Jeudi 04 août 2011

The principal varieties of starch

 It is said by Mr. Brande, that it is on this agitation in the cooler, that the whiteness and fineness of grain in the refined sugar depends. The crystals being broken by the agitation, and the whole converted into a granular mass, facilitates the drainingoff of the coloured liquid. After this it is placed in conical cups of earthern ware, of the well known form, called sugar loaf. These moulds have apertures at the bottom, to which stoppers are fitted After the sugar is placed in them, and has become cold, the stoppers are removed and the loaves are allowed to remain in them until another portion of molasses drains off, which leaves the sugar much whiter than before. This last operation is assisted by heat. When this is done, pipe-clay carefully mixed up with water to the consistence of cream, is put upon the loaves to the thickness of about an inch; the water from this slowly percolates the
tinge of the molasses, runs into the pots. After this the loaves are dried by heat, and put up in papers for sale.
534. When sugar is heated it fuses, becomes brown, evolves a little water and is resolved into new arrangements of its component elements. If suddenly elevated to a temperature of about 500 degrees it bursts into flame.
535. Sugar is composed in round numbers of about 42 parts of carbon, 51 of oxygen, and 7 of hydrogen.
536. Starch or Fecula may be separated from a variety of vegetable substances; it is contained in wheat and other esculent grains and in several roots.
Obs. The process for obiainiug starch consists in diffusing the powdered grain or the rasped root in cold water, which becomes white and turbid. After some hours the grosser parts are separated by a strainer, and the liquor which passes deposits the starch, which is then washed in cold water and dried in a irentle lieat
537. Starch is insoluble in alcohol and in ether, and occasions no precipitate in the greater number of metallic solutions.
loaves, and washing the solid sugar
Obs. The most characteristic property of starch, is that of forming a blue compound with iodine.
538. During the germination of seeds the starch is converted into sugar.
539- Starch may also be converted into sugar by mixing it with sulphuric acid and water.
luxp. Digest a pound of starch in six or eight pints of pure water, rendered slightly acid by two or three drachms of sulphuric acid. The mixture should be simmered for two days, adding fresh portions of water to compensate for the loss by evaporation. The acid is then saturated by chalk, and the mixture filtered and evaporated to the consistence of syrup. This syrup has a sweet taste, and by purification in the usual way, it affords crystalized sugar. The quantity obtained exceeds the weight of the starch by about one tenth. Starch is composed of about 43 parts of carbon, 48 of oxygen, and 7 of hydrogen ^= 100.
OAs. The principal varieties of starch are the following. Arrow root, Potatoe starch, Sago, Tapioca, Cassava, Salop, ami the starch of wheat.
540. Gluten may be obtained from wheat flour, by forming it into a paste and washing it under a small stream of water. The starch is thus wasted away, and a tough elastic substance remains which is gluten.



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The liquor which is drained

jThe ingredients of plants are distinct substances, formed by their secreting organs, and separable from each other without destructive distillation.
531. They are separated by certain solvents which have the power of dissolving some, but not the others. Thus water dissolves gum, but not resin ; while alcohol will take up the resin and leave the gu.-u, &c.
Obs. The solvents made use of for separating the ingredients of vegetables, are hot aud cold water, alcohol, ether, and some of the acids.
2. The following are the principal ingredients, or what are called the proximate principles of vegetables. Some account of the most important among them will be given.
1. Gum. 9. Fixed oil.
2. Sugar. ,10. VolatUe oil.
3. Starch. 11. Camphor.
4. Gluten. 12. Resins.
5 Extractive and Lignin 13. Narcotic principle.
6. Tannin. 14. Bituminous substances.
7. Colouring matter, 15. Vegetable acids.
8. Wax.
532. Gum. Gum Arabic may be taken as a specimen of pure gum. It dissolves in water forming a viscid solution, or mucilage from which it may be obtained in its original state by evaporation. It is insoluble in alcohol, which therefore causes a white precipitate in its aqueous solution.
Obs. 1. Gum is decomposed by sulphuric and nitric acids : the former produces water, acetous acid, and charcoal; tbe latter among other products converts a portion of the gum into a white acid substance, called mucous acid.
2. When gum is submitted to destructive distillation it affords carbonic acid, and carburetted hydrogen, empyreumatic oil, water, and a quantity of impure acetic acid.)
533. Sugar. Sugar may be extracted from a number of vegetables, and several roots, but is chiefly obtained from the sugar cane, a plant which thrives in hot climates. The juice of this plant is expressed and evaporated with the addition of a small quantity of lime, until it acquires a thick consistency; it is then transferred into wooden coolers, where a portion concretes into a crystalline mass which is drained, and then forms what is called muscovado or raw sugar. The liquor which is drained off is called molasses.
Ob Raw sugar is purified by the following process. It is dissolved in water mixed with lime and bullock's blood. This composition is agitated to mix the blood and water well together. The use of the lime is to mix with the molasses and render it more soluble, and consequently to facilitate its separation from the sugar. This operation is done in pans, under which a fire is now kindled, and when the liquor begins to boil, the albumen of the blood coagulates, rising to the top and bringing with it such impurities as the sugar contained. The liquor being kept gently simmering, the impurities are constantly rising to the surface, from whence they are removed by a skimmer. When the solution is judged to be sufficiently clear, it is placed in smaller pans and boiled rapidly until it becomes so thick, as that a small quanlitv beingf


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