Why must the flame test wire be dipped in dilute hydrochloric acid and heated until it burns colourlessly before each sample?

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Question

Why must the flame test wire be dipped in dilute hydrochloric acid and heated until it burns colourlessly before each sample?

Accepted Answer

Residue from an earlier sample would give a false flame colour — Award 1 mark. Traces of sodium in particular produce a strong yellow that masks weaker colours, so the wire is cleaned until no colour of its own remains.

Answer

Heating converts the wire into a metal oxide that holds the sample

Answer

The acid makes the wire able to conduct electricity

Answer

The acid stops the wire from melting in the flame

Answer

Residue from an earlier sample would give a false flame colour

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