Qualitativeldentificatlon of Potassium Ions Using Didymium Glasses In inorganic qualitative analysis the bright yellow color produced in the flame test hy sodium ions masks the less intense violet h e from potassium ions. The standard procedure to observe the emission from potassium is to place two small plates of dark-blue cobalt glass between the flame and the observer. Much persistence an the part of the student is needed to learn to perform this test correctly due to the low light transmission of the cobalt glass and the short duration of the potassium h e . Many students in my classes confess to being unable to judge the presence or absence of potassium and, in frustration, guess at the answer. The didymium glasses used by glass blowers, which contain arnixture of praseodymium and neodymium oxides, absorbs the intense sodium D line and little else. Students using didymium glasses had no trouble determining the presence or ahsence of potassium when their unknown contained sodium. A single pair of these glasses was effectively shared by a laboratory section. Wllliam F. Wood Humboldt State University Arcata. CA 95521
1024
Journal of Chemical Education
