186 Gms. of purest aniline are heated with the same volume of 100 % (glacial) acetic acid in a bolthead of 1/2 litre capacity. Highly concentrated acetic acid has a strong action on most metals, for which reason it is necessary to work in glass vessels in the laboratory. The temperature is kept at 130o for ten hours, using a reflux condenser, after which about 25 c.cs. water and acetic acid are distilled off through a Liebig condenser and then a further 50 c.cs. of glacial acetic acid are added. During the second day sufficient water and acetic acid are distilled off for the temperature of the melt to rise to 240o. A further 70 gms. of acetic acid distil over, the strength of the last fraction being over 80 %. The acetylation is now practically quantitative. The acetanilide is poured into a copper tray and the hard melt finely powdered. Yield about 270 gms. acetanilide.

A still purer product is obtained by stirring the powdered melt with a little water at 700, after which it is cooled down, filtered off, washed and dried. In this way the last traces of acetic acid are removed. The acetanilide so obtained has a melting-point of 110-111o.

186 gms. Aniline. 168 gms. Glacial acetic acid.

50 c.cs. Glacial acetic acid.

Nitro-acetanilide.

200 Gms. of dry,finely powdered acetanilide are added to 800 gms. concentrated sulphuric acid of 66° Be., using the apparatus described on p. 5. The temperature should not rise above 250, as hydrolysis otherwise occurs. The acetanilide dissolves completely to a clear solution in the course of an hour or two. The liquid is now well cooled, and a mixture of 154 gms. nitric acid of 60 % (400 Be.) and 150 gms. of 92 % sulphuric acid are added during about one hour. The nitrating temperature should not exceed 2-3 °, or else rather much orthonitro compound is formed. When all has been added stirring is continued for at least a further three hours, the liquid being preferably allowed to stand all night. A test portion of the mixture on pouring into water and boiling with soda lye should give no odour of aniline.

The product is now poured, with good stirring, on to 500 gms. of water and 500 gms. of ice. The nitro-acetanilide is at once precipitated, and may be filtered off after an hour without loss. With proper working the theoretical quantity of nitric acid will suffice as is often the case in colour technology. No harm, however, results from a slight excess, as a second nitro group can only be introduced into the molecule with difficulty. The nitro-acetanilide left on the filter is now thoroughly washed with water, then stirred up with a litre of water, sufficient soda added to give a distinct blue colour to litmus paper, and boiled. As a result of this treatment only the o-nitro-acetanilide is hydrolysed. The product is filtered at 500 and well washed out with water. The yield so obtained is about 90 % of theory.

200 gms. Acetanilide 800 gms. H2So4, 66° Be.

154 gms. Hno3 (60 %). 150 gms. H2So4, 66° Be.

500 gms. Water. 500 gms. Ice.

The hydrolysis of the acetyl derivative is always carried out with soda lye; the moist press-cakes of nitro-acetanilide are stirred up with an equal weight of water and the suspension then boiled with 200 gms. of 35 % soda lye. The reaction must remain distinctly alkaline. After about three hours a test portion should give a clear solution in hydrochloric acid, thus indicating complete saponification. The liquor is then cooled to 400 and filtered. The product is carefully washed with cold water and is then chemically pure. Yield about 100 gms. nitraniline from 93 gms. aniline.

Nitro-acetanilide from 200 gms. Acetanilide.

200 gms. NaOH

(35 %).