A purple ring at the junction of two layers on adding $\alpha$-naphthol and concentrated $\mathrm{H}{}_2\mathrm{SO}{}_4$ (Molisch test) is given by

Concentrated $\mathrm{H}{}_2\mathrm{SO}{}_4$ dehydrates carbohydrates to furfural derivatives, which condense with $\alpha$-naphthol to give a purple ring. Ethanol, ethanoic acid and ethyl ethanoate are not carbohydrates and give no such ring.