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Previous Next The best candle and soap tips online! MATERIALS USED IN THE MAMJFACTURE OF SOAPS. b'J »re decomposed, forming volatile asids of a disagnxable and irritating odor. At a still greater heat they form a combustible gas which has three tirii'es the illuminating power of coal gas and is very much purer. The fatty bodies are of very great importance in r umerous industries, in domestic economy and for lubricating machinery, but perhaps their greatest and meat important use is in the fabrication of Boap and candles, so indispensable ia all civilized countries. "We have already mentioned that the true properties and constituents of oils and fats were unknown until Chevreul, Scheele,and others published the results of their researches, their uature and elementary composition, and gave a scientific character to all manufactures into which they entered and .particularly to the making of soap and candles. These researches have been fully confirmed by all later experiments, and possess so much interest and importance that we shall endeavor to give this branch of the subject thorough and complete treatment. The fats and oils finding application in the manufacture of soap are either of vegetable or urimal origin, anl either liquid, as linseed oil, hemp oil, olive oil, poppy oil, fish oil, etc., or they are more or less solid, as tallow, lard, palm oil, cocoa-nut oil, etc. Under the influence of alkalies, and the bases of metallic oxides generally, they are all decomposed into various sebacic acids and glycerine. Liquid fata, >'. e. oils, assume at a low temperature a firm consistency (linseed oil only at 27° below 0 C, 16.6° F.), while the solid fats, i. e., tallow, etc., at an increased temperature become oily (some oven below 100° C, 212° F.). All fats and fatty oils are according to their chemical composition called glyecrides, i. e., glycerine combnations in wb'ieh are comprised according to the theoretical view, of 3 atoms of water or 3 atoms of hydrogen of the glycerine, which is according to the general chemical formula CftH8Oa, and 3 atoms or equivalents of sebacic acids. According to the first or older view glycerine is considered — 011,0., + 3HO, and contains, according to this view, a substance, the so-called glyceryl-oxide or lipyloxide, = CgH^O^ winch occurs in glycerine with 3 equivalents of water, but ap- T$ TECHNICAL TREATISE OK SOAP AND CANDLES. pears in the fats combined with 3 equivalents of sebacicacids. In the fats we find especially palmitic acid of glyeeryl-oxide or so-called pal mitin =CnIls03 4- 2(C3iII3,O3), furthermore stearie acid glyeeryl-oxide, so-culled stearine = CJIJOJ + 3(CMHMO3), and finally olaic aid of glyeeryl-oxide or so-called oleine = CH,O, + 3(ClfiIl33O3). According to a more modern view, glycerine is considered as a so-called triple acid alcohol = C^T,1 [ O6, in which the tliree separately written hydrogen equivalents (H3) are represented in the fats by 3 equivalents of the above-mentioned sebacicacids. The pal mi tin of the fata is accord- hig to this tivpalmilin =C6/-r,jTT n x \06; the stearine is tristearine = C6 /rt JTT n O4; the oleine is trioleiue = 0.. The pure fats of the vegetable as well as of the animal kingdom, the tallows no less than the lards and oils, are not combinations of merely one sebacic acid with the above mentioned glyeeryl-oxide, but contain altogether at least one liquid fat, i. ?., the combination of one solid and one liquid acid, with gly col-oxide. These combinations have a consistency similar to the sebacic acids contained in them, but are somowhat more fusible. Many fats of the most varied origin differ in the pure state only by the relative quantities of the same solid and liquid combinations, which they obtain tine from the other; for instance, olive oil and human fat; others, however, contain the same solid fat as these, but as to their combinations and their properties are an essentially different liquid acid in combination with the glyeeryl-oxide. In others again, for instance palm oil and cocoa-nut oil, the solid acid certainly, aid perhaps also the liquid acid, isapecu-liar acid. Ingeneral,we have at the ordinary temperature the firm combinations called sfeanaes,and the liquid combinations called oleines. However, we mean by stearine, stearie glyeeryl-oxide, the combination of a specific accurately known solid acid, which is contained in many animal fats, especially in that of oxen, sheep, etc. By the term oleine or elaiue, oleic 71 MATERIALS USED IN THE MANUFACTURE OF SOAPS. or elaie acid glyeeryl-oxide, we mean the liquid combination which occurs in a great many animal fats, as well as in many vegetable fats, and in both the sunie chemical combination exists. A number of vegetable oils, however, contain another oleic acid, which is sometimes called oleineacid. It possesses the property of drying to a tough solid body when exposed to the uii1, while common oleic acid only thickens to a smeary fatty substance. For this reason the oils which contain the former are called drying oils, and the others fat oils. The second combination of a solid sebainc acid with glyceryloxide, which is sometimes mixed with stearine and again with