40. Saccharum officinarum, Linn.—The Sugar Cane.
Tribe V. Andropogoneae, Kunth.
Sex. Syst. Triandria, Digynia.
(Saccharum; caulis succus praeparatus purificatus crystallinus. Sacchari Faex; succus praeparatus impurus, L.—Saccharum commune; Sacchari Faex; Saccharum purum, E.—Saccharum purificatum; Refined Sugar; White Sugar.—Theriaca; Treacle; Molasses; or the concentrated uncrystallized juice, D.)
History.—The manufacture of sugar is said by Humboldt to be of the highest antiquity in China. Cane-sugar was known to the ancient Greeks and Romans, and was considered by them to be a kind of honey. Possibly, Herodotus [Lib. iv. Melpomene, cap. cxciv.] refers to it when he says that the Zygantes make honey in addition to that which they get from bees.
Theophrastus [De Melle.] calls it mel in arundinibus; Dioscorides [Lib. ii. cap. civ.] terms it σακχαρον; Pliny [Hist. Nat. lib. xii. cap. xvii.] saccharum. Humboldt [Journal of Science and Arts, vol. v. p. 15.] adopts too hastily, I think, the opinion of Salmasius, that the latter writers meant the siliceous product of the Bamboo, viz., Tabasheer; for, in the first place, as they arrange it with honey, it was probably sweet, which tabasheer is not; secondly, the Sanscrit name for sugar is Sarkura; [Royle's Essay, p. 83.—In his more recent work, called Cosmos, Humboldt (Sabine's transl. vol. ii. pp 109 and xxvi.) states that the Sanscrit name for sugar is the source of the Greek and Semitic names for it.] thirdly, a passage in Lucan [Lib. iii. v. 237.] seems distinctly to refer to the sugar-cane: "Quique bibunt tenera dulces ab arundine succos." Surely no one will pretend that the bamboo is a "tenera arundo?" [References to passages in other ancient authors will be found in the notes to Valpy's edit. of Pliny's Hist. Nat. vol. iv. 2193; see, also, Moseley's Treatise on Sugar, Lond. 1799.]
Botany. Gen. Char.—Spikelets all fertile, in pairs; the one sessile, the other stalked; articulated at the base, two-flowered; the lower floret neuter, with one palea; the upper hermaphrodite, with two paleae. Glumes two, membranous. Paleae transparent, awnless; those of the hermaphrodite flower minute, unequal. Stamens three. Ovary smooth. Styles two, long; stigmas feathered, with simple toothletted hairs. Scales two, obscurely two or three-lobed at the point, distinct. Caryopsis smooth (?), loose (?) (Kunth).
Sp. Char.—Panicle effuse. Flowers triandrous. Glumes obscurely one-nerved, with very long hairs on the back (Kunth).
The stem is solid, from six to twelve feet high. Leaves flat. Panicle terminal, from one to three feet long, of gray colour, from the long soft hair that surrounds the flower. Paleae rose-coloured.
Kunth admits four varieties:
α. commune, the common yellow cane, called by the Bengalees Poori, and, by the West Indians, the Creole Cane or Native Cane, from its having been the one originally introduced into the New World.
β. purpureum, the purple cane, called by the Bengalees Kajooli, and which is said to yield juice one-eighth richer than the yellow cane.
γ. giganteum, the giant cane, a large light-coloured cane, called by the Bengalees Kullooa. It grows in a low swampy soil, where the other two will not succeed. Its juice is weaker than that of the yellow cane, but the plant grows to a much larger size; and it is, therefore, much cultivated in India.
δ. tahitense, the Tahita cane, commonly called the Otaheite cane.
Hab.—It is cultivated in both Indies. Its native country is uncertain.
Two other species of Saccharum are cultivated for the sugar they produce:—
S. violaceum, Tussac, Antill. i. 160—Kunth, Agrostogr. i. 474; Violet Sugar-cane. (By some authors considered to be identical with Tahiti sugar cane above mentioned.)—Cultivated in both Indies.
