JaNI ARV 1. 1916] 



THE INDIA RUBBER WORLD 



167 



The Manufacture of Aniline Oil. 



WITH IX the past five years the use of aniline in rubber 

 i»oods manufacturing has increased to a marked 

 degree the world over. Of late, special attention has 

 been drawn to it by governmental investigations, as, for ex- 

 ample, that cited in the December 1915 number of The India 

 Rubber World on "Industrial Poisons in Rubber Manufac- 

 ture." The nature, source and method of matuifacture of aniline 

 is therefore of present interest. 



The chemist, Unverdorben, discovered the liquid now 

 known as aniline in 1826, among the products of the dry 

 distillation of indigo. In 1834 it was found by Runge in 

 coal tar and was named by him kyanol or blue oil because it 

 produced a blue coloration with hypochlorite. Fritsche in 

 1841 gave it the present name of aniline after the indigo 

 plant anil, from which he obtained it by distilling with potash. 

 Commercially, aniline is obtained by a series of chemical 

 transformations, beginning with coal tar. Among the prod- 

 ucts liberated from coal tar by distillation is benzole. Ben- 

 zole, when acted upon under suitable conditions with mixed 

 nitric and sulphuric acids, is converted into nitro-benzole. 

 Xitro-benzole may further be acted upon and chemically 

 "reduced" to aniline oil. The illustration, for which we are 

 indebted to the courtesy of the J. P. Devine Co., BufTalo, 

 Xew York, represents, in elevation, the assembly of a modern 

 aniline manufacturing plant. The apparatus is in two groups, 

 each operated continuously in 8-hour shifts. 



MAKING NITRO-BENZOLE. 



In the nitro-benzole section there are two nitrating units 

 alternated in service for continuous production. Each kettle 

 has connection with an independent acid tank and both dis- 

 charge their contents into the same "acid egg" or reservoir 

 from which, by compressed air, the nitro-benzole is elevated 

 into either of the two washers for purification, preparatory to 

 going into the storage tank. The capacity of each nitrating 

 kettle is, of course, the same, since they are designed to be 

 operated alternately. This capacity should not exceed, say, 

 200 gallons, in order that the heat of the reaction may be 

 safely regulated by the water jacket circulation. 



The nitrating kettle is built of acid-resisting cast iron, with 

 extra heavy walls. Mounted upon the kettle, with suitable 

 connections to it, is a water-cooled condenser for cooling the 

 vapors arising from the reaction and returning them to the 

 kettle. .\ hopper is also provided for introducing saltpeter 

 in lieu of nitric acid, when desired. The contents of the 

 kettle are mixed by a mechanical agitator operated by a 

 tight and loose pulley on a shaft bevel-geared to the vertical 

 shaft of the agitator. In some forms of nitrating apparatus 

 the control of the temperature is ohtained by means of water 

 circulation through a long lead coil located within the kettle. 



In operation, a mixture of nitric and sulphuric acids, of 

 specified strengths, is intimately mingled by air agitation. 

 The mixed acid is then run into the charge of benzole in the 

 nitrating kettle and the agitator set in motion at about 60 

 revolutions per minute. The heat of the reaction is not 

 allowed to rise above 140 degrees F. This is effected by regu- 

 lating both the rate of entrance of the acid and the cooling 

 circulation in the water jacket. Agitation is continued for 

 about 4yi hours after the final addition of acid, when the 

 benzole has been fully nitrified or changed into nitro-benzole. 

 At this point the contents of the kettle are allowed to settle 

 for several hours. The waste acid goes to the bottom and is 

 run off into the air pressure "acid egg" below, thence it is 



blown to a concentrating department for rectification. The 

 nitro-benzole is next run into the egg and transferred to one 

 of the washers; here it is cleansed by water agitation, settled 

 out by standing, and finally discharged into the storage tank. 

 In practice the yield of nitro-benzole from benzole is 154J^ 

 per cent by weight. The theoretical yield is 157.6 per cent. 



M.\KING .\.\ILI\K (III.. 



The aniline section of the plant is somewhat more extensive 

 than the nitro-benzole part. There is an acid tank connected 

 to the reduction kettle; also a condenser mounted upon the 

 latter, and various connections for the introduction of the 

 nitro-benzole and the iron borings used in the reaction of 

 reduction. A mechanical stirrer is operated by a tight and 

 loose pulley, bevel-geared to the shaft of the stirrer or 

 agitator. The kettle itself is made of extra heavy cast iron, 

 with its bottom section provided with a removable lining 

 of special, hard and acid-resisting cast iron. This is essential 

 for protection of the body of the kettle from the grinding 

 effect of the mass of iron borings in long continued move- 

 ment, as well as from the corrosive effect of the acid. The 

 agitator or stirrer has a tubular shaft to permit the access 

 of steam to the contents of the kettle. 



To produce aniline, the reduction kettle is charged with 

 nitro-benzole and, from the acid tank, diluted hydrocliloric 

 acid is next admitted, followed by a slow feed of common 

 cast iron borings, both acid and borings being in definite 

 proportion to the charge of nitro-benzole to be reduced. 

 The iron borings are fed progressively, as required, and it 

 takes several hours for the admission of the total amount 

 needed. 



The reaction having been started, distillation proceeds and 

 the distillate entering the condenser is returned to the kettle. 

 The materials are added to maintain a constant level in the 

 kettle. If the reaction becomes too violent, loss is occasioned 

 by the formation of benzene. The reduction is complete when 

 the kettle contains only aniline oil, water and oxide of iron. 

 The supply of steam, at this point, is increased so as to 

 distill over the aniline oil and water, both of which are piped 

 to the receiver separators. Here the water and aniline oil 

 separate by standing for 48 hours. The water contains about 

 3 per cent of aniline oil and is removed to a boiler, located 

 near the reduction kettle. Here it is steam-heated and passed 

 over into the reduction kettle to save the contained aniline 

 from waste. 



The oxide of iron from the reduction kettle is dried and 

 may be prepared for use in the purification of coal gas from 

 sulphur, or for the manufacture of cheap black paint. 



The settled aniline oil in the separators is charged into the 

 vacuum still for purification before storage. The total yield 

 of pure aniline oil obtained from nitro-benzole is 71>4 per 

 cent. .-\s pure benzole yields 154i/' per cent nitro-benzole. 

 and the latter 71)4 per cent of pure aniline oil, the total yield 

 of pure aniline oil from pure benzole is practically 111 per 

 cent. 



.Aniline oil has a boiling point of 364.6 degrees F., specific 

 gravity of 102.65 at 60 degrees F. If sold as pure it should 

 not contain over one-half of one per cent of water, and 

 should be free of nitro-benzole. A delicate test for the 

 presence of nitro-benzole in aniline oil is to shake a sample 

 violently for a few minutes, and notice the color of the froth 

 so produced. The merest trace of nitro-benzole present will 

 giv» a very distinct yellow coloration. 