oleine, is called pahnitin (margarine), and the acid palmitic acid (margaric acid) is next to the oleic acid the most extensively distributed sebasic acid. It is found as a solid ingredient along with stearic acid in ox-tallow, and in fat as well as drying- oils, and pa Ira oil. The pure combinations of the above-mentioned substances are odorless; but the most of the raw fats, those of the vegetable kingdom as well as of the animal kingdom, possess a specific odor, by which they may be distinguished from one another. In some, it originates from an admixture of volatile oils, for instance, in the oil of mace; in others from glyeeryl-oxide combinations with volatile acids, for instance, lactic acid, valerianic acid, capronic and hircinic acids, as in mutton tallow; in others, as in linseed oil, the odor depends upon unknown admixtures. To the touch the fats are known by their specific lubricity, in water they are all insoluble, most of them also in alcohol, excepting castor oil. Heated alcohol takes up a goodly amount of the fats, which after cooling ofl' again almost entirely separate, but they are freely soluble in ether, volatile oils, sulphuret of carbon, chloroform, acetone, and pyrolig-neoua acid (wood spirit). They are rich in hydrogen and oxygen, of the latter they contain 70 to 80 per cent, but nitrogen (azote) is not contained therein. Their specific gravity is always less than that of water, and changes according to the kind of fat between 0.910, and 0.930 at 15° C. (i>9° F.). The fats in fluid condition expand at every increase of tera- 72 , TECHNICAL TREATCSE ON SOAP AND CANDLES. peratureover 1° C. (33.8° F.) by T,'ir5toT-(f15B of their volume, so that at 120° C. (248° F.) they have ^ more volume than at 0° C. (32° F.). In the dark they become phosphorescent, by a slight increase of temperature ; the real fat oils and fats boil only at 170 to 250° C. (338 to 482° F.),the drying oils, however, beween 100 and 115° O. (212 and 239° F.). No fat can be distilled without decomposition; while it boils at the high temperature of 800° C. (572° F.), the escaping vapors are not those of the un decora posed oils, but those of the formed products cf decomposition, which, according to the applied temperature, as well as to the amount or kind of the divers eebaeic acids contained therein, vary very mueh. The glyceryl-oxiie is first decomposed, a very volatile body is formed, which is violently irritating to the eyes, at the ordinary temperature is liquid, soluble in water, and is called acrolein. By this property, it is easily ascertained whether a fat-like substance is really fat, a combination ofglyceryl-oxide, or not; for the least amount of glyceryl-oxide makes itself noticeable by the intensely sharp smell of acrolein. The oleic acid, too, will be in a great measure decomposed, and but little distils over unchanged. From it is formed the so-called sebacie acid, with a series of substances such as carburetted hydrogen gas, the so-called oil-forming gaa (chiefly illuminating gas) and like carburetted substances. If steario acid Le presenr, it separates in palmitic acid and also in several carburetted substances, and even the palmitic acid does not distil entirely over unmixed, although a large part thereof is found among the products of the distillation. If the pressed or rendered fats are exposed to the air, they absorb oxygen, at first slowly but afterwards more rapidly. During the process the ao-ealled drying oils cover themselves with a skin, ami thereby withstand the influence of the air much longer. Tiie other oils or fats become somewhat tousrh mid thick, and gain a disagreeable odor, show an acid reaction, and taste sharp and are gritty. This is especially the case when theoils have absorbed much albumen and similar matter from the organs of plants or animals from which they have been obtained. By the shaking tip of such oils in hot water MATERIALS USED IN THE MANIXFACT (THE OF SOAPS- 73 and a small quantity of hydrate of dolomite, this condition, which is called rancid t may be changed. Many acids absorb the glyceryl-oxide entirely or partly from the sebacic acids. If a little hydrate of sulphuric acid for instance is carefully mixed with olive oil, so that no heating ensues, glycerine will be separated, which with the sulphuric acid combines and forms a compound of glycerine and sulphuric acid, while the sebacie acid is free. But if the oil is carefully mixed with half its volume of hydrate of sulphuric acid, then the sebacie acids combine also with the sulphuric acid and form bodies ivhich by the addition of water are decomposed, transferring all the sulphuric acid thereto, in cold air gradually, by boiling at once, into several other acids, among which, however, neither palmitic nor oleic acid is found. Upon the influence of sulphuric acid on fats, rests in part its application in purifying the same. The oils obtained from seeds by pressure are never free from albumen and other impurities; a moderate addition of sulphuric acid causes these substances to coagulate and produce in water soluble glycerine sulphuric acid. If, on the other hand, too much sulphuric acid is used, there will be formed monomargarie, hydrornargaritic, hydromargarie, monoleic, and