SOAP. —Analysis.

784

rotating fan to produce an intimate admixture andminute division of the tallow. Figs. 8 and 9 showthe apparatus. An upright shaft, a, Fig. 8, whichmay be of wood or iron, and from which arms,aaaa, radiate to the sides of the caldron, is fixedpermanently or temporarily in the copper. If moreconvenient, a cylinder (Fig. 9) may be employed,

Fig. 9.

I> Di

m.-.

I.- mm

Hfcjlj

with a shaft, A, passing through it horizontally, andfrom which arms, c c c c c c, radiate, when a rotatorymotion will thoroughly incorporate the fatty matterand the lye. For 2lr tons of tallow the cylindershould be about 6 feet in diameter and 12 feet inlength. At l>D are doors for filling and dischargingthe materials. The agitation must be continued forabout three hours, or until the tallow is completelysaponified, which is known by the mass becomingthick, after which it is allowed to stand from one tofour days, according to the quantity of the paste.As soon as the mass thickens and the lye is absorbed,the cylinder should be emptied and the contentsturned into an ordinary caldron, preparatory to beingfinished and converted into soap by any of the ordi-nary methods.

French Toilet Soaps .—The soap is cut into thinshavings by being pressed against a rotating wheel,having on its circumference a number of cuttingblades.

The laminae are then mixed with the requisiteperfumes and colouring matters, and transferred toa mixing machine. Fig. 10 represents a mixer which

Fig. 10.

is much used in France . The soap cuttings, withthe necessary ingredients to form the toilet soap,are placed in the hopper, n. Three pairs of cylinders,set in motion by the gearing, ABCDFG, the dispo-

sition of which is readily understood, crush themixture into a paste. The distance of these crush-ing rollers is regulated by the screws, II n'. Themixture is carried upwards by the lower rollers, andpasses through the upper series, S, which convey itinto the hopper, M. This hopper when full is opened,and the paste falls into the lower hopper, N, whenceit is again sent through the machine.

Soaps coloured with ochre, vermilion, or metallicoxides are passed five or six times through themachine; white soaps or dyed soaps two or threetimes only.

When the paste is perfectly homogeneous, a catch,which holds the plate, P, in position, is let go, andthe mixture falls into the box, K.

The mass of moist soap is then weighed into lumps,and moulded, either by hand or by suitable presses,into the required shape, and placed in a dryingchamber. When sufficiently hard, the cakes arestamped in moulds, and finally polished with a littlealcohol to give them a good surface.

In the case of the best soaps the process of dryingand moulding is repeated several times.

Fig. 11 is a moulding machine for cheap toilet soaps.The soap paste is placed in the cylinder, c; here itis pressed upon by a piston moved slowly down-wards by the rod, A. At the bottom of the cylinder,

Fig. 11.

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C, the soap passes into moulds, and is hero sub-mitted to the action of another piston, movinghorizontally, which stamps the maker’s name, andgives a polish to the surface. Round the cylinder,C, a current of steam circulates, to maintain thesoap at the necessary degree of fluidity.

Analysis. —The proportion of water in mottled ormarbled soap should never exceed 30 to 35 per cent.Properly prepared white soap should not containmore than from 40 to 45 per cent, of water. Fre-quently, however, the proportion amounts to 55 or60 per cent., and cases have been known in whichsoaps combined with from 83 to 84 per cent, ofwater have been sold. This is either added directlyto the soap when run into the frames, or the soap