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Previous Next The best candle and soap tips online! TECHKICAL TREATISE OS SOAP AND CANDLES. MATERIALS USED IK THB MAMTFACTURE OF SOAPS. 49 second at Drejze. The fabrication of soda was rapidly growing, and in 1800 glasses were seen at the exposition of industry, sent l>y the manufactory of Saint-Gohain, prepared with artificinl soda. However, the new product had one defect which often cansed it to be rejected by the trade; thia defect consisted in its sulphuretted nature. D'Arcet found •the cause of that imperfectiou. Leblanc's furnace was rectangular, and the flarr.e was not active enough in the angles, and there resulted a partial transformation of the sulphate of soda into sulphuret of sodium. D'Arcet rounded off the angles, and transformed the rectangular furnace into an elliptic one. With this im proven lent, the fabrication of artificial soda rapidly increased, and in 1812, notwithstanding the absolute prohibition of foreign sodas, the price of that substance had diminished fully two-thirds. Fabrication of Crtttle Soda.—This fabrication comprises three distinct opcratbus, whieh are: 1. The transformation of the chloride of sodium (common salt) into sulphate of soda, by sulphuric acid; 2. The mixture of the sulphate of eoda with the chalk and charcoal; 3. The calcination of the soda, or the conversion of the sulphate of soda into carbonate, in a reverbcratory furnace. Sulphate of Soda.—The sulphate of soda manufactured in France and England is destined for the preparation of crude soda. The processes followed in its manufacture vary according to the localities. "When hydrochloric acid has to be collected, common salt is decomposed b}- sulphuric acid in cast-iron cylinders, heated in various ways. But at Marseilles, where t'ne fabrication of artificial soda constitutes one of the most important trades, the greater part of the hydrochloric acid produced during the operation is lost. The sulphate of S4«la is directly prepared in reverbera-tory furnaces by decomposing salt by sulphuric acid. These furnaces are generally divide'l into two com part me nte. The part placed near the heiirth is destined for the fabrication of the crude Boda (carbonate of soda); the second part is separated from the first by a low brick wall; the side of this part is formed of hard stoue, in whigh a cavity is cut; it is in this cavity that the sulphate of soda is prepared, by the re-tetion of sulphuric acid on salt. Tlie proportions of acid and salt generally used are :— 2000 Its. 3200 '? Salt Sulphuric acid at 5CP The salt is first introduced into the cavity, then the sulphuric acid at 50° is poured upon it. Under the influence cf heat the decomposition takes place; the hydrochloric acid resulting from, the reaction is disengaged, and the aul-jhuric acid combines with the soila to form eulphateof soda. The operation lasts from three to four hcurs. It is ascertained that it is finished, when the mixture has acquired a pnsty consistency, and when no mare hvdrocliloric acid is disengaged. To bleach the sulphate and disengage the last portions of hydrochloric acid it contains, the temperature of the furnace is raised. When the salt is sufficiently dried, it is taken out. If the operation has boon well conducted, a nearly white sulphate is obtained. Thus prepare!, tlie salt constitutes an acid sulphate. It is specially employed to prepare soft, or porely alkaline soda. The above quantities give from '2200 to 2260 lbs. of sulphate of soda well prepared, or from 110 to 113 lba. of sulphate for 100 of salt. By a litter process the hydrochloric gf.s forming liydrochrotic acid is saved, thus preventing the escape of the gas which contaminates the air of the neighborhood. Mixture.—This operation consists in mixing the sulphate of soda, previously calcined, with the proper proportions of carbonate of lime and charcoal. To obtain an alkali of a high degree, it is essential that the quantities shmilu be in such proportions, that the sulphate of soda will be entirely transformed into carbonate. Thenry indicates the respective proportions of the substances to be employed; but ir. practice, the doses of carbonate of lime and charcoal have to be increased. Not only is a more complete decomposition of the sulphate of soda attained, but the insolubility of the sul- TE3HNICAL TBEATISI OH SOAPS AHD CANDLES. MATERIALS USED IS THB MANUFACTURE OF SOAPS. 51 phuret of salcinm is also determined by the formation of an oxy-sulpliuret of that baBe, nearly insoluble in cold water; then by lixiviating the crude soda with cold water, the solution contains only the slkali nearly free from sulphuret. The bes: proportions to use are:— 3000 lba. 2100 " 1100 " CaMned snlpbate of soda Dry carbonate of lime . Charcoal To render the reaction more easy, the substances are previously ground in vertical mil!?, then passed through a metallic sieve. The carbonate of lime must be perfectly dry ; generally it ;s desiccated by ex [Kitting it for a few days on top of the arch of the furnace. The mixture of the substances being intimately eŁ'ected,the calcination is proceeded with. Calcination.—As we hare already said, the furnaces are generally made in two compartments. The first, where the temperat ire is the highest, is used to calcine the soda; in the second, tho waste heat is atilized to prepare the sulphate of soda. When an operation is begun, the furnace must be brought np to a strong red heat before introducing the mixture. That condition being complied with, introduce the mixture into the furnace,and after spreading it as evenly as possible, leave it >'X|ioeed for some time to the action of the heat. In order to have an equal and regular heat, the fire requires great attention, especially at the beginning of the operation. When the reaction begins, the mixture sot tens and agglutinates, and the parts exposed to the highest temperature begin to melt. At that moment, stir the mixture with a:i iron rod so ns to hasten the decomposition of the Bulph;ite. From this time, feed the furnace with fresh fuel so as to obtain a bright and cortinued fire. Continue to stir the mixture from time to time. It is ascertained that the operation is f.lmost finished when the fusion ia nearly complete, and when the incandescent substance throws out luminous* jeta, which burn with a white or bluish flame. These jots. Previous Next
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