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SUGAR MANUFACTURE Sugar-See also:cane is a member of the grass See also:family, known botanically as Saccharum officinarum, the succulent stems of which are the source of cane sugar . It is a tall perennial grass-like plant, giving off numerous erect stems 6 to 12 ft. or more in height from a thick solid jointed See also:root-stock . The stems are solid and marked with numerous shining, polished, yellow, See also:purple or striped See also:joints, 3 in. or less in length, and about 11 in. thick . They are unbranched and See also:bear in the upper portion numerous See also:long narrow grass-like leaves arranged in two rows; the See also:leaf springs from a large sheath and has a more or less spreading blade 3 ft. in length or longer, and 3 in. or more wide . The small See also:flowers or spikelets are See also:borne in pairs on the ultimate branches of a much branched feathery plume-like terminal See also:grey inflorescence, 2 ft. or more long . See also:Production of flowers is uncertain under cultivation and See also:seed is formed very rarely . The plant is readily propagated by cuttings, a piece of .the See also:stem bearing buds at its nodes will root rapidly when placed. in sufficiently moist ground . The sugar-cane is widely, cultivated in the tropics and some sub-tropical countries, but is not known as a See also:wild plant . Its native See also:country is unknown, but it probably originated in See also:India or some parts of eastern tropical See also:Asia where it has been cultivated from See also:great antiquity and whence its cultivation spread westwards and eastwards . See also:Alphonse de See also:Candolle (Origin of Cultivated See also:Plants, p . 158) points out that the See also:epoch of its introduction into different countries agrees with the See also:idea that its origin was in India, See also:Cochin-See also:China or the See also:Malay See also:Archipelago, and regards it as most probable that its See also:primitive range extended from See also:Bengal to Cochin-China . The sugar-cane was introduced by the See also:Arabs in the See also:middle ages into See also:Egypt, See also:Sicily and the See also:south of See also:Spain where it flourished until the abundance of sugar in the colonies caused its cultivation to be abandoned . Dom Enrique, See also:Infante of See also:Portugal, surnamed the Navigator (1394—1460) transported it about 1420, from See also:Cyprus and Sicily to See also:Madeira, whence it was taken to the Canaries in 1503, and thence to See also:Brazil and Hayti See also:early in the 16th See also:century, whence it spread to See also:Mexico, See also:Cuba, See also:Guadeloupe and See also:Martinique, and later to See also:Bourbon . It was introduced into Barbadoes from Brazil in 1641, and was distributed from there to other See also:West See also:Indian islands . Though cultivated in sub-tropical countries such as See also:Natal and the See also:Southern states, of the See also:Union, it is essentially tropical in its requirements and succeeds best in warm See also:damp climates such as Cuba, See also:British See also:Guiana and See also:Hawaii, and in India and See also:Java in the Old See also:World . The numerous cultivated varieties are distinguished mainly by the See also:colour of the internodes, whether yellow, red or purple, or striped, and by the height of the See also:culm . Apart from the sugar-cane and the See also:beet, which are dealt with in detail below, a brief reference need only be made here to See also:maple sugar, See also:palm sugar and See also:sorghum sugar . Maple Sugar.—This is derived from the See also:sap of the See also:rock or sugar maple (Ater saccharinum), a large See also:tree growing in See also:Canada and the See also:United States . The sap is collected in See also:spring, just before the foliage develops, and is procured by making a notch or See also:boring a hole in the stem of the tree about 3 ft. from the ground . A tree may yield 3 gallons of juice a See also:day and continue flowing for six See also:weeks; but on an See also:average only about 4 lb of sugar are obtained from each tree, 4 to 6 gallons of sap giving I lb of sugar . The sap is purified and concentrated in a See also:simple manner, the whole See also:work being carried on by farmers, who themselves use much of the product for domestic and culinary purposes . Palm Sugar.—That which comes into the See also:European See also:market as Jaggery or khaur is obtained from the sap of several palms, the wild date (See also:Phoenix sylvestris), the See also:palmyra (Borassus fiabellifer), the coco-See also:nut (Cocos nucifera), the gomuti (Arenga saccharifera) and others . The See also:principal source is Phoenix sylvestris, which is cultivated in a portion of the See also:Ganges valley to the See also:north of See also:Calcutta . The trees are ready to yield sap when five years old; at eight years they are mature, and continue to give an See also:annual See also:supply till they reach See also:thirty years . The collection of the sap (toddy) begins about the end of See also:October and continues, during the cool See also:season, till the middle of See also:February . The sap is See also:drawn off from the upper growing portion of the stem, and altogether an average tree will run in a season 350 lb of toddy, from which about 35 lb of raw sugar—jaggery —is made by simple and See also:rude processes . Jaggery production is entirely in native hands, and the greater See also:part of the amount made is consumed locally ; it only occasionally reaches the European market . Sorghum Sugar.