des.

_Type 1.--Aldehyde group potentially active, reducing sugars:_

Sugar Components
Maltose Glucose and glucose
Gentiobiose Glucose and glucose
Lactose Glucose and galactose
Melibiose Glucose and galactose
Turanose Glucose and fructose

_Type 2.--Non-reducing sugars:_

Sucrose Glucose and fructose
Trehalose Glucose and glucose

The disaccharides of Type 1 reduce Fehling's solution and form hydrazones
and osazones, although somewhat less readily than do the hexoses. They all
show mutarotation and exist in two modifications, indicating that the
component groups have the closed-ring arrangement.

The disaccharides of Type 2, since they contain no potentially active
aldehyde group, do not reduce Fehling's solution, nor form osazones;
neither do they exhibit mutarotation. The only disaccharides which occur as
such in plants are of this type. Disaccharides of Type 1 may be obtained by
the hydrolysis of other, more complex, carbohydrates.

All disaccharides are easily hydrolyzed into mixtures of their component
hexoses, by boiling with dilute mineral acids, or by treatment with certain
specific enzymes which are adapted to the particular disaccharide in each
case (see page 55, also Chapter XIV).

=Sucrose= (cane sugar, beet sugar, maple sugar) is the ordinary "granulated
sugar" of commerce. It occurs widely distributed in plants, where it serves
as reserve food material. It is found in largest proportions in the stalks
of sugar cane, in the roots of certain varieties of beets, and in the
spring sap of maple trees, all of which serve as industrial sources for the
sugar. In the sugar cane, and beet-roots, it constitutes from 12 to 20 per
cent of the green weight of the tissue and from 75 to 90 per cent of the
soluble solids in the juice which can be expressed from it. Its universal
use as a sweetening agent is due to the combined facts that it crystallizes
readily out of concentrated solutions and, hence, can be easily
manufactured in solid form, and that it is sweeter than any other of the
common sugars except fructose.

Sucrose is a non-reducing sugar, forms no osazone, and is not directly
fermentable by yeast, although most species of yeasts contain an enzyme
whic