The purity of the methyl fluorone was controlled by the melting point of its acctyl derivative. Methyl fluorone is stable in the solid state, but not in ethyl alcohol solution. The solubility of the pure methyl fluorone which we prepared is 0.095% in ethyl alcohol, only a fifth of the solubility of the product used by P. Wenger, R. Duckert and Cl. Blancpain. We prefer the filter paper technique to that of a spotting plate or micro test tube. We were led to reject the use of tartaric solutions pH 4. recommended by the abovementioned authors, and prefer solutions in 1 N HCl. In employing the filter paper impregnated with a drop of the saturated alcoholic solution of methyl fluorone, antimony and molybdenum produce a colour change from yellow to red. germanium and tin a slight change from yellow to orange. If the filter paper is impregnated with a drop of acid solution (I N HCl) of methyl fluorone in alcohol, the sharpness of the reaction of antimony and molybdenum is appreciably increased, whilst the colouration due to germanium and tin do not interfere. By treating the spot with a few drops of H 2O 2 + HCl, the colouration due to molybdenum disappears and the reaction for antimony, which was selective, now becomes specific for this element.