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 168 C. It is some- 

 what less soluble in water than glucose. It is dextrogjo-ate, and according 

 to NEUBERG 1 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 irr 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* 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. 



4 Svensk. Farmac. Tidskr, No. 6, 1907. See also Maly's Jahresb., 37, p. 95. 



