SOAP. —Boiling. 773

again into a state of homogeneous mixture—calledthe “close state,” as contradistinguished from thecondition in which the soap is granulated andseparated from the liquid contents of the pan; andif he has not already added his full complement ofoils or fats, he completes the addition of them,adding also strong lyes until he finds the mixturehas acquired a strongly alkaline taste. He then addssufficient common salt to cause the separation of thesoap from the alkaline solution, and boils the soapfor some hours in the presence of the alkaline solu-tion, to insure the whole of the fatty matter beingcombined with alkali.

If it is intended that the product should be framedas a “ curd” soap, it is allowed to remain quiescentfor a few hours, so that the lyes may subside; andthe soap is then skimmed off and transferred to the“frames,” in which it solidifies by cooling, and is thendivided, by cutting with wire, into slabs and bars.

If the soap contains rosin as part of its acidconstituents, it requires a further operation beforeframing. This consists in melting the curd soap(after the abstraction of the alkaline lyes from thelower part of the pan) with the addition of water,and boiling the mixture by steam or fire, or bothsteam and fire, so as again to produce a homogeneouscompound containing an indefinite proportion ofwater, and allowing this compound to remain quies-cent for two days, when a separation takes place,resulting in the elimination of a definite compound,containing in 100 parts about 65 of fatty acids, 6 - 5of soda, and 28‘5 of water. This forms the upperstratum of the soap-pan, underneath which is anindefinite compound, technically called “ nigre,”containing a much larger proportion of water.

When it is judged that the separation of thesecompounds has been well effected by subsidence, theupper portion, or definite compound, is usuallytaken out of the soap-pan by ladling, and trans-ferred to frames to solidify by cooling. The residualportion, which contains an excess of alkali, as wellas of water, is boiled up with salt and the additionof fatty materials, to form the succeeding boil of soap.

In Germany the kettle is charged with 190 gallonsof soda lye of 30° B., and 2000 lbs. of the best meltedsuet. When the mixture becomes milky it is keptgently boiling for two hours, the source of heat isthen removed, and after two hours’ repose the lye isdrawn off. The operations are continued as abovedescribed. When the soap forms by pressure clearsolid scales between the fingers, the magma is cooledby throwing in some buckets of lye, and soon after ithas settled drawn off clear. After the heat is with-drawn 9 or 10 gallons of lye are poured into thekettle, and when fusion is complete a trial of thepaste is made with the spatula. If it runs from thelye water is added; if it does not run, it must beboiled a little longer, adding a bucket of watercontaining a third of its weight of common salt insolution, in order to effect the separation of the soapfrom the water. When this separation appears to beperfect, after an hour or more of repose, the water,which contains the greater part of the alkaline lye

remaining from the first boiling (generally of a verydeep bottle-green colour), is drawn off. The boilingis renewed with addition of about eight buckets ofwater, and when the incorporation is complete anexamination with the spatula must be made to ascer-tain whether the soap runs from the water. If itdoes, water is added in small quantities until thisceases, and the pasty mass moves tremulously. Tofinish the operation the contents of the kettle arewell boiled, and unless the soap has a bluish tint (inwhich case it must have another washing), the fire isextinguished, or the steam shut off, the kettle care-fully covered, and the whole left to rest for a day ormore, and then ladled off into the frames.

In the United States of America the followingprocess is pursued:—The strength of the lye em-ployed differs accordingly as the fat to be saponifiedis richer in olein or in solid constituent. The opera-tion is commenced by pouring the lye into the boilingcaldron to a third of its capacity. This is thenheated to ebullition, and the oil is now poured in.The reaction is such that a magma is immediatelyformed. The proper formation of this magma isconsidered to be the most delicate and importantpart of the whole process ; and if badly managed, amuch greater quantity of lye is required to form thesame weight of soap than otherwise would be. Afterpouring in the fat, the heat is decreased by openingthe doors of the furnace ; and when the mixture iscomplete, if necessary a further quantity of weaklye is added gradually, and with constant stirringduring the addition, so as to insure thorough con-tact. The mass should remain homogeneous; thefat should neither rise to the surface nor descend tothe bottom. If it rises, it is necessary to add morestrong or weak lye, according to the capacity of thecaldron. If the lye is in excess, a further quantityof fat must be added—always stirring briskly uponany addition of new material. The operation re-quires from eighteen to twenty hours for completion.It may, however, be greatly accelerated by throwingin the scrapings or the waste of soap already made.An excess of soda is recognized by the liquidity andtransparency of the paste. The presence of a largeproportion of common salt in the soda also preventsmore or less the proper formation of the magma.When this is the case to any considerable extent,the use of soap scraps is indispensable. The nextstep in the process is the removal of the largequantity of water which was required for the amplesaponification of the fat. This is effected by theaddition of lyes containing common salt, and after-wards boilingthemixture from fifteen to twenty hours,constantly stirring during ebullition. When the massopens in different places, the separation is esteemedcomplete. The fire is withdrawn, and the whole isnow allowed three or four hours’ repose, after whichthe settled waste lye is drawn off. A further quantityof lye, charged with common salt, is now added, and themixture is gently boiled—the operator being carefulto remove from the sides of the caldron any adher-ing soap, so that all portions may be in contact withthe lye. The mass now acquires more consistence.