If sugar is kept a short time in a state of fusion at 160° C., it is converted into one molecule of Grape Sugar and one of Levulosan; the former can be either isolated by crystallization or destroyed by fermentation, the latter being incapable of crystallizing or of undergoing fermentation.
cane-sugar which has been melted at 160° C. is deliquescent and readily soluble in anhydrous alcohol, and its rotatory power is diminished or entirely destroyed. It is no longer crystallizable, and its fusing point has become reduced to about 93° C. Yet before undergoing these evident alterations, it assumes an amorphous condition if allowed to melt with a third of its weight of water, becoming always a little coloured by pyrogenous products. In the course of time, however, this amorphous sugar loses its transparency and reassumes the crystalline form. Like sulphur and arsenious acid, it is capable of existing either in a crystallized or an amorphous state.
If sugar is heated to about 190° C. water is evolved, and we obtain the dark brown products commonly called Caramel or Burnt Sugar. They are of a peculiar sharp flavour, of a bitter taste, incapable of fermenting and deliquescent. One of the constituents of caramel, Caramelane, C₁₂H₁₈O₉, has been obtained by Gélis (1862) perfectly colourless. When the heat is augmented, the sugar at last suffers a decomposition resembling that which produces tar ([see p. 621]), its pyrogenous products being the same or very analogous to those of the dry distillation of wood.
Varieties of Cane-sugar—The experiments of Marggraf referred to at [p. 717, note 9], showed that cane-sugar is by no means confined to the sugar cane; and it is in fact extracted on an extensive scale from several other plants, of which the following deserve mention:—
Beet Root—The manufacture of cane-sugar from the fleshy root of a cultivated variety of Beta maritima L., is now largely carried on in Continental Europe and in America, and with admirable results.
Of fresh beet root, 100 parts contain on an average 80 per cent. of water, 11 to 13 of cane-sugar, and about 7 per cent. of pectic and albuminous matters, cellulose and salts. Of the total amount of juice which the root contains, eight-ninths are extracted; and by the best process now in practice, 8 to 9 parts of sugar from every 100 parts of fresh root. The yield of crystalline sugar is still on the increase, owing to continual improvements in the mechanical and chemical parts of the process.
Palm—Several species are of great utility for the production of the sugar called by Europeans Jaggery.[2693] This substance is obtained by the natives of India in the following manner:—The young growing spadix, or flowering shoot, of the palm is cut off near its apex; and an earthen vessel is tied on to the stump to receive the juice that flows out. This vessel is emptied daily; while to promote a continuous flow of sap, a thin slice is cut from the wounded end. The juice thus collected, if at once boiled down, yields the crude brown sugar known as jaggery. If allowed to ferment, it becomes the inebriating drink called Toddy or palm wine; or it may be converted into vinegar. The spirit distilled from toddy is Arrack.
Of the sugar-yielding palms of Asia, Phœnix silvestris Roxb., which is supposed to be the wild form of the date palm, is one of the more important. The coco-nut palm, Cocos nucifera L.; the magnificent Palmyra palm, Borassua flabelliformis L.; and the Bastard Sago, Caryota urens L., also furnish important quantities of sugar. In the Indian Archipelago, sugar is obtained from the sap of Arenga saccharifera Mart., which grows there in abundance as well as in the Philippines and the Indo-Chinese countries. It is also got from Nipa fruticans Thunb., a tree of the low coast regions, extensively cultivated in Tavoy.
De Vry[2694] has advocated the manufacture of sugar from the palm as the most philosophical, seeing that its juice is a nearly pure aqueous solution of sugar: that as no mineral constituents are removed from the soil in this juice, the costly manuring, as well as the laborious and destructive processes required to eliminate the juice from such plants as the sugar cane and beet root, are avoided. And finally, that palms are perennial, and can many of them be cultivated on a soil unsuitable for any cereal.
Maple—In America, considerable quantities of sugar identical with that of the cane are obtained in the woods of the Northern United States and of Canada, by evaporating the juice of maples. The species chiefly employed are Acer saccharinum Wangenh., the Common Sugar Maple, and its variety (var. nigrum) the Black Sugar Maple. A. Pennsylvanicum L., A. Negundo L. (Negundo aceroides Moench.) and A. dasycarpum Ehrh. are also used; the sap of the last is said to be the least saccharine.