2. What is the purpose of using the cobalt glass in the identification of sodium and potassium?
An intense yellow flame confirms the presence of sodium ions. [ The presence of potassium ions is indicated by a pale violet flame which appears reddish-violet through cobalt glass.
In a mixture that may contain Na and K salts, it could be difficult to see the pale violet flame of potassium through the intense yellow flame of sodium.
For identification of potassium, it is necessary to view the
flame through an optical filter to eliminate as far as possible the colors due to sodium, calcium, and other interfering ions. ]
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