(Toluidine; Xylidine; Meta-nitraniline.)

9.3 Gms. (1/10 mol.) aniline are stirred up by means of a glass rod with 30 c.cs. hot water and 25 c.cs. concentrated hydrochloric acid are then added in a thin stream. The solution is allowed to cool somewhat, and when it has reached 400 sufficient ice is added to bring the temperature down to o°, leaving a slight excess of ice. A solution of 7 gms. 100 % sodium nitrite (20 % solution)1 is then added rapidly with vigorous stirring. This solution of nitrite is best kept as a stock solution standardized by means of pure sulphanilic acid. The diazotization is complete as soon as a drop of the dia-zonium solution reacts with potassium iodide paper and with Congo paper. Every diazotization should be followed by means of both of these reagents. The diazotization occupies about 2 minutes (half an hour on the large scale), the end-temperature being about 70 and the total volume about 250 c.cs.

In the cases of p-toluidine and chloraniline a certain amount of the hydrochloride often separates out during the ice-cooling, but rapidly disappears during the diazotization.

p-Nitraniline.

(o-Nitraniline, etc.)

As the salts of p-nitraniline are unstable in aqueous solution, the base must be brought into reaction in a very finely divided condition.

14.5 Gms. (1/10 mol.) commercial nitraniline are dissolved in 30 c.cs. concentrated hydrochloric acid and 30 c.cs. water at 80-900, and the clear solution is then allowed to flow in a fine stream on to 50 c.cs. of water and 50 gms. of finely crushed ice with good stirring; final temperature about 8o°. 7 Gms. sodium nitrite as 20 % solution are then run in with vigorous stirring; the temperature rises to 15o, and the solution becomes clear in a few seconds. The liquid is tested with Congo- and nitrite-paper. On the large scale, also, the nitrite must be run in very rapidly under the surface of the liquid, as otherwise considerable quantities of diazo-amino compounds are formed.

a-Naphthylamine.

14.3 Gms. (1/10 mol.) a-naphthylamine are dissolved in 22 gms. 30 % hydrochloric acid and 100 c.cs. hot water, and the solution is then cooled down to o° with 200 gms. ice. 60 Gms. salt are added, and, as soon as the temperature has gone down to -5o, 20 gms. 20 % sulphuric acid, and then, quickly, 7 gms. 100 % sodium nitrite as 20 % solution. The diazotization is completed in a few minutes, the sparingly soluble sulphate of naphthylamine going into solution. The final volume is about 800 c.cs. and the temperature below o°.

1 Volume per cent.: 1 litre = 200 gms. 100 % sodium nitrite.