S. sinense, Roxb., Fl. Ind.; China Sugar-cane.—Cultivated in China, where sugar is made from it.
Composition of the Sugar-cane.—Avequin [Journ. de Chimie Méd. t. ii. 2de Sér. pp. 26 and 132, 1836.] analyzed the Tahiti and ribbon varieties of the fresh sugar-cane of Louisiana, and Dupuy [Quoted by Dumas, Traité de Chimie, t. vi. p. 299, 1843.] analyzed the fresh sugar-cane at Guadaloupe. Peligot, [Journ. de Pharm. t. xxvi. p. 154, 1840.] by combining the composition of cane juice with that of the dried canes sent him from Martinique, has also deduced the composition of the fresh cane. More recently, Casaseca [Ann. de Chim. et Phys. 3me Sér. t. xi. p. 39, 1844.] analyzed the sugar-cane of Cuba.
|Dupuy.||Peligot.||Tahiti Cane.||Ribbon Cane.|
|Mucilaginous, resinous, fatty, and albuminous matter||-||-||0.415||0.441|
|Salts||0.4||-||Salts, silica,and oxide of iron||0.358||0.368|
The dried sugar-cane was analyzed by O. Hervy. [Journ. de Pharm. t. xxvi. p. 569, 1840.]
The composition of sugar cane ash is an important consideration for the sugar planter, as it enables him to deduce the most appropriate manure for promoting the growth of the cane. [For analyses of the ash of the entire sugar-cane, as well as of the crushed and pressed cane (megass), see Johnston's Lectures on Agricultural Chemistry, pp. 393 and 628, 2d edit. 1847. The same author also gives the formula for a special manure for the sugar-cane, deduced from the analyses of the ash (op. cit. p. 614).]
The sugar-cane, especially the violet variety, is coated by a glaucous powder of a peculiar kind of wax, which has been called cerosine or sugar-cane wax. [Journ. de Pharm. t. xxvi. p. 738, 1840.] This is fusible at 180° F., and dissolves in boiling alcohol: the alcoholic solution, even when it contains but a small quantity of cerosine, gelatinizes or solidifies on cooling like an alcoholic solution of soap. The composition of this wax is C48H50O2 (Dumas).
Extraction of Cane-juice.—Cane-juice is generally extracted from the stems by means of a sugar mill. The canes, when ripe, are cut close to the ground, stripped of their leaves, and carried in bundles to the mill-house, where they are twice subjected to pressure between iron rollers, placed either vertically or horizontally. The residue of the canes which have been thus crushed and deprived of their juice is called megass.
Other methods of extracting the cane juice have been suggested. The hydraulic press has been introduced into Jamaica and St. Vincent's. By Michiel's patent it is proposed to macerate thin slices of the cane in a mixture of lime and water, so as to coagulate the albuminous matters but to extract the sugar. It has also been proposed to extract the sugar in Europe from the canes imported in the dried state. [For further details, see Dr. Evans's Sugar-Planters Manual, 1847.]
Properties of Cane-juice.—Cane-juice is pale yellowish -gray, and has an agreeable sweet taste and a faint fragrant odour. As it flows from the mill it is frothy, and, owing to the suspension in it of finely-divided matter, is turbid or opalescent. Its sp. gr. ranges from 1.067 to 1.106: Mr. Fownes [Pharmaceutical Journal, vol. viii. p. 15, 1848.] found it to be from 1.070 to 1.090. By boiling, its turbidity is commonly a little increased, and sometimes a few small flocks are separated from it. Both nitric acid and corrosive sublimate occasion, after a time, a very slight precipitate. A large addition of alcohol throws down flocks resembling gum or dextrine. A few drops of sulphate of copper, and an excess of caustic potash, occasion, on heating, a very abundant red precipitate of suboxide of copper, indicative of the presence of glucose or grape-sugar.
According to Mr. Fownes, the juice contains the following substances: Cane-sugar in great quantity, a notable amount of glucose or grape-sugar, gum or dextrine, phosphates of lime and magnesia, some other salt of lime and magnesia, sulphates and chlorides, potash and soda, and lastly, a peculiar azotized matter belonging to the albuminous family, forming an insoluble compound with lime, not coagulable by heat or acids, and readily putrefiable. Of ordinary vegetable albumen there are but indistinct traces, and of caseine or legumine none. Avequin found a portion of cerosine or sugar-cane wax in cane-juice. It is detached from the canes in the mill.
