The identification of barbituric acids by the x-ray powder diffraction method is discussed from the practical point of view. Data are presented showing the advantage of preparing the <i>p</i>-nitrobenzyl derivative whenever identification of the isolated free acid is either doubtful or considered impossible. A detailed account of the experimental micro technique is given and the applicability of the technique to pharmaceutical products as forensic specimens is discussed.
J. A. R. Cloutier and Jane M. Manson, "Identification of Barbiturates by X-ray Diffraction Powder Patterns of Their p-Nitrobenzyl Derivatives," Appl. Spectrosc. 15, 60-64 (1961)