SUGAR (Fa., Sucre; GER.) Zucker).
Tbe term " sugar " was originally employed and intended to classify all substances having a sweet flavour, and thus came to be used almost indiscriminately for cane-sugar, fruit-sugar, sugar (acetate) of lead, and other bodies possessing that property. At present, in a general sense, it is reserved almost exclusively to denote cane- and beet-sugar (true crystallizable sugar). In chemistry, the word " sugar " is applied generically to a large class of organic bodies intermediate between starch and alcohol, termed " carbohydrates," each having 6-12 atoms of oxygen and hydrogen combined in the proportion to form water ; they are nearly allied to, and may be considered as derivatives of, the hexatomic alcohols (0611,06), of which, mannite may he taken as a type. Indeed, mannite, which can hardly be strictly classed as a true sugar, may be artificially formed from glucose (C,H„08) by treatment with sodiurn amalgam, the glucose thereby taking up 2 atoms more of hydrogen, and becoming converted into mannite :— Glucoae. Marmite.
C,111206 + 2 H = C6H,40e Although the hexatomic alcohols are not to be regarded as true sugars, still, as each of them possesses a marked saccharine flavour, and presents some of the other characteristics of the true sugars, it will be convenient and instructive to include them in the subjoined tabular classification :— The properties by which the members of these groups may be distinguisbed are mainly :— (1) By boiling with acids (even dilute), the hexatomic alcohols and the glucoses are but little affected, while tbe saccharoses are converted into glucoses ; (2) the varying powers possessed by many of their solutions, particularly the glucoses and saccharoses, in rotating the vibration-plane of a ray of polarized light ; (3) the tendency of the glueoses to enter into fermentation, while the hexatomic alcohols are unfermentable, and the saccharoses are either unfermentable, or only partially fermentable and with great difficulty ; most of the last, however, are converted into glucoses by the action of ferments, some of which, such as diastase (a principle formed during the germination of seeds) and synaptase (a princiiile found in almonds and other fruit-kernels), have special effects. The saccharoses are also converted into glucoses by the saliva, and the juices of
the stornach and intestines ; and 801110, as cane-sugar, meiely by prolonged heating or boiling in water. Some other ferments, such as Torula cerevisim and Penicillium glaucum, seem to possess the property of converting some saccharoses into glucoses, before promoting the special fermenta tions produced by their propagation. The fermentable sugars (Call,20a) which are capable of direct vinous fermentation are invert sugar (a mixture of dextrose and lasvulose), dextrose, lasvulose, galactose, maltose.
The members of the first group (hexatomic alcohols) demand no further consideration here. The most important commercially is mannite (see Drugs—Manna, pp. 817-8). The members of the second group (isomeric glucoses) will be spoken of generically at greater length, and the principal ones are specially dealt with under Honey (pp. 1127-30), Drugs—Mauna (p. 810), Fruit (pp. 1022-9), Beverages—Wine (pp. 432-50), and sub-sections of the present article.
Invert sugar (0,111,06) can be produced from crystallizable sugar by the action of acids, diastase, heat, salts, &e. It is easily fermentable, forms salts with metallic bases, is found in the juices of many plants, and is present in very large proportion in the juice of unripe sugar-cane ; it is manufactured on a large scale from grain or starchy materials by treatment with a mineral acid, and conversion with high-pressure steam (see Starch-sugar); as thus prepared, it is uncrystallizable, of a slightly sweetish flavour, and can be concentrated to a thick jelly or to a solid state; heated with a solution of cane-sugar, it converts nearly its own weight of that substance into the unorys tallizable form ; with alkalies, it darkens in colour, and forms soluble salts with them; it reduces an alkaline solution of a cuprio salt ; as a syrup, it is almost colourless, and, in the solid form, the colour varies according to the care taken in its preparation. The two bodies of which it is compost (I, namely dextrose or dextro-glucose and bevulose or hevo-glueose, differ in rotatory power, aud in other particulars; they are, however, seldom met with in a separate state.