Cane-juice has been analyzed by Proust, [Ann. de Chim. lvii. 131.] by Avequin, [Journ. de Chim. Méd. t. ii. 2de Sér. p. 26, 1836.] by Peligot, [Journ. de Pharm. t. xxvi. p. 154, 1840.] by Plagne, [Ibid., p. 248, 1840.] and by Casaseca. [Ann. de Chim. et de Phys. 3me Sér. t. xi. p. 39.] The following are their more important results:—
|Various organic matters||0.140||0.23||0.8317||0.12|
It appears, therefore, from these analyses, that cane-juice contains about 20 per cent. of saccharine matter. Or, assuming that the juice has an average sp. gr. of 1.073, the quantity will be 18 per cent. Moreover, according to both Peligot and Casaseca, the whole of the saccharine matter is crystallizable, or true cane-sugar; the uncrystallizable sugar, or molasses, which is obtained by evaporation from the juice, being the product of alterations effected in the crystallizable sugar by the operation: but Mr. Fownes observed that this statement must be received with some reservation.
Of late years, concentrated West Indian cane-juice has been imported. It contains nearly half its weight of granular sugar, besides a variable amount of molasses.
Clarification of Cane-juice.—The clarification or defecation of cane-juice is effected, usually in large copper vessels of the capacity of 300 or 400 gallons, by the combined use of heat and lime: the latter is technically called "the temper." The heat serves to coagulate any vegetable albumen which may be present. The lime neutralizes the free acid and combines with the peculiar albuminous or proteine body mentioned by Mr. Fownes, and forms a coagulum, the separation of which is promoted by the heat. Part of it rises to the top as a scum, and the remainder subsides as a thick muddy deposit.
Various other substances [See Dr. Evans's Sugar-Planter's Manual.] have been tried as a substitute for lime with more or less success. Diacetate of lead has been employed for this purpose, but its use has been discontinued on account of a great number of persons having suffered the ill effects of this metal from partaking of sugar prepared with it.
Concentration of the Cane-juice.—The clarified juice should be filtered prior to evaporation. This, however, is not usually practised. It is generally drawn off from the clarifier into a copper boiler, where it is evaporated and skimmed. It is then passed successively through a series of boilers, the last of which is called the teache. When it has acquired a proper tenacity and granular aspect, it is emptied or "skipped" first into a copper cooler and afterwards into a wooden vessel, where it is allowed to crystallize or grain. The concrete sugar is then placed in casks (usually sugar hogsheads) perforated with holes in the bottom, each of which is partially closed by the stalk of a plantain leaf. Here the sugar is allowed to drain for three or four weeks. It is then packed in hogsheads and sent to this country under the name of muscovado or raw sugar.
The drainings, or uncrystallized portion of sugar, constitute molasses. This is received in an open cistern beneath.
The feculencies separated in the clarifying vessel, and the skimmings of the evaporating coppers, are employed in the manufacture of rum.
Properties of Raw Sugar.—Raw sugar is a mixture of crystallizable and uncrystallizable sugar, contaminated by various organic and mineral substances. Its mineral constituents are, according to Avequin, silica, phosphate and subphosphate of lime, carbonate of lime, sulphate of potash, chloride of potassium, and the acetates of potash and lime.
The raw sugar of the shops reddens litmus, and is not completely soluble in alcohol. Its aqueous solution yields precipitates with the diacetate of lead, oxalic acid, and caustic ammonia; and is frequently darkened by the addition of the sesquichloride of iron. By keeping, strong raw sugar becomes weak—that is, soft, clammy, and gummy. This change the late Mr. Daniell [Quarterly Journal of Science, vi. 38.] ascribed to the action of the lime.
Sugar Refining.—The following is a sketch of the process as usually practised in London: Raw sugar is dissolved in water by the aid of steam (this process is called giving the sugar a blow-up). The liquid is then heated with bullock's blood [At one time hydrate of alumina, under the name of finings, was used in addition to blood.] (technically called spice), and filtered through canvas bags (called Schröder's bags). The clear liquor is allowed to percolate slowly through a bed of coarse-grained animal charcoal placed on a woollen cloth, supported on a false bottom of basket-work, and contained in a large wooden vessel. The depth of the bed of charcoal varies in different refining-houses. I have seen it three feet deep; but I am told that some refiners employ a bed twenty feet in depth. The filtered liquor, which is nearly colourless, is conveyed to a copper vessel (Howard's vacuum-pan), where it is boiled by the aid of steam, under diminished atmospheric pressure, at a temperature of about 170° F.
