the neighborhood of the melting point of the steroid, in the hope of providing additional information on the nature of the phenomenon. SUMMARIZING REMARKSBecause deteriorated spectra are seldom observed with hand-ground preparations, it might seem preferable to forego the practical convenience of the mechanical vibrator and resort to hand grinding in the routine preparation of potassium bromide disks. How-ever, there is the problem of polymorphism to consider, and frequently, though not invariably, the vibrator technique helps to eliminate ambiguities arising from this cause.With this in mind, the authors adopted the following routine procedure for the preparation of potassium bromide disks of steroids.The steroid (2 mg.) and potassium bromide (400 mg.) are weighed successively into the capsule of the vibrator and vibrated with an agate ball for 15 minutes. The material is then transferred to the die, which is evacuated and the powder is pressed at 7 tons per sq. inch for a minimum of 3 minutes, after which the pressure and vacuum are released and the pellet is removed. The pellet is next heated at 105°for a minimum of 5 minutes. If it remains clear, its spectrum is determined.If it becomes opaque during the heat treatment, the disk is reground by hand, using a mortar and pestle, the resultant powder is repressed and the spectrum of the new disk is accepted for characterization of the compound. ACKNOWLEDGMENTThe author wishes to thank T. F. Gallagher and R Norman Jones for helpful discussion and Beate B. Spiegel for technical assistance.

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Compounds of high nitrogen content, such as may be derived from guanidine and its substitution products, are often unstable and in many cases offer very little means for chemical identification. However, the nitrogen groups present lend themselves to infrared absorption studies, and the present investigation was undertaken to characterize such groups by this technique. Infrared absorption spectra of thirty-eight substituted guanidines and related substances are presented. The groups which have been studied are

The reaction of organic isothiocyanates with sodium azide in ethanol and water has been investigated. Water is shown to be the more advantageous solvent for this reaction giving higher yields and initially purer 1-siibstituted-tetrazoline-5-thiones. A series of these latter compounds was made by this procedure. The yield of product appears to be dependent on the electrical properties of the substituent of the isothiocyanate, the yields decreasing as the electron-donating properties increase. A series of new 4-substituted-thiosemicarbazides has been prepared and converted by diazoti~ation to thc corresponding 5-(substituted)aminothiatrlazoles. A theory to account for the differences in the mode of reaction of hydrazoic acid and azide ion is prese~lted and discussed. The bdsic conversion of 5-(substituted)am~no-thiatriazoles to 1-substituted-tetrazolinethiones may involve a simple dearrangementrearrangement mechanism complicated by side reactions. A sulntnary of known isomeric 5-(substitutetl)aminothiatriazoles and 1-substitutcd-tetrazolinethiones is presented.

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