In a 250-ml. Erlenmeyer flask provided with a two-holed stopper which has a slit cut in one edge to serve as an air vent and which holds a thermometer, the bulb of which reaches almost to the bottom of the flask, is placed 31.5 g. (0.5 mole) of anhydrous nitric acid (Note 1). The flask is cooled below 10° in ice water, and 51 g. (0.5 mole) of acetic anhydride (Note 2) is slowly added from a buret through the second hole in the stopper in portions of about 0.5 ml. at a time. The temperature of the reaction mixture is never allowed to rise above 10° (Note 3). After about 5 ml. of the acetic anhydride has been added the reaction becomes less violent, and larger portions, increasing gradually from 1 to 5 ml., may be introduced at a time with constant shaking. After all the acetic anhydride has been added, the stopper and the thermometer are removed. The neck of the flask is wiped clean with a towel, and the flask is then covered with an inverted beaker and allowed to come up to room temperature in the original ice bath (Note 4).

The mixture is allowed to stand at room temperature for 7 days (Note 5), and the tetranitromethane is separated by pouring the mixture into 300 ml. of water in a 500-ml. round-bottomed flask and steam distilling (Note 6). The tetranitromethane passes over with the first 20 ml. of the distillate. The heavy product is separated from the upper layer of water, washed first with dilute alkali, finally with water, and dried over anhydrous sodium sulfate. The yield of tetranitromethane is 14–16 g. (57–65%). The product should not be distilled, as it may decompose with explosive violence. Tetranitromethane must be kept out of contact with aromatic compounds except in very small test portions, since violently explosive reactions can occur (Note 7).