102 DEXTROSE. 



synthetic production. It would be out of place here to enter into the 

 details of Fischer's work, and it must suffice to say that he has not 

 merely synthetised both dextrose and Isevulose, and definitely estab- 

 lished the fact that they are respectively an aldehyde and ketone of 

 the hexacid alcohol C 6 H 8 (OH) 6 , but has in addition succeeded in 

 producing artificial sugars containing seven, eight and nine carbon 

 atoms 1 . In connection with the latter an interesting question arises 

 as to the probable effects on animal metabolism of their introduction 

 into the body instead of the natural sugars. 



The osazones. The compounds of the sugars to which this generic 

 name is applied are formed when solutions of the sugars are warmed 

 for some time on a water-bath with phenyl-hydrazin and dilute acetic 

 acid, and separate out either in an amorphous or crystalline state. 

 Their formation takes place in two stages. In the first the sugar 

 combines, as do the aldehydes and ketones, with one molecule of the 

 base to form a compound which is in most cases readily soluble and 

 is known as a hydrazone. In the second stage the first-formed 

 hydrazone is oxidised by the excess of phenyl-hydrazin present, and the 

 substance thus produced unites with another molecule of the base to 

 form the osazone. As already stated the osazones of the various sugars 

 differ characteristically in their solubilities, melting-points and rotatory 

 powers. They hence afford an invaluable means not only for detecting 

 and isolating the sugars but also for discriminating between sugars 

 whose optical and reducing powers may afford an insufficient distinction. 

 Further, in some cases the osazones have provided a means of ascertain- 

 ing the molecular formula of certain sugars and of determining the 

 constitution of others. The characteristic properties of the several 

 osazones are given below under the respective sugars. 



THE DEXTROSE GROUP. 



1. Dextrose (Glucose, Grape-sugar). 



C 6 H 12 6 - [COH - (OH . OH) 4 - CH 2 . OH]. 



Is found in minute but fairly constant quantities as a normal 

 constituent of blood, lymph and chyle. Its occurrence in the liver has 

 been already referred to ( 465) in connection with diabetes, a disease 

 which is characterised by the large amount of dextrose which is present 

 in the blood and the still larger amount in the urine. The question 

 whether dextrose is a normal constituent of urine has led to much 

 dispute, but it now appears probable that it is present in minute 



1 Fischer u. Passmore, Ber. d. d. chem. Gesell. Jahrg. xxm. (1890), S. 2226. 



