IN connexion with a problem of biosynthesis, we had occasion to prepare a sample of ethanol in which some of the α-hydrogen atoms were replaced by deuterium. This was done by heating propionic acid with deuterium sulphate, recovering the labelled propionic acid and treating its silver salt with bromine in carbon tetrachloride; the resulting ethyl bromide was hydrolysed by heating with water or with aqueous silver sulphate. Absence of deuterium from the methyl group of this alcohol was proved by oxidation to acetic acid with aqueous potassium permanganate. The silver salt of this acetic acid contained very little deuterium (0·03—0·06 per cent excess), and this was not due to exchange with the aqueous medium during oxidation, for a parallel experiment on ordinary ethanol in a heavy water medium also afforded deuterium-free silver acetate. Analysis of the labelled ethanol as ethyl 3 : 5-dinitrobenzoate indicated a deuterium excess of 40 'atom per cent' on the two α-hydrogen atoms. The sample was thus a mixture of CH3CH2OH, CH3CHDOH and CH3CD2OH.