THE CARBOHYDRATES. 3 



action on polarized light, they exist in three modifications, 

 but those derived from the pentosanes are dextrogyrate. 

 Pentose solutions when heated with phloroglucinol or orcinol 

 and HC1 (sp. gr. 1.09) acquire respectively a cherry- red or 

 green color and posses characteristic absorption spectra. 

 The pentoses are non-fermentable and yield with phenyl- 

 hydrazin osazones having characteristic properties. Boil 

 some cherry gum for some hours with 1 per cent H 2 S0 4 . 

 Test the solution for pentose as follows: 



(a) Saturates c.c. of HC1 (sp. gr. 1.09) with phloroglucinol 

 by warming on the boiling-water bath. A slight excess of 

 the phloroglucinol is advantageous. Add to this a few c.c. 

 of the pentose solution and continue the heating. Grad- 

 ually a cherry-red color develops in the solution and the 

 latter shows characteristic absorption bands between D 

 and E. 



(6) Try the same test using orcinol instead of phloro- 

 glucinol. The solution turns reddish, then reddish blue, and 

 finally green, with a precipitate of that color settling out of 

 the solution. This precipitate is soluble in amyl alcohol, in 

 which solvent it also has characteristic absorption bands 

 between C and D. 



(c) Prepare pentosazones after the method employed 

 on p. 5. 



HEXOSES OR MONOSACCHARIDES, C 6 H 12 6 . 

 DEXTROSE. LEVULOSE. GALACTOSE. 



The monosaccharides, in general, are soluble, crystalline, 

 and optically active bodies which yield, upon boiling with 

 alkalies, oxidation products and caramel; they reduce metal- 

 lic oxides in alkaline solution; ferment with yeast and with 

 bacterium lactis ; and give, with phenylhydrazin, osazones 



