of group I11 interfere, but that only a few of the anions cause trouble.Engel ( 2 ) modified the test by causing a blue stain to be formed on the surface of a casserole upon evaporation of the solution and detected 3 X 10-8 gram of magnesium. His test is valid TABLE