—The stem of the See also:Guinea See also:corn or sorghum (Sorghum saccharatum) has .long been known in China as a source of sugar . The sorghum is hardier than the sugar-cane; it comes to maturity in a season; and it retains its maximum sugar content a considerable See also:time, giving opportunity for leisurely harvesting . The sugar is obtained by the same method as cane sugar . Cane Sugar Manufacture.—The value of sugar-canes at a given See also:plantation or central factory would at first sight appear commercial to vary directly as the amount of saccharine See also:con-values of tamed in the juice expressed from them varies, sugar-canes. and if canes with juice indicating 90 Beaume be made a basis of value or See also:worth, say at 1os. per ton, then canes with juice indicating in degrees Beaume 10° 9° 8° 7° 6° and containing in sugar . . 18•o5 %l 16'23% 14.42 % 12'61% Io.8o % would be worth per ton . . . II/Iy 1o/– 8/too 7/9: 6/8 But this is not an accurate statement of the commercial value of sugar-canes—that is, of their value for the production of sugar to the planter or manufacturer—because a properly equipped and balanced factory, capable of making See also:loo tons of sugar per day, for too days' See also:crop, from canes giving juice of g° B., or say 1o,000 tons of sugar, at an aggregate See also:expenditure for manufacture (i.e. the annual cost of See also:running the factory) of £3 per ton, or f30,000 per annum, will not be able to make as much sugar per day with canes giving juice of 8° B., and will make still less if they yield juice of only 6° B . In practice, the expenses of upkeep for the See also:year and of manufacturing the crop remain the same whether the canes are See also:rich or poor and whether the crop is See also:good or See also:bad, the See also:power of the factory being limited by its power of evaporation . For example, a factory able to evaporate 622 tons of See also:water in 24 See also:hours could treat l000 tons of canes yielding juice of 90 B., and make therefrom 100 tons of sugar in that time; but this same factory, if supplied with canes giving_ juice of 6° B., could not treat more than 935 tons of canes in 24 hours, and would only make therefrom 62.2 tons of sugar . The following table may be useful to planters and central factory owners . It shows the See also:comparative results of working with juice of the degrees of See also:density mentioned above, under the conditions described, for one day of 24 hours, and the real value, as raw material for manufacture, of cane giving juice of 6° B. to to° B., with their apparent value based solely on the percentage of sugar in the juice . The canes in each See also:case are assumed to contain 88 % of juice and 12 % of fibre, and the extraction by milling to be 75 % of the See also:weight of canes—the evaporative power of the factory being equal to 622 tons per 24 hours . The factory expenses are taken at £30,000 per annum, or £3 per ton on a crop of Io,000 tons (the sugar to cost £8 per ton all told at the factory)—See also:equivalent to £3oo per day for the loo working days of crop time . Degrees Beaume . 6° 7° 8° 9° 10° Tons of canes 935.6 956.2 977.4 See also:I000 1023.8 crushed per day Tons of juice ex- 701.7 717.2 733.I 750 767.9 pressed . . Tons of water 622 622 622 622 622 evaporated Tons of 1st Mas- 79.7 95.2 III•I 128 145.9 secuite Tons sugar of all 62.2 74.3 86.7 too 114.0 classes recovered See also:Total output of 6220 7430 867o 10,000 11,400 sugar in 100 days . Tons Total value of all £800 £912 sugars per day at £8 per ton . £497, 6/–£594, 4/–£693, 6/– Less factory ex- £300 £30o penses per day . £300 £300 £300 Leaves for canes £500 £612 crushed . . . £197, 6/–£294, 4/–£393, 6/– Real value of See also:lot– II/Hi canes per ton . 4/24 6/2 8/– A value 6/8 7/94 8/to; 10/- II/I4 seeparent preceding Table) But it is obvious that it would not pay a planter to sell canes at 4s . 24d. a ton instead of at 1os. a ton, any more than it would pay a factory to make only 62.2 tons of sugar in 24 hours, or 6220 tons in the crop of too days, instead of 10,000 tons . Hence arises the imperative See also:necessity of good cultivation by the planter, and of circumspection in the See also:purchase and See also:acceptance of canes on the part of the manufacturer . The details of manufacture of sugar from canes and of sugar from beetroots differ, but there are five operations in the production of the sugar of See also:commerce from either material which are See also:common to both processes . These are: I . The extraction of the juice . 