A Manual of the Chemistry of the Carbon Compounds

286 THE CHEMISTRY OF
sugar contained in layers of equal thickness. The saccnaroineter of
Soleil, an instrument in general use for this purpose, is provided with
a graduated cirole, divided in such a way that 100 divisions express
the rotation caused by a plate of quartz of one millimetre thickness.
Now, as exactly the same rotation is produced by a layer of a solution
of cane-sugar having a length of 20 centimetres, and containing
164*71 grammes of sugar in one litre, it is only necessary, in order to
asoertain the quantity of sugar contained in a substance, to dissolve
16471 grammes in water, diluting to one litre, and observing the
rotation which it produces; the number of divisions being equal to
the percentage of sugar.
When sugar is boiled with dilute sulphuric acid, it takes water up,
and is resolved into equal parts of dextrose and levulose :—
CttH^)n + H2O = C8H18O8 + C0HI2O0
The same decomposition occurs in a solution to which yeast has
been added. The solution of these two glucoses turns the polarized
light to the left hand, the specific rotatory power of levulose being
«reater than that of dextrose, and a mixture of these two sugars is
therefore called inverted sugar.
When sugar is heated above its melting-point, it loses water, and a
brown amorphous bitter substance called caramel remains behind.
At a still higher temperature it blackens; inflammable gases are
given off, consisting of marsh-gas, carbon, monoxide, and dioxide; and
a distillate is obtained, containing aldehyde, acetic acid, acetone, aud
furfurol, while porous oharcoal is left behind
Strong sulphuric acid decomposes sugar when heated, and a concentrated
sugar solution, even at the common temperature, with
copious evolution of sulphur dioxide and formation of a voluminous
black carbonaceous mass. The destructive distillation of a mixture
of lime and cane-sugar yields marsh-gas, carbon dioxide, acetone,
mtacetone C^oO, and isoplwronc 00HMO. Metacetone is a colourless
liquid, boiling at 84°, and possessing an aromatic smell On oxidation
with chromic acid, it yields carbon dioxide, acetic acid, and
propionic acid. Isophorone is an oily liquid, boiling at 210" aud
having a sweet aromatic odour.
Sugar is an alcohol of an octad radical; by heating it with a large
excess of acetic anhydride to 160°, the acetate CKHuO3(C3HaO2)8 is
obtained as a viscid liquid.
Dilute nitric acid oxidizes cane-sugar to sacchario acid, which by
further oxidation is converted into tartaric acid and oxalic acid, but
by the action of a mixture of strong sulphuric and nitric acid it
yields the nitrate O^gO^NOj),, which is an amorphous, explosive
body.
Cane-sugar forms also metallic compounds; its aqueous solution
dissolves caustic lime, baryta, magnesia, and lead oxide: these solutions
have a strong alkaline reaction and a bitter taste, and are
decomposed by carbon dioxide. Copper oxide and ferric oxide also