Production—No crystals are found in the parenchyme of the cane, the sugar existing as an aqueous solution, chiefly within the cells of the centre of the stem. The transverse section of the cane exhibits numerous fibro-vascular bundles, scattered through the tissue, as in other monocotyledonous stems; yet these bundles are most abundant towards the exterior, where they form a dense ring covered with a thin epidermis, which is very hard by reason of the silica which is deposited in it.[2688] In the centre of the stem the vascular bundles are few in number; the parenchyme is far more abundant, and contains in its thin-walled cells an almost clear solution of sugar, with a few small starch granules and a little soluble albuminous matter. This last is met with in larger quantity in the cambial portion of the vascular bundles. Pectic principles are combined with the walls of the medullary cells, which however do not swell much in water (Wiesner).
From these glances at the microscopical structure of the cane, the process to be followed for obtaining the largest possible quantity of sugar becomes evident. This would consist in simply macerating thin slices of the cane in water, which would at once penetrate the parenchyme loaded with sugar, without much attacking the fibro-vascular bundles containing more of albuminous than of saccharine matter. By this method, the epidermal layer of the cane would not become saturated with sugar, nor would it impede its extraction,—results which necessarily follow when the cane is crushed and pressed.[2689]
The process hitherto generally practised in the colonies,—that of extracting the juice of the cane by crushing and pressing,—has been elaborately described and criticised by Dr. Icery of Mauritius.[2690] In that island, the cane, six varieties of which are cultivated, is when mature composed of Cellulose, 8 to 12 per cent.; Sugar, 18 to 21; Water, including albuminous matter and salts, 67 to 73. Of the entire quantity of juice in the cane, from 70 to 84 per cent. is extracted for evaporation, and yields in a crystalline state about three-fifths of the sugar which the cane originally contained. This juice, called in French vesou, has on an average the following composition:—
| Albuminous matters | 0·03 |
| Granular matter (starch?) | 0·10 |
| Mucilage containing nitrogen | 0·22 |
| Salts, mostly of organic acids[2691] | 0·29 |
| Sugar | 18·36 |
| Water | 81·00 |
| 100·00 |
There is also present in the juice a very small amount of a slightly aromatic substance (essential oil?) to which the crude cane sugar owes a peculiar odour which is not observed in sugar from other sources. The first two classes of the above enumerated substances render the juice turbid, and greatly promote its fermentation, but they easily separate by boiling, and the juice may then be kept a short time without undergoing change. In many colonies the yield is said to be far inferior to what it should be; yet the juice is obtained in a state allowing of easier purification, when its extraction is not carried to the furthest limit.
In beet root as well as in the sugar cane, cane-sugar only was said to be present; Icery however has proved that in the cane some uncrystallizable (inverted) sugar is always present. Its quantity varies much, according to the places where the cane grows, and its age. The tops of quick-growing young canes yielded a vesou containing 2·4 per cent. of uncrystallizable sugar; 3·6 of cane sugar; and 94 of water. Moist and shady situations greatly promote the formation of the former kind of sugar, which also prevails in the tops, chiefly when immature. Hence that observer concludes that at first the uncrystallizable variety of sugar is formed, and subsequently transformed into cane-sugar by the force of vegetation, and especially by the influence of light. Perfectly ripened canes contain only ¹/₇₅ to ¹/₅₀ of all their sugar in the uncrystallizable state.
Description and Chemical Composition—Cane-sugar is the type of a numerous class of well-defined organic compounds, of frequent occurrence throughout the vegetable and animal kingdoms, or artificially obtained by decomposing certain other substances; in the latter case, however, glucose or some other sugar than cane-sugar is obtained. cane-sugar, C₁₂H₂₂O₁₁, or C₁₂H₁₄(OH)₈O₃, melts, without change of composition, at 160° C., several other kinds of sugar giving off water, with which they form crystallized compounds at the ordinary temperature.
cane-sugar forms hard crystals of the oblique rhombic system, having a sp. gr. of 1·59. Two parts are dissolved at 15° C. by one part of water,[2692] and by much less at an elevated temperature; a slight depression of the thermometer is observable in the former case. One part of sugar dissolved in one of water, forms a liquid of sp. gr. 1·23; two of sugar in one of water, a liquid of sp. gr. 1·33. Sugar requires 65 parts of spirit of wine (sp. gr. 0·84) or 80 parts of anhydrous alcohol for solution; ether does not act upon it.
A ray of polarized light is deviated by an aqueous solution of cane sugar to the right, but by some other kinds of sugar to the left, as first shown by Biot. These optical powers are highly important, both in the practical estimation of solutions of sugar, and in scientific studies connected with sugar or saccharogenous substances. The optical as well as chemical properties of sugar are altered by many circumstances, as the action of dilute acids or alkalis, or by the influence of minute fungi. Yeast occasions sugar to undergo alcoholic fermentation. Other ferments set up an action by which butyric, lactic or propionic acid are produced.
cane-sugar is of a purer and sweeter taste than most other sugars. Though it does not alter litmus paper, yet with alkalis it forms compounds some of which are crystallizable. From an alkaline solution of tartrate of copper, cane-sugar throws down no protoxide, unless after boiling.