102 DEXTROSE. 



dextrose and Itevulose, and definitely established the fact that they 

 an- respectively an aldehyde and ketone of the hexacid alcohol 

 C 6 H 8 (OH) C , but has in addition succeeded in producing artificial 

 sugars containing seven, eight, and nine carbon atoms. 1 In connec- 

 tion with the latter an interesting question . arises as to the prob- 

 able 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 pheuyl- 

 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 iso- 

 lating 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 

 ascertaining the molecular formula of certain sugars and of deter- 

 mining 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-(CH.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 constit- 

 uent of urine has led to much dispute, but it now appears 

 probable that it is present in minute amounts. 2 The experimental 

 difficulties of detecting traces of sugar in this excretion are con- 

 siderable. There is no dextrose normally in bile. 



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



2 For literature and results see Neubauer u. Vogel, Analyse des Hams (Ed. ix. 

 1890), S. 41. 



