In the cobalt nitrate charcoal cavity test, heating a certain white powder with cobalt nitrate solut — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Zinc salts leave a white residue of $ZnO$ upon heating. When moistened with cobalt nitrate and reheated, a double oxide of zinc and cobalt ($ZnO \cdot CoO$ or $ZnCo_2O_4$) is formed, which is green in color and known as Rinmann's green.