The term sugar is applied, in a general sense, to the sweet principle of plants, fruits, and trees. There are several different kinds of sugar. Three kinds exist in or are produced from sugar-cane, called, respectively, cane sugar, fruit sugar, and grape sugar. The last two rarely occur separately or apart from some portion of cane sugar, together with impurities and vegetable substances derived from the cane, and forming together an amorphous compound, variously termed uncrystallizable sugar, glucose, molasses, or sirup.
This substance crystallizes readily from a pure solution, forming bold, transparent, colorless crystals, having the form of a modified, oblique, rhombic prism, as exhibited in rock candy. It has a pure sweet taste, is quite devoid of odor, very soluble in water, and nearly insoluble in absolute alcohol. The formula of its: composition is, 12 equivalents carbon, 11 equivalents hydrogen, and 11 equivalents oxygen. Its sweetening property is greatly superior to that of grape sugar or glucose. Cane sugar is believed to be exclusively the product of nature. All attempts to produce it by artificial means have failed. It is, however, easily transformed or degraded to fruit or grape sugar, and in all the ordinary methods of producing sugar from its natural sources, a large per centage is converted to uncrystallizable sugar in the process. This reduces the commercial and intrinsic value of the product, and imposes a heavy discount. upon the business. No part of the process of sugar-making demands more attention than the means of preventing the conversion of cane sugar, when present, to uncrystallizable sugar.
The elements which enter into the composition of this substance are the same as appear in cane sugar, differing only in the proportions of hydrogen and oxygen, or the elements of water, to the carbon, and only to the extent of one equivalent of each in this respect. Fruit sugar is composed of 12 equivalents. carbon, 12 equivalents hydrogen, and 12 equivalents oxygen, It is uncrystallizable, and when pure has an intensely sweet taste. It occurs in fresh grapes, and many other fruits, particularly in such as contain considerable natural acid. It constitutes the sweet of new honey, and is probably the first product of cane sugar, starch, and lignine, when operated upon artificially, to effect their conversion. It differs from both cane sugar and grape sugar in rotating the plane of polarization to the left, and is for this termed, scientifically, lœvo-glucose.
This body is composed of 12 equivalents carbon, 14 equivalents hydrogen, and 14 equivalents oxygen. The nodulous masses of sugar which appear in old dry raisins and the solid portion of candied honey afford the best natural illustrations of this substance. Cane sugar, starch, lignine, and some other substances, are susceptible of conversion into grape sugar. It is probable that grape sugar never occurs originally in nature, but is always the result of changes either natural or artificial imposed upon other bodies. Professor Anthon, of Prague, having devoted much time to the study of this substance, has succeeded in producing it, artificially, in almost a pure state, in which condition it affords regular, palpable, crystalline forms, unlike the warty and needle-like. grains by which it was formerly distinguished. His researches afford new and important light upon this subject, revealing the fact that but little was formerly known with reference to the so-called grape sugar. This substance, like cane sugar, rotates the plane of polarization to the right, and is hence called dextro-glucose.
CONVERSION OF CANE SUGAR TO GLUCOSE.
Dense solutions of pure cane sugar in closed vessels, at ordinary temperatures, undergo no change. Dilute solutions in closed vessels are but slightly altered after long periods, but exposed to the air speedily change, being first converted to fruit sugar, afterwards to grape sugar, and subsequently fermenting. A solution of pure cane sugar, of the density of 25° Beaumé, boiled in an open vessel for two hours, becomes partly converted. At greater densities the conversion occurs sooner and more rapidly, about in proportion to the increased temperature of ebullition. Cane sugar is changed more rapidly by boiling if agitated so as to expose it to the air, or if a current of air be passed through the boiling liquid. Acids effect the complete conversion of cane sugar to glucose; strong mineral acids more rapidly than weak vegetable acids, and both much more rapidly with boiling them with cold solutions, the changes being in proportion to the strength of the acid and the temperature employed.
Alkalies promote conversion much less than acids. Some of them, such as
lime, the chlorides of alkaline earths, the normal sulphates and carbonates, when
added to solutions of pure sugar, or when boiled with them, do not increase or
accelerate conversion. Their presence, however, hinders or wholly prevents
crystallization, Two parts of common salt, or of chloride of calcium, in one hundred parts of cane sugar dissolved, will prevent recrystallization. Solutions of
pure sugar with lime, when boiled, suffer conversion less than without lime, and
when long kept they exhibit greater stability than when lime is absent; but with
impure solutions, at temperatures favorable to fermentation, lime promotes conversion.
Deastase, an active principle existing in the buds of plants and germs of grain, causes rapid conversion of cane sugar at ordinary temperatures. At boiling heat it is coagulated and rendered inert. This is an insidious agent, and its presence may be apprehended in the juice of cane which exhibited, before being harvested, a tendency to sprout at the joints.
Sugar-cane exposed to a temperature as low as 30° or 31° while standing in the field freezes, causing a rupture of the juice cells, and allowing the pure sugar- water which they contain to mix with the crude sap. This excites the first step in the fermenting process, and in a very few hours, if the canes remain exposed to a warm sun, complete conversion of all the crystallizable sugar they contain takes place. If stored in large unventilated shooks, or closely packed in sheds, or put up when wet so that any part of the mass heats to even a moderate degree, conversion of sugar and subsequent fermentation occurs at the point affected, attended with the development of all the inexplicable agencies by which fermentation is communicated. In a short time the whole mass partakes of the infection. The first step in the changes which thus occur is the conversion of crystallizable to uncrystallizable sugar, and this may take place before active fermentation is indicated, and without being even suspected.
Cane sugar contained in the expressed juice of sorghum, if the temperature is above 60°, begins to undergo conversion almost as soon as pressed from. the stalks, more rapidly as the temperature is higher. In close humid weather, or when warm rains prevail, particularly if accompanied with lightning, complete conversion occurs in a short time, followed or attended with the development of lactic acid, and exhibiting a condition of the juice entirely different from that which results from ordinary vinous fermentation. Small portions of juice left over in pipes or vessels, or minute fragments of saturated bagasse remaining in the mill, soon become changed, and when mixed with fresh juice excite the state or condition which they have acquired, the vinous state exciting the vinous fermentation; the acetic, the lactic, the mucous or viscid, and the putrid, each exciting in juice, first, conversion of cane sugar to glucose, followed by further changes to the particular state of the excitant, respectively.
