Describe the principle and procedure of the flame test.

Here's the answer to your question:

The flame test is a qualitative analytical procedure used to detect the presence of certain metal ions based on the characteristic color they impart to a flame.

Principle:
When metal salts are heated in a flame, the metal ions absorb energy, causing their electrons to jump to higher energy levels (excited state). These excited electrons are unstable and quickly return to their original lower energy levels (ground state), emitting light of specific wavelengths. The color of the emitted light is unique to each metal, allowing for its identification.

Procedure:

1. Clean a platinum or nichrome wire by dipping it in concentrated hydrochloric acid ($\text{HCl}$) and heating it in a non-luminous flame until no color is observed.
2. Dip the clean wire into concentrated $\text{HCl}$ again.
3. Touch the wet wire to a small amount of the solid sample to pick up some of the substance.
4. Introduce the wire with the sample into the hottest part of a non-luminous Bunsen flame.
5. Observe and record the characteristic color of the flame.
6. Clean the wire thoroughly before testing another sample to avoid contamination.