224 ANILINE AND ANILINE DYES.— Manufacture of Fuchsine.

containing about half its weight of dry colour. Somevarieties of aniline oil require more antimonic anhy-dride than others; thus, for some kinds equal weightssuffice, whilst for others 25 parts of aniline hydro-chloride require 35 of anhydride. (Sieberg, Dingler'iPol. Journal , clxxi. 3G6.) IIkiiiann states that thisprocess is very long and inconvenient, and is, in fact,“ of no value,” as useful magenta cannot be made byits means; the manufacture of magenta in this waywas, however, carried on by the inventor, in Glas-gow , on a large scale for several years (several cwts.of aniline being worked up daily).

The reaction of nitrobenzol on aniline, or an anilinesalt, appears to be commercially applicable as a meansof producing fuchsine, though till recently it has notfound much favour; certain metallic salts greatlyfacilitate the reaction. Holliday heated to 227° 0.for several hours a mixture of aniline of high boilingpoint 2 parts, commercial hydrochloric acid 2 parts,4 and nitrobenzol about 1 part, and obtained a “melt”containing much fuchsine.

Staedeler has published the results of several ex-periments on the reaction of nitrobenzene on anilineand toluidine, showing that blue, violet, and rosecolouring matters are readily obtainable, according tothe nature and proportions of the materials used andthe heat employed in its duration.

Courier has patented, amongst other processes,the heating together of the following mixtures for theproduction of rosatoluidine, rosaxylidine, and viol-aniline products respectively:—(1.) “ Coupler’s nitro-toluol ” (a mixture of para- and meta- nitrotoluene),95 parts; Coupler's toluidine (a mixture of para- andmeta- toluidine), 67 parts; hydrochloric acid, 65 parts;and ferrous chloride, or an equivalent quantity of ferricchloride, 7 parts. (2.) Coupier’s xylidipe, 75 parts;and Coupier’s nitroxylol, 105 parts.

Schutzexberger states that the dyestuff obtainedby process (1) is identical with ordinary rosaniline,whilst the yield is as great, if not greater (Jahresrbericht, 1869, 1162). Greiff, on the other liapd• (Ibid. 1163), found that much resinous matter wasformed, and also a large quantity of a dirty violetproduct.

Lautii adds stannous chloride to a mixture ofaniline and nitrobenzol, when an energetic actionensues. By adding boiling water when the tintbecomes dark brown, a solution containing muchfuchsine is obtained.

Meister Lucius and BruNing have recentlyrevived the manufacture of fuchsine by the reactionof nitrobenzol on aniline, and are now sending intothe market considerable quantities of fuchsine madein this way. Like the rubine prepared by means ofmercuric nitrate, this dyestuff is free from arsenic,and hence is specially suitable for the artificial color-ation of edible substances. Their process of manufac-ture is stated to differ from that of CouriF.R in certainparticulars, although based on the same principles.

Medlocic’s process for the manufacture of fuchsineis by heating 2 parts of aniline with 1 of “dry arsenicacid.” Ilis specification was so worded that his pro-cess, as actually patented, was practically valueless,

and considerable litigation was the result. Arsenicanhydride, As 2 0 6 , appears to be. in fact, incapableof transforming aniline oil into fuchsine; in order toform this dyestuff it is essential that a hydrated oxideof arsenic should be present, i.e., that the elementsof water should be present, associated with those ofarsenic anhydride, forming what is now spoken ofas arsenic acid, e.g., As 2 0 6 ,311,0, or H 3 As() 4 . Avery concentrated aqueous solution of this substanceis used, the excess of water being volatilized beforethe reaction is completed.

The arsenic acid was formerly prepared by actingon white arsenic (As 2 0 3 ) with nitric acid. A cheaperprocess is to treat the arsenious oxide suspended inwater, or preferably dissolved in hydrochloric acid,with chlorine; it is usually employed in the form ofa syrupy liquid, containing from 70 to 75 per cent,of As 2 0 6 . The first method adopted was to heat amixture of about 100 parts of aniline oil, and 150 to160 of this acid (or a proportionally larger quantityof a weaker acid) in an iron pot, preferably enamelledinternally, set either in a sand or hot-air bath, orbetter still, in an oil bath, and covered with a hoodconnected with a flue, to avoid injury to the work-men by the vapours evolved. The heat being gentlyraised with continual stirring, water was evolved, to-gether with some aniline vapours; the mass graduallyacquired a deep brownish red tint, becoming thickerand thicker, the temperature gradually rising to apoint between 150° and 190°, too high a temperaturebeing avoided as prejudicial to the yield and purity ofthe colouring matter. From time to time sampleswere drawn, and when these presented the rightappearapee, possessing after cooling a metallic bronzedtint, and breaking with a clean shining fracture, theheat was discontinued; the product (technicallycalled the “melt”) being ladled out on to iron platesto cool. When solid, the cakes were pulverized andthen subjected to further treatment with solvents toextract the red colouring matter.

Numerous improvements and modifications havebeep made in this first rough process. In the firstplace, the aniline volatilized was a considerable sourceof loss; this was avoided by applying a cover andcondensing worm to the pot. The next improve-ment was to use larger vessels, in which, by applyingmechanical agitators moved by steam power, a muchmore uniform quality of product could be obtained.The ladling out of the “melt” while yet fluid, andthe pulverization of the solidified mass, constantlyexposed the workmen to the injurious action of thevapours; again, the presence of unaltered aniline inthe “melt” is prejudicial to the effectual extractionof fuchsine, or, at least, lengthens the process, thefinal products (rosaniline salts) being less easilypurified by crystallization in presence of aniline saltsthan in their absence. Besides these imperfections,it frequently happened that unsuitable aniline oilswere employed, occasioning a great deficiency in theyield. Thus Nicholson and other manufacturerssoon found practically that a body containing nearly100 per cent, of pure aniline (i.e., an oil made froma benzol boiling at 81° or thereabouts, and boiling at