When the requisite degree of concentration has been attained, a valve is opened in the bottom of the vacuum pan, and the syrup allowed to escape into a copper vessel (heater), enveloped by a jacket, so as to enable it to be heated by steam. The syrup is then transferred to conical moulds (made of earthenware or iron), whose orifices are closed by a paper plug, and the next morning, when solidified, these moulds are carried to the curing-floor, when the stoppers are withdrawn and the moulds placed in pots, in order to allow the green syrups to drain off: these are made into an inferior sort of refined sugar (brown lumps). The loaves are then either clayed or sugared, generally the latter.
Claying ["Claying sugar, as they report here, was first found out in Brazil: a hen, having her feet dirty, going over a pot of sugar by accident, it was found under her tread to be whiter than elsewhere."—Sloane's Jamaica, vol. i. p. 61.] (which is now almost entirely out of use) consists in pouring clay and water on the base of the sugar loaf: the water slowly percolating through the sugar, a portion of which it dissolves, carries with it the colouring matter and other impurities. Sugaring is effected by substituting a saturated solution of pure sugar (called liquor) for the clay and water; it washes out the colouring matter, but does not dissolve the pure sugar. The loaves are afterwards dried in a stove, and put in blue paper for sale. [For further details, consult a paper by Messrs. Guynne and Young, Brit. Ann. of Med. June 23 and July 14, 1837; also, Dr. Ure's Dict. of Arts, art. Sugar.]
The following may be regarded as an approximation to the produce of 112 lbs. of raw sugar by the above process:—
|Refined sugar||79 lbs.|
|Treacle||16 (12 lbs. solid matter)|
The animal charcoal used in sugar refining is changed every week, and of course is a more powerful decolorizer when fresh than when it has been used several times. It follows, therefore, that the quality of the refined sugar obtained varies with the day of the week—that is, with the age of the charcoal. At the commencement of the week, when the charcoal is fresh, the finest white loaves of sugar are made; about the middle of the week titlers and lumps are obtained; and, at the end of the week, bastards.
In the process of sugar refining, various salts have been proposed to be used as defecators; such as the trisacetate of lead, [Guynne and Young, British Annals of Medicine, vol. i. p. 778, and vol. ii. p. 42, 1837.] acetate of lead, [Sievier and Scoffern, Pharmaceutical Journal, vols. ix. and x.] bisulphite of lime, [Melsen, Pharmaceutical Journal, vols. ix. and x.] sulphate of tin, [Warburton, Pharmaceutical Journal, vol. x. p. 82.] &c. The salts of lead are probably the most effective agents, but, on account of their poisonous properties, are dangerous to the public health. [See Pharmaceutical Journal, vol. x.]
Properties.—Common or cane-sugar is the sweetest of all kinds of sugar. When pure, it is white and odourless. It is very soluble in water, both hot and cold (see Syrupus, vol. i. p. 153); is soluble in rectified spirit, but not in ether. Its watery solution, aided by heat, decomposes some of the metallic salts (as those of copper, mercury, gold, and silver); but several of them (as the diacetate of copper and nitrate of silver) require nearly a boiling temperature to change them. A dilute watery solution of common sugar, with a little yeast, undergoes the vinous fermentation. Sugar promotes the solubility of lime in water, and forms both a soluble and an insoluble compound with oxide of lead.
Cane-sugar is capable of existing either in the crystallized or amorphous state. In this respect it resembles sulphur (see vol. i. p. 355).
1. Crystallized Cane-sugar.—To this division are referred sugar-candy and the ordinary loaf and lump sugar of the shops. By the slow cooling of a saturated aqueous solution of sugar, we obtain the large and fine crystals which constitute the commercial sugar-candy (saccharum candum), and of which three kinds are kept in the shops; namely, white candy, prepared from pure sugar; brown candy, prepared from brown sugar; and pink or rose candy, prepared from sugar artifically coloured (probably by cochineal).
The crystals of sugar are doubly oblique prisms, and, therefore, have two axes of double refraction [Sugar-candy makes an interesting polariscope object. It is usually cut so as to show one only of its two systems of rings.] (see vol. i. p. 187). Their sp. gr. is 1.6065.