In the operation of boiling cane juice, particularly the juice of sorghum canes, which contain a large proportion of earthy salts and azotized matter, conversion of sugar to glucose occurs extensively. If large quantities of juice are operated upon at one time, involving a long exposure of the solution to boiling heat, the conversion becomes total, and this result is inevitable. Other effects of an injurious character are produced by protracted exposure of the juice, or rather of the dense and nearly concentrated solution to heat, which will be referred to hereafter.
VARIETIES OF CANE WITH REFERENCE TO SUGAR.
The Imphee or African canes have been found more productive of sugar than the Chinese; although all varieties have afforded crystallizable sugar, and its production or occurrence, unexpectedly to the operator, is frequent, and is becoming more common every year.
The Imphee canes, the variety known as Oomseeana, by some called Otaheitan, is most distinguished as a sugar-producing cane. The stalks of this variety are tall, the panicle close, seeds nearly enclosed in the hulls, which are a dark purple, nearly black; color of the seeds orange, or a dingy brown. The joints of the stalk are short at the base, and increase in length towards the top, as do nearly all the imphees. This cane does not resist winds well, but is frequently blown down flat, forming a tangled mass, very difficult to harvest.
The peculiar imphee odor is very prominent in the Oomseeana. It reveals itself to the passer-by while growing in the field, and very decidedly in the vapor while boiling. The sirup partakes of the same, and on this account the variety is rejected by many cultivators, notwithstanding its superior sugar-producing qualities.
Nee-a-za-na or white imphee produces sugar frequently. The panicle of this variety is short and compact, the upper part generally drooping. Seeds large and very abundant, projecting beyond the hulls, and presenting a lighter appearance than any other variety. The seeds are in fact white, except the portions which project beyond the hull, which acquire a light brown tinge. The stalks are short and heavy, joints of graduated lengths. This cane stands erect with much stability. It should be worked early, before the seeds begin to harden. The imphee odor is less marked in this variety than in the Oomseeana, and it affords a light colored, pleasant sirup. The sugar from it appears in large well-defined crystals, and it is drained or “purged” with more facility, perhaps, than any other variety. The product of Oomseeana per acre is generally less than that of other varieties.
A variety known as Shla-goo-va or red imphee, not largely cultivated, has been little tested with reference to its sugar-producing qualities, though the occurrence of sugar in its sirups has been reported in a few instances. The panicle of this variety is long and somewhat bushy, the foot stalks slender, inclined to droop, in some cases very long, and presenting the appearance of broom-corn, The seeds are closely encased in the hulls or glumes, and these of a dark red color when fully ripe, approaching a purple hue. Stalks tall and slender, joints in graduated lengths, liable to fall or be blown down by winds.
Black imphee is an early variety, not very productive and not generally popular, though a few operators report well of it. Panicle short, compact, seeds closely encased, glumes glossy black, stalk short, color of sirup dark and flavor generally rank.
Liberian, a variety of imphee but recently introduced to notice in the northern States, and not yet extensively cultivated. This is a very promising cane, and the indications are that it will afford sugar. It is very distinctly marked by its seeds, which are small, very round, and of a rich cranberry color. The panicle is large, compact, the seeds being closely compressed except at the top, where a clump of more flexible foot stalks appear, which bend over and droop a little. The stalk is large, but shorter by one or two feet than the Oomseeana; distance between the joints graduated, sometimes very short at the base, but increasing to a good length above; affords a great quantity of juice of average saccharine richness, and of a very pure sweet taste; color of sirup light, flavor mild, betraying but little of the peculiar imphee quality. This cane stools out abundantly from the seed, affording, in good ground, a heavy stand from two or three grains in a hill. It stands up rigidly against all winds; in this respect being greatly superior to any other variety. The Liberian appears to retain its identity, refusing to amalgamate with other canes even when grown in close proximity to them. It is, however, suspected that other canes, particularly the Oomseeana, become impregnated by the Liberian, displaying in the color and shape of the seeds evidences of the admixture.
The sorgo or Chinese cane is more generally distributed and much more extensively grown in the northern States than the imphees. It is most highly esteemed for productiveness, and for the quality of its sirup, being usually more mild and pleasant. It rarely affords crystallizable sugar, and until recently was considered incapable of producing it. Considerable sugar was, however, made from sorgo in the season of 1865. A barrel of sugar, made by Walter Edgerton, Henry county, Indiana, from Chinese cane, was exhibited to the Cincinnati Horticultural Society in the spring of 1866, and found to be of very superior quality, having large, bold grains, and quite free from the gummy principle which is commonly present in these sugars. It is, however, entirely certain that the sorgo or Chinese cane has been less productive of crystallized sugar than the imphees and, from what is at present known, it affords less promise for the sugar-making enterprise. The results of another year may, however, change or invert the popular notion upon this subject and give sorgo the priority. Inversions of prevailing opinions upon similar questions have been frequent in the experience of cane-growers, and it would be unwise to abandon the idea of producing sugar from the sorgo cane until much more carefully tested.
The sorgo cane is tall and slender, distances between nodes nearly uniform; panicle branching, showing a cone-shaped outline; seeds nearly enclosed in hulls, but when fully ripe expanding the hulls and revealing the yellow or brownish tinge of the exposed part of the seed; juice rich, tolerably abundant; quality of sirup more mild and pleasant than that of the imphees generally.
This cane is very liable to fall down of its own weight, and a strong wind upon a heavy growth prostrates it, reducing the whole to a tangled and impenetrable thicket. This is a common and a very important objection to the Chinese variety.
Early sorgo, a variety or rather a class of canes designated by this name, has been cultivated to a small extent. The only respectable cane of this class is one which was developed from the regular sorgo by careful selection. A gain of two or three weeks in time of maturity was. obtained, and this quality has remained permanent; but it was secured at some sacrifice of length and size of stalk. It is distinguished from the regular sorgo by the increased size and greater prominence of the seed, and by a downy growth near the margin of the glumes, particularly toward the points, imparting a grayish cast to the panicle when seen from a little distance. Its capacities as a sugar-bearing cane, if it have any, remain undiscovered. Several canes of this same class have appeared under various names, coined. or imported, for the purpose of giving effect to schemes of speculation. They appear to be derived from an amalgamation of the sorgo, perhaps the early sorgo above referred to, and the black imphee. The yield of sugar from these fancy canes is prodigious, if advertisements can be relied upon, but, unfortunately, the newspaper traditions have not been realized in practice.
