Explain charcoal cavity test?

The charcoal cavity test is a test used in chemistry to identify basic radicals in a salt by observing color changes during heating in a charcoal cavity.

In this test, a small cavity is made in a piece of charcoal using a knife or needle. A mixture of the salt and sodium carbonate is placed in the cavity. The mixture is then moistened slightly and heated using a blowpipe flame. The metal part of the salt reduces to its metallic form, and a color or deposit may be seen in the cavity, depending on the metal present. This test helps detect metals such as lead, copper, and zinc. 

For example, lead gives a gray metallic bead, copper gives a red coating, and zinc forms a white coating. It is an old but effective qualitative method for identifying metal ions. The test is especially used in inorganic qualitative analysis in school and college laboratories.

The charcoal cavity test is simple, low-cost, and gives quick results, making it ideal for basic chemistry identification experiments.