Common crystallized sugar is permanent in the air and phosphorescent in the dark when struck or rubbed. When heated, it melts and soon becomes coloured. By this process, its tendency to crystallize is diminished or destroyed.
The commercial varieties of common crystallized cane-sugar are of two kinds—white or brown. The first is refined sugar.
1. Purified or Refined Sugar (Saccharum, L.; Saccharum purum, E.; Succus concretus purificatus, D.; Saccharum purificatum) is met with in the shops in conical loaves (loaf sugar) or truncated cones, called lumps (lump sugar), of various sizes and degrees of purity. Small lumps are called titlers. The finest refined sugar (saccharum albissimum) is perfectly white, and is termed double refined; the inferior kind (saccharum album) has a slightly yellowish tint, and is called single refined. Both varieties are compact, porous, friable, and made up of small crystalline grains.
2. Brown Sugar (Saccharum commune, E.; Saccharum fuscum; Succus concretus non purificatus, D.) occurs in commerce in the form of a coarse powder composed of shining crystalline grains. It is more or less damp and sticky, and has a peculiar smell and a very sweet taste. Its colour is brownish-yellow, but varying considerably in intensity. Muscovado, or raw sugar, has the deepest colour, and is intermixed with lumps. Bastard is a finer kind, prepared from molasses and the green syrups. The Demerara crystal sugar is the finest: its colour is pale yellow, and its crystals are larger and more brilliant than the preceding varieties.
2. Amorphous Cane-sugar.—When syrup or a strong solution of crystallized cane-sugar is rapidly boiled down, and then poured out on a marble or metallic plate, it congeals in an amorphous, vitreous, more or less coloured mass, usually called boiled sugar, of which barley-sugar (saccharum hordeatum), acidulated drops, and hard-bake, are familiar examples. During the preparation of barley-sugar and acidulated drops, the confectioners usually add a small quantity of cream of tartar to the melted sugar, in order to destroy its tendency to crystallize. Vinegar and tartaric acid are mentioned by some writers as being used for this purpose.
If when the melted sugar has partially solidified, but while it is yet soft, it be hung on a hook and rapidly and repeatedly drawn out, it becomes opake and white. This pulled sugar was formerly termed sugar penides (saccharum penidium).
When crystallized cane-sugar is subjected to a temperature of about 356° F., it melts; and, at a higher temperature, begins to give off water and to suffer decomposition. If the heat be gradually augmented, it becomes brown, evolves a remarkable odour, loses its sweet taste and acquires a bitter one. In this condition it is called caramel (from καιω, I burn, and μελι, honey), or burnt sugar (saccharum tostum). It enjoys acid properties, and is composed, according to Peligot, [Peligot, Ann. Chim. et de Phys. lxvii. p. 175.] of C24H18O18
Molasses and Treacle.—These are viscid, dark brown, dense liquids, composed of amorphous or uncrystallizable sugar, crystallizable sugar, gum, extractive, various salts, and water. They are frequently confounded, but in trade are considered distinct.
1. Molasses (more correctly Melasses, from mel, honey, because it is soft and sweet like honey) is the drainings from raw or muscovado sugar. West India molasses is occasionally imported for refining. It yields brown sugar, or bastard, and treacle.
2. Treacle (Theriaca, D.; Feax Sacchari, L. E.) is the viscid, dark brown, uncrystallizable syrup which drains from refined sugar in the sugar moulds. It is thicker than West Indian molasses, and has a somewhat different flavour. Its sp. gr. is generally 1.4; and it contains, according to Dr. Ure, on an average, 75 per cent. of solid matter. Payen says that it may be regarded as a saturated solution of crystallizable sugar, of which it contains from 40 to 50 per cent. of its weight. It is employed in the manufacture of gingerbread, and, by poor people, as a substitute for sugar. It is also sometimes used to yield, by fermentation, an alcoholic liquor— either to be drank as a kind of beer, or to yield, by distillation, spirit. It is sold under the names of "melasse de la Cochinchine" and "prepared melasse," to be taken with lentilmeal (sold as ervalenta or revalenta arabica), as a remedy for habitual constipation.
