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Previous Next The best candle and soap tips online! TECHNICAL TREATISE ON SOAP AN© CANDLES. NEW SOAPS BY NEW METHODS. 345 is obtained ; the soap then is not marbled at the time; the mixture of the soaps of iron, alumina, and lime, colored by sulphuretted lye, is still in solution in the mass, but by de-grees.and by the progressive cooling, the soaps of alumina and lime, being less soluble and less fusible than the soap of soda, separate and divide in the mass of soap, which is white for the. greater portion, but is streaked with strongly colored runs, which are formed by those portions of the soap in which has concentrated the mixture of the soaps of'iron, lime, and alumina, colored blue by the action of the sulphuretted lye. The marbling of the soap is not an effect produced by a simple mechanical mixture of two soaps, one of which is colored ; the cause which controls its formation belongs to a more elevated order, for the separation of soaps having different bases, during the cooling in the frame, is effected by the action of that force which separates alloys at the time of their solidification, the effect of which is known by the name of liquation, and to which we attribute the formation of granites, etc., and in general, that of all the primitive crystallized rocks. In the fabrication of the bar soap by using sulphuretted lyes, a white soap is obtained, because the liquefaction is carried to the point where the paste is fluid enough to permit the whole of the blue colored soaps of iron, alumina, and lime being heavier to separate completely and fall to the bottom of the kettle. The mixture of soaps of iron, alumina, and lime, dissolved in ordinary soap, and colored by the action of the sulphuretted lye, quickly loses its color in the air under the influence of water and the excess of alkali the soap contains; the blue color by disappearing leaves a yellow trace, so much darker when there is more iron in thesoap, which is due to this, that the mixture of the soaps of iron, alumina, lime, and soda, being desulphuretted, is colored only by the iron soap which has an ochreous yellow color. These yellow lines are not wanted by the consumer, and they result in a loss to the soap-maker. It is required that the soap shall have a marbling of a line dark blue, and that the part of the soap thus shaded shall become red in the air, by absorption of oxygen. In conclusion, for the marbling of soap, the follosving conditions have to be fulfilled :— 1. To have in the mass the quantity of iron soap necessary to give the required degree of coloration. 2. That the iron soap shall be combined with a sufficient quantity of soap of lime and alumina, so as to produce a transparent, homogeneous, and properly shaded marbling. 3. To have all the time, but especially at the end of the coction, a proper excess of sulphuretted lye in contact with, the soap. 4. That the cooling in the frame is managed in such a manner as to produce the required marbling. Instead of saponifying with weak l}7es, and in deep and conical kettles, I operate in large sheet-iron vats being three times as long as they are wide, heated below only by the waste heat of the ordinary kettles, and I use strong caustic lyes containing a little common salt, instead of using weak lyes and gradually increasing their density. The heat communicated to the vats is not above 50° C. (122° F.), and may be sufficient only to keep the fatty body perfectly liquid. . Instead of stirring the mixture by ebullition, I use a mechanical stirrer conveniently fixed, which multiplies, more economically than the ebullition, the points of contact between the fatty body and the lye. The stirring is continued until the chemical combination which constitutes the soap is completed, which is ascertained by the strength of the lye, which must remain the same, and the complete solubility of the soap in boiling water. The soap is then converted into small round grains without adherency, and swimming on the excess of caustic lye; the saponification is then finished. The vat in which this operation takes place has its edges elevated about three feet above the large, deep, and conical kettle in which the eoction is finished. A wooden gutter is used to transfer the soap from the vat into the kettle; the old lye, remaining in the bottom of the vat, is drawn off, and 346 TECHNICAL TREATISE ON SOAP AND CANDLES. NEW SOAPS BY NEW METHODS. 347 a new operation may be begun. As for the soap in grains which has been introduced into the large kettle with new lye, its saponification is completed, and the coction is conducted as usual; it is also converted into white or marbled soap. To manufacture white soap, it is not necessary to add coloring matter; but for the marbled soap, the mass must be colored in the vat at the beginning of the saponiiicatioi). This coloration is managed as follows:— In a kettle, I prepare a mixture of soaps of alumina, lime, and lead, by decomposing in the order indicated below, by an excess of soap dissolved in water, solutions of acetate of lead, chloride of calcium, and alum. The mixture obtained is kept under water, and is used to color marbled soap, which is done by adding at the beginning of the operation enough of the mixture to give to the mass the proper shade. The sulphuretted lye used in the saponification quickly gives to the soap of lead the blackish-blue color necessary to color the marbling, and consequent^', it is easy by different trials to obtain the required shade. What we have said of the marbling of soap, proves that there is a necessary relation between the beauty or the perfection of the marbling of the soap, and the quantity of water it contains. A well-marbled soap cannot contain more than 33 to 34 per cent, of water, while white soap may receive more without losing its good appearance, and it is even whiter when it contains more water. To manufacture white soap containing, like the marbled soap, 33 per cent, of water, lyes free from sulphides must be used, which may increase the expense of fabrication. "We have noticed this fact, because it is generally believed that the preference given to marbled soap is ridiculous and without foundation, while on the contrary, this preference is the result of a long experience. SOAPS BY STEAM PRESSURE. In the processes for making soap by pressure and by agitation, using carbonated alkalies, we would call attention to that of Messrs. Bennett and Gibbs, of Buffalo, N. Y., who have made an improvement in that process, by combining 348 Previous Next
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