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Previous Next The best candle and soap tips online! 3B8 TECHNICAL TREATISE ON SOAP AND CANDLES. NEW SOAPS BY NEW METHODS. 339 action takes place, at 260° C. (500° F.), and the mixture becomes much puffed up, in consequence of a great development of carbonic acid gas. Towards the end, the temperature must be somewhat increased, in order to decompose the last portions of neutral fat. After a few hours a semi-liquid, yellowish mass is obtained, which, during its cooling off, becomes more consistent. In water it dissolves gradually to an opalescent liquid, which in every respect acts like a solution of common soap. The carbonated alkalies, as also culinary salt, cause therein a separation of soda-soap, which collects upon the surface of the liquid. Saponification of Fats by Sulphuretted Alkalies.—This method has been proposed by Pelouze. Despite this authority, we have not been able to discover in this new method any special advantage; for although an equivalent of sulphide of sodium, where this, like the soda, is produced on a large scale, may be cheaper than an equivalent of caustic soda, there are nevertheless other inconveniences which are much greater, since the alkalies form in themselves a proportionately cheap iugredient of the soap, and there is therefore caused, by the cheaper sulphide of sodium, no essential reduction in the prices of the soaps. In the practical performance, the fats are treated in exactly the same manner with a solution of sulphideof sodium, as the common method with soda-lye. The saponification ensues by means of sulphide of sodium very quickly and under a development of sulphuretted hydrogen gas, which, on account of its very disagreeable smell and its poisonous properties, must be made harmless. This may be done most advantageously by burning it, and the sulphurous acid which ' is produced by the process of burning may be applied in the fabrication of sulphuric acid. But this presupposes a very extensive and complicated business, such as would hardly be suitable for many soap-manufactories. Moreover, according to Dullo, the soap made with sulphide of sodium retains a bad smell, which cannot be removed, and finally the manufacture of white soaps with sulphide of sodium would become en- tirely impossible, on account of the unavoidable admixture of coloring substances. The Process of Mege Mouries—This process requires a particular notice here, as when first made known it attracted great attention, which has however subsided, though it has resulted in suggestions which have been utilized particularly in France, especially for making the sebacic acids in the manufacture of candles. He found that the neutral fats in the oil seeds during germination, as well as in the animal organism during life, are in the condition of movable globules, which offer a great surface to the action of reagents. In this globular state, fats exhibit some peculiar properties of which we shall only notice such as are interesting to the soap-maker. Fat, as for example tallow, in the ordinary state, becomes rancid by exposure to the air; in the globular state, in a milky form, or in a dry state, or in the form of a white powder, it remains unaltered any length of time. In practice it is obtained by mixing melted tallow at 45° C. (113° F.) with water at the same temperature, holding in solution 5 to 10 per cent, of soap. It is difficult to combine tallow, in its ordinary state, with hot salty caustic lyes ; but in the globular state the lye is immediately absorbed in proportions varying with the temperature. Each globule, as it is attacked by the alkali, quickly gives up its glycerine, and in a very short time each globule of fat is transformed into a globule of perfect soap. This result is obtained in two or three hours. These saponified globules heated to 60° C. (140° F.) give up the excess of lye with which they are charged, and retain only water sufficient for ordinary soap. They become eventually transparent, and by stirring form a layer of melted soap above the lye. The saponification is so complete, that to prepare commercial stearic acid, it is only necessary to add a corresponding quantity of diluted sulphuric acid, and the fatty acids may be separated from the solution of sulphate of soda. By melting with steam, crystallizing and pressing when cold, a commercial stearic acid is obtained perfectly pure, melting at from 57.7° to 58.8D C. (136D to 138° F.), while the oleic acid flows off' nearly colorless. This latter acid is of a 340 TECHNICAL TREATISE ON SOAP AND CANDLES. NEW SOAPS BY NEW METHODS. 341 better quality than many fixed oils, and more useful to manufacture white soap of first quality either alone or mixed with some other fatty substances. By using it alone, it has only to be neutralized by weak lyes ; the formation of the soap takes place immediately, and it can be melted at once. If mixed with some other fat, this fat has to be transformed into the globular state and the saponification is effected in six hours ; and in twenty-four hours a soap may be prepared which is as neutral and nearly as good as the best olive oil soap. Thus not only is time saved, but there is no loss of fat as in the ordinary process of boiling soap. Knapp attributes the great efficacy of the globular state not so much to the globular form as to the microscopic size of the tallow globules, which maybe attacked to their centre by the lye, while a large lump of tallow, under the same circumstances, would soon be coated with a stratum of soap of a thickness which would render it impossible to penetrate it. As to the saponification in the kettle, there is, strictly speaking, only an emulsion of fat obtained, a homogeneous milky mass, formed by the union of the melted tallow with the lye; moreover, soap is simultaneously produced by the first contact of these substances. This emulsion, after standing a few hours in the cold, becomes gradually saponified. It might be expected that the process would be more rapid under the influence of heat and agitation, but this is not the case, and the hypothesis is that, in the boiling, each fat globule is immediately enveloped in a coating of stearate of soda, which protects the nucleus from further saponification. W like manner, and upon the same principle, heated soap bubbles are only denuded of their gelatinous coating, and the mass becomes a thickish soap solution rather than a chemical compound. Again, concentrated soap in the heated mass will retain a, considerable quantity of fat in solution, consequently diminishing the action of the alkali. This may be remedied by the addition of a middling strong lye ; but in any case, cooling and quiet are found to promote the combination of fnt with alkalies, after having been heated for a sufficient length Previous Next
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