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Home > 8[eotfie gravity. PBr cent. Specific...
Previous Next The best candle and soap tips online! 8[eotfie gravity. PBr cent. Specific grafily. Per cent. 3.00 77.8 no 29.0 1.85 63.6 1.36 26.0 1.78 58.8 1.32 23.0 1.63 46.6 1.2ft 19.0 1.56 41.3 1.33 16.0 1.50 Sfi.8 1.18 13.0 1.47 ;-u.o 1.L2 9.0 1.44 31.0 1.06 4.7 It is almost needless to explain that the specific gravity of the solution increases with the amount of caustic soda dissolved in it. In another section we will give the necessary wo:king tables for manipulation. On the score of economy in the cost of soajv-maker's lye, there might be conditions where the barilla, kemp, and other soda ashes could be economically used, but they can hardly apjrty to this country, unless it be in the far West, where many natural sources of soda are found, and where there are several soda works already established, and whose products rival the English. 60 TECHNICAL TREATISE ON SOAPS AND CANDLES. MATERIALS CSED IN THE MANUFACTURE OF SOAPS. 61 CAUSTIC SODA FROM CRYOLITE. From cryolite, a mineral found in Greenland, a caustic soda is now made in this country, Germany, and Denmark, which is nearly free from impurities. Cryolite is the fluoride of aluminum and soda, and in preparing the soda, the sodium aluminate is dissolved out with water, and decomposed with carbonic acid, the hydrate of alumina being separated, and formed into an alum useful in the arts. The remaining carbonate of eoda is dissolved find condensed to form crystallized carbonate of soda, or it is decomposed with lime to form caustic soda, in the manner already described. The sodas from this source are eo nearly pure that they claim a preference in the manufacture of most soaps, particularly those made by the cold or extempore process when all the impurities the alkalies may contain remain in the soap. Cryolite is also the most convenient source of aluminum, a valuable silver-like metal. AMMONIA. Ammoniaque, Fr. Ammoniak, Ger. Volatile alkali. This important alkali deserves mention here, but has few properties applicable to our art, unless in an analytical test in some experiments, when it can be recommended as a normal alkali free from impurities. For soap it has no practical use, though we find several patents have been given for its addition to other soap where it is claimed to improve its detersive action. It has many uses in pharmacy and the arts, but they are foreign to the subject of our work. B-UBimuM AND CAESIUM are alkalies recently discovered which'are analogous to potash in their character, but have no application in the art of making soap, as they are scarce and expensive. LIME. ChauXy Fr. Kalk, GJer. Lime,called quicklime and caustic lime, is,chemically, calcium oxide, and does not occur naturally, but always with au acid oxide, as carbonate, sulphate, silicate, etc. The use of lime to the aoap-niaker is important, for by its power of extracting the carbonic acid from alkalies, they are thereby made caustic and suitable for combining with the fatty acida and forming soap, though it does not form a component part of it. A soap can be made of lime and a sebasic acid, but it is insoluble. Lime used for technical purposes is prepared by calcining natural carbonate of lime in kilns. During the burning the carbonic acid is disengaged, and quicklime is the product of tlie calcination. The qualities of lime essentially depend on the purity of the carbonate used to prepare it. When the calcareous stone (carbonate of lime) is mixed with large proportions of quartz, magnesia, or alumina, a lime of an inferior quality is obtained, which slacks with difficulty, and forms, with water, a paste without homogeneity. It is then called poor, and is rarely used in soap-making. Lime prepared with a carbonate sensibly pure, that if, which contains only traces of foreign matters, is of a superior quality, and is called fat. It rapidly combines witfi water, and grows vtry warm. If very little water is added, it slacks and forms a white and light powder, with a burning and caustic taste, and turning the blue vegetable colors green. Lime thus prepared is known by two different names. For the chemist it is hydmted lime, for the manufacturer it is slacked lime. If a sufficient quantity of water is poured on slacked lime, it combines with that liquid. The elevation of temperature, which takes place during the combination, often reaches 350° C. (662° F.). If the quantity of water is large enough, a more or less thin paste is obtained, which is called milk of lime. It is always in this form that lime is used to prepare caustic lyes of potash or soda. 62 TEOUSXAL TREATISE ON S0AP3 AND CANDLES. MATERIALS USED IK THE MANUFACTURE OF 30AP3. 63 Lime recently burned is white, or slightly colored, if the limestone used to prei-are it contains oxide of iron. To ascertain if it is completely caustic, treat a few drachms by nitric: ;icid. If the lime is entirely caustic, it ought to dissolve in the acid without disengaging carbonic acid. If there is any effervescence during the solution, it ia a proof that it still contains carbonate of lime, which has not been transformed into caustic lime. Entirely caustic lime is more desirable, aa it decomposes the carbonates of potash and soda better. Its density ie not constant, it varies according to the nature and purity of the carbonates which have produced it. Its mean specific gravity is 2.4. Quicklime exposed for some time iu the air, attracts its water and carbonic acid : it is transformed into carbonate of lime. In this state it has lost all its causticity, and does not possess the property of depriving the carbonates of potash and soda of their carbonic acic. Water will dissolve a certain proportion of lime. Very exact and recent experiments have shown that one thousand parts of water dissolve one of quicklime. That small quantity is, however, sufficient to communicate to water a strong alkaline reac;ion, and restore the blue of litmus paper, reddened by an acid. Lime-water is u val Jable reagent for ascertaining the causticity of lyes of potash and soda. Pour a small quantity of the lye to be tested into a glass, and add to it perfectly limpid lime-water ; it' the lye is completely caustic, the two liquors remain limpid ; if, on the contrary, there ie in the lye a portion of undeemuposed alkaline carbonate, a white precipitate of cf.rbonate of lime is produced. Lime plays an important part in the preparation of lyes. It is the essential ami indispensable agent of their causticity. When we examine the preparation of lyes, we shall indicate the special conditions of this operation, one of the most important in ita manufacture. We may here state that lime is not an integral part of soap—its action being chemical. It with the <*-arbonic acid of the alkaline carbonate Previous Next
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