SOIL AND CULTIVATION.
The subject of soil for cane, particularly when sugar is contemplated, is important. Roots of plants take up fluids from the soil; these contain. soluble matters of various kinds, some of which are required for the growth of the plant and are appropriated to that purpose, but by far the larger portion taken up is not required, and is either excreted, or, at the time the cane is harvested and severed from the roots, remains in the crude sap. When the cane is ground, the crude sap with all the soluble earthy matters which it contains is pressed out, and forms a portion of the juice. Rank soils, containing a large portion of soluble salts, particularly those of a saline nature, are highly unfavorable; they oppose the production of sugar in three ways:
first, by preventing its development in the cane;
secondly, by promoting the conversion of crystallizable sugar during the process of boiling; and
thirdly, by obstructing the crystallization of that which remains. Badly-drained lands, even if not rich, by retaining their moisture for long. periods, losing it only by the slow process of evaporation, contain a large percentage of deleterious salts.
Fresh undigested manures, or those containing a large percentage of ammoniacal salts, (as stable manure, hog manure, and some of the guanos,) are injurious, particularly when applied to undrained or highly retentive land. Professor James F. Johnston, referring to the presence of earthy salts in the juice of the sugar beet, and the effects of manures in the same connexion, writes: “Certain sirups remained behind, which, though they certainly contained cane sugar, refused stubbornly to crystallize; and the reason of this was traced to the presence of saline matter, chiefly common salt, in the sap. This salt forms a compound with the sugar and prevents it from crystallizing. And so powerful is this influence that one per cent. of salt in the sap will render three per cent of the sugar uncrystallizable. To overcome this difficulty, new chemical inquiries were necessary. As results of these inquiries it was ascertained, first, that the portion of sugar was larger and of salt less in beets not weighing more than five pounds. The first practical step, therefore, was, that the sugar manufacturer announced to the cultivators, who raised the beets, that in future they would give a less price for roots weighing more than five pounds. Next, that a crop raised by means of the direct application of manure, contained more salt and gave more uncrystallizable sugar than when raised without direct manuring. A larger price, therefore, was offered for roots grown upon land which had been manured during the previous winter; a still higher price for such as were raised after a manured crop of corn; and a still higher price when, after the manuring, two crops of corn were taken off before the beet was sown.”
Few plants are so deep-rooted as the sorghum. The roots have been traced to the depth of more than four feet; hence it would be inferred that the quality of the cane must be affected by the nature of the subsoil. This is found to be the case. Sandy or gravelly subsoils are most favorable for developing the pure saccharine properties of the cane. This, of course, results mainly from their affording drainage, carrying off the stagnant fluids which would otherwise remain in the soil surrounding the roots. This suggests the idea of underdraining, and in soils which are not naturally drained, underdraining is almost indispensable. It is very much more necessary with cane than any other crop. Professor B. Silliman, jr., in concluding a course of lectures upon cane culture in Louisiana, enforeed the subject of draining in the strongest terms. He said that, “if called upon to give three rules which he regarded as most important for success in cane husbandry, the first would be drainage; the second, drainage; and the third, DRAINAGE.” The conditions which affect tropical cane doubtless produce a corresponding effect upon ours, and the rules above given may be confidently commended to all who contemplate producing sugar from sorghum: It is hardly necessary to add, in this connexion, that deep ploughing, or, if convenient, subsoiling, is in order, and extremely appropriate for cane.
Cultivation should be thorough and frequent in the early stages of growth, but deep ploughing, or even working with the cultivator, should be suspended. after. the plants have acquired a height of three or four feet. The roots permeate the soil, extending quite across the rows, and when severed by the plough or cultivator the growth is arrested, and the cane acquires a premature and a dwarfed maturity.
TIME OF HARVESTING CANE
Until recently the opinion has prevailed that cane for making sugar should be thoroughly ripe; that it could not remain standing in the field too long, provided it escaped the frost; but lately, this notion has been somewhat modified. The frequent occurrence of sugar in sirup of immature or unripe cane recently attracted attention, and was published. his called to mind numerous similar instances which had escaped notice until the subject was suggested, and these were multiplied in number until something like a case for early or premature harvesting was made out. The matter cannot, however, be considered as definitely settled until the results of the season of 1866 shall have been determined. Many will carefully test the cane at different periods or stages of maturity, so that, after the next year, it will be fully understood. The precise stage of maturity most favorable for the production of crystallizable sugar, according to the new theory, is just after the seeds are formed, and before they begin to harden. As cane matures quite unevenly, it will be necessary, in making accurate tests, 10 select stalks of uniform maturity, rejecting such as are not sufficiently or too much advanced.
In all cases, when working for crystallizable sugar, the two joints of cane next to the ground, and two joints from the top, (besides the arrow,) should be rejected. The cane should be cut close to the ground without removing the blades or the top; these, together with the two joints at the butt, to be removed as the cane is worked. It would be best to allow but little time between harvesting and working the cane, and on no account should it be stored and allowed to remain long in large shooks. It is almost demonstrable that no cane sugar is developed under any circumstances after the cane is harvested. The changes that occur after the cane is cut, if any, must be in their nature depreciative, consisting in the transformation of crystallizable to uncrystallizable sugar. The rind of the cane and the sheath surrounding the stalk will, of course, dry, if grinding is delayed, and give off less crude sap; but if the purpose is to produce sugar, the main point must be kept constantly in view, and all considerations which relate merely to the quantity of the uncrystallizable product must be disregarded. Sugar alone crystallizes, and this can be easily separated from or purged of any impurities or offensive matters. So far as the crude matters oppose crystallization they:are to be avoided, but the “curing process” is attended with more loss of crystallizable sugar than their presence in the juice would occasion.
But little need be said upon this point. The mill should be absolutely clean, no fragments of old bagasse left adhering to parts reached by the juice. If the cane is newly harvested and not thoroughly ripe, it will part with most of its juice without very close pressing, and that which remains in the bagasse can well be spared. Bagasse of green cane repressed affords a juice, which is not very sweet, but which is very green and offensive.
TANKS AND VESSELS.