Chemical Characteristics.—As a species of sugar, [Mannite, glycyrrhizin, glycerine, and some other sweet substances, which were formerly called sugars, are, by modern chemists, excluded from the list of sugars, properly so called, because they are incapable of undergoing the vinous fermentation.] cane-sugar is known by its susceptibility of undergoing the vinous fermentation; that is, of suffering a peculiar decomposition into alcohol and carbonic acid. For this purpose it is dissolved in water, and to the solution a small portion of yeast (dry yeast is to be preferred) is added, and the mixture exposed to a temperature of about 70° F. Effervescence soon takes place, carbonic acid is evolved, and a vinous or alcoholic liquor is produced. In this process the cane-sugar combines with water, and becomes grape-sugar, C12H12O12, which, by fermentation, is resolved into four atoms of carbonic acid, 4CO2, and two atoms of alcohol, 2C4H602.
The quantitative determination of sugar is effected by ascertaining the amount of carbonic acid evolved during fermentation. 171 grains of sugar-candy furnish 88 grains, or about 186.4 cubic inches of carbonic acid gas. At mean temperature and pressure, 100 cubic inches,or 47.2 grains, of carbonic acid gas are given out by 91.7 grains of sugar-candy. In round numbers, we may say that one cubic inch or half a grain of carbonic acid gas is equal to one grain of sugar-candy. [Full directions for the quantitative determination of sugar by fermentation are given by Dr. Miller, in the article Organic Analysis of the Cyclopaedia of Anatomy and Physiology, vol. iii. p. 799.]
Cane-sugar is distinguished from other kinds of sugar by the following characters:—Its crystallizability in prismatic crystals, its very sweet taste, its ready solubility in water, its solution being charred and letting fall a brown or black powder when heated with a few drops of oil of vitriol, but being unchanged when treated in the same way with caustic potash—and by the difficulty with which it reduces the blue hydrated oxide of copper to the orange suboxide.
Grape-sugar reduces the hydrated oxide of copper to the suboxide with great facility. The test is applied thus: Add to the saccharine solution a small quantity of a solution of caustic potash, and then a few drops of a weak solution of sulphate of copper; taking care that the alkali is in excess. Then apply heat: if grape-sugar be present, an ochre-yellow or red precipitate of suboxide of copper is formed before ebullition takes place. Uncrystallizable sugar, as well as sugar of milk, also readily reduces the oxide; but this effect does not take place with crystallizable cane sugar; or rather, a higher temperature or a longer action of the ingredients is required to produce the effect. This is called Trommer's test.
A solution of crystallizable cane-sugar is distinguished from solutions of some other kinds of saccharine matters by possessing the property of right-handed circular polarization.
If a ray of common light (Fig. 216, a) be polarized by reflection at an angle of 56°.45 from the surface of glass [The plane polarization of the ray may be effected by a Nichol's prism instead of a glass-mirror. The use of a silvered glass-mirror is objectionable, on account of its producing elliptical polarization.] (b), the plane polarized ray (c), which is thus obtained, transmitted through a pure solution of crystallizable cane-sugar (d), and the emergent ray (e) analyzed by a double refracting rhomb of calcareous spar (f), two coloured images are perceived (Figs. 216 and 217); one (o) caused by ordinary refraction, the other (x) by extraordinary refraction. The colours of the images are complementary; that is, when one image is red, yellow, or blue—the other is green, violet, or orange. By rotating the analyzer (the rhomb of calcareous spar), the colours change: if the rotation be right-handed (that is, as we turn a screw or corkscrew to make it enter), the sequence of the colours is red, orange, yellow, green, blue, indigo, and violet.
Sequence of Colours for a Solution of Crystallizable Cane-sugar, as obtained by the right-handed Rotation of the Analyzer.
|Ordinary Image.||Extraordinary Image.|
|Yellow||Indigo / Violet.|
|Indigo / Violet||Yellow.|
In one complete revolution of the analyzer, each of the colours of the spectrum occurs twice for each image. [The nature of the present work does not admit of a further elucidation of circular polarization, which I have here introduced as an aid in the qualitative determination of a saccharine solution. Biot has applied it to the quantitative determination of sugar. To his various papers contained in the Memoires de l'Académie des Sciences, and especially to his Instructions Pratiques sur l'Observation et la Mésure des Propriétés Optiques appellées rotatoires, Paris, 1845, the reader is referred for further information. See, also, the article Saccharimétrie Optique, in Pelouze and Fremy's Cours de Chimie Générale, t. iii. p. 337, 1850.—A popular sketch of the subject will be found in my Lectures on Polarized Light, published by Messrs. Longman and Co.—A very admirable report on this and other methods of effecting the qualitative and quantitative analysis of sugars, syrups, and molasses, by Professor R. S. McCulloch, is contained in a Letter from the Secretary of the [United States] Treasury to the United States Senate, read Feb.21, 1843.]
