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Previous Next The best candle and soap tips online! and falls to the bottom, while the soap ia floating on the top, forming into slabs, and theu into grains or curds, when the heat is removed, allowed to rest, that the spent lye may subside and be run off, or the aoap may be ladled out into frames; and the soap is made. Soap as here noticed is also insoluble in Btrong lyes, and when it has taken up all that it can, or becomes from long boiling saturated, it floats upon the surface of the lye, though it is possible to add water or weak lye and it is often filled or sophisticated in this manner. Other salts have the property of separating soap from its lyes, as chloride of potassium, acetate of potassium, chloride of ammonium, or sal ammoniac and sulphate of soda, the latter salt, however, is sometimes added to soap made from weak stock, bone, or kitchen fat, etc., having the property of hardening it and making it more marketable, but it must be in limited quantities in strong solution and after the soap is framed, and stirred in mechanically, that it may not decompose the soap. Carbonate of soda has also this hardening property,and like the sulphate it must be added iu strong solution and crutched into the finished soap. From what we have already said, it will be gleaned by the intelligent reader that the saponification of the ordinary fatty bodies with the usual alkalies and the formation of marketable soaps is iut a complicated matter but a simple process, demanding, however, much care and exactness, and resolveB itself irto the neutralization of the fatty acids with the caustic alkalies. Thus we will analyze a etearine soap: stearate of soda,, CluHi!0Ou-|-3(NaO.HO),= 3(NaO.C30H3JO3) or stearic acid soda, and CaH,Ofl or glycerine. f 833 parts stenric acid ) g. ye 9l8 par(s fi0Rp 890 parte stearine { " ., T*icacid 5 { S7 " water *give 92 part" fif1?0"*** Similar equations apply to almout all other combinations of the fatty acida with the bases. Soaps made with potash lye are always soft and retain their glycerine, and, owing to the hygroscopic character of 11 162 TECHNICAL TREATISE OS SOAP ASD OAKDLES. SAPONIFICATION. 163 the base, they are constantly absorbing water from the atmosphere and bccomi ng softer, 100 parta of potash soap having been known to absorb 25 parts of water in a few w^eks. These soaps are very rarely neutral but almost always contain free alkali, caustic or carbonated lye. Yet they are an important article of commerce, having various uaea in the arts, and are in many countries used for domestic purposes, particularly in countries where wood is abundant and is used as fuel and wood ashes are plenty. The making of hard soap from potash lye is done by first saponifying with wood-ash or potash lye and then cutting the soap with culinary salt, forming a double tiecomposition, the chlorine of the salt uniting with the potash forming chlorate of potash, the soda uniting with the fatty acid and forming a hard soap. While it is impossible to extract all the potash by this means, it is, however, no disadvantage, but tends to improve the quality by keeping the soap plastic. In this decomposition the soap also loses all its glycerine, it being carried down with the sub-lye. The neutral fats may also be decomposed by means of super-heated steam at 260° to 330° C. (500° to 626^ F,). Tilghman has invented an apparatus for thia purpose, for the production of glycerine on an extensive scale. The glycerine at this temperature separates, and the sebacic acids resulting are readily saponified in carbonated alkali. This process ia conducted on an improved method by Milly, with the addition of a little hydrate of lime (milk of lime) in connection with a pressure of steam at 7 to 8 atmospheres, 170° C. (838° F.). The resulting lime soap, the fatty acids, and the glycerine could be easily separated. By using one-half of one per cent, of caustic alkali at the above-mentioned preasure and heating, the glycerine will be separated in about 10 hours and can be drawn from the bottom of the covered boiler, while the remaining sebacic acids can be formed into soap in the usual manner. Or this process can be conducted by means of a still and worm, distilling off the sebacic acids and afterwards extracting the glycerine from the residuum. In either case the 8GH. 3 0 sebacic acids can be easily saponified, having a greater affinity for the alkalies when they have parted with their glycerins. Glycerine now of great value for such varied purposes is made in one or other of the above described processes, but generally by means of super-heated steam acting upon beef or mutton tallow or hog's lard, in the process of making stearic acid for candles, to which all of these processes are applicable. This process has in view the production of those useful substances, stearic acid for candles, oleie acid for soaps, and glycerine for the arts and for pharmacy. The different changes may be explained thus;— SOMHJ(O Below is a more simple equation, and one that will explain quite as well the usual changes that take place when two soap materials are brought into contact to form a soap; fur instance, if we take neutral stearine with hydrate of soda, the reaction may be stated thus:— stearate of oxide of glyceryl + soda + water = stearate of eoda + hydrate of the oxide of gWceryl Glycerine. Hard soap. Of course the same simple equation can be applied to oleine, substituting it for stearine. We have remarked that the consistency of a soap is affected by the melting-point of the fats used, and is more or lesa hard accordingly, and it may frequently occur that the manufacturer will have many soap greases such as bone fat, glue fat, kitchen grease, etc., and some that are recovered from offa! and wool washing, etc. Thesegreaaes are technically called " weak stock," and produce when used alone, and particularly with rosin,too soft asoap, that melts and wastes in the water in using. These soaps can be improved by an artificial hardening by adding 5 per cent, of crystals of sulphate of soda dissolved in the least possible amount of water, or the addition of 10 to 15 per cent, of the solution of silicate 164 Previous Next
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