These should he scrupulously clean, particularly with reference to any trace of acidity. If filters are used, the arrangement of them should be such as to keep the straw or other filtering medium covered with juice while employed; and if emptied at any time, leaving the surface of wet material exposed to the air, the contents of the filter should be. renewed. No ordinary condition is more favorable for exciting vinous and acetous fermentation in cane juice than that afforded by the contents of a filtering vessel when emptied of juice and exposed to air.
The use of alkaline agents in the juice of our sorghum canes is attended with results which do not follow. when they are used in the juice of tropical canes. Neutralizing with lime is an immemorial custom in the tropics, and no sugar- boiler would think of dispensing with it, or some full equivalent. The cause of the difference referred to is not well understood. Our canes contain a greater percentage of. glucose, and this has. been named as a reason. It is true that lime forms a compound with grape sugar, but it combines only a little less readily with cane sugar. This explanation is not satisfactory to any intelligent observer of the phenomenon. Lime applied to sorghum juice in quantity sufficient to neutralize the free acid produces invariably a dark inky complexion in the sirup, and a strong, and, to many, an extremely offensive taste.
Chalk or pulverized carbonate of lime is but slowly acted upon. Filtering hot juice through a mass of finely broken limestone decomposes the carbonate slowly, but the quantity of lime appropriated is not sufficient to. produce any perceptible effect upon the acid of the juice. Calcareous clays have been used with but little benefit. Carbonate and bicarbonate of soda and potash affect the color and taste of the sirup like lime, while they are less appropriate in other respects.
Bisulphate of lime is an acid [not really. It's actually a salt that, when dissolved in pure water is of almost-neutral pH. -ASC]. It decolorizes, assists in defecation, and serves in a remarkable manner to prevent every kind of fermentation. The quantity appropriate to be used is very small—so insignificant that no injurious effect can follow. One pint to a hundred gallons of juice is enough. The sulphurous acid which it contains is supposed to assimilate free oxygen from the juice, removing thereby the active agent of fermentation, the sulphurous being converted into sulphuric acid, the latter combining with lime, forming the insoluble sulphate of lime which comes off with the seam. Probably but a small portion of the sulphurous acid is thus converted, while the remainder being volatile escapes in boiling, leaving a small quantity of free lime in the juice in excess of that required by the sulphuric acid. The objection urged against the use of bi-sulphate of lime is, that it renders sugar deliquescent. When first introduced employed in Louisiana, it was doubtless used in immoderate quantities. There can hardly be an objection to using the small portions named above, and from very careful observation of its effects the writer is inclined to recommend it, particularly in operations conducted with reference to granulated sugar. Notwithstanding all that is said and all that is realized from the use of quick-lime in sorghum juice, there seems to be a necessity for employing it in sugar-making operations. The presence of acid in the boiling juice and sirup must tend to increase conversion of cane sugar to glucose, and there appears to be no adequate remedy but by the employment of a moderate quantity of lime.
It is, therefore, recommended, and, in combination with bisulphate of lime, to be used in the following manner:
The bisulphate should be introduced into the juice as soon as possible after it leaves the mill, and before it passes through the filter. One mode is to allow it to drop from a vessel, holding a measured quantity, into the stream of juice as it flows from the mill. If this cannot be conveniently arranged, it may be poured into and thoroughly mixed with the juice in appropriate quantities.
The quick-lime, having been slaked by immersion in boiling water, and having been thoroughly mixed with water to the consistency of milk, may be carefully added to the juice, the last thing before it goes to the pan. On no account should tempering with lime be undertaken without litmus paper to determine the effect as lime is added. After adding a portion of lime and thoroughly incorporating it with the juice, apply the litmus paper, and if the original color produced by the juice has been modified from a scarlet to a pink, approaching a purple, probably enough has been used. Complete neutralization of the acid should not be attempted. Clear lime water, in place of milk of lime, is sometimes recommended. Larger quantities are required to produce a perceptible modification of the acid, and if used in quantities sufficient to effect the object, the result is the same in all respects as if milk of lime were used.
GENERAL REMARKS. UPON EVAPORATING.
The art of producing sugar from sorghum, while it depends upon every step in the progress of the work, from the selection and planting of the seed to the final operation of draining the crystallized sugar, may be said to hinge upon the process of evaporating; as it is in this that all the prudence and skill of the operator are required. This subject embraces, first, the means of separating the sugar from the impurities with which it comes associated; and, secondly, the means of expelling the excess of water without developing a dark color in the concentrated sirup, or causing conversion of crystallizable to uncrystallizable sugar. Processes for accomplishing both of these are known and in successful use in large sugar-making operations, both with the beet and the tropical cane; but they are expensive, complicated, and entirely beyond the reach of the northern farmer, who produces his crop of sorghum as an incidental and generally a subordinate farm crop. The question for practical consideration in this connexion is, how shall the work of evaporating sorghum juice for the production of sugar be accomplished by simple and inexpensive means, accessible to the ordinary farmer? [Let's pause for a moment and reflect on how the USDA USED TO care about small farmers! That needs to happen again! -ASC]
If cane juice containing crystallizable sugar could be instantly deprived of its excess of water and the impurities which it originally contains, no appreciable conversion of sugar would occur, the solution would be colorless, and the cane sugar would immediately crystallize out, in clear, bold grains, from which the uncrystallizable portion would readily drain. But the work of evaporating requires time, and when performed in an open evaporator under ordinary atmospheric pressure, it requires a high degree of heat, the effect of which is, as has been stated, to develop color and convert crystallizable sugar: A dense viscid condition of the sirup is also produced by the same cause, which retards or totally prevents the crystallization of any cane sugar which may remain unconverted; or if the molecular attraction is powerful enough to overcome the obstructions and a tardy crystallization is displayed, the viscid or gummy medium refuses to separate or drain from the sugar. The difficulties here referred to are encountered in all sugar-making operations. They constitute the great and universal impediment to the production of pure sugar from its various sources in nature. It is to avoid or counteract these that vacuum pans, bone coal filters, the desiccating, the refrigerating, and numerous other processes have been devised. While these difficulties pertain to the juices of all plants worked for sugar, they are most formidable in the juice of the beet and sorghum. The beet sugar enterprise came near being abandoned on account of difficulties of the nature here referred to, and its success was only established after the employment of extraordinary means, suggested by long experience and the highest scientific aids, and these included with the abundant use of animal carbon and evaporating in vacuo. It should not, therefore, be surprising to any one acquainted with the nature of our sorghum juice and its similarity to the juice of the beet, that the production of sugar by the simple, and in many cases inappropriate, means has not been more frequent. By similarity, it is not meant that the juice of the beet and sorghum are identical. The saccharine substance of the beet consists more generally and more exclusively of cane sugar, while it contains a greater proportion of earthy salts and other impurities. These are so abundant that a sirup of beet produced by the simple process employed with sorghum would be extremely offensive.