liydroleic acids, which are very limpid and contain less carbonic acid than oleic and margaric acid. In the melting of tallows and animal membranes, we must be careful in the application of sulphuric acid. A large quantity of this acid makes the melting easier, but we obtain, as experience teaches, tallow which is very fusible, which for the manufacture of candies is not desirable, and obviously originates from the formation of hydromargaric acid, etc. In order to obtain the hardest possible tallow for chandlers, such as even in warm weather may be moulded and may be easily taken from the moulds, the melted tallow should be permitted to cool oft1 very slowly. Stearitie and palm itin will then separate in noticeable crystals, and in a temperature of 20° to 25° C. (t>83 to 77= F.), a largo part of the oleiu 74 TECHNICAL TREATISE ON SOAP AKD CANDLES. can be removed by pressing. Thus a tallow is obtained which at all seasons of the year may be manufactured into candles. These are harder, lees fusible, and whiter, since the olein is generally of a yellowish hue. Such candles are in the market under the name of stearine candles, which must not be confounded with stearic acid candles, which are sometimes also called stearine candles. This will be more fully explained in the section on candles. Diluted nitric acid at first acts on the oils similarly to sulphuric acid. It sets ore part of the glycerine free. Concentrated acid, however, reacts very strongly with it; they froth violently, and at times even ignition ensues. A great number of products of oxidation are thus formed—volatile and less volatile acids. Nitric acid causes a very singular change in the olein, the sebacic acid, and the fats. The olein of the drying oils doea not undergo this chancre. Without withdrawing from the olein its glyceryl oxide, the nitric acid will change it at the ordinary temperature into a white body, called elaidin, and the acid produced therefrom, the elaiodie acid, is not liquid like the oleic acid, but solid. Both these acids have the same chemical composition. The salifiable bases decompose, as has already been observed, the combination of the sebacic acid with the glyceryl oxide, and unite with the stearic, palmitic, and oleic acids, and all other Bobacic acids, into salts, which are called soaps when the base is an alkali, and plasters when the base is protoxide of lead (litharge). The- glyceryl oxide separates, by the combining of 1 eq. of the eame with 8 eq. of water, into glycerine. Oaaetic ammonia produces the same decomposition, but only after a very long time; or it unites witli the oils into a thick and milky fluid, which is known under the name of volatile liniment. Carbonated fixed alkalies form also creamy liquids, from which, however, diluted acids separate the fat unchanged. Culinary salt and sulphate of copper are dissolved by the fats without changing them. The number of tlie various fats found in the animal and vegetable kingdoms is infinitely large; almost every kind MATERIALS USED IN THE MANUFACTURE OF SOAPS. 75 possesses a fat or oil which, either on account of its smell, color, etc., difters from the other. In a great parl these differences exist only in the various quantitative mixtures of the liquid and solid parts, and are caused by small, unessential admixtures, a small amount of volatile substances which are to be considered as unessential to the fat. There have been very many different kinds of solid and liquid fats found which have not yet been thoroughly examined.. FATS OF ANIMAL OKIGIN. Tallows are those fats or greases obtained from the ox, the sheep, the goat, and the deer, and are the hardest, having the highest melting point. The first two named find the most prominent application in the manufacture of soaps, and are mixtures of oleine, margarine, and stearine, in varying proportions, according to the age, the -season, and the nature of the food. Animals fed upon dry food furnish the most solid tallow, that of those that are pastured is less so, while those fed upon swill furnish a very soft grade. It is also noticed that fat produced in summer is softer than winter fat. The fat occurs enveloped ir. very thin cellular tissues which are moist in fresh tallow and are easily decomposed and soon undergo a change in the air. It is necessary therefore, especially in summer, to keep it in a cool place or at once to separate it from the membranes fcy rendering. Besides the. three constituents above mentioned, tallow contains the glycerides of some volatile sebacic acids, as lactic, capric, capronic, and valerianic acids, besides some peculiar matters not yet fully tested and explained. To obtain the tallow from the membranes which surround it, the fatty tissues are cut into small cubes, placed in a suitable vessel and exposed to a heat which exceeds that of boiling water. In the heat the membranes are destroyed, the melted tallow runs out and can be separated from the membrane by straining. This process ha3 been in practice a long time and is so still. Sometimes a still higher temperature is applied in order to cause the residium to undergo a T8 TECHNICAL TREATISE ON 6OAP AND CASDLES. roasting, thereby trying to obtain a greater yield of pure tallow. In