Lime saponification

Tikis ash contains carbonate of soda sometimes to tho amount of ninety-five or ninety-six per cent, It is, however, essentially necessary in the production of soap, that the alkali should bo rendered caustic—-that Is, set free from combination by the removal of carbonic acid as, if it be in chemical union with any other body, it has no decomposing power over the oils or fats. Even if combined with the weakest acids, saponification will not ensue and the greatest care should, therefore, be exercised in tin s preliminary process—the preparation of the lies. The process for causticlzing is the same in principle for tile preparation both of soda and potassa lies, It depends upon tiro greater affinity of lime than of soda or potassa for carbonic acid, and the decomposition is one of tho most simple, thus—... 

CANDLE.—Read, in connection with the processes described at pages 430,431 —The operations of saponification of the fat, and decomposition of the lime-soap by sulphuric acid, have been hitherto effected in open vessels, under the ordinary pressure of the atmosphere. An improvement on this plan has been recently proposed by M, Delapchiek, of Besangoo, who substitutes dose vessels in Order to saponify the fat. Wash and decompose the lime-soap under a pressure of about twenty-two pounds to the square inch, by which the operations are considerably facilitated, and their duration shortened. The products by this process are said to be superior to those obtained in open vessels, and a considerable economy of flaid is effected. The apparatus consists essentially of a horizontal boiler, with a man-hole and two safety valves at the top, The heat is furnished by a large steam-pipe, running in a depression along the bottom of the boiler. The... 

Toluene, formaldehyde, HC.1, calcium hydroxide, and UNO , comprise the chargestock. In step 1 of this process, the toluene is reacted with concentrated HC1 at about 70°C along with paraformaldehyde. This accomplishes chloromethylation of approximately 98% of the toluene. In step 2, saponification of the chloromethyltoluene is effected with lime and H20 under pressure and at about 125°C. The product is methylbenzyl alcohol. In step 3. the methylbenzyl alcohol is oxidized with HNO3 (dilute) under a pressure of about 20 atmospheres and at a temperature of about 170°C. The main products are o-phthalic acid in HNO3 solution and insoluble terephthalic acid. 

Derivation (1) Chlorohydration of propylene followed by saponification with lime, (2) peroxidation of propylene, (3) epoxidation of propylene by a hydroperoxide complex with molybdenum catalyst. 

Acrylamide, CH2=CH —CONH2, is obtained by the saponification of acrylonitrile. After neutralizing with lime and filtering, the acrylamide crystallizes out on concentrating. 

By M. J. Pelouze.—One of the oldest and most skilful candle-makers in Prance, M. de Milly, made a series of important expeiiments on the saponification of fatty matters, and especially suet, by lime, in which he demonstrated that a much smaller percentage of lime than was ordinarily employed would effect the complete saponification of the fatty matter. Having reduced the pet ceutage of lime from 15 to 9 or 9 per cent., he subsequently reduced the proportion to 4 per cent, of the fatty matter operated upon, the condition being that of subjecting the lime, water, and fatty matter to an elevated temperature. The operation was performed in a metallic boiler, which was maintained for several hours at a temperature corresponding to a pressure of 5 to 6 atmospheres. 

It must be admitted that the saponification of suet by means of 4 per cent, of its weight of lime presents several distinct phases in which a basic or neutral soap is formed at first and is then ohang ed into a relatively acid soap. 

In this instance, since the molecular weight of stearin is 890 and that of milk of lime is 74, it is at once apparent that for every 1,780 parts of stearin, 222 parts of milk of lime or 168 parts of quicklime, CaO, would be required. It is found in practice, however, that an excess of 3-5 per cent, above the theoretical quantity of lime is necessary to complete the hydrolysis of a fat when carried on in an open vessel at 100°-105 0., but that if the saponification be conducted under pressure in autoclaves the amount of lime necessary to secure almost perfect hydrolysis is reduced to 2-3 per cent, on the fat, the treatment of fats with 3 per cent, of hme under a pressure of 10 atmospheres producing a yield of 95 per cent, of fatty acids in seven hours. The lower the pressure in the autoclave, the lighter will be the colour of the resultant fatty acids. 

Magnesia,— It has been proposed to substitute magnesia foi lime in the process of saponification under pressure, but comparative experiments with lime and magnesia, using 3 per cent, of lime and 2 7 per cent, of magnesia Soc, Ghem. Ind., xii., 163), show that... 

Whilst saponification is proceeding, the sugar solution is prepared by dissolving 50 lb. cane sugar in 50 lb. water, at 168° P. (76° 0.), to which may be added 5 lb. soda crystals, and any necessary colouring matter. The water used for this solution should be as soft as possible, as hard water is liable to produce opaque streaks, of lime soap. 

Constitution op Oils and Fats, and their Saponification. Researches of Chevreul and Berthelot—Mixed Glycerides—Modem Theories of Saponification—Hydrolysis accelerated by (1) Heat or Electricity, (2) Ferments, Castor-seed Ferment, Steapsin, Emul-sin, and (3) Chemical Reagents, Sulphuric Acid, Twitchell s Reagent, Hydrochloric Acid, Lime, Magnesia, Zinc Oxide, Soda and Potash. 

In the chlorohydrination step, the reactants propylene and hypochlorous acid (chlorine and water) are converted into two propylene chlorohydrin isomers (90% l-chloro-2-propanol and 10% 2-chloro-l-propanol). Yields of up to 94% can be achieved in modern commercial plants. The main by-products formed in this reaction step are dichloropropane (3-10%), dichloropropanol (0.3-1.2%), and dichlorodiisopropyl ether (0.2-1.7%). In the second step (dehydrochlorination, also called epoxidation or saponification ) the aqueous propylene chlorohydrin solution is treated with slaked lime or caustic soda. Propylene oxide and calcium or sodium chloride are formed. In a commercial process 1.4-1.5 units of chlorine are consumed to produce one unit of propylene oxide. Typical by-products are monopropylene glycol, epichlorohydrin, glycerol monochlorohydrin, glycerol, propanal, and acetone. In dehydrochlorination, propylene oxide yields of up to 96% can be obtained. 

Soap greases (calcium base grease is an example) are made by cooking a mixture of a suitable fatty acid and a portion of the petroleum oil with calcium hydroxide. When the saponification of the acid by the lime is complete, the water content is adjusted and the remainder of the oil incorporated. A fine mesh wire screen removes impurities and lumps before packaging (Imperial Oil). 

The reactions involved in the various methods for carrying out this process are theoretically as follows — ((/) In tlic saponification with alkalies, e.g. with lime —... 

Among all the processes by which satisfactory saponification takes place, that formerly possessing the greatest importance is that in wliicli quicklime was employed, as on tlic one hand quicklime is cheaply obtained, and on tlie other liand it also has tlzc advantage tliat the lime soap is insoluble, and can therefore be easily separated from the liquid. It was earried out in the following manner —... 

One assists tho saponification by the continuous passage of steam, and by the uninterrupted motion of tlie stirring gear. The commencement of the saponification shows itself by the tliickening of the mass, an appearance which usually manifests itself three or lour hours after tho beginning of tlic operation. Later small particles of lime soap unite into small lumps, which rise to tlic surface. After the expiration of seven or eight hours tlio saponification is complete, and the vessel contains by this time a solid mass which, if the operation has been rightly carried... 

A modification of this process is that in whidt a much smaller quantity of lime suffices for saponification, if one allows the lime to act on the fat under a steam-pressure cf about ten atmospheres. Under these conditions it is sufficient to employ two to three per cent lime to bring about complete saponification, as acid lime salts are forined from the fatty acids. 

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