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Home > The first process, however, ia...
Previous Next The best candle and soap tips online! The first process, however, ia generally used because the crystallized carbonate of Boda can be extracted from the crude lyes, while, by the second, it is necessary to employ the refined salt of soda. The mother-liquor from the first crystallization yields after a strong concentration at 34° B. a new quantity of crystals of soda, vhich can be purified by dissolving; it in talf its weight of boiling water. The uncryetallizab'e mother-liquor is used to prepare a caustic salt of soda of a weak Regrets. This salt contains only from 40 to 50 per cent, of pure soda. Crystallized carbonate of soda contains 62.80 per cent, of water, so that 100 pounds represent only 37-20 of dry carbonate. This salt is very soluble in water. Boiling water dissolves almost its own weight, and eold water almost half. In the arts, the great solubility of this salt is utilized to purify it; for this purpose it is dissolved ii> the least possible quantity of boiling water. The liquor is left to crystallise, and it deposits, by cooVng, fine crystals of pure carbonate of soda. This salt is thus formed :— 13.43 21.78 62.80 100.00 Cftibonic acid Soda Water . Caustic Salts of Soda.—The caustic salts of soda represent for the same weight, a larger quantity of pure soda than the same salts when carbonated. Starting from this pr.neiple, there is nn advantage in :ising salts of soda, the carboniu acid ot" which has been partly or totally eliminated, for the ponderal quantity of the missing acid is substituted by an equivalent weight of pure soda. It is thus that in their dif-erent applications of industry, caustic alkalies produce, at equal weights, more considerable results than when hi the state of carbonates. The fabrication of the caustic salts of soda is very simple. For this purpose it is sufficient to raix the crude soda with 30 per cent, of powdered lime (hyd/ated lime), and proceed 58 TECHNICAL TREATISE ON SOAPS AND CANDLES. with the Hxiviation in the same manner as in the preparation of the salt of soda. The result of the washing gives lyes marking about 25° B. These lyes, being claniied by settling, are rapidly evaporated to dry ness in cast-iron kettles. The salt is drained and carried into a reverheratory furnace, where it is spread in a layer from three to four inches thick. The furnace is at first heated moderately to dry the salt slowly without melting it, then the temperature is raised until it becomes red. This is an essential condition to expel the water, and destroy the organic matters, which color it. During the operation the mass is stirred, so as to multiply the points of contact of the substance with the caloric. The product thus obtained is white, and excessively caustic. Exposed to the air it absorbs carbonic acid, and passes to the state of carbonate. Salts of soda, more or less caustic, are also found in the trade. They are prepared with the mother-liquors from the fabrication of the crystals of soda. These liquors contain in solution, large proportions of caustic soda mixed with different, salts principally with sulphates and chlorides. By concentrating them to dryness, and incinerating the residuum, a kind of caustic salt of soda is obtained. Prom these remarks it may be seen that owing to the facility of obtaining the artificial caustic soda which ie now made ready for use and in a very nearly pure state, and that almost alt manufacturers of soap are at present using it in their works, most of the caustic, soda of commerce will bear analysis for its percentage1 of sodium hydrate. We give the analysis of an English caustic soda, branded 70°, which we have tested. Sodium hydrate ; 83.840 chlorate 4.G8G chloride 6.523 BUlpliite 4.503 sulphate 0.039 silicate 0.470 Aluminum trace MATEEIALS USED IN THE MANDF.ACTURE Of SOAPS. d\) This shows at a glance that the caustic soda made for the manufacture of soap is reasonably pure—this sample showing no trace of carbonate of soda, the other sails not being in sufficient quantity to impair the soap, which if boiled would almost entirely precipitate w'.th the waste lye. The healthy rivalry of the manufacturers of soda is such that an impure article could scarcely find a market. . These sodas possess many advantages to the soap-maker in these days over those formerly in use, and a saving of much time and labor that had to be spent in making caustic the sodas of commerce, which were of such varying qualities and strengths, and filled with so many foreigr. salts, that it required an expert chemist to analyze them. At present, when we know the relative purity or strength of a certain make of soda, and by test ascertain the amount of caustic soda it contains, the hydrometer of Biiamu will give us the specific gravity, and we can easily judge of the quantity necessary to use. The following table may prove useful in this connection. Previous Next
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