A description of the apparatus and processes employed in beet sugar factories, or in the sugar houses of the tropics, would afford hardly a suggestion of practical use in domestic operations with sorghum.
The bone coal filter and the vacuum pan are the most appropriate means known to man for producing sugar from its solutions; but they are not appropriate, and cannot be considered az having any place in this connexion, as they do not meet the popular purpose which is intended to be subserved in this paper.
Conversion of sugar occurs, as has been shown, from prolonged exposure of the solution to intense heat. Brief exposure to intense heat, or prolonged exposure to moderate heat, is not attended with much loss or injury. The vacuum pan operates upon the latter principle. Under a vacuum, boiling may be carried on at temperatures much below that of boiling water; and this permits the boiling of cane juice in large charges, requiring several hours for its concentration. But the vacuum pan, which affords the means of boiling upon this principle, not being attainable by the sorghum operator, he must, if possible, accomplish the same end by the other method—that of brief exposure to intense heat. If the excess of water in cane juice could be instantaneously expelled, the results would be as satisfactory as they are with the vacuum pan. But as time must be employed, it is obvious that the shorter the time the better will be the results. In considering the subject of evaporating cane juice in open pans, then, the following may be given as a maxim of universal application: Other things being equal, that process which concentrates with the briefest exposure to heat is the best process.
These are used but by few operators in sorghum, They are no more economical than properly constructed apparatus worked by direct fire, and afford no advantage whatever except convenience and facility in controlling the heat. These are overbalanced by the great expense of apparatus; by the necessity of working in large batches enough to cover the pipes; and by the difficulty of discharging the finished sirup clean from the evaporator, a portion being necessarily left adhering to the pipes, which becomes candied by the heat of the metal, and must be cleaned off at some trouble and loss, or be left to impart a dark color and an offensive taste to the next batch.
“Steam-jacket” evaporators have been used. Kettle-shaped evaporators, surrounded by a steam chamber, can be conveniently and securely made, and for many purposes these steam-heated kettles answer very well, but not for sorghum. They must necessarily be made to contain a considerable quantity of juice; then, the heating surface is insufficient, and the solution is exposed to a long, sluggish process of boiling, than which nothing could be more fatal to crystallizable sugar.
Steam has been applied to the bottoms of flat pans. This permits the heat to be applied to a shallow body of juice, and secures the rapid concentration of the quantity acted upon, but the difficulty of constructing the apparatus renders it expensive and almost impracticable. A pressure of steam sufficient to evaporate rapidly, when applied to the under surface of a flat metal plate, tends to produce an upheaval which must be counteracted by numerous stay bolts, so nicely and securely fitted as to remain steam-tight. Pans of this description have been constructed and found to operate well when perfectly made, They afford the only known mode of evaporating by steam adapted to making sugar from sorghum.
From the repeated reference which has already been made to the destructive effects of heat upon sugar juices, it might seem that the subject had received sufficient attention. It is, however, impossible to give undue prominence to this point in operations with sorghum, particularly in working for sugar. It is a matter of first and greatest importance. In considering the claims of evaporators, then, the most important question has reference to the capacity afforded for reducing juice suddenly to sirup. Pre-eminent capacity in this respect compensates for inferiority in any and all others. Extra labor and attention, waste of fuel, inconvenience of all sorts in an apparatus, may be endured. It may fail to afford means of good defecation [previously used in this article with some connection to how we think of the word today. However, the author is using this word in a sense tied to the Latin faec, which meant dregs or lees. Thus "defecation" is being used to describe the separation of solid material from the pure syrup. -ASC] —even this may be submitted to; for if the juice is reduced to sirup so suddenly that the sugar is left intact, or unchanged by heat, it will readily crystallize out of the solution, and can then be separated from the uncrystallized portion which will retain the impurities. But if, on the other hand, the apparatus be faultless in all respects except that it provides for working upon considerable quantities of juice at a time, or from any other cause involves longer exposure of juice to heat and the consequent conversion of crystallizable to uncrystallizable sugar, the enterprise, so far as sugar is concerned, is a total failure. The result may be a very clear, nice sirup, but it will be uncrystallizable; or if not all converted, and a crop of puny crystals appear, they will be inseparable from the dense and gummy medium in which they are contained.
The importance of rapid boiling in small batches is recognized by all experienced operators in sorghum. All know that. protracted, sluggish boiling imparts an inky hue and a rank disagreeable taste to the sirup. It is not, however, so generally understood, or admitted, that the gummy, viscid condition of the sirup, and conversion of cane sugar, is produced by the same cause. Some even suppose that the yellow, waxy scum, which appears in the last stages of boiling, is original in the juice, and by prolonging the boiling this may be, in a great measure, brought to the surface and eradicated from the sirup. Yet no one has ever found this adhesive substance to diminish in quantity as the boiling and the operation of expelling it is continued; on the other hand, the careful observer must notice that, in place of disappearing, it accumulates more rapidly than it is removed, and that this gummy principle is, in fact, a product of the very means employed to expel it.