2 . The See also:purification or defecation of the juice . 3 . The evaporation of the juice to See also:syrup point . 4 . The concentration and See also:crystallization of the syrup . 5 . The curing or preparation of the crystals for the market by separating the See also:molasses from them . Extraction of Juice.—The juice is extracted from canes by squeezing them between rollers . In India at the See also:present day there are See also:thou-sands of small See also:mills worked by See also:hand, through which ExtracK/on the See also:peasant cultivators pass their canes two or three by Pressure. at a time, squeezing them a little, and extracting per- haps a See also:fourth of their weight in juice, from which they make a substance resembling a dirty sweetmeat rather than sugar . In Barbadoes there are still many estates making good Mascabado sugar; but as the juice is extracted from the canes by windmills, and then concentrated in open kettles heated by See also:direct See also:fire, the See also:financial results are disastrous, since nearly See also:half the yield obtainable from the canes is lost . In the best organized See also:modern cane sugar estates as much as 121% of the weight of the canes treated is obtained in crystal sugar of high polarizing power, although in See also:Louisiana, where cultivation and manufacture are alike most carefully and admirably carried out, the yield in sugar is only about 7% of the weight of the canes, and sometimes, but seldom, as much as 9% . This is due to conditions of See also:climate, which are much less favourable for the formation of saccharine in the canes than in Cuba . The See also:protection afforded to the planters by their See also:government, however, enables them to pursue the See also:industry with considerable profit, notwithstanding the poor return for their labour in saleable produce . As an instance of the See also:influence of See also:climatic conditions combined with high cultivation the cane lands of the See also:Sandwich Islands may be cited . Here the tropical See also:heat is tempered by See also:constant See also:trade winds, there is perfect See also:immunity from hurricanes, the See also:soil is peculiarly suited for cane-growing, and by the use of specially prepared fertilizers and an ample supply of water at command for See also:irrigation the See also:land yields from 50 to 90 tons of canes per See also:acre, from which from 12 to 14% of sugar is produced . To secure this marvellous return, with an annual rainfall of 26 in., as much as 52,000,000 gallons of water are pumped per 24 hours from artesian See also:wells on one See also:estate alone . With an inexhaustible supply of irrigation water obtainable, there is no See also:reason why the lands in Upper Egypt, if scientifically cultivated and managed, should not yield as abundantly as those in the Sandwich Islands .
In the See also:Paris See also:Exhibition of 1900 a cape-crushing See also: b . Canes vary very much in respect of the quality and also as to the quantity of the juice they contain . The quantity of the juice is the test to which recourse must be had in judging the efficiency of the extraction, while the quality is the See also:main See also:factor to be taken into See also:account with regard to the results of subsequent manufacture . For the application of the foregoing considerations to practice, the subjoined table has been prepared . It shows the greatest quantity of juice that may be expressed from canes, according to the different proportions of fibre they contain, but without employing maceration or imbibition, to which processes reference is made hereafter . The percentages are percentages of the See also:original weight of the uncrushed canes . Per Per Per Per Per Per Cent . Cent . Cent . Cent . Cent . Cent . Percentage of fibre to II 12 13 14 15 in canes . . . Percentage of juice 90 89 88 87 86 85 in canes . . . Percentage of juice 10 II 12 13 14 15 retained in me- gass . . . . Percentage of maxi- 8o 78 76 74 72 70 mum expression . Percentage of best 79 76.9 74.9 72.9 70.6 68.5 average expres- See also:sion, in practice . Percentage of juice It 12.1 13.2 14.3 15.4 16.5 See also:left in megass, in practice . The British Guiana Planters' Association appointed a sub-See also:committee to See also:report to the West India See also:Commission on the manufacture of sugar, who stated the following: With canes containing 12% fibre the following percentages of sugar are extracted from the canes in the See also:form of juice: Single crushing 76% Double crushing 85% Double crushing with 12 % dilution 88 % Triple crushing with to % dilution 90 % See also:Diffusion with 25% dilution 94% These results are equivalent to 66.88 % extraction for single crushing . 74'80% „ ,, double crushing . 77'44% „ ,, double crushing with 12% dilution .
79.20% ,, triple „ to%
82.72 % ,
.
„ diffusion with 205%
To prevent the serious loss of juice left in the megass by even the best double and triple crushing, maceration or imbibition was introduced
.
