ELEMENTS OF MATERIA MEDICA.

584

called syrup: it is thick, adhesive, and, by drying on paper, forms akind of varnish. A watery solution of sugar, aided by heat, decom-poses some of the metallic salts (as those of copper, mercury, gold, andsilver); but several of them (as the diacetate of copper and nitrate ofsilver) require nearly a boiling temperature to change them. Sugar pro-motes the solubility of lime in water, and forms both a soluble and aninsoluble compound with oxide of lead. Sugar is soluble in alcohol,but not so in ether. A dilute watery solution of common sugar, witha little yeast, undergoes the vinous fermentation.

Purified or refined sugar (saccharum, Ph. L.; saccharum purificatum,Ph. Ed.; succus concretus purificutus, Ph . D.) is met with in the shopsin conical loaves or lumps (loaf or lump sugar) of various degrees ofpurity. The finest (saccharum albissimum ) is perfectly white, and istermed double refined; the inferior kind (saccharum album ) has a slightlyyellowish tint, and is called single refined. Both varieties are compact,porous, friable, and made up of small crystalline grains.

Brown sugar (saccharum fuscum; saccharum non purificatum, Ph. Ed.;succus concretus non purificatus, Ph . D.) occurs in commerce in the formof a coarse powder composed of shining crystalline grains. It is moreor 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 withlumps. Bastard is a finer kind, prepared from molasses and the greensyrups. The Demerara crystal sugar is the finest: its colour is pal 0yellow, and its crystals are larger and more brilliant than the precedingvarieties.

Treacle (fwx sacchari, Ph . L.; syrupus empyreumaticus, Ph. Ed.,syrupus empyreumaticus, anglice molasses, Ph. D.) is the viscid, dark brown,uncrystallizable syrup which drains from the sugar-refining moulds. It lSthicker than West Indian molasses, and has a different flavour. E ssp. gr. is generally T4; and it contains, according to Dr. Ure, on anaverage, 75 per cent, of solid matter.

Chemical Characteristics. —Sugar is known by its sweet taste, h ssolubility in hot and cold water and in alcohol, its being decomposed)with the evolution of charcoal, by sulphuric acid, its conversion intooxalic and other acids by nitric acid, its fusing, charring, emitting aremarkable odour (called the odour of caramel), and inflaming by heat)and, lastly, by its not causing, when pure, any precipitate with acetate ° rdiacetate of lead. Susceptibility of vinous fermentation and crystalliz 3 ^bility are properties not common to all varieties of sugars, as the foliowi»t,table shews:—

1. Sugars SUSCEPTIBLE OF VINOUS FERMENTATION. . a)1 d

(a) Crystallizable. This division includes common sugars (viz. cane, mapf'

beet-root sugars) and granular sugars (viz. grape, honey, starch, and «sugars).

( b ) Uncrystallizable. Called liquid or mucous sugars, as that in treacle.

2. Sugars unsusceptible of vinous fermentation. broo 10

(a) Crystallizable. Here belong milk sugar and mannite (this includes mus

sugar). ... ft nd

(b) Uncrystallizable. Under this head are placed glycyrrhizin, sarcocol i ,

glycerin.

Composition. —The following is the ultimate composition of sugar •