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Previous Next The best candle and soap tips online! For Oleic Acid C1M H1M Oia- 012 = 748 884 156 TECHNICAL TREATISE OX SOAP AND CAKDLES. SAPONIFICATION. 157 SECTION" VII. SAPONIFICATION—THEORETICAL, CHEMICAL, AND PRACTICAL. SOAP, in common parlance, means that in common u8e for various purposes, and is a chemical compound resulting from certain constituents derived from fats, oils, and greases of various kinds, both animal and vegetable, with certain sali-fiable bases, which, in the kind of which we write and called detersive soapa, are potash and soda. Chemists apply the name of soap to any compound of the fatty acida with a base: thus we have lead soap, used in pharmacy, and called diachylon plaster. Zinc soap is also used in medicine and in painting. Lime, magnesia,tin, copper, mercury, silver, and gold are made into soaps that find various uses in the arta. Of all these we have but little to write except of .ime anap, which has great importance in the fabrication of stearic acid for candles. These processes will, however, be treated of in our section on candles. Caesium and rubidium (oxides of) may also be used in forming soaps having the properties of a potash soap; but, as these two alkalies have thus far been found in nature in but limited quantities, they cannot have any application to our art. Before Chevreut made known his researches, it was supposed :hat fats and oils formed a combination with alkalies. He, hewever, explained tliat fats, when saponified and again separated, had properties quite different from those existing before saponification, and showed that fata and oils are compounds of peculiar acids, stearie, palmitia, oleic, etc., nonvolatile substances, while fats which have a peculiar odor have in addition to these acids volatile fatty acids, as butyric, valerianic, etc., and they were all combined with a sweet principle known as glycerine. Berthelot held and proved that all the fats and oils used in the fabrication of soap are ethers of glycerine C3IISO3, that C II ' substance beingviewed as a trivalent alcohol Vrs - Or Pal- mitin, for instance, the principal constituent of palm oil, is glyceryl tripalmitate, that is, glycerine in which three atoms of hydrogen are repUced by the radical of palmitic acid CII ) on3 rf n fQi* Stearne (tristearine) and oleine (trioleine) have an analogous constitution. When the fats, jalm oil for instance, are saponified with caustic alkalies, say caustic soda, the fat, that is the ether, is decomposed into alcohol, i.e. glycerine, and the palmitate of sodium, i. e. the soap, is formed, according to the following equation:— Tripalmitin \ orx3 ur r\ i 0, and caustic soda 3NaOH glycerine Cj^ I 03 and sodium palmitate 3 j jj1^1*0 jO. The glycerine formed in the process of saponification remains after the separation of the soap dissolved in ihe mother liquor, and can be separated and utilized. Besides tlio mode of saponification of fats and oils by means of the metallic bases, i. e, alkalies, there are several other modea, as by acids, by heat, by 3team, and by fermentation, which will be explained in their appropriate place. Thus, though, we find'that the fats and oils consist of so many different and distinct substances, they are chiefly distinguished by consistency at ordinary temperatures, the liquid part being called olein and the (-olid stearine, and their consistency depending upon the preponderance of one or the other of these constituents. Correctly speaking, stearine the solid part may not be all stearine, bat may contain margarin, palmitin, etc., while the oleine may contain margarin, cocin, etc. Yet when any of the fatty acids are separated th enaction with the alkalies is the same, and they can. be united in the same manner to form soaps, but the soaps formed 158 TECHNICAL TREATISE ON SOAP AND CANDLES, will owe their greater or less solidity to the amount of the solid or liquid constituents of the fatty bocly or sebacie acid. In the saponification of the fats with hydrate of lime for the purpose of forcing stearic acid for candles and separating the oleic acid and liberating the glycerine, either of the acids is the more readily saponifiable, and for the oleic acid the lye need not be entirely caustic, as it can be saponified with carbonated lyes. In this process glycerine, which we have explained is a kind of alcohol, takes up the elements of water with which it had previously been formed with the fatty acids. Glycerine forni3 about 8 to 10 per cent, of the neutral fats, lard being usually richer in this valuable article. It must not, be supposed that in the production of soap the materials combine as readily or as rapidly or with the same exactness as ordinary salts form to make a union or a decomposition, for it is not a momentary process. On :he contrary, it occupies a considerable length of time, and ttie formation of the soap is not complete until in the boiling process the fat is first made into a milky emulsion with the weaker lye, and,by the further addition of alkali, it becomes saturated, and finally finished and separated from the mother-lye,and is ready for use. Oi, again, when the soap is made by the extempore or cold process, it is at first combined mechanically ; it has to remain in the frames for some hours that the materials may react spontaneously upon one another, and, by increased heat of the chemical action, saponification is completed. So we rind that saponification does not take place suddenly and throughout, but passes through several stages, and only gradually are the seLaeic acids decomposed and formed into salts, or, in other words, soaps. When, however, we melt tallow with as little heat as possible, say about 37.7° C. (100° F.), and add half Us weight of strong alkali of 36° P. of the same temperature,and constantly stir for some time, we will find it suddenly acquire a solid consistency, with a great elevation of temperature, proving the great chemical attraction of the materials. Yet saponi-fieation is not yet complete, for it eeems to have an exces3 of Previous Next
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