When sorghum was first introduced, operators took counsel from the only, sources which they could consult—the familiar modes employed in concentrating the sap of the sugar maple, and the practice of the sugar-planter of the south. Cast iron sugar kettles, of the largest attainable dimensions, were put to use, and these being deemed insufficient, many procured cauldrous made for the purpose, which would hold several hundred gallons. The sirup resulting from these formidable boilers disappointed expectation, It was dark, strong, offensive, and by universal consent christened “cane-olina tar.” Sorghum was regarded as a failure by many, and the enterprise came near being abandoned. But experiments with juice boiled in tin cups and basins on kitchen stoves had been incidentally tried by a few persons, and the results of these were so entirely different, and the sirup so greatly superior to that which had been obtained by boiling in large batches, that the theory of rapid boiling in shallow pans was suggested from many quarters, and universally adopted. The new revelation which was thus made opened a hitherto unoccupied field for invention, and a great multitude of “new and useful improvements” in sorghum evaporators immediately appeared; and these, propagating, have continued to multiply with a sort of generative ratio of increase to the present time, the original key of shallow evaporation being preserved in nearly all. Two different and distinct modes of shallow evaporation are employed. One consists in operating upon a batch or charge of juice, which is received into the evaporator either in the original green state, or after being first defecated by a previous process, and is finished and struck off in one body. The other consists in receiving either the green or defecated juice continuously, in a small stream, into one end of the evaporator, and discharging the finished sirup continuously from the other end, the juice being concentrated to a proper degree during its passage, and while in motion through the pan. The first is called the “intermittent process,” and the other is called the “continuous process.” Numerous plans have been invented and used for evaporating by the intermittent method. They all relate to economy in construction and in the use of fuel, or to convenience in management. Some of them provide for receiving the green juice into large evaporators, where it is defecated, thence transferred to tanks or vessels, in which suspended impurities are allowed to settle, and thence to small evaporators, where it is finished. The success of this mode of evaporating, when the operation is conducted for sugar, depends mainly upon the quantity operated upon in the last stage. If very small, and the boiling quickly performed, the conversion of crystaliizable sugar may be inconsiderable. he finishing pans should be thoroughly cleansed at the end of each strike. The settling process must receive particular attention, as the juice, if allowed to remain in the tanks long after the temperature is somewhat reduced, is liable to ferment, or to undergo an incipient change, which, although it might, not be perceptible in the quality of a sirup, might be fatal to the production of sugar. A more simple process, but. much less perfect in its results, is where the green juice in a considerable body is taken into the evaporator, and directly boiled down to sirup. If the operation is conducted upon small charges, the conversion of sugar will be trifling, but in order to accomplish much work, large evaporators and large charges must be used.
The plan of boiling in a series of four or five small pans upon one furnace is used to some extent. They are each charged with a few gallons of juice, and placed crosswise upon the furnace, over the fire, and for some distance back over the flue. When the juice in the first pan over the fire is sufficiently concentrated, the whole series is moved or slid forward the width of a pan, which removes the front one from over the fire upon supports arranged to receive it, and leaves a space in the rear, which is covered by a newly charged pan. The pan of finished sirup is then emptied, cleaned, and charged with fresh juice, ready to take its place in the rear when another pan is removed from the front. Between the “intermittent process,” according to any plan that may be adopted, and the “continuous,” there is this specific difference: In the former the quantity of juice operated upon at one time must be sufficient to cover the bottom of the pan so deep that, even in the last stages, when the sirup becomes dense and sluggish, it will have sufficient volume to give it mobility, and cause it to circulate freely from one part of the pan to another; for if so shallow as to refuse to circulate, the parts exposed to the greatest heat, remaining undisturbed, will suddenly become unduly concentrated and burn upon the pan. By the continuous process the heat is applied, not to a body of juice at rest, but to a moving current or stream—each part being displaced or pushed forward by that which follows. The portion of the pan occupied by sirup in the last stages is very small compared with the whole surface of the pan, and in this the sirup is kept in motion or carried along towards the exit by the less dense sirup in the rear, so that the depth of sirup may be very shallow, and the whole time during which any portion of it, in its critical stage, is exposed to heat may be but a few seconds, or, at the most, but one or two minutes. Practically, the quantity of sirup acted upon at any one time, in the last or finishing stages, would be appropriately stated in gills, while by the “intermittent process” it would be stated in gallons, and the difference in time of exposure of dense solution to heat by the two modes is necessarily and inevitably about in a corresponding ratio.
Evaporators constructed to operate upon the continuous principle are of two kinds. One provides for the direct flow of the juice from the entrance to the exit end of the pan; and the other provides for an indirect flow, or the passage of the juice through narrow transverse channels back and forth, until by successive steps it reaches the exit end. In the first the whole width of the pan is the width of the channel through which the juice flows, and this plan does not provide adequately for the successive displacement and advancement of all portions of the juice. The less concentrated portions may find their way along, and appear in advance of, the more concentrated portions, mixing therewith, and occasionally producing a complete mixture of green juice and nearly finished sirup. Cross-bars or ledges with gates, or provided with openings for an underflow, are generally used. These hold back the green scum, and prevent it from flowing down, but do not wholly restrain the green juice from advancing prematurely.
By the transverse or indirect flow the juice is confined to channels but a few inches wide, and all must pass through the same channels, each portion being exposed to the same heat, each being displaced by the portion which follows, at the same time displacing that which is in advance. At the side of the pan it leaves the channel which it has traversed, and enters the next in advance, through which it returns to the other side, thus flowing back and forth through the whole series, until it reaches the last channel, where, if the flow has been properly regulated, the juice will have been fully concentrated, and may escape from the pan through the exit spout. At the centre of the pan, in each channel, the juice is exposed to the greatest heat, and will there boil violently; at the sides the boiling will subside, to be renewed again at its next transit. The juice is thereby subjected to an alternate boiling and subsiding operation, which is most favorable for the separation of impurities, these being cast up more abundantly, in all cases, at the moment fluids pass from a state of rest or subsidence into ebullition.
The continuous transverse current process of evaporating was discovered by Mr. D. M. Cook, of Mansfield, Ohio, and it is believed to be the best plan for evaporating sorghum juice that has yet been devised. It meets all the requirements of the business; that is, it affords the means of obtaining perfect defecation, and enables the juice to be concentrated with the briefest exposure to heat, being at the same time economical and convenient. The occurrence of sugar from sorghum has been almost exclusively in cases where the Cook sugar evaporator has been used. A very large proportion of all the sugar made from sorghum has been made by the use of this apparatus.
With regard to the facilities for defecation afforded by the different evaporators in use nothing need be said. All provide for removing the scum, and the different modes provided are commended more by fancy than any intrinsic difference, though the process of Mr. Cook is believed to produce a better separation of impurities than when the boiling occurs without the interruptions which he provides. But, when working for sugar, the defecation of the juice is, as has been said, of less importance than rapid concentration.