The megass coming from the first mill MaceratMn was saturated with See also:steam and water, in weight equal or lmhibito between 20% and 3o% and up to 40 % of the original t/on
.
weight of the uncrushed canes
.
Consequently, after
the last crushing the mixture retained by the residual megass was not juice, as was the case when crushing was employed without maceration, but juice mixed with water; and it was found that the loss in juice was reduced by one-half
.
A further saving of juice was sometimes possible if the market prices of sugar were such as to compensate for the cost of evaporating an increased quantity of added water, but a limit was imposed by the fact that water might be used in excess
.
Hence in the latest designs for large factories it has been proposed that as much normal juice as can be extracted by double crushing only shall be treated by itself, and that the megass shall then be soused with twice as much water as there is juice remaining in it; after which, on being subjected to a third crushing,-it will yield a degraded juice, which would also be treated by itself
.
It is found that in reducing the juice of these two qualities to syrup, See also:fit to pass to the vacuum pans for cooking to crystals, the total amount of evaporation from the degraded juice is about half that required from the normal juice produced by double crushing
.
Great improvements have been made in the means of feeding the mills with canes by doing away with hand labour and substituting See also:mechanical feeders or rakes, which by means of a mechanical simple steam-driven mechanism will See also:rake the canes improve-
from the cane wagons on to the cane-See also:carriers
.
By menta. the See also:adoption of this system in one large plantation
in the West Indies, cru§See also: These attachments, first invented by See also:Jeremiah See also:Howard, and described in the United States Patent See also:Journal in 1858, are simply hydraulic rams fitted into the See also:side or top caps of the mill, and pressing against the side or top See also:brasses in. such a manner as to allow the side or top roll to move away from the other rolls, while an See also:accumulator, weighted to any desired extent, keeps a constant pressure on each of the rams . An objection to the top cap arrangement is, that if the See also:volume or feed is large enough to lift the top roll from the cane roll, it will simultaneously lift it from the megass roll, so that the megass will not be as well pressed as it ought to be; and an objection to the side cap arrangement on the megass roll as well as to the top cap arrangement is, that in case more canes are fed in at one end of the rolls than at the other, the roll will be pushed out farther at one end than at the other; and though it may thus avoid a breakdown of the rolls, it is See also:apt, in so doing, to break the ends off the See also:teeth of the See also:crown wheels by putting them out of See also:line with one another . The toggle-See also:joint See also:attachment, which is an extremely ingenious way of attaining the same end as the hydraulic attachments, is open to the same objections . extraction of cane juice by diffusion (a See also:process more fully de-scribed under the See also:head of beetroot sugar manufacture) is adopted in a few plantations in Java and Cuba, in Louisiana Extraction and the Hawaiian Islands, and in one or two factories'''' a in Egypt; but hitherto, except under exceptional by Diffusion . conditions (as at Aska, in the See also:Madras See also:Presidency, where the See also:local See also:price for sugar is three or four times the See also:London price), it would not seem to offer any substantial See also:advantage over double or triple crushing . With the latter system practically as much sugar is obtained from the canes as by diffusion, and the resulting megass furnishes, in a well-appointed factory, sufficient See also:fuel for the crop . With diffusion, however, in addition to the strict scientific See also:control necessary to secure the benefits of the process, fuel—that is, See also:coal or See also:wood—has to be provided for the working off of the crop, since the spent chips or slices from the diffusers are useless for this purpose; although it is true that in some plantations the spent chips have to a certain extent been utilized as fuel by mixing them with a portion of the molasses, which otherwise would have been sold or converted into See also:rum . The best results from extraction by diffusion have been obtained in Java, where there is an abundance of clear, good water; but in the Hawaiian Islands, and in Cuba and Demerara, diffusion has been abandoned on several well mounted estates and replaced by double and triple crushing; and it is not likely to be resorted to again, as the extra cost of working is not compensated by the slight increase of sugar produced . In Louisiana diffusion is successfully worked on two or three large estates; but the general See also:body of planters are shy of using it, although there is no lack of water, the See also:Mississippi being near at hand . Purification.