Page:The American Cyclopædia (1879) Volume XV.djvu/457

 SUGAR 441 at 57 F., -79-5 at 125-5 F., and -53 at 194 F. It occurs, associated with dextro-glu- cose, in honey and many fruits. A mixture of Isevulose and dextro-glucose constitutes fruit sugar, fructose, or invert sugar, which is also laevo-rotatory, because the specific rotatory power of Isevulose at ordinary temperature is greater than that of dextro-glucose. 4. Man- nitose, produced by the oxidation of mannite, is uncrystallizable and fermentable, but has no action on polarized light. 5. Galactose, formed by the action of acids on milk sugar, crystallizes more readily than ordinary glu- cose, has a dextro-rotatory power of 83'3, and is easily fermentable. 6. Inosite occurs in the muscular substance of the heart and other organs of the animal body, in green kidney beans, and in other plants. It forms prisms resembling gypsum, soluble in water, but insoluble in alcohol and ether. It does not ferment with yeast, but in contact with cheese, decaying flesh, or membrane, with chalk, it undergoes lactous fermentation, producing lactic, butyric, and carbonic acids. It has no optical rotatory power. 7. Sorbine occurs in the juice of the mountain ash berry. The juice on standing deposits brown crystalline matter, which by recrystallization forms crys- tals belonging to the trimetric system. It dissolves easily in water, and has a very sweet taste. It is converted by hot nitric acid into oxalic acid, and does not ferment with yeast, but like inosite undergoes lactous fermenta- tion. It has a rotatory power of about 47. 8. Eucalyne is found with other kinds of sugar in the so-called Australian manna, which falls in opaque drops from various species of euca- lyptus. Its optical rotatory power is about +50. Besides these glucoses, there are su- gars which may be regarded as formed by the combination of two or more molecules of glucose with the elimination of a number of molecules of water. These sugars have been called polygluccsic alcohols, having the for- mula Ci 2 H 22 Ou. 1. The most important mem- ber, as well as the most important of all the sugars, is cane sugar, or saccharose, which is found in the juice of many of the grasses and the sap of several forest trees, particularly the hard maple, in the roots of the beet, pars- nip, mallow, and several other plants, and in most sweet fruits, associated with laevulose and dextro-glucose (currant sugar, fructose). "Walnuts, hazelnuts, and almonds contain only cane sugar. Honey and "the nectaries of flowers contain cane sugar together with in- vert sugar. Pure cane sugar separates from a solution by slow evaporation in large trans- parent colorless crystals, having the figure of a modified monoclinic prism. From hot sat- urated solutions it is obtained in masses of smaller crystals (loaf sugar). Its optical rota- tory power is +73-8 ; its sp. gr. 1*6, unchange- able in the air. When heated a little above 320 it is converted, without loss of weight, into a mixture of dextro-glucose and Isevo- lusan, the anhydride of Isevulose (Ci 2 H 22 O n = CeHjaOe + CaHioC^ or Ifflvolusan). It changes with loss of water into other substances as the temperature rises, until at 410 a brown sub- stance called caramel is formed, which consists of a mixture of several compounds, all result- ing from the elimination of the elements of water from sugar. As the temperature rises gases are evolved, consisting of carbonic oxide, marsh gas, and carbonic acid, and a distillate is obtained consisting of brown oils, acetic acid, acetone, and aldehyde, a quantity of charcoal remaining in the retort. By pro- longed boiling with water, cane sugar is con- verted into invert sugar, the transformation being accelerated by the presence of acids, es- pecially sulphuric. It is not directly ferment- able, but by the action of yeast is resolved into dextrose and Isevulose, which then enter into fermentation. It is a reducing agent, capable of readily taking the oxygen from sev- eral oxides and metallic salts. It forms with chlorate of potassium a mixture which deto- nates on percussion, and burns vividly in con- tact with oil of vitriol. It is distinguished from glucose by not turning brown when triturated with alkalies ; but it combines with the alkalies, forming compounds called su- crates. 2. Parasaccharose, Ci 2 H 22 On, is pro- duced by the spontaneous fermentation of a solution of cane sugar containing ammonium phosphate. Its rotatory power is +108. 3. Melitose, Ci 2 H 22 On, is found in the Australian manna, associated with mannitose. The crys- tals which are deposited from the aqueous solution are hydrated, the formula being Ci 2 H 22 O n + 3H 2 O. At 212 F. they give off two molecules of water, and at 286 become anhydrous. Its rotatory power is +102. Melitose ferments by the action of yeast, but is first resolved into glucose and eucalyne. 4. Melezitose, Ci 2 H 22 On, is a kind of sugar found in the so-called manna of Briancon, which exudes from the young shoots of the larch. It is not as easily acted on by reagents as the foregoing. Its rotatory power is about +94. 5. Trehalose, Ci 2 H 22 On, 2H 2 O, is obtained from trehala manna, the produce of a species of echinops growing in the East. It forms rhombic crystals, which when heated below 212 F. slowly give off their molecules of water. Its rotatory power is +199. With strong nitric acid it forms a detonating nitro- compound. It is not readily acted on by re- agents. 6. Mycose, isomeric with trehalose, and also containing two molecules of water, is obtained from the ergot of rye by precipi- tating the aqueous extract of the fungus with basic acetate of lead, removing the lead from the filtrate by hydrosulphuric acid, evaporating to a sirup, and leaving the liquid to crystallize. Its rotatory power is +192-5. 7. Milk sugar, or lactose, contains one molecule of water, the formula being dJI^On + HaO.^ It is an im- portant constituent of milk, and is obtained by evaporating the whey to a sirup, from which