It is not considered necessary to refer to the modes of working the different evaporator, as all information required is furnished by the circulars of manufacturers. An attempt has been made to explain only the leading features of the different systems of evaporating, with particular reference to their adaptation to the work of producing sugar from sorghum. The reader, if satisfied that the difficulties to be encountered in the operation have been correctly represented, will have little difficulty in determining from a general description of the different systems of evaporating, which is most appropriate to the work.
This term properly applies to an auxiliary process employed upon the semi- sirup while in progress, or upon sirup which, being once concentrated, is afterward reduced with water and treated anew. For making sugar the shortest and most, direct process from juice to sirup is the best, and will result in the greatest quantity, and in the best quality of sugar. Reducing sirup with water, and subjecting it to treatment in connexion with, or followed by reboiling, involves, of course, a new exposure to heat, and is obnoxious to all the objections which have been so often referred to in connexion with boiling. There are no means at present known by which sorghum sirup can be made more readily crystallizable than it is when boiled down direct with proper defecation, except by filtering with bone coal, which, not being practicable on a small scale, cannot. be considered as an appropriate subject in this connexion, Numerous processes have been invented, patented, and sold for effecting the crystallization of sorghum sirup, and hundreds of thousands of dollars have been paid for them by sanguine and over-credulous operators; but not one of the many which have come to the knowledge of the writer contains a single new and useful suggestion, while most of them betray the most the most profound ignorance of the art upon which the patentees profess to have made improvements. Nine-tenths, and probably more, of all the sugar which has ever been produced from sorghum has occurred through the direct and ordinary means employed for making sirup, and generally without any purpose or expectation on the part of the operator that the sirup would granulate, or, in ordinary language, “turn to sugar.” The result occurred from the accidental and unpremeditated compliance with all the conditions necessary for the production of sugar. These conditions are all that are required in making sugar from sorghum, and none of them are patented, and no patented invention will supply their place, or compensate for non-compliance with them.
It is difficult to give particular directions upon this subject. The sugar boiler very readily acquires familiarity with the appearance of sirup in its last stages, and can determine the density it has attained by the manner of boiling, usually by the peculiar appearance and sound emitted by the steam as it escapes from the boiling mass. As it approaches the finishing point, the steam is liberated in lively puffs, with a slight noise; gradually the sirup becomes more sluggish, and the steam seems to break away with more difficulty; still later, the foam subsides somewhat, and the steam escapes with a more sharp and angry puff; at the same time the sirup assumes a glistening, some say a “sugary” appearance. This is generally regarded the finishing point for sugar. With sorghum sirup it is better not to be too dense. The stage before the last above described is more appropriate. The sirup, after being removed from the fire, is discharged into coolers, and should then be reduced in temperature, by any appropriate means, as rapidly as possible, at least as low as to the temperature of 200°. Some practise stirring or agitating the sirup violently in the last stages of boiling, and for some time after being removed from the fire. The first facilitates the escape of steam, and preserves a lower temperature by several degrees in the boiling sirup, which is an important advantage. A plan of evaporating, at what is called “low temperature,” is effected by rotating a series of disks, partly submerged in the sirup, which brings up and exposes a large amount of surface to the air. This is a systematic plan of “agitating” boiling sirup, and the process is regarded as an improvement. When working by the intermittent or “batch” system it is an advantage to stir from the bottom of the evaporator, as it assists the naturally sluggish circulation, and prevents portions of sirup from remaining too long in contact with the heated bottom plate. Agitation long continued, after the sirup is removed from the pan, produces a foamy state of the whole mass, which is probably a mechanical condition favorable for granulation, though this condition is generally sought to be avoided in tropical sugar-making.
If a special effort has been made for sugar, it should not terminate when the sirup has reached the cooler, but be continued to the end. When it is not convenient to establish a room for graining, the sirup may be put into barrels and placed in a cellar, or room, where the temperature will be even, and as warm as can be secured. Granulation may occur in a few weeks or months. Occasional stirring or disturbing the barrels will be of advantage. Many sirups will, however, fail to show any signs of granulation under these circumstances, which would, if otherwise treated, afford a large display of sugar. The impulse to grain must be very strong when it manifests itself, as it often does, in sorghum tightly barrelled, and taking all the chances of temperature which may befall it.
A properly constructed room for graining is an important part of the operation of sugar-making, and no operator in sorghum should complain of failure to produce sugar who has not employed a graining room, or specific means equivalent thereto, to secure granulation.” The room may be of any convenient dimensions and arrangement, provided with places to bestow the sirup, and the means of heating and preserving a uniform temperature. The following plan will be found convenient, or it will at least afford the main features or elements required, and enable the operator to construct understandingly, with such changes or variations as his own ingenuity may suggest. It may be constructed as a “lean- to” against the side of some other building, or it may be partitioned off from the inside of the sugar-house or other building. For a room to contain twelve or fifteen barrels of sirup, let the dimensions be eight by twelve feet on the inside; make it as close and impervious to air as possible. Arrange all along on the two sides, stands for drawers, which are to be forty inches long, twenty-four inches wide, and three inches deep on the inside; the drawers to have their places in the stands one above another as high as convenient, say six feet, and to have a space of two inches between each. This will give for each drawer a space of six inches, and each stand will accommodate twelve drawers. Allow for three stands on each side of the room, six in all, and the room will accommodate seventy-two drawers. Each drawer can be filled with sirup to the depth of two inches, when it will contain about eight gallons, or for seventy-two drawers, five hundred and seventy-six gallons. Place in the room a good airtight stove, which, upon being supplied with large wood, will give off a regular heat, without renewal, for twelve hours. If the room is made very tight with plastering or paper, an auger hole may be made near the floor, and another near the top of the room for ventilation; but it is rare that any special provision for ventilation will be required. There is much more danger that the room will not be made sufficiently close, and will be allowed to cool off frequently in the intervals of replenishing the fire. The sirup, as soon as cooled down to a temperature of 100°, may be conveyed to the graining room, and deposited in the drawers, either a full supply to each, or a small quantity to be added afterwards. While the drawers are being filled, and as often as convenient afterwards, the sirup may be stirred. For this purpose use a wooden instrument, formed by a rod of sufficient length, say thirty inches, with a wooden blade nailed across the outer end, forming a T. It can be worked conveniently without moving the drawers, as the two inches of space provided between them affords room. The temperature of the room should be raised, and kept as near as possible between 90 and 100°. It will do no harm if the temperature falls for a few minutes—while the door is open, or the operator working in the room—as the temperature of the sirup will not be sensibly affected by a temporary change.
