212 THE CARBOHYDRATES. 



when 0.2 gram of the osazone is dissolved in 4 cc. pyridine and 6 cc. 

 absolute alcohol. 



OFNER has made objections to the use of methylphenylhydrazine 

 in the detection of levulose. He has obtained the osazone from dex- 

 trose and methylphenlhydrazine, although the osazone is formed much 

 more quickly with levulose than with dextrose. Only when the separa- 

 tion of the osazone crystals with methylphenylhydrazine after the addi- 

 tion of acetic acid takes place within five hours at ordinary temperatures 

 is the presence of levulose positively proven (OFNER l ). 



The use of secondary asymmetric hydrazines as a general reagent for ketoses 

 and as a means of separation from aldoses is objected to by OFNER. 



Levulose, as above stated, is best obtained by the hydrolytic cleavage 

 of inulin, by warming with faintly acidulated water. 



d-Sorbinose (sorbin) is a ketose obtained from the juice of the berry of the 

 mountain ash under certain conditions. It is crystalline and levogyrate, and 

 is converted into d-sorbite by reduction. 



i 



Appendix to the Monosaccharides. 

 a. Amino Sugars. 



The amino sugars, as intermediary bodies between the carbohydrates 

 and oxyamino-acids, are of great physiological interest, and this interest 

 has become still more important since NEUBERG was first able to pre- 

 pare the corresponding amino-aldehyde from glycocoll and then also 

 from other amino-acids. From the ethyl ester of glycocoll in acid solu- 

 tion NEUBERG 2 obtained the amino-acet aldehyde, NH 2 .CH 2 .CHO, by 

 treatment with sodium amalgam. This aldehyde is very unstable and 

 has a tendency to condensation with ring formation, and NEUBERG 

 obtained therefrom by oxidation with corrosive sublimate and caustic 

 soda, pyrazine according to the equation : 



On account of this tendency to ring-formation the amino-acetalde- 

 hyde as well as the amino-aldehydes as a group, stand, according to NEU- 



1 Ber. d. cU chem. Gesellsch.. 37. and Zeitschr. f . physiol. Chem.. 45. 

 id., 41. 



