226 ANILINE AND ANILINE DYES.— Manufacture of Fcciisine.

boiler set horizontally; b, b, is the spindle, and c, c,are the vanes of the agitator; d , d, the steam pipesfor heating contents of boiler; e, the dischargingcock; f steam tube; and < 7 , the cogwheel communi-cating motion to the agitator. When worked upwith hot water (or other solvent) the dyestuff isextracted without necessitating a previous pulver-ization of the cake. Lixiviation , after the fashion ofthe alkali manufacture, is ineffective for fuchsine-making, the insoluble matter being of a viscid resin-ous nature. Great loss of dyestuff is occasioned bythe mechanical covering up of its particles, unless acontinuous agitation is kept up; even as it is, theinsoluble residues left after treating the crude fuch-sine often contain 3 to 4 per cent, of rosaniline.

As before stated, in the first days of fuchsine-making the crude melt was often sold to the dyer, whosimply dissolved it in hot water, filtered, and used theliquor. A demand for a purified article, however,soon sprung up. At first the colour maker contentedhimself with simply extracting the soluble dyestuffwith boiling water, filtering through beds of sand,and precipitating the clarified liquor with commonsalt in excess. A mixture of arseniate and hydro-chloride insoluble in brine was thus thrown down.It was soon found that hydrochloric acid was a muchbetter solvent than plain water. The liquors obtainedby this means were precipitated by common salt, orby addition of just sufficient soda to saturate the acidand form brine, and the precipitate, consisting mainlyof fuclisine hydrochloride, was redissolved and re-crystallized ; or they were precipitated by lime, soda,&c., in excess, and the precipitate dissolved up in someother acid (e.g., nitric, oxalic, or acetic), and thecorresponding salt thus formed was purified by crys-tallization. The arsenious chloride vapour evolvedby the hydrochloric acid, and the aniline vapoursthrown off by the action of the alkalies, were highlyinjurious to health.

Habedank proposed the following modification ofthe process for obtaining the hydrochloride ( Dingier'sPol. Journal, clxxi. 73)—1 part of “melt” and 5 ofwater are used, and as much common salt as is equiva-lent to the arsenic acid originally employed; these arethoroughly boiled together, when rosaniline hydro-chloride is formed, insoluble in the saline liquor con-taining sodium arsenite and arseniate. This liquor isrun off and the resinous mass thoroughly boiled withwater: an impure solution of rosaniline hydrochlorideis obtained, filtered, and then allowed to crystallize,and the crystals purified by repeated crystallization.By this process the rosaniline arseniate and arseniteare converted into hydrochloride without the evolu-tion of arsenical vapours.

The filtration of the liquors is best effected bymeans of the following device (Fig. 5)—ordinaryfilters are practically useless, as they rapidly becomeclogged by the viscid insoluble matter. A tube, a, a,dips down nearly to the bottom of the boiler, b, b;on this tube is a nearly spherical expansion, c, c, con-sisting of two concave iron vessels capable of beingunited together by a flange and screw bolts, d, d:between the mouths of these two vessels is strained

a sheet of felt or other filtering material, a perforatediron plate, e, being fixed above to prevent rupture ofthe filter cloth. The boiler is so constructed that itcan be made steam tight; when steam is admittedthe pressure forces the liquid up the pipe, a, a, andthrough the filtering cloth upwards to a receivingtank. The tarry matters being thus left on the underside of the filter drop off by their own weight andfall back into the boiler. A set of these filters is soarranged that any one can be shut off, the hemi-spheres opened, and a new filter-cloth substitutedfor the old one with-out interfering with Fi s-

the action of theothers. Differentlyshaped filters con-structed on the sameprinciples are fre-quently employed.

The liquid massobtained by the im-proved process, orthe crude “melt,”is usually treated inone of the followingways, viz.: — ( 1 )

Boiling with hydro-chloric acid, and pre-cipitation of thedyestuff with sodiumcarbonate, as de-scribed below (chalk,limestone, or marblepowder, may also beused instead of car-bonate of soda). ( 2 )

Boiling with wateralone, or preferably

with water very - .™™.. T

feebly acidified with hydrochloric acid, and subse-quent filtration and treatment of the filtrate withcommon salt. (3) Boiling with water and excess oflime, chalk, or soda. In each of these processes theboiling is best effected under pressure, time and labourbeing saved, and more concentrated solutions obtained.

For the first method the following proportionsmay bo taken:—Solid “ melt,” or its equivalent ofliquefied mass, 11 parts; hydrochloric acid, 2 parts;water, 33 parts. Steam is passed through for threeor four hours, or until the residue becomes pulveru-lent and contains little or no red soluble matter; theliquor is then filtered and treated with sodium car-bonate in quantity just equivalent to the sum of thearsenic and hydrochloric acids present. Itosanilinehydrochloride is precipitated, being insoluble in theresulting soda liquors, and floats to the top, beingbuoyed up by the carbon dioxide bubbles formed,an d is skimmed off, dissolved in water by means ofsteam, and crystallized. The first crystals are redis-solved in a boiler provided with an agitator, and thesolution filtered and allowed to crystallize. Theresidue left on the filter consists for the most part olhumus-like bye products along with mauvaniline,