THE SUGAR REFINER.

BOILING HOUSE.

Although sugar was known from very early times, it was used only in medicine, and was supposed to be a sort of honey found upon canes in India and Arabia. It is frequently mentioned by the very early writers. The cultureof the canes seems to have been confined to the islands of the Indian Archipelago, and the kingdoms of Bengal, Siam, &c. The traffic in sugar was so lucrative that the Indians concealed the mode of preparing it, stating to the merchants of Ormus, who imported it with gums and spices, that it was extracted from a reed, whereupon many unsuccessful attempts were made to find it in the reed-like plants of Arabia. In 1250 the great discoverer, Marco Polo, visited the country of the sugar cane, and the merchants afterwards sent to the place of its growth, instead of buying it at Ormus. For a long period the use of sugar in England was confined to medicines, or to preparing choice dishes at feasts; and this continued till 1580, when it was brought from Brazil to Portugal, and thence to our country.

Cultivators distinguish three great varieties of canes—the Creole, the Batavian, and the Otaheite. The Creole cane is indigenous to India, and was transplanted thence to Sicily, the Canary Isles, the Antilles, South America, and to the West Indies. It has dark green leaves, and a thin but very knotty stem. The Batavian or striped cane, which has a dense foliage, and is covered with purpled stripes, is a native of Java, where it is chiefly cultivated for the manufacture of rum; it is also met with in some parts of the New World and the West Indies. The Otaheite variety grows most luxuriantly, is the most juicy, and yields the largest product. It is cultivated chiefly in the West Indies and South America; it ripens in ten months, and is hardier than the other varieties.

The sugar cane, being originally a bog-plant requires a moist, nutritive soil, and a hot tropical or sub-tropical climate. It is propagated by slips or pieces of the stem, with buds on them, and about two feet long. It arrives atmaturity in twelve or sixteen months, according to the temperature; the leaves fall off towards the following season, and the stem acquires a straw-yellow colour. The cane is cut by some planters before the flowering season, but it is more usual to cut it some weeks after. The plantations are so arranged that the various divisions of the fields may ripen in succession. The land should be supplied with manure rich in nitrogen, but not containing much saline matter. After the harvest the roots strike again, and produce a fresh crop of canes; but in about six years they require to be removed.

The time for cutting the canes varies with the soil and season, and the different varieties of cane. In a state of maturity the canes are from six feet to fifteen feet in length, and from one and a half inch to two inches in diameter. The usual signs of maturity are a dry, smooth, brittle skin, a heavy cane, a grey pith, and sweet and glutinous juice. Canes should be cut in dry weather, or the juice will be found diluted with an excess of water. When cut they are tied up in bundles, and conveyed to the crushing mill, particular attention being paid that the supply should not exceed the demand, otherwise the cut canes would ferment and spoil.

The sugar cane grows from pieces or slips of itself, containing germs, and these develop rootlets at the joints, which draw sustenance to the young shoot as it increases. In the course of time the buds in the radicle, or root-joints of the first cane, throw out roots, and form a radicle for a second stem; and in this way, under favourable circumstances, several canes are produced from the parent stock for a period of about six years, and sometimes for several more. They, however, diminish every year in length of joint andcircumference, and are inferior in appearance to the original plant; but they yield richer juice, and produce finer sugar.

Filtering Bag.

The sugar exists in the cells of the cane in a state of solution, and is extracted therefrom by pressure. With this, as with other branches of industry, science has of late years stepped in, and has greatly facilitated the process of extraction and manufacture. It may be as well to give here a summary of the processes employed in the preparation of raw sugar: The canes are passed through the mill, and the juice thus extracted from them runs from the mill into a tank, whence it is pumped to cisterns for supplying theclarifiers, heated by steam, where it is purified. From thence it is run intobag filters, by which the mechanical impurities are removed. It is then run intocharcoal filtersto remove the colouring matter of the juice. The filtered juice is then run off into tanks and is drawn thence by vacuum into thevacuum pan, where it is granulated, and from whence it is finally discharged for packing. When the steam clarifiers are not employed the cane juice is run into a series of pans orteachesover open fires. This apparatus is also known as a “battery,” and forms another method of purification.

Stirring Rod. Ladle. Scraper. Crowbar Wrench.

