MOST text-books of organic chemistry contain the statement that formic acid and formates owe their reducing character to the presence of an aldehyde group in their molecule, quoting in support of this their ability to reduce ammoniacal silver nitrate to the metal; while this reaction certainly is given by aldehydes, it is not specific for this class of compound since many other acids, such as tartaric or citric, similarly reduce silver nitrate. The reduction of mercuric chloride to mercurous chloride by formates likewise offers no support for the aldehyde theory, since aldehydes in general, including formaldehyde, cannot effect this change. Actually, formates give none of the reactions which characterize an aldehyde; thus they fail to restore the colour to Schiff's reagent, produce no reaction with 2.4 dinitrophenylhydrazine hydrochloride, and above all do not reduce Fehling's solution, which is probably the most specific of all aldehyde reagents.