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Home > Sdistances employed Suluble parts inaotuTjle...
Previous Next The best candle and soap tips online! Sdistances employed Suluble parts inaotuTjle part to produce a-'ho*. for til)of ashea. fat 100 of ashei White Beccli . . 19.33 80.78 Red Beech . 16.30 83.70 Oak . . 13.00 83.00 Lime tree . . 10.80 89,20 Birch tree . . 16.00 84.00 Alder tree . . 18.80 81.30 Fir tree . 2.170 74.:so Pine .... . 13.60 86.40 . S3 00 75.00 TValnot tree . 15.40 84.60 Elderberry . 31.50 68.50 Straw .... . 10.10 89.G0 Stalks of Potatoes . 4.30 95.80 Fern .... . S9.00 71.00 Among the insoluble compounds, the cirbonate of lime predominates: after being well washed and dried, the in-eoluble residuum does not contain leas than 75 tj 90 per cent, of its weight of carbonate of lime; the phosphates of lime and magnesia, aili«a, etc., are the compounds which generally accompany it. Their proportiou varied between the limits of from 25 to 10 per cent. Essentially formed of carbonate cf potash, a small quantity of sulphate of potash and chloride of potassium, and of a trace of silicate of potash, the soluble compounds which alone have to fix our attention present, in tlie relative proportions of these different salts, variations which iire interesting to notice. The following table enables us to establish the composition of the mixture of soluble salts extracted from the ashes of some vegetables. 32 TECHNICAL TRBATISE OS 83AP AND CANDLES. MATERIALS USED IN THE MANUFACTURE OP SOAPS. 33 Birch. ?In. Ort. HaliMrr?. Fir tree. Carbonic acid . . Sulphuric " . . Chlorine. . . . 0.170 0.023 0.003 0.010 0.347 0. 1.000 1.00-i 1.000 1.000 0.988 1.000 Such are the principal variations in their composition that the different vegetable Bpecies present. . However, whatever is their composition, the extraction of the potash is effected in the same manner. The ashes remaining after the combustion are carefully lixiviated, and furnish liquors which, evaporated to dry ness, yield a colored residuum called saint. This, by a simple purification by tire,ia transformed into commercial carbsnate of potash. EXTRACTION OF POTASH. The industrial fabrication of potash from ashes is carried on only in countries where wood is abundant. Thus the largest quantity of that employed in the arts, comes from Russia or from this country. As ire have before said, vegetables when fully developed contain a smaller proportion of Baits of potash than when their vegetation is lees advanced. Starting from thia principle, confirmed by experience, branches, small trees, and herbaceous plants must be preferred,as being richer in salts of potash. If the operation is conducted with the latter vegetables, they are to be cut carefully,and spread on a dry and Bruno th place, where they are left until completely dried; after their desiccation, they are collected and put into beans, near by the place where they are to be burned. In damp countries they are dried under large sheds. When trees are burned for the purpose of extracting potash, they are divided into large pieces and dried in the open air. The processes of combustion nre not the same in every country. Formerly, and even yet in some localities, the combustion was effected ou the ground. For this purpose an open place is selected, and several heaps of plants are formed, and are set on tire; as fast as the combustion takes place, new plants are added. When they are all burned, let the ashes cool, then spread them under sheds where they are .exposed to the air for a few days, so that all the potash they contain may be transformed into the carbonate by absorbing carbonic acid from the air. The ashes are then lixiviated with water, in wooden or in east-iron vats. The liquors are afterwards evaporated to drynosa in cast-iron kettles. The ;crudc potash, resulting from this evaporation, is bleached and granulated in a reverberating furnace. .? Combustion of (be Plants in Furnaces.—The combtstion in furnaces, now in use in several manufactories, gives a larger quantity of ashes, the incineration of which is more complete than when the combustion takes place in the open air. 13y this process, the combustion of the plants is conducted in furnaces made of refractory bricks ; they are provided, at their lower part, with a cast-iron grate, under which is a large ash-pan, also made of bricks, the object of which is to receive the ashes from the incineration of the plants. To render the combustion more uniform and complete, pipes disposed around the base of the furnace, bring cola air unJer the grate. To preserve the inside of the furnace from the destructive action of the fire, the bricks are covered with a coating of tilay about otic-third of an inch thick, which, before beginning the operation, is allowed to dry for several dtys. All the preliminaries being arranged, throw on the grate a few armfuls of dry plants, and set them on lire ; wlieu the combustion is well established, feed the fire with new loads of materials, which are proportioned to the intensity of the combustion, which ought to be neither too slow nor too rapid. In the latter case, a too rapid combustion will occasion a certain loss of alkali, which volatilizes; in tie first case, the operation if too much prolonged, becomes difficult, and gives imperfect results, because there i ami ways a certain quantity of organic matter which is not burned; but by 35 34 TECHNICAL TREATISE ON SOAP AND CANDLES. ?practice, the operation may be regulated at will by means of the pipes which bring cold air under the grate. When ttie combustion is too rapid, slacken it by closing the pipes; when too slow, allow the cold air to come uuder the grate. The operation is well established only after a few hours. To obtain a complete incineration, stir the fuel from time to time witli a long iron roil, so as to permit the fire to act equally on the entire mass. When the vegetables are too dump, they sometimes form agglomerations of ashea on the grate, wheh render the combustion slower; to destroy these agglomerations and give a new Btart to the combustion, pass an iron hook between the liars of the grate. During all the lime of the operation, the ashes which are produced fall in tr.e form cf powder into the ash-pun placed under the grate, from which, when they have filled the pan about three-foilrtl.s full, they are taken with a shovel and carried into a buiUing, where they are spread on the ground in beds three or four inches thick. From time to time the surface ie stirred, so ae to assist the transformation of the potash into carbonate. It is to facilitate this reaction, that ashes recently calcined are exposed to the air for a few dayrf before being lixivuted. Leaehirg or Washing of the j1M«.—This operation has for its object the extraction of the carbonate of potash, existing in the asl es. To proceed, use wooden or sheet-iron vats, of a capacity of 200 to 250 gallons—generally 8 or 10 are disposed one over the other; they receive the name of barrel;. the nurnler of barrels varies according to the importance of the fabrication. Each vat is provided with a double bottom covered with a strainer which acts as a filter. By this means clear and limpid lyes are obtained. These vats have, at the boitoni, a cock to draw off the lye. The vats being thus disposed, charge them to four fifths of their cajacity with ashes, and pour on them a quantity of water sufficient to cover them entirely. After standing from fifteen to eighteen hours, open the cocks, and collect the lye in a spec.al receiver, fty using this lye instead of water for the treatment of new ashc3, we obtain after twelve or nfteei. MATERIALS USED IK THE MANUFACTURE OF SO.VPS. hours of reaction, a new lye marking from 10° to 12° Baume, which can be brought up to 15° or 18° by successive passages through new ashes; but thia method, which is long and costly, is not much employed, the manufacturer generally preferring to have liquors at 103 or 1^°. Continue the lixiviatioti of the ashes hy successive washings with pure water. It is ascertained that the material is completely exhausted when the liquid has lost all alkaline taste, but there is a more exact process, which is to collect some of the liquid and try it with the areometer. The instrument will descend to 0° if the a3hes are completely exhausted. The lye thus obtained, besides the foreign salts, contains the carbonate of potash in solution ; it is generally colored brown, clue to a pnmll quantity of organic matter, which has escaped the combustion. The liquors marking from 10° to 12° are evaporated in a series of cast-iron kettles heated by the same hearth. The evaporated water is replaced by the addition of fres-i liquors. When the lyes have acquired a syrupy consistency, they are evaporated to dry ness in a thick cast-iron kettle. The operation is finished when the substance becomes dry and friable. The crude potash thus obtained is strongly colored brown. To bleach it, it is placed in a reverberatory furnace, heated to whiteness. Towards the end cf the operation, the temperature is raised enough t<> redden the salt, expel the water, and destroy the organic matter which colors it. It is, however, very essential, that-the temperature should not be too high, for then the potash would experience a kind of vitrification which, would render it. heavy and difficult to dissolve in water. When the potash has become white, that is the moment to take it from the furnace. PoUsh well prepared is light, porous, and strongly alkaline. Exposed to the air, it attracts moisture and becomes deliquescent. The loss experienced by the crude potash, when calcined, is about fifteen per cent. Red American Potash.—Potash deprived of carbonic acid ty lime lias received the name of caustic potash. All com- 36
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