—The second operation is the coagulation of the albumen, and the separation of it with other impurities from the juice which holds them in suspension or solution . The moment the juice is expelled from the cells of the canes chemical See also:inversion commences, and the sooner it is stopped the better . This is effected by the addition of See also:lime to neutralize the See also:free See also:acid . As See also:cold juice has a greater See also:affinity for lime than hot juice, it is best to treat the juice with lime when cold . This is easily done in liming or measuring tanks of known capacity, into which the juice is run from the mill . The requisite amount of See also:milk of lime set up at 10° Beaume is then added . Cream of lime of 17° Beaume is sometimes used, but the weaker solution is preferable, since the proper proportion is more easily adjusted . In Demerara and other places the juice is then heated under pressure up to 220° F. to 250° F. for a few moments, on its way to a steam and juice separator, where the steam due to the superheated juice flashes off, and is either utilized for aiding subsiding the steam supplied to the multiple effect evaporators, Tan or for See also:heating cold juice on its way to the main heater, ks . or it is allowed to See also:escape into the See also:atmosphere . The boiling juice is run down into subsiding tanks, where it cools, and at the same time the albumen, which has been suddenly coagulated by momentary exposure to high temperature, falls to the bottom of the tank, carrying with it the vegetable and other matters which were in suspension in the juice . After reposing some time, the clear juice is carefully decanted by means of a See also:pipe fixed by a swivel joint to an outlet in the bottom of the tank, the upper end of the pipe being always kept at the surface of the liquor by a See also:float attached to it . Thus clear liquor alone is run off, and the mud and cloudy liquor at the bottom of the tank are left undisturbed, and discharged separately as required . In Australia a continuous juice separator is generally used, and preferred to See also:ordinary subsiding or filtering tanks . It is a cylin-Continuous drical See also:vessel about 6 ft. deep, fitted with a conical /See also:aloe bottom of about the same See also:depth . Such a vessel is Separator. conveniently made of a diameter which will give the cylindrical portion sufficient capacity to hold the juice expressed from the cane-mill in one See also:hour . The hot liquor is con-ducted downwards" in a continuous steady stream by a central pipe to eight See also:horizontal branches, from which it issues into the separator at the level of the junction of the cylindrical and conical portions of the vessel . Since the specific gravity of hot liquor is less than that of cold liquor and since the specific gravity of the scum and particles of solid matter in suspension varies so slightly with. the temperature that practically it remains constant, the hot liquor rises to the top of the vessel, and the scums and particles of solid matter in suspension See also:separate themselves from it and fall to the bottom . By the mode of See also:admission the hot liquor at its entry is distributed over a large See also:area relatively to its volume, and while this is necessarily effected with but little disturbance to the contents of the vessel, a very slow velocity is ensured for the current of ascending juice . In a continuous separator of which the cylindrical portion See also:measures 13 ft. in diameter and 6 ft. deep (a suitable See also:size for treating a juice supply of 4000 to 4500 gallons per hour), the upward current will have a velocity of about i See also:inch per minute, and it is found that all the impurities have thus ample time to separate themselves . The clear juice when it arrives at the top of the separator flows slowly over the level edges of ,a See also:cross See also:canal and passes in a continuous stream to the service tanks of the evaporators or vacuum See also:pan . The sloping sides of the conical bottom can be freed from the coating of scum which forms upon them every two or three hours by two rotatory scrapers, formed of L-irons, which can be slowly turned by an attendant by means of a central See also:shaft provided with a suitable handle . The scums then See also:settle down to the bottom of the See also:cone, whence they are run off to the scum tank . Every twenty-four hours or so the flow of juice may be conveniently stopped, and, after all the impurities have subsided, the superincumbent clear liquor may be decanted by a See also:cock placed, at the side of the cone for the purpose, and the vessel may be washed out . These separators are carefully protected by non-conducting See also:cement and wood lagging, and are closed at the top to prevent loss of heat ; and they will run for many hours without requiring to be changed, the duration of the run depending on the quality of the liquor treated and amount of impurities therein . Smaller separators of the same construction are used for the treatment of syrup . In Cuba, Martinique, Peru and elsewhere the old-fashioned double-bottomed defecator is used, into which the juice is run Double- direct, and there limed and heated . This defecator is Dobouble made with a hemispherical See also:copper bottom, placed in bottomed an See also:outer See also:cast-See also:iron casing, which forms a steam jacket, Defecators . and is fitted with a cylindrical curb or See also:breast above the bottom . If double-bottomed defecators are used in sufficient number to allow an hour and a half to two hours for making each defecation, and if they are of a size which permits any one of them to be filled up by the cane-mill with juice in ten to twelve minutes, they will make as perfect a defecation as is obtainable by any known system; but their employment involves the expenditure of much high-pressure steam (as exhaust steam will not heat the juice quickly enough through the small surface of the hemispherical inner bottom), and also the use of See also:filter presses for treating the scums . A great See also:deal of skilled superintendence