LEVULOSE. 211 



is readily soluble in water, but nearly 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. Levulose ferments with 

 yeast, and gives the same reduction tests as dextrose, and also the same 

 osazone. It gives a compound with lime which is less soluble than the 

 corresponding dextrose compound. Levulose is not precipitated by 

 sugar of lead or basic lead acetate. 



Levulose does not reduce copper to the same extent as dextrose. 

 Under similar conditions the reduction relationship is 100:92.08. 



In detecting levulose and those varieties of sugar which yield levulose 

 on cleavage we make use of the following reaction, suggested by SELI- 

 WANOFF : To a few cubic centimeters of fuming hydrochloric acid add 

 an equal volume of water and a small quantity of the sugar solution or 

 of the solid substance and a few crystals of resorcinol, and apply heat. The 

 liquid becomes a beautiful red, and gradually a substance precipitates 

 which is red in color and soluble in alcohol. According to OFNER 1 the 

 mixture must not contain more than 12 per cent HC1, and the boiling 

 must not be continued longer than twenty seconds, otherwise glucose, 

 mannose, and indeed maltose, may give a similar reaction. R. and O. 

 ABLER 2 perform the test with glacial acetic acid and a drop of hydro- 

 chloric acid and some resorcinol, in which case a reaction with aldoses is 

 not obtained. SELIWANOFF'S reaction, which according to ROSIN may 

 be made more delicate by a combination with the spectroscopic examina- 

 tion, is, as NEUBERG 3 has shown, a general reaction for ketoses. 



The naphtho-resorcinol reaction as suggested by B. TOLLENS and 

 RoRivE 4 can be carried out as follows: A few particles of the sugar and 

 about the same quantity of naphthoresorcinol are treated with about 10 cc. 

 of a mixture of equal volumes of water and concentrated hydrochloric acid, 

 of sp. gr. 1.19. This is slowly heated to boiling over a low flame, and this 

 continued for 1-3 minutes. The fluid becomes more purple or violet 

 than with SELIWANOFF'S resorcin test. The spectroscopic examination 

 shows a faint band in the green. 



According to NEUBERG, 5 methylphenylhydrazine is an excellent 

 substance to use for the separation and detection of levulose, as it gives 

 a characteristic levulose methylphenylosazone. This osazone when recrys- 

 tallized from alcohol melts at 153. It shows a dextrorotation of 1 40' 



1 Monatshefte f. Chem., 25. 



2 See foot-note 5, p. 203. 



3 Zeitschr. f. physiol. Chem., 31; Rosin, ibid., 38. 



4 Ber. d. d. chem. Gesellsch., 41, p. 1783 and Tollens, ibid., 41, p. 1788. See also 

 Mandel and Neuberg, Biochem. Zeitschr. 13. 



5 Ber. d. d. chem. Gesellsch., 35; also Neuberg and Strauss, ibid., 36. 



