ANILINE AND ANILINE DYES.— Manufacture of Euciistne. 223
nitrate, 1 part, and free aniline, from 6 to 8 parts; butit is somewhat difficult to avoid rise of temperatureand consequent deflagration. The yield by this processis from 7 to 8 per cent, as a maximum, and the pro-duct is much more impure than that obtained by thepreceding methods. From the crude melt a purifieddyestuff is obtained, by boiling with twenty times itsweight of water; unaltered aniline carrying fuchsinenitrate with it rises to the surface ; this is skimmedoff and filtered whilst hot through sand, and crudefuchsine nitrate is obtained on cooling as 'a greenishpasty mass with metallic lustre. Either benzol (boil-ing between 60° and 100° C.) or ether may be usedto dissolve out the aniline, chrysaniline, mauvaniline,&c. The residue is cooled with caustic soda or potashley, the aniline nitrate is decomposed, aniline beingcarried off by the steam. The mixture of bases(rosaniline, violaniline, c%c.) is then treated withdilute hydrochloric acid, which takes up chiefly therosaniline ; on cooling the liquors deposit rosanilinehydrochloride.
Notwithstanding the considerable difficulties in theway of making this process work commercially, ithas been from time to time revived and repatentedwith but slight modifications; thus Hughes patenteda method the same in principle—viz., heating togethera mixture of aniline oil, 20 parts, and nitric acid ofspecific gravity 1'36, 6J parts. After the water hasdistilled off, the materials are kept at 150°-200° C.for an hour, gently boiling ; a dark red syrup is thusobtained, which is treated with water and soda toneutralize free acid, and then well washed to removeunaltered aniline nitrate.
In 1862 Laurent and Casthelaz preparedcrythrobenzol by mixing together 12 parts of nitro-benzol, 24 of iron filings, and 6 of ordinary hydro-chloric acid, and allowing the mass to stand for 24hours. The production of colour is much facilitatedby heating the mixture. Bolley was unable toobtain any colouring matter by action in the cold.Coupler has proposed a very similar method, con-sisting in the heating of a mixture of aniline ferrouschloride and nitrobenzol to 200° (see infra).
The carbon tetrachloride process was thus workedby Monnet and Dury :—A digester furnished with asafety valve and a thermometer was heated, first to116°-118° C., by superheated steam, and finally to170°-180° C. After cooling the mass was extractedwhilst still warm, and boiled with water so as to getthe dyestuff in solution. The proportions used wereaniline oil, 4 parts, and carbon tetrachloride, 1 part.The yield is stated to be much superior to thatobtained by means of tin chloride,
Delvaux heated a mixture of dry aniline hydro-chloride 100 parts, aniline oil 72 parts, and dry sand1000 parts, to 110°-120° C. for 15 hours. On boilingthe product with water, a large quantity of fuchsineis dissolved out as hydrochloride; the remainder canbe extracted by alcohol, or by first boiling with analkali and then with dilute hydrochloric acid. Lauthhas proposed a similar process for the preparation ofParis violet from methyl aniline.
Smith’s antimony process is thus carried out: 6
parts of antimony are heated with 29 of pure nitricacid of sp. gr. 1-44, added in small portions, from halfto three quarters of an hour being required for 3 kilos,of antimony. The vessels used are of earthenware,fixed inside cast-iron pans with Roman cement. Thenitrous fumes given off are utilized for vitriol making.Constant stirring throughout the oxidation processis necessary; finally a white, very acid, and slightlydamp powder is obtained. This is heated for 12hours till dry, and is then calcined at a dull red heatin cast-iron vessels, in batches of 50 kilos., till allfree nitric acid and moisture is driven off. A yellowpowder of antimonic anhydride then results.
Eight vols. of aniline are mixed with nine of com-mercial hydrochloric acid of sp. gr. 1T05, and thewhole evaporated on a sand bath till thick whitevapours are evolved ; it is very essential that no freeacid should be here present. This can be readilyeffected by an exact neutralization of the acid byaniline; the point of neutrality being determined, notby the ordinary test papers, but by means of papersoaked in fuchsine solution. A violet or bluish tintis given to the paper by a trace of acid.
Twenty-five kilos, of dry aniline hydrochloride arecharged into an earthenware conical pot, set in aniron pan heated to 240° C. by a paraffin bath. Whenthoroughly melted, 32 kilos, of antimonic anhydrideare added in four batches, hour by hour with constantstirring. A tolerably energetic action is set up, butthis soon subsides, and altogether ceases in from fiveto six hours. The “melt” is then ladled out bycopper ladles and allowed to cool.
During the melting from 2£ to 3 kilos, of freeaniline, and 2 to 2^ kilos, of water pass off; theseare condensed by a head connected with a condensingworm, a draught being kept up by placing the freeend of the worm in connection with a chimney.
The “ melt” is powdered and mixed with 22£ kilos,of coarsely powdered soda crystals, and 30 litres ofwater; carbonic acid is disengaged. The whole isthen heated to 80° C. for an hour with continualstirring, allowed to settle, the deposit strained oncalico, and slightly washed with cold water. Themoist solid mass is then heated with 300 litres ofwater in a copper boiler by means of steam. Thesolution, after settling, is filtered into crystallizingpans. The residue is again treated with 200 litres ofwater, and the liquor also filtered into crystallizingpans. The insoluble portion is boiled with another
100 litres of water, and the colour precipitated fromthe solution by common salt; and finally tire resi-dues are exhausted with water, and the liquors used,together with the mother liquors from the crystalliz-ing pans, for the treatment of a fresh batch. Whenthe impurities become so concentrated in the liquorthat the dye will not crystallize properly, but requiresto be precipitated by common salt, the antimony isregained from the insoluble residue by heating withcarbonate of soda, common salt, and charcoal, in aspecially constructed furnace. Two - thirds of theantimony used is thus regained in the metallic state.
The yield of moist fuchsine obtained is about 7 to 7jkilos., in certain cases as high as 12 to 12J kilos.,