is also required, and first cost is comparatively large . When a sufficient number are not available for a two hours' defecation, it is the practice in some factories toskim off the scums that rise to the top, and then See also:boil up the juice for a few minutes and skim again, and, after repeating the operation once or twice, to run off the juice to separators or subsiders of any of the kinds previously described . In Java and See also:Mauritius, where very clean canes are grown, double-bottomed defecators are generally used, and to them, perhaps as much as to the quality of the canes, may be attributed the very strong, See also:fine sugars made in those islands . They are also employed in Egypt, being remnants of the plant used in the. days when the juice passed through See also:bone-See also:black before going to the evaporators . A modification of the system of double-bottom defecators has lately been introduced with considerable success in See also:San Domingo and in . Cpba, by which a continuous and steady See also:discharge Contlauous of clear defecated juice is obtained on the one hand, and Defecaton. on the other a comparatively hard dry cake of scum or cachaza, and without the use of filter presses . These results are brought about by adding to the cold juice as it comes from the mill the proper proportion of milk of lime set up at 8° B., and then delivering the limed juice in a constant steady stream as near the bottom of the defecator as possible; it is thus brought into immediate contact with the heating surface and heated once for all before it ascends, with the result of avoiding the disturbance caused in the ordinary defecator by pouring cold juice from above on to the surface of the heated juice, and so establishing down-currents of cold juice and up-currents of hot juice . In the centre of the defecator an open-topped cylindrical vessel is placed, with its bottom about 6 in. above the bottom of the defecator and its top about 12 in. below the top of the defecator . In this vessel is placed the See also:short See also:leg of a draw-off See also:siphon, reaching to nearly the bottom . The action of the moderate heat, 2 1o° F., on the limed juice causes the albumen in it to coagulate; this rising to the surface collects the cachazas, which form and float thereon . The clear juice in the meantime flows over the edge of the cylindrical vessel without disturbance and finds its way out by the short leg of the siphon, and so passes to the canal for See also:collecting the defecated juice . The admission of steam must be regulated with the greatest nicety, so as to maintain an equable temperature, 208° to 210° F., hot enough to See also:act upon the albumen and yet not enough to cause ebullition or disturbance in the juice, and so prevent a proper separation of the cachazas . This is attained by the aid of a copper pipe, 4 in. in diameter, which follows the See also:curve of the hemispherical bottom, and is fitted from one side to the other of the defecator;, one end is entirely closed, and the other is connected by a small pipe to a shallow circular vessel outside the defecator, covered with an india-See also:rubber See also:diaphragm, to the centre of which is attached a See also:light See also:rod actuating a steam throttle-See also:valve, and capable of being adjusted as to length, &c . The copper pipe and circular vessel are filled with cold water, which on becoming heated by the surrounding juice expands, and so forces up the india-rubber diaphragm and shuts off the steam . By adjusting the length of the connecting rod and the amount of water. in the vessel, the amount of steam admitted can be regulated to a nicety . To make this apparatus more perfectly automatic, an arrangement for continually adding to and mixing with the juice the proper proportion of milk of lime has been adapted to it; and although it may be objected that once the proportion has been determined no See also:allowance is made for the variation in the quality of the juice coming from the mill owing to the See also:variations that may occur in the canes fed into the mills, it is obviously as easy to vary the proportion with the automatic arrangement from time to time as it is to vary in each separate direction, if the See also:man in See also:charge will take the trouble to do so,' which he very seldom does with the ordinary defecators, satisfying himself with testing the juice once or twice in a See also:watch . The scums forming on the top of the continuous defecator become so hard and dry that they have to be removed from time to time with a specially constructed See also:instrument like a See also:flat See also:spade with three flat prongs in front . These scums are not worth passing through the filter presses, and are sent to the fields direct as manure . The scums separated from the juice by ordinary defecation entangle and carry away with them a certain amount of the juice with its contained saccharine . In some factories they Treatment are collected in suitable tanks, and steam is blown into T eat them, which further coagulates the albuminous See also:par- ticles . Scums . These in their upward passage to the top, S where they float, free themselves from the juice, which they leave below them comparatively clear . The juice is then drawn off and pumped up to one of the double-bottomed defecators and redefecated, or, where juice-heaters have" been used instead of defecators, the scums from the separators or subsiders are heated and forced through filter presses, the juice expressed going to the evaporators and the scum cakes formed in the filter presses to the fields as manure . |