SOAP.— Curd. Yellow.

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are frequently piled upon the floor without usingany frame, but the lower bars of soap are apt toget misshapen from the weight of the superincum-bent mass.

The bars of soap, when sufficiently hard, arestamped, either by a press with suitable box anddie, or, in the case of bar soap, with a stereotypeplate, which conveys its impression by being struckwith a mallet.

White Soap — Cued Soap. —The material em-ployed may be tallow or lard, or olive or well-bleached palm oil, or mixtures of these in almostany proportion. To produce 1 ton of soap, from10 to 14 cwts. of tallow or olive oil are required.The process of saponification is conducted as abovedescribed, with but slight variation, attending moreparticularly to the complete removal of the alumino-ferruginous impurities of the lye, which otherwiseimpart to the soap a more or less intense colour.Their removal is effected by boiling the soap severaltimes with fresh lyes, or by thinning out the soapwith a little lye, and applying gentle heat, thencovering the caldron carefully, and allowing it tosettle. The upper strata of soap is afterwardsladled out and run into the cooling frames.

In place of this process, Andekson at this stage,instead of boiling out the head, and finishing asheretofore practised, pumps out or draws off thestrong lye on which the materials have been boiled,and then adds weak lye or water in successive por-tions, and boils the whole until the mass assumes aproper appearance for fitting. The mixture is nowallowed to stand at rest for from twenty-four toforty-eight hours, or until the nigre or imperfectportion of the soap is deposited. This latter maythen be separated, either by pumping it off fromunder the purified compound into an adjacent kettle,or by removing carefully the upper stratum ofpurified soap by means of ladles or buckets.

Whichever method be pursued, the cleansedmaterial must now be treated with the proper finish-ing lye for curd soap, which being added, the wholeis boiled until the soap becomes of sufficient con-sistence to be transferred to the cooling frames.When the materials employed in the production ofthis soap are very impure, the fitting or purifyingprocess as above described is repeated one or moretimes; in which case, after the first separation ofthe imperfect soap, the remaining partially-purifiedmaterial is treated with a lye only of moderatestrength, instead of the ordinary finishing lye, andthe whole is boiled with weak lye or water untilsufficiently diluted to allow the proper performanceof the fitting process—after which, time is allowedfor deposition, the imperfect soap is again removed,and after the addition of the finishing lye, the re-mainder is boiled to a curd as before. The furthertreatment of the separated nigre or imperfect soap,and its conversion into mottled soap, is effected byadding to it in an ordinary caldron the usual finish-es lye for a mottled soap, and boiling until it is°f proper consistence to be removed to the frames.The quantity obtained from one charge of soap by

the fitting or purifying process is not enough to beconveniently boiled by itself ; it is therefore setaside, and six or more batches operated upon atone time.

The average composition of ordinary white tallowsoap is—of alkali, t part; of fatty acids, about 9parts; and 5 to 8 parts of water. In England byfar the greater quantity of curd soap produced ismade from tallow or mutton suet and soda only.Some manufacturers, however, substitute for one-fourth of the tallow as much lard or olive oil, anda soap is produced greatly superior in quality, andless liable to change by exposure. Soap made solelyof tallow is, besides, inconveniently hard, and verydifficult of solution. In France and on the Con-tinent, when tallow is saponified, olive oil is alwaysadded in the proportion of 20 to 25 per cent, of theoleaginous material. In England lard is not un-frequently used as the softening agent; and whenapplied in about the same proportion, answers everypurpose, while it has the advantage over olive oilthat it does not detract from the whiteness of thesoap. English white or curd soap is largely usedby the cloth manufacturers of Yorkshire , and thelace and stocking bleachers of Nottingham . Tallowis not saponified to a very considerable extent onthe Continent; but in its stead, olive oil mixedwith about one-fifth of rape oil is used in the manu-facture of hard soaps. This addition of rape oil isalways resorted to, because olive oil alone yields asoap as hard and compact, and as difficultly soluble,as soap made wholly of tallow and alkali. This,however, is not the case with rape oil, and otheroils of a similar nature—that is, such oils as becomethick and viscid by exposure—experience havingdemonstrated, though the reason is as yet unknown,that the oils which turn viscid the soonest by ex-posure, yield with soda softer soaps than thosemade with oils which, like olive oil, remain longlimpid under the influence of the air. The admix-ture of rape oil with olive oil has therefore the effectof modifying the degree of hardness of the soap,just as when lard is saponified in conjunction withtallow.

Yellow Soap. —This variety of soap differs fromother kinds in containing rosin. This substance, aspreviously observed, enters into combination withthe alkalies, producing a detergent compound sol-uble in water. The combination, which cannot becalled saponification, takes place equally well withcarbonated as with caustic alkalies. The soap separ-ates on the surface when an excess of carbonate isused, or in the presence of common salt, as a thick,slimy, brown mass, smelling strongly of rosin, andcontaining 15'8 per cent, of soda. Besides the rosin,common fat or inferior tallow, palm oil is also usedto a considerable extent. The usual proportion ofpalm oil and rosin are 3^ parts of the former to 1 ofthe latter; sometimes the proportion is still greater,and the soap produced is then soft and dark coloured.When the saponification of the oil is nearly complete—that is, at the last charge of the lye—the rosin isintroduced in a state of coarse powder, and well