The original crushing apparatus of India was a kind of squeezing mortar, made out of the hollow trunk of a tamarindtree, and worked by a yoke of oxen, the pestle or stamper being a strong beam eighteen feet long, and rounded at the bottom so as to squeeze or crush the canes in the mortar. Mills similar to those used for crushing oil seeds were used—as were also several other forms of apparatus—before rollers were introduced. Stone and iron rollers were first used, with the axes in a vertical position, but thehorizontal was soon found to be the more convenient and economical. The importance of a systematic mechanical arrangement appears to have awakened attention during the reign of Charles the Second, for in 1663, Lord Willoughby and Lawrence Hyde (second son of Edward, Earl of Clarendon, High Chancellor of England) associated themselves with one David de Marcato, an inventor, and obtained a patent for twenty-one years for making and framing sugar mills. In 1691, John Tizack patented an engine for milling sugar canes, &c.; but in this, as in the previous case, it is not specified how the mill should be made. Later on in 1721, William Harding, a smith, of London, who had been many years in Jamaica, and was skilled in the manufacture of sugar mills, having observed their imperfections, how that they were chiefly made with large wooden cogs cased with iron, endeavoured while abroad to improve their construction, but failed for want of competent workmen. On his return to London he made models of sugar mills which were approved by the Royal Society. These mills were fitted with cast iron rollers and cog wheel gearing, and were worked by water power; from description they appear to be the type of mills of the present day. Some forty-five years later, Yonge and Barclay, ironfounders, of Allhallowslane, City, applied friction wheels to sugar mills. In 1773, John Fleming, a mill carpenter, proposed an arrangement of windmill sails which turned a vertical timber shaft shod with iron, and which gave motion to two hard wooden rollers, between which the cane was guided and squeezed. In 1807, H. C. Newman, of St. Christopher, West Indies, designed a mill to be worked by horse power. He used cog and crown wheels to give motion to three upright rollers, and the arrangement was considered one which greatly augmentedthe power and execution of this class of machinery. In 1821, John Collinge, of Lambeth, improved cast iron sugar mills by casting the rollers on wrought iron shafts, instead of keying them on, as previously done. In 1840, James Robinson patented improvements in sugar mills, which consisted in using four rollers, one large one and three smaller ones beneath, placed horizontally, and gearing by cogs into each other. Up to that time three rollers onlyappear to have been used. He also proposed to use six rollers, which are fed from an endless band passing over the rollers. He cast the rollers and shafts in one piece, cored out to admit steam to facilitate the extraction of the juice from the cane during crushing. He also proposed to tin the interior of vacuum pans, &c. Various other arrangements have been patented, but it is unnecessary here to enumerate, much less to describe, them. The foregoing examples give an idea of the progress of the subject during nearly two hundred years. The last ten years have seen rapid strides made in improving the make of mills, and the general arrangement of sugar works.

Sparla. Trowel. Chisel. Hammer. Loosening Stove. Crowbar Hammer. Scoop for filling Moulds.

Cane juice, as expressed by the mill, is an opaque, slightly viscid fluid, of a dull grey, olive, or olive green colour, and of a sweet balmy taste. The juice is so exceedingly fermentable that, in the climate of the West Indies, it would often run into the acetous fermentation in twenty minutes after leaving the mill, if the process of clarifying were not immediately commenced.

The processes followed in the West Indies for separating the sugar from the juice are as follows: The juice is conducted by channels from the mill to large flat-bottomedclarifiers, which contain from three hundred to a thousand gallons each. When the clarifier is filled with juice, a little slaked lime is added to it; and when the liquor in the clarifier becomes hot by a fire underneath, the solid portions of the cane juice coagulate, and are thrown up in the form of scum. The clarified juice, which is bright, clear, and of a yellow wine colour, is transferred to the largest of a series of evaporating coppers or pans, three or more in number, in which it is reduced in bulk by boiling; it is transferred from one pan to another, and heated until thesugar is brought to the state of a soft mass of crystals imbedded in molasses—a thick, viscid, and uncrystallizable fluid. The soft concrete sugar is removed from the coolers into a range of casks, in which the molasses gradually drains from the crystalline portion, percolating through spongy plantain stalks placed in a hole at the bottom of each cask, which act as so many drains to convey the liquid to a large cistern beneath. With sugar of average quality, three or four weeks is sufficient for this purpose. The liquid portion constitutes molasses, which is employed to make rum. The crystallized portion is packed in hogsheads for shipment as raw, brown, or muscovado sugar; and in this state it is commonly exported from our West Indian colonies.

Besom. Lump Mould. Loaf Mould.

The refining of sugar is mainly a bleaching process, conducted on a large scale in England. There are two varietiesproduced by this bleaching, viz. clayed and loaf sugar. For clayed sugar, the sugar is removed from the coolers into conical earthen moulds called formes, each of which has a small hole at the apex. These holes being stopped up, the forms are placed apex downwards in other earthen vessels. The syrup, after being stirred round, is left for from fifteen to twenty hours to crystallize. The plugs are then withdrawn, to let out the uncrystallized syrup; and the base of the crystallized loaf being removed, the forme is filled up with pulverized white sugar.

This is well pressed down, and then a quantity of clay mixed with water is placed upon the sugar, the formes being put into fresh empty pots.

The moisture from the clay, filtering through the sugar, carries with it a portion of the colouring matter, which is more soluble than the crystals themselves. By a repetition of this process, the sugar attains nearly a white colour, and is then dried and crushed for sale.

But loaf sugar is the kind most usually produced by the refining processes. The brown sugar is dissolved with hot water, and then filtered through canvas bags, from which it exudes as a clear, transparent, though reddish syrup. The removal of this red tinge is effected by filtering the syrup through a mass of powdered charcoal, and we have then a perfectly transparent colourless liquid.

In the evaporation or concentration of the clarified syrup, which forms the next part of the refining process, the boiling is effected (under the admirable system introduced by Mr. Howard) in a vacuum, at a temperature of about 140° Fahrenheit. The sugar pan is a large copper vessel, with arrangements for extracting the air, admitting the syrup, admitting steam pipes, and draining off the sugarwhen concentrated. In using the pan a quantity of syrup is admitted, and an air pump is set to work to extract all the air from the pan, in order that the contents may boil at a low temperature. The evaporation proceeds, and when completed the evaporated syrup flows out of the pan through a pipe into an open vessel beneath, called thegranulating vessel, around which steam circulates, and within which the syrup is brought to a partially crystallized state. From the granulators the syrup or sugar is transferred into moulds of a conical form, which were formerly made of coarse pottery, but are now usually of iron. In these moulds the sugar whitens and crystallizes, the remaining uncrystallized syrup flowing out at an opening at the bottom of the moulds. This syrup is reboiled with raw sugar, so as to yield an inferior quality of sugar; and, when all the crystallizable matter has been extracted from it, the remainder is sold as treacle. The loaves of sugar, after a few finishing processes, are ready for sale.

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