ANILINE AND ANILINE DYES.— -Manufacture of Rosaniline Salts. 227

chrysotoluidine, and sometimes lakes formed by thepresence of alumina in the sodium carbonate used.Violaniline is not present, its hydrochloride beingpractically insoluble.

The mother liquors arising from the recrystalliza-tion are often used over again in place of water,either to redissolve the first batch of crystals, or totreat the crude “ melt.” In this way the 'chrysotolui-dine taken up together with the rosaniline is concen-trated in the liquor (chrysotoluidine salts are moresoluble than rosaniline salts in slightly acid solu-tions); and as one result the fuchsine made is aptto contain a little of this substance, giving it a scarletshade. In some factories the mother liquors are pre-cipitated by common salt, and the scarlet or crimsondyestuff thus thrown down (consisting of fuchsinemore or less mixed with chrysotoluidine) is sold underthe name of Cerise, Scarlet Magenta, &c., or is keptapart for the manufacture of certain dyestuffs madefrom impure fuchsine, e.g., browns, greys, &c., &c.

For the second method, the following proportionsmay be used:—Crude fuchsine, 100 parts; hydro-chloric acid, 1 part. Steam is blown through for fouror five hours, and the resulting liquors filtered intolarge tanks: 120 parts of common salt is then addedin small quantities, the liquid being agitated; therosaniline hydrochloride thus thrown down is slightlywashed and recrystallized as before.

For the third method, the one most generallyadopted at the present day, the crude fuchsine isthoroughly boiled with an excess of lime, and a suf-ficient bulk of water to dissolve all the rosanilinepresent, for several hours : in case a “ melt” has beenused not previously freed from undecomposed anilinesalts, the aniline is by this means liberated and ex-pelled. Solid arseniate and arsenite of calcium areformed and separated by filtration while boiling hot;on cooling, a crop of crystals of impure rosaniline inthe free state is obtained. The mother liquors maybe used for the treatment of a fresh batch, ormay be employed for the preparation of inferiorqualities of dyestuff. It usually happens that acertain quantity of rosaniline is left in the limemud; this is most completely extracted by treatmentwith dilute hydrochloric or sulphuric acid, and preci-pitation of the rosaniline solution by common salt.The first crystals of rosaniline may be purified byanother crystallization from water; or they may betreated with twice their weight of alcohol, and thefiltered solution distilled (mauvaniline is thus leftun dissolved, whilst the chrysotoluidine is only par-tially dissolved). Usually, however, these crystals areconverted into some rosaniline salt, e.g., the hydro-chloride, and this salt purified by crystallization. Aslight excess of acid being used, the chrysotoluidineis left in the mother liquors, whence it is sometimesextracted for sale under the names of Chrysaniline,Aniline yellow, Victoria orange, &c. Some manufac-turers employ chalk, baryta, or soda in place of lime.

Yield of Rosaniline .—The amount of crystallized saltobtainable from a given quantity of aniline oilnecessarily varies with the nature of the oil, and theway in which the manufacture is effected. By the

improved process for fuchsine-making, coupled withthe hydrochloric acid and carbonate of soda processfor dissolving out and purifying the rosaniline hydro-chloride, for every 100 parts of aniline originallyemployed from 25 to 30 parts of dry crystallizedrosaniline hydrochloride can be obtained (Giraiidand De Laire). According to Reimann, 34 lbs. ofmagenta (rosaniline hydrochloride?) maybe obtainedfrom 1 to 2 cwts. of aniline oil of suitable composition.Kletzinsky has, however, stated that from 100 partsof aniline and 200 of arsenic acid, 50 parts of purecrystallized red are obtainable (Jahresbericht, 18G4,820).

By the process of R. Smith with antimonic anhy-dride, 100 parts of aniline oil yield from 30 to 50 ofmoist paste of colouring matter, containing half itsweight of dry hydrochloride, from 10 to 12 partsof aniline being regained during the heating processby condensation of the vapours evolved (Sieburg).This, therefore, represents a yield of between 17 and29 parts of hydrochloride per 100 of aniline actuallyused. Bolley states that 40 per cent, of the weightof aniline used may be regarded as a very high yieldof crystallized fuchsine, and 33 per cent, as an aver-age amount. Rosenstiehl states that the yield of drycrystallized aniline red obtainable on the large scaleaverages from 27 to 30 parts per 100 of aniline used,whilst Levinstein estimated it at 20 parts; probably28 per cent, may be taken as a fair average yield.The mercuric nitrate process is stated to yield, whenproperly conducted, quite as large an amount ofcrystallized fuchsine as is obtainable by means ofarsenic acid under the most favourable circumstances.According to Monnet and Drury, the yield of reddyestuff by the carbon tetrachloride process will com-pare favourably with that obtainable by any othermethod.

Schutzenberger states that by the reaction ofaniline oil on commercial nitrobenzol a yield isobtained quite as great as that by means of arsenicacid, if not greater; Coupier says that by this pro-cess a yield as high as 40 per cent, of crystallizedcolouring matter can be obtained, and that this dyesshades twice as dark as those given by an equal weightof ordinary commercial fuchsine.

Preparation of Rosaniline Salts. — As mentionedabove, Azaleine and Rubine are virtually the nitratesof rosaniline. From the hydrochloride of rosanilinethe free base is commercially prepared by dissolvingthe salt in a large bulk of boiling water, adding anexcess of boiling alkaline solution, and continuingthe boiling for some hours; the liquor is then filteredwhile hot into crystallizing vats, where the free baseseparates on cooling as nearly colourless crystals.Care must be taken that there is sufficient waterpresent to retain the whole, or almost the whole, ofthe free rosaniline in solution ; to avoid inconvenientlylarge bulks of liquors, the solution is best effectedunder pressure.

To form the acetate, rosaniline is dissolved inboiling acetic acid, containing one-fifth as muchglacial acid as there is used rosaniline, two and a halftimes as much water being also present. To obtainan easily crystallizable salt, glacial acid, free from