Several α-hydrazino carboxylic acids and their m-nitrobenzal hydrazones have been prepared and characterized. The latter and two of the former have not been previously reported. The α-hydrazino acids were found to react with ninhydrin to yield Ruhemann's purple, but in much lower yield than the corresponding amino acids. However, hydrazine itself yields a different colored product. Various aspects of the reaction between ninhydrin and the α-hydrazino acids were investigated and a mechanism for the formation of Ruhemann's purple is suggested.