general though, this method remains imperfect and a larger or smaller loss of tallow is sustained, much remaining in the tissues, which are but imperfectly opened by this operation and become 30 hard that they yield the tallow under the press with difficulty. Furthermore it is an impossibility to obtain an even temperature with which to operate through the entire melting process. On the bottom it becomes too high, to the detriment of the color and quality of the tallow. Finally during the melting process are developed from the aniiiml substances gaseous and other vapors of a disgusting odor. The application of steam in lieu of a free fire is but a slight improvement, because the temperature remains too low and besides by the immediate contact of steam with the fat, the substance of the membrane is changed into glue, which can be separated from, the tallow only with great difficulty. In hermetically sealed vessels by an increased pressure and a direct stream of steam the raw tallow may be melted, the fat finally separating ftom the glue solution which settles on the bottom. That in the process of mere melting the membrane yields the fat with so much difficulty, is demonstrated especially in the fact that the tissues are not completely destroyed and opened. To manipulate to a more complete opening, various means have been proposed and applied, which answer the purpose equally well BO that one or the other is brought into use. Most convenient is the method of allowing the lumps of tat, instead of cutting them into small pieces, to pass through narrow rollers whereby all tissues are opened, and after this the tallow may be rendered in tie heat. Another process (by Evrard) consists in the mixingaud warming of 300 parts of cut tallow with caustic natron lje (made of 1 part calcined soda dissolved in 200 parts water). The odorous substances, partly volatile acids, comline with the natron and remain in the lye dissolved, while the pure fat is separated. By this mode Faiszt obtained from 100 parts of raw, 88 parts of pure tallow, and from ihe lye by the addition of acid 8 parts more. MATERIALS USED IN TUE MANUFACTURE OF SOAPS. 77 hence together 96 parts. In this manner all the fat may be obtained,and yet no special advantage is found in this process, especially if we consider the labor, and also the circumstance that in this case no greaves or cracklings are yielded which find a good and profitable use in feeding1 swine and dogs. In the same manner D'Arcet, according to his acknowledged excellent method, brings diluted sulphuric acid to operate on the raw tallow whereby the important advantage is had, that, by the chemical destruction and opening of the tissues, the development of the fetid vapors ia lessened and they become more bearable. According to D'Arcet the raw tallow is melted with half its volume of water, to which has previously been added 8.3 per cent, of sulphuric acid, keeping the entire mass boiling until the separation of fat and tissues is finished. Although this operation was originally calculated for an open fire, it may nevertheless be performed over steam, since by the acid the separation of fat is furthered in a high degree. In the apparatus of Taulet the heating of steam is performed from the outside, in that of Chamby by a direct introduction of steam, whereby the greaves or cracklings are so loosened that they are pressed out with ease, or by mere reboiling render the tallow completely. Exi>erimerits with the first apparatus yielded 2 to 4 per cent, more than the operation over an open fiie. With regard to the direct introduction of Bteam, experience has taught to apply Ios3 water by an increase of acid, {. e,, to apply about one-fifth water witli b* per cent. acid, since by means of the condensed water the proper proportion is established. On the same principle aa that of D'Arcet, the method of Lefevere is founded. He prescribes the maceration of the cut-up tallow for three or four days in the diluted acid, and then the remelting of it in fresh water. As long as fresh tallow, or at least eome which is not too old, is worked, the methods before mentioned are ample, even the simple rendering, especially if the raw tallow has been pressed through rollers. It matters not whether by the one or the other method a few per cent, of fat more or less are gained, if the remaining greaves 78 TECHNICAL TREATISE ON SOAP AND CANDLES. can be used for feeding? cattle and swine. Experiments of comparison whether the yield by the one or the other method of melting tallow !s more j.nttitable are still wanting. The statement that so tni:eh pure tallow was obtained from 50 kilogrammes means nothing, since the mw tallow is uu-equal in fat, nnd yield-; a: one time more, nt olhers less, so that a superabundance of membranes 13 on band. The real drawback that presents i'self in the rendering out by melting is the unbearable smell, winch becomes, not only for the immediate neighborhood hut for a wide circle, a source of the greatest nuisance, so that especially in larger cities frequent complaints are entered against this evil. Many propositions have therefore been made, to have the rendering of tallow performed in Ruch a manner that the bad smell may not appear. The mest thorough investigations have been made by Stein, and later by Grodhaus and Fink, in Darmstadt. It is known that the smell of the bad tallow is caused by the decaying of the membranous |»art9, which thereby taint the fat which in it pure irate is lc& changeable. The chemical change must have gnat similarity with that which ensues in the formation of cheese, wherein fat and azotic substances by mutual contact succumb to corruption. In this case at least so much is known—that the smel! emanates chiefly from acids which develop their smell not only while free but even while latent in bases. Resting on this, Stein deemed it possible to remove the fetid smell of the tallows melting by a double p.