vessel, reaching nearly to the bottom of the cylinder. The upper part of this tube is connected with the machinery (G), while the surface of the tube is fitted with steel projections. The tube serves to admit steam, as well as acting as a stirring apparatus. Sometimes, instead of this tube, a solid iron axle is employed, and in this case there is a separate steampipe (D). Through the opening at K the materials for making aniline are put into the apparatus, while the volatile products are carried off through E. H serves for emptying and cleaning the apparatus. The S-shaped tube connected with the vessel B acts as a safety valve. When it is intended to work with this apparatus there is poured into it through K 10 parts of acetic acid at 8° B. (sp. gr. 1·060), previously diluted with six times its weight of water; next there are added 30 parts of iron filings, or cast-iron borings, and 125 parts of nitrobenzol, and immediately after the stirring apparatus is set in motion. The reaction ensues directly, and is attended by a considerable evolution of heat and vapours. Gradually more iron is added until the quantity amounts to 180 parts. The escaping vapours are condensed in F, and the liquid condensed in R is from time to time poured back into the cylinder A. The reduction is finished after a few hours.”
3. From INDIGO:—Powdered indigo is added to a boiling and highly concentrated solution of caustic potash, as long as it dissolves and hydrogen gas is liberated; the resulting brownish-red liquid is evaporated to dryness, and the residuum is submitted to destructive distillation in a retort, which, owing to the intumesence of the mass, should be strong and spacious. The ANILINE is found in the receiver under the form of a brownish oil mixed with ammoniacal liquor, and by separation from the latter, and subsequent rectification, is obtained nearly colourless. It may be further purified, as in the preceding processes.—Prod. 18 to 20% of the indigo employed.
4. By fusing, with proper precautions, a mixture of isatine and hydrate of potassium (both in powder); a retort connected with a well-cooled receiver, being employed as the apparatus. Said by Profs A. W. Hofmann and Muspratt to be “the most eligible process for isolating” aniline.[65]
[65] Muspratt’s ‘Chemistry,’ i, 599.
5. From anthranilic acid mixed with powdered glass or sand, and rapidly heated in a retort.
6. By treating an alcoholic solution of benzine with a little zinc and hydrochloric acid.
7. By heating phenyl-alcohol with ammonia in sealed tubes.
In Zinin’s process the nitrobenzol is dissolved in alcohol, and the solution, after the addition of ammonia, is saturated with sulphuretted hydrogen. After standing some time the solution deposits a large quantity of sulphur, and the liquid yields aniline.
Many other reducing agents have been proposed for the conversion of nitrobenzol into aniline, such as arsenite of sodium, powdered zinc, &c., but on the large scale they have all been found inferior to the process of Béchamp. Kremer’s process consists in heating one part of nitrobenzol in a proper apparatus with five of water and two and a half of zinc dust. When the reaction is completed the aniline, amounting to about 65% of the weight of the benzol, is distilled off in a current of steam.