Composition.—The following is the ultimate composition of sugar:—
|Atoms.||Eq. Wt.||Per Cent.|||||Atoms.||Eq. Wt.||Per Cent.|
|Carbon||12||72||47.05||| Anhydrous sugar||1||153||89.47|
|---||-----||------||| Crystallized sugar||1||171||100.00|
|Anydrous sugar ||1||153||100.00||||
 Peligot, Ann. de Chim. et de Phys. lxvii. p. 124.
Adulteration; Purity.—The purity of genuine sugar is readily judged of by its physical or sensible qualities. The impurities may also be detected by chemical means, but it is rarely necessary to resort to these. A solution of pure sugar is colourless, and yields no precipitate with oxalic acid, diacetate of lead, or caustic ammonia. Pure sugar is completely soluble in rectified spirit.
Brown sugar of commerce contains crystallizable and uncrystallizable sugar, woody tissue of the sugar-cane, vegetable albumen, siliceous particles, sporules and filaments of fungi; and, in most samples, a peculiar species of mite (Acarus), which has been called the sugar mite [Pharmaceutical Journal, vol x. pp. 343 and 396, Jan. and Feb. 1851; Lancet for Jan 18 and 25, 1851.] (acarus sacchari). In most cases the animal is dead, but frequently it is met with in the living state. Starch or flour is also said to be found in brown sugar.
Various adulterations have been practised on sugar. The most important of these is the intermixture of starch sugar. A few years ago I inspected an extensive manufactory of sugar from potato-starch at Stratford, in Essex: the sugar obtained was sold for the adulteration of brown sugar, and the molasses produced was consumed in an oxalic acid manufactory. Brown cane-sugar adulterated with starch sugar is less sweet, less readily soluble in water, and less crystalline and sparkling than pure brown cane-sugar. Moreover, potato-sugar always contains sulphate of lime, the detection of which (see the tests for sulphuric acid and lime, pp. 368 and 562) in a suspected sample of sugar is, therefore, of some value. It has been proposed to detect the presence of potato-sugar by Trommer's test (see ante, p. 150) and by caustic potash. But though Trommer's test readily detects starch-sugar in a solution of white cane-sugar, the detection is not so easily effected by it in a solution of brown cane-sugar, because the uncrystallizable cane-sugar, or treacle, which is present readily reduces the blue hydrate of copper to the orange suboxide—acting thus like starch-sugar. Chevallier [Journ. de Chim. Méd. t. viii. 2de Sér. p. 472, 1842.] proposes to detect starch-sugar in cane-sugar by means of caustic potash: Boil the suspected sugar in a ley of caustic potash: if no starch-sugar be present, the liquor remains colourless; but, on the contrary, it becomes brown if starch-sugar be present. But this test, like the last one, is better adapted for detecting starch-sugar in white cane-sugar than in the ordinary brown cane-sugar of the shops. [On a trial for the recovery of excise duties on potato-sugar, it was stated that this sugar possessed only three-fifths of the sweetening properties of genuine cane-sugar, and that it was mixed with whiting, bone-dust, &c. previous to its being offered for sale. (Pharm. Journ. vol. i. p. 603, 1842.)]
Farinaceous substances and dextrine may be detected by boiling the suspected sugar in water and testing the decoction, when cold, with iodine, which causes a blue colour with starch and a purplish colour with dextrine.
Gum is distinguished from sugar by its insolubility in rectified spirit.
Various other substances have, it is said, been used for the adulteration of sugar; as finely-powdered marble, chalk or whiting, sand, bone-dust, and common salt. With the exception of salt, all the substances here mentioned are insoluble in water, and by this character, therefore, may be readily separated from sugar. Common salt may be detected in a solution of the suspected sugar by the ordinary tests for that substance (see vol. i. p. 537).