-ineiple, by either suppressing the corruption or by making their bal smelling product odorless. The experiments which Stein made in the first direction were whereby he applied either antiseptics,aB for instance sulphuric acid or tannin, or such substances as destroy putrids, as neutral chromate of potassa, hypermanganesie acid with sulphuric acid and also nitric acil; all these however have not had a satisfactory result, and the required operations were moreover too complicated. Stein therefore searched for the other principle by disinfecting the odorous products and thus removing the trouble caused in rendering tallow. lie then started with the belief MATERIALS USED IK THE MANUFACT0HE OF SOAPS. 79 that they are predominant volatile oils, so that it was necessary to change them into salts, which on their part would be without smell or of a lesser odor. In tins case too the purpose could obviously be reached in a dual manner. The salts mentioned could he formed in the liquid itself, or, since the odoriferous acids must needs be volatile, could be formed outside. For the first case lime-water was tried, which manifestly must needs work similarly to Evrard's met bod (lye of soda), but in preference to this possessed the undeniable advantage of an always even and very great degree of dilution, so that the free acids in all probability became neutralized, but no fat was saponified, and possibly the lime combinations of the acid were of a lesa fetid smell than the natron combinations. In fact the smell decreased in a noticeable manner when it was placed in lime-water; but when it was melted therewith, the smell increased, ao that the application of lime-water must be avoided. In a very ingenious manner Stein now tried the conversion of the bad smelling acids into ethyl-oxide salts, which have even an agreeable smell. Although a v^ry successful result was hereby reached because the smell vanished and did not reappear even in the process of melting, however another circumstance happened which retarded the process. The sulphuric acid which separates from the sulphuric ether acid (necessary in the forming of the ethyl-oxide) furthers the solution of the glue producing formation, in consequence whereof the formation of an emulsion ensues from which the fat can be separated only with difficulty. Hence this process of melting bad also to be abandoned. It now only remained to cause the escaping odors, after corning forth, to be made harmless. This process too is based on the idea that these substances are acids, which might be bound by an acidifiable base, and for such Stein applied hydrate of lime in combination with coarse-grained charcoal— the lime to retain the bad smelling acids, the coal the other bad smelling combinations. For this purpose a 5 to7| centimetre (1.96 to 2.94 inch) wide sieve-crown, which could bo placed steam-tight upon the steamboiler, which in place of 80 TECHNICAL TREATISE ON SOAP AND CANDLES. the sieve bottom was covered with canvas, filled with slackened lime and fresh-burned charcoal of hazelnut size, nnd thus placed upon the melting vessel. All vapors which escaped from the latter had to pass through the lime-coal mixture, and proved on their exit perfectly odorless. Although the melting of tallow under application of the described apparatus, which Stein calls the "charcoal cover," ia sufficient for the strictest requirements in regard to the objectionable smell, this process will not meet with general use, since it requires a steam-tight sealing of the charcoal cover upon the netting vessel, which in operations in larger quantities is only fulfilled with difficulty. To this must be added, that for every renewed melting a new filling of the cover with lime and charcoal will be necessary. This process can only be called practical it' applied in the melting by steam; but if—as is still the practice in most soap-boiling establishments—the melting is performed over an open fire, where in tlie cover a paddle has to be applied, in order to stir the tallow, then the products escape through the opening for the paddle and enter the work-room. To avoid this, the cover and paddle ought to be connected air-tight by means of an India-rubber hose. There is therefore no doubt, after the above stated experiments of Stein, that the smell, which is caused by the melting of old lallow, nuiy be removed by chemicals, in one way or another; the carrying out on a larger scale, however, is obstructed by s Previous Next
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