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FRUCTOSE. 217
carbohydrates, especially varieties of gums and mucilaginous bodies.
It is also obtained on heating cerebrin, a nitrogenized glucoside prepared
from the brain, with dilute mineral acids.
It crystallizes in needles or leaves which melt at 1G8° C. It is some-
what less soluble in water than glucose. It is dextrogyrate, and according
to Neuberg l
has a rotation (a) D =+81°. With ordinary yeast galac-
tose is slowly, but nevertheless completely, fermented. It is fermented
by a great variety of yeasts (E. Fischer and Thierfelder), but not by
Saccharomyces apiculatus,2
which is of importance in physiological-
chemical investigations. Galactose reduces Fehling’s solution to a
less extent than glucose, and 10 cc. of this solution are reduced, accord-
ing to Soxhlet, by 0.0511 gram galactose in 1 per cent solution. Its
phenylosazone melts according to Neuberg at 196-197° C, and is soluble
with difficulty in hot water, but with relative ease in hot alcohol. Its
solution in glacial acetic acid is optically inactive. In the test with
hydrochloric acid and phloroglucin galactose gives a color similar to that
of the pentoses, but the solution does not give the absorption spectrum.
On oxidation it first yields galactonic acid and then mucic acid, and
these serve in the detection of galactose.
d-Fructose (levulose) also fruit-sugar, occurs, as above stated, mixed
with glucose, extensively distributed in the vegetable kingdom and
also in honey. It is formed in the hydrolytic cleavage of cane-sugar
and several other carbohydrates, but it is very readily obtained by the
hydrolytic splitting of inulin. In extraordinary cases of diabetes mellitus
we find fructose in the urine. Neuberg and Strauss 3
have detected
fructose with positiveness in human blood-serum, and exudates in cer-
tain cases.
Fructose crystallizes with comparative difficulty in coarse crusts
or warts or in fine needles. C. Morner 4
has obtained crystals 2-3 mm.
long which belonged to the rhombic system, and neither melted nor lost
in weight on heating to 100° C. The melting-point is 110° C. Fructose
is readily soluble in water, but almost insoluble in cold absolute alcohol,
though rather readily in boiling alcohol. Its aqueous solution is levogy-
rate. C. Morner found the rotation for a 10 and 20 per cent solution
was (a) D =—93° and —94.1° respectively. Fructose ferments with
yeast, and gives the same reduction tests as glucose, and also the same
osazone. It gives a compound with lime which is less soluble than the
corresponding glucose compound. Fructose is not precipitated by
sugar of lead or basic lead acetate.
1
See C. Oppenheimer, Handb. d. Biochem. 1, p. 197.
2
See F. Voit, Zeitschr. f. Biol., 28 and 29.
3
Zeitschr. f. physiol. Chem., 36, which also contains the older literature.
* Svensk. Farmac. Tidskr, No. 6, 1907. See also Maly’s Jahresb., 37, p. 95.
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