Physiological Effects.—Sugar, considered as an article of food, is an alimentary principle which belongs to the class of "elements of respiration," (see vol. i. p. 117.) It contributes to the formation of fat and of lactic acid, and by its oxidation furnishes heat. It has recently been detected in the tissue of the liver, but in no other organ. [Comptes rendus, xxvii. p. 514; Chemical Gazette, March 1, 1849.]
It disagrees with some dyspeptics, and is reputed to have a tendency to cause flatulency and preternatural acidity (by the formation of lactic acid?) of the primae viae.
Treacle, and therefore raw sugar, check the tendency to constipation.
Uses.—Sugar is used dietetically, medicinally, and pharmaceutically. Medicinally, it is but little employed. In the form of lozenges, sugar-candy, &c, it is slowly dissolved in the mouth to allay tickling cough. As a chemical antidote, it has been recommended in poisoning by the salts of copper, mercury, silver, gold, and lead. [Vogel and Buchner, in Schweigger's Journ. xiii. 102; xiv. 224.] But any advantage procured by its use in these cases is referable to its demulcent and emollient properties, and not to its chemical influence. The same remark may be made with respect to the benefit said to have been obtained by the use of the juice of the sugar-cane in poisoning by arsenious acid. [Chisholm, Quarterly Journal of Science, x. 193.] Powdered white sugar is sometimes sprinkled over ulcers, to remove spongy granulations, denominated proud flesh. The same remedy has also been employed for the removal of specks on the cornea.
In pharmacy, the uses of sugar are much more extensive. It serves to preserve, to give flavour, bulk, form, colour, cohesiveness, and consistence; to subdivide and to suspend oily substances in aqueous liquids. To fulfil one or more of these objects, it is a constituent of syrups, elaeosacchara, conserves, electuaries, confections, lozenges, some pills and powders, &c. For making pills, treacle serves to give cohesiveness, to preserve the pill-mass soft, prevent mouldiness, and in some cases to check chemical changes. As an antiseptic, it is used for the preservation of various medicinal organic substances. It acts in at least two ways—by excluding air and by absorbing moisture (see vol. i. p. 205); and perhaps, also, in some other way—as when it promotes the solidification of pectine. Sugar is also useful in preserving some inorganic compounds: thus it checks, though it does not absolutely prevent, the higher oxidation of some of the protosalts of iron; hence its use in the ferri carbonas saccharatum (see vol. i. p. 724). and syrupus ferri iodidi (see vol. i. p. 744).
It is employed in the manufacture of oxalic acid; and it is sometimes used in distilleries to yield, by fermentation, alcohol. The Edinburgh College directs it to be used in the rectification of sulphuric acid (see vol. i. p. 359).
As a test, it is sometimes used in the laboratory in conjunction with oil of vitriol, to detect the cholic acid of bile.
1. SYRUPUS, L. [U.S.]; Syrupus simplex, E. D.; Syrup; Simple Syrup.—(Sugar lb iij [lb v, D. (lb iiss, U. S.)]; Water Oj [Oij, D. (Oj, U. S.)]. Dissolve the sugar in the water by a gentle heat.)—By keeping for several months, syrup undergoes some molecular changes, by which its power of producing right-handed circular polarization is considerably diminished.
The proportion of water and sugar used by the London College is, by weight, water 1 part, sugar 1.9748 parts; by the Edinburgh College, water 1 part, sugar 2.1942 parts—or, very nearly, water 1 part, sugar 2 1/5 parts; and, by the Dublin College, water 1 part, sugar 2 parts.
In order to yield a clear and bright syrup, distilled water and well-refined sugar should be employed. Ordinary spring water becomes turbid by boiling, owing to the precipitation of carbonate of lime. [See some observations by Mr. Savory, on the preparation of syrup, in the Pharmaceutical Journal, vol. ii. p. 452,1843.]
The sp. gr. of boiling syrup should be 1.264 (equal to 30° of Beaume's areometer). When it has cooled down to 60° F., its sp. gr. should be 1.321 (equal to 35° of Beaume's areometer). The Dublin College states the sp. gr. of simple syrup to be 1.330.
Syrup is used in medicine to give flavour, cohesiveness, and consistence.
2. LIQUOR SACCHARI TOSTI; Caramel; Burnt Sugar.—This is a useful, innocuous colouring agent. It is prepared by melting half a pound of brown sugar in an iron pot, and applying heat until the liquid acquires a deep brown colour; then adding a gallon of boiling water.