In a 5-l. round-bottomed flask, fitted with an efficient reflux condenser of wide bore, are placed, in the following order, 80 g. of powdered crystalline ferrous sulfate (Note 1), 865 g. (687 cc., 9.4 moles) of c.p. glycerol (Note 2), 218 g. (213 cc., 2.3 moles) of aniline, 170 g. (141 cc., 1.4 moles) of nitrobenzene, and 400 cc. of concentrated sulfuric acid (sp. gr. 1.84) (Note 3). The contents of the flask are well mixed and the mixture heated gently over a free flame. As soon as the liquid begins to boil, the flame is removed, since the heat evolved by the reaction is sufficient to keep the mixture boiling for one-half to one hour. If the reaction proceeds too violently at the beginning, the reflux condenser may be assisted by placing a wet towel over the upper part of the flask. When the boiling has ceased the heat is again applied and the mixture boiled for five hours. It is then allowed to cool to about 100° and transferred to a 12-l. flask; the 5-l. flask is rinsed out with a small quantity of water.

The 12-l. flask is then connected with the steam-distillation apparatus shown in Fig. 24, a 12-l. flask being used as a receiver (Note 4); steam is passed in (without external heat) until 1500 cc. has distilled (ten to thirty minutes). This removes all the unchanged nitrobenzene (10–20 cc.). The current of steam is then interrupted, the receiver is changed, and 1.5 kg. of 40 per cent sodium hydroxide solution is added cautiously through the steam inlet. The heat of neutralization is sufficient to cause the liquids to boil and thus become thoroughly mixed. Steam is then passed in as rapidly as possible until all the quinoline has distilled. In this process, 6–8 l. of distillate is collected (two and one-half to three and one-half hours are required, unless a very efficient condensing apparatus is used, under which conditions the distillation may be complete in one-half to one and one-half hours). The distillate is allowed to cool, and the crude quinoline separated. The aqueous layer of the distillate is again distilled with steam until all the quinoline has been volatilized and collected in about 3 l. of distillate.

This 3 l. of distillate is then mixed with the first yield of quinoline, and 280 g. (150 cc.) of concentrated sulfuric acid is added. The solution is cooled to 0–5°, and a saturated solution of sodium nitrite added until a distinct excess of nitrous acid is present (as shown either by starch-potassium iodide paper or by the odor). This generally requires 50 to 70 g. of sodium nitrite. The mixture is then warmed on a steam bath for one hour, or until active evolution of gas ceases, and is then distilled with steam until all the volatile material has been expelled (4 l. of distillate will result). The receiver is then changed and the mixture in the distillation flask is neutralized, as before, with 700 g. of 40 per cent sodium hydroxide solution. The quinoline is distilled exactly as described above, the aqueous portions of the distillate being distilled with steam until all the quinoline has been isolated. The crude product is then distilled under reduced pressure, and the fraction which boils at 110–114°/14 mm. is collected. The forerun is separated from any water which may be present, dried with a little solid alkali, and redistilled. The total yield is 255–275 g. (84–91 per cent of the theoretical amount based on the aniline taken) (Note 5).