 |
Home > TECHNICAL TREATISE ON SOAP AND...
Previous Next The best candle and soap tips online! TECHNICAL TREATISE ON SOAP AND CANDLES. THE FABRICATION OF SOAPS. 253 carbonate of soda, even if dissolved in thirteen times its weight of water and boiled with a small overplus of lime, does not yet impart all its carbonate to the lime. The following are the results of these experiments:— By 1 part anhydrous carbonate of soda and 5.8 parts water, remain undecomposed .... 15.62 p. c. NaO.CO2. " 1 part anhydrous carb. of soda and 8.2 parts water 8.78 " " 4.19 1.39 11.8 13.3 Even by the application of thirteen and one-third parts its weight of water to that of carbonate of soda, and the required amount of lime, there were 1.29 per cent, remaining undecomposed ; it also made but a trifling difference when a larger overplus of lime was applied. Since it is known by experience that lyes which contain 9 per cent, of their contents in carbonate of soda will saponify the neutral fat?, those who deem this an advantage, may dissolve the soda in eight or nine parts its weight of water, and then add the necessary quantity of lime and boil it. Meanwhile the solution becomes somewhat weaker by changing the lime into hydrate of lime, which imparts its water to the lye, because the carbonate of lime retains no water. To acquire a perfectly free carbonic acid lye, we would, according to the above experiments, probably have to apply fifteen times the amount of water of the weight of the pure carbonate of soda, and obtain hence a lye of 3.9 per cent, caustic soda, which, of course, is tolerably weak. But a lye of from 5 to 7 per cent. is in most cases suitable, i. e., such as is obtained by dissolving carbonate of soda in ten times its weight of water. For pure carbonate of potash, the same proportion must be used, and a lye is thus obtained of nearly 7 per cent, caustic potash. By these calculations it is self-evident, that we should only consider the contents of pure carbonate of alkali, so that for instance 50 kilogrammes (110 lbs.) of a potash, which contain but 65 per cent, pure carbonate of potash, we dissolve in 325 kilogrammes (715 lbs.) of water, and a soda of 35 per cent, pure carbonate of soda in 425 kilogrammes (935 lbs.) of water. After having in this manner made the solution, and having brought the entire quantity to a boil, we begin with the addition of the previously weighed and slaked lime (milk of lime) in gradual portions, while the liquids are kept slowly boiling, and continue thus for a short time, after having added the last portion of lime. By this operation the lime which at first was of a gelatinous consistency is changed into the crystalline or grainy state, and may then be lixiviated with the greatest ease. When the boiling has lasted about half an hour, the fire is removed, when the carbonate of lime will soon settle on the bottom and the finished lye stand clear above it. After having cooled off so far, that the finger may be placed in it without scalding, the drawing off is commenced. This is best performed by means of a copper siphon, or in place of such by one made of tin-plate. The siphon is filled with water and boths ends are closed with the thumbs of both hands, which as they have to come into contact with the lye are previously rubbed with fat, or still better with paraffine. The residue, the carbonate of lime, is carried into the filtering apparatus, which has a sieve bottom, covered with coarse canvas, or cotton cloth, in such a way that none can escape spreading, the pulpy mass as evenly as possible thereon, to allow of a complete filtration, and fill the space above it with pure water, until it forms a layer equally as high as the carbonate of lime, and filters completely. If the necessary care and attention have in every particular been given, the lixiviation may be considered as finished, and the lime exhausted; but for a second time pure water may be poured upon the lime, and this very weak lye may be used for preparing the lye in the next operation. Preparing Potash Lye from Wood-ashes.—"Where there is opportunity to purchase large quantities of good wood-ashes cheaply, their use offers, for the preparation of potash-lye, immense economical advantages over the use of potash. The manipulation is somewhat different from that of potash. After having, in the manner heretofore described, ascertained the contents of carbonate of alkali of the wood-ashes, the required amount of lime is calculated that is 254 TECHNICAL TREATISE ON SOAP AND CANDLES. THE FABRICATION OF SOAPS. 255 necessary to change it into caustic potash. The lime is slaked to powder and mixed with the wood-ashes as thoroughly as possible. This mixture is placed in a wooden, or still better in an iron vat, in which is inserted a sieve bottom covered with straw, now adding sufficient water to it so that a thick paste is formed which is left at rest for 24 hours. It must be- observed that the layer is everywhere of equal height, and no gutters are formed, through which the water might flow off" without having previously absorbed the caustic potash. Now pour water into the yet empty part of the vat and permit the lye to draw off. The space between the blind and the real bottom must have an opening immediately under the former, so that the air can escape. The lye which collects between the two bottoms is drawn off by means of a stopcock, and carried to a second vat, which is prepared in the same manner as the first. It may also be passed into a third vat, but in every case the quantity of water must be so proportioned, that only lyes of 7 per cent, caustic potash are produced. Of this strength, the lyes may be used for saponification of the fats; but they contain as a rule such large amounts of sulphate of potash and chlorate of potash that muddy soft soaps would be obtained. It is therefore necessary to condense them to 22 to 25° B., when after cooling off the greater part of these foreign salts crystallize. For use the lyes are again diluted with water till they reach the desired strength. Preservation of the Lyes.—Although it is not common to prepare large quantities of lyes in advance and to preserve them for a longer period, yet it may be advantageous under certain circumstances, especially if the necessary vessels are at hand, to lay up a supply of caustic lyes; to avoid the absorption of carbonic acid, and to lose thereby more or less of their efficacy. Strictly hermetically tight vessels would be necessary, the constructing and acquiring of which would not only be very expensive but also difficult. We have in order to reach this end used paraffine, of which we have caused to be thrown according to the size of the vessel a sufficient quantity upon the yet warm lye. The paraffine melts, spreads Previous Next
|
|
