In a 1-l. round-bottomed flask equipped with an efficient water condenser are placed 148 g. (2 moles) of ethyl formate (b.p. 52–53°) and 150 ml. of 95% ethanol. One hundred and twenty grams (2 moles) of 85% hydrazine hydrate is added cautiously to this solution (Note 1) with shaking over a period of 10 minutes. After the reaction has subsided, the solution is refluxed on a steam bath for 18 hours. The bulk of the water and ethanol is now removed by evaporation under reduced pressure until the volume in the flask is about 150 ml. The resulting syrup, crude formhydrazide, is heated under atmospheric pressure for 3 hours, during which time the temperature of the bath is raised from 150° to 200°. After cooling to about 100°, the oil is taken up in 50 ml. of 95% ethanol, and 5 g. of Norite is added. The filtered solution is then diluted with 75 ml. of ether and placed in an icebox to cool. The crystalline product is filtered, washed with 50 ml. of 1:2 ethanol-ether, and dried. The yield of aminotriazole, melting at 77–78°, is 55–60 g. (65–71%) (Note 2). If a purer product is desired, the crude, washed material may be recrystallized, using 2 ml. of warm 95% ethanol per gram of compound followed by the addition of 2.5 ml. of ether, and chilling. The melting point of the purified product is 81–82°.

The residual amine in the filtrate may be isolated in the form of the hydrochloride. The combined solutions are evaporated on a steam bath, 50 ml. of concentrated hydrochloric acid is added, and heating is continued for 2 hours. On cooling, the syrupy solution crystallizes. It is triturated with 50 ml. of ethanol, and the 4-amino-1,2,4-triazole hydrochloride is filtered, washed with a little ethanol, and dried. The yield of the hydrochloride is 10–18 g. (8–15%); the salt melts at 147–148° and may be recrystallized from 95% ethanol, using 10 ml. per gram; the melting point is thus raised to 151–152°.