By the time the last drawers are filled, it is hoped the sirup in the first will have become well granulated, or resolved into “mush sugar,” when the drawers can be emptied and again filled with sirup; but if granulation is not supposed to be complete, and it is thought best to give more time, store the sirup whick may be made while the drawers remain thus oceupied, in any convenient place, but without any attempt to effect its granulation until it can be transferred to the graining room, as nothing would be gained.
DRAINING OR PURGING.
This is the last and not the least difficult operation to be performed. The facility with which the uncrystallized portion of the mush or “rough” sugar can be separated from the solid grains will depend much upon the success which has attended all the previous operations. If the cane was good, if the evaporation was conducted without the development of an undue quantity of that tenacious, gummy principle which is the great obstacle to the work of draining, and if the granulation occurred without too much time in the hot room, then the draining will be attended with little trouble, The more quickly sugar grains, the more easily and perfectly it can be purged. If considerable time is required, particularly when the mass is exposed in open vessels to warm temperature, the uncrystallizable portion becomes condensed by desiccation, and may be rendered almost solid; in which case it is impracticable to separate the sugar without reducing the mass with warm water, and this is necessarily attended with the dissolving of a portion of the solid sugar.
Many different modes of draining sorghum sugar have been suggested, and several have been patented and extensively sold through the country. In connexion with these, a great number of (so-called) processes for “making sugar from sorghum” have been introduced. Enormous sums have been paid by producers for these so-styled “processes.” Space will not permit them to be referred to separately, but this paper would be incomplete if it failed to warn sorghum-growers, and all who are interested in the subject, against the absurd pretences and fraudulent practices of these peddlers of “rights” for making sorghum sugar. Not one of the processes for making sugar from sorghum, or for draining sorghum sugar, which has been patented and sold since the introduction of the plant, contains a single essential element of novelty. All, without exception, consist of either slight and immaterial variations from processes which formerly existed and belonged to the public; or, if they present elements of novelty in the form of agents and substances not formerly used, they are, in all cases, not only non-essential and useless, but often absurd, and not unfrequently positively injurious. And yet for these miserable pretences sorghum-growers of the country have paid, at a moderate estimate, not less than four hundred thousand dollars. This is not the place to explain how it is that patents are obtained for trivial and useless inventions. It may, however, be remarked that a large proportion of all the patents issued are for really worthless inventions, or for trifling and unimportant modifications of that which was formerly known. But a patent covers only that which is found by the office to be new, and this may be an immaterial part of all that the applicant describes in his specification. An old and well-known process may be changed by adding another element, or slightly modifying those which formerly existed, so as to produce a new process, but the change may be no improvement—it may produce no difference whatever in the effect; still it is a new process, and the applicant, if he swears that he believes his alleged invention to be “useful,” is entitled to and can claim letters patent for it. The letters patent, however, cover, as has been said, only that which was new. They cannot deprive the public of that which was formerly public, and cannot give to a patentee anything more than he has invented. This brief explanation seems to be required in this connexion, as the opinion prevails somewhat that the broad seal of the Patent Office granted to an inventor implies that the august head of that department, and the entire government through him, certifies to the great value of any patented invention, and to the truth of all the patentee has been pleased to say about it. This popular superstition is of great service to dealers in worthless patents, for it predetermines a thing patented to be new and valuable, and this causes purchasers to neglect to examine and scrutinize the merits of an invention.
The operation of draining should always be performed in a warm room, and
the temperature of the sugar to be drained should be about blood heat, if it can
be brought to that temperature slowly without the application of fire directly to
the mass. If sorghum sugar crystallizes out of a solution not very dense and
waxy, it may be transferred to moulds for draining. These may consist of vessels of any convenient size and shape. Cone-shaped vessels are most commonly
used. The arrangement of them should be such as to allow them to be filled,
and, after standing a few hours (perhaps days) until the sugar “sets,” a plug
can be withdrawn from the bottom to allow the molasses to come off. It will
frequently happen that molasses refuses to separate from the sugar. When the
plug is withdrawn, both come off together. This mode of draining can only be
applied to sorghum sugar under the most favorable circumstances. It will rarely present itself in a condition to be thus treated, and other means must be
resorted to. Among the many which have been used are the following:
Place the mush sugar in a coarse cloth or bag,,and suspend it until the molasses drips away. After the dripping ceases, the sugar may be thoroughly mixed with a very small quantity of water and again hung up to drain; and this may be repeated, if desired, until the sugar becomes nearly white, though the operation will be attended with some loss of sugar by dissolving. Another mode consists in enclosing the mush sugar in bags and subjecting it to pressure. After once pressing, the sugar may be mixed thoroughly with a small quantity of water and re-pressed, repeating as many times as may be necessary or desirable. This is a very old process, but, like many other old processes, has been re-invented, and “rights” to employ it have been extensively sold. The most appropriate and effectual means of draining sorghum sugar is by the centrifugal process. This has been used in the tropics for many years, and is an old process, although it has been made the subject of several new patents for so-called improvements, and an attempt is made to establish a monopoly of the right to drain sugar by centrifugal means. It is a public right, and any ordinary mechanic can construct a machine, on a small scale, adapted to the work. The machine consists of a cylindrical screen, carried usually by a vertical shaft. revolving at a high velocity, The speed should be nearly as great as would be appropriate for a circular saw of corresponding diameter. An outer case surrounds the screen. The mush sugar is placed in the screen, either when in motion or at rest, care being taken to distribute it evenly around upon all sides. The sirup or liquid portion is caused to force itself out through the meshes of the screen by the centrifugal action, and is caught in the outer case, from which it should be conducted away by a spout, A small machine, with a screen twelve inches in diameter and six inches deep, can be made to run by hand, though the speed must be high, and the work of draining by hand is necessarily laborious. The quantity which a hand machine is capable of draining in an hour depends upon the condition of the sugar. Two or three times as much, power is required with sugar in one state as in another; and sometimes it is found impossible to produce any separation by the centrifugal, without adding. considerable water and greatly reducing the viscid, adhesive medium in which, the sugar is contained. It is perhaps safe to say that with a light-running. hand machine and a fair quantity of mush sugar, from fifteen to twenty pounds. of dry sugar per hour may be produced.