SOAP.— Mottled.

caldrons a circular ring of pipe, of about 1^-inchbore, and perforated -with small boles, is fixed inthe well of the kettle, just below the flange or joint,keeping it sufficiently off the bottom to allow astirrer to be used to scrape the bottom when neces-sary. The pipe is supplied with atmospheric airfrom a cylinder blast, or other suitable forcingapparatus, and is connected with the latter by meansof a pipe attached thereto, and rising up to the topof the kettle, where it is furnished with a stop-eockand union-joint, for the purpose of connecting ordisconnecting the parts of the pipe within and with-out the copper.

For a good yellow soap, 90 gallons of lye ofspecific gravity 1T4 = 28° Tw. are run into thecaldron. The fire being kindled, the caldron ischarged with 2050 lbs. of grease; and as soon asthe lye is at or near the boiling point, the blast iscommenced, keeping up a brisk fire, so as to continuethe materials in the kettle as near ebullition aspossible. When the lyes are exhausted, an addi-tional quantity is gradually added until the grease,oil, or fatty matter is taken up; 550 lbs. of rosinare then added—a bucketful at a time, with morelye occasionally, until 300 gallons of the strengthabove-mentioned have been used, keeping the blastin action the whole time, and the contents of thekettle as nearly boiling as possible. When thewhole of the rosin is melted, and thoroughly incor-porated with the saponaceous mass, and the strengthof the iyes taken up, the blast should be stopped,and the contents of the boiler briskly boiled, andthen allowed to rest, that the spent lyes may sepa-rate and deposit. These being now drawn off, thesoap is then brought to strength by fresh lyes, as inthe ordinary process of soap-boiling. During theoperation of the blast the soap must be kept in anopen or grained state; and for this purpose salt orbrine is to be added when necessary. Experiencehas shown that it is better not to make a change oflye during the operation of the blast, when lye ofthe strength above-mentioned is used; but if weakerlye is employed, one or more changes may be made.It is found desirable, also, that the soap should bekept in a weak state during the passage of the streamsof air through the materials, otherwise it is apt toswell up, from the air hanging in the grain; andthis is found troublesome to remove, requiring longboiling. If dark-coloured materials are used, it iswell to keep the blast in operation three or fourhours after the rosin is melted, provided the soapymass is kept weak and open or grained.

Normandy 's Process .—By this process a soap isobtained from the cheaper oils, possessed of detergentproperties and a degree of hardness approachingto that obtained by the employment of the morevaluable fats and oils.

When the soap is made in the usual manner, andis ready to be cleansed, there is to be introducedand crutclied into it a certain quantity of neutralanhydrous sulphate of sodium, or of hyposulphiteof soda, or of the two salts conjointly.

The “ salt-cake ” is treated with a quantity of hotVOL. II.

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water, less than is necessary to dissolve the wholeof it, and to the saturated solution thus obtained asmuch solution of caustic or carbonate of alkali isadded as is necessary to impart to the liquid a faintalkaline reaction. This addition is made not onlyto saturate any free acids that may be present, butalso to remove the ferric oxide always contained incrude salt-cake, and which, by this treatment, willbe precipitated. When this precipitate has com-pletely subsided, and the supernatant liquor isperfectly clear, as much of the latter is added to thesoap paste as is necessary to confer upon it therequisite degree of hardness when cold—the par-ticular quantity varying according to the nature ofthe fat or oil saponified, or to the proportion ofrosin present. The mixture of salt-cake solutionand of soap are thoroughly incorporated by stirringor crutching, continuing the agitation until themass has become so hard that the stirring can be.nolonger practised. When hyposulphite of soda isused, it should be dissolved in very little hot water,and the solution added to the soap exactly as abovedescribed.

Mottled Soap—Marbled Soap. —In the manu-facture of this variety of soap, the same kinds ofmaterials are used as for white soap, and its differentappearance arises from the different mode of treat-ment of the soap, after the completion of saponifi-cation. By a reference to the general process ofsoap-making given above, it will be observed thateven after the complete formation of soaps, that is,when the whole of the oil or fat used is decomposed,and the oily acids have entered into combinationwith alkali, the soap still requires further treatmentbefore it is brought into a marketable condition. Itexists now in the form of immovable globules, and it. is necessary to cause these to coalesce into a homo-geneous mass. This is effected by a process termedfitting, which consists in the fusion of the contentsof the boiling caldron in a weak lye or in water, andafterwards boiling the whole for a longer or shorterperiod, according to the kind of material operatedupon, the mass being prevented from boiling out ofthe copper by dashing shovels into it, so as to breakthe froth and favour evaporation. During this pro-cess in making white or curd soap, the more or lesscoloured impurities of the materials, termed ni.gre ornigger, fall to the bottom; but in making mottledsoap, the mixture is left in a thick or viscid state, sothat the impurities cannot subside, and is trans-ferred to the frames in this condition. To producea good marbled soap, it is necessary that this latteroperation be very carefully conducted; as, if toogreat a quantity of liquid be added, or if the mix-ture of soap and water or weak lye cools too slowly,all the colouring matter falls to the bottom, leavingthe upper stratum of soap perfectly white, while, onthe other hand, if it becomes too quickly cold, thesoap remains in the granular condition. In somecases the mottling is produced, or at least the pro-portion is increased, by sprinkling on the surface ofthe soap, after being boiled with the last service oflye, a small quantity of very strong sulphuretted