SYNTHETIC WORK IN CARBOHYDRATES 337 



means of their hydrazones and osazones. 1 " However, with the 

 exception of mannose, the hydrazones of other sugars are mostly 

 soluble in water. Hence, the reaction with phenylhydrazine 

 is carried on to a further state, which results in the formation 

 of the insoluble osazones. These compounds differ decidedly 

 in color and system of crystallization. They have sharp melt- 

 ing-points, which lead to their easy identification. 



Another class of substances, which are called mercaptals, 

 and are compounds of sugar with sulphur, of the composition 

 CH 2 OH(CHOH) 4 CH(S 2 C 5 H) 2 , furnishes a means of separat- 

 ing and distinguishing the aldehyde sugar compounds. 



The synthetical sugars containing 7, 8, and 9 carbon atoms, 

 derived from the groups containing less carbon atoms, may 

 be made by Kiliani's method. 



It is an interesting fact that the sugars containing 3, 6, and 

 9 atoms of carbon are fermentable; while those containing 

 4, 5, and 7 atoms of carbon cannot be fermented. 



Fischer has suggested wherein the interest of these massive 

 sugar molecules lies. It is in physiological research. He has 

 proposed, as worthy of attention, that these higher synthetical 

 sugars be experimented with as to their full physiological value. 

 Possibly the tissues of animals nourished with these higher 

 sugars may yield other chemical products; the liver may give 

 a new glycogen, and a new acid may be found in the milk secre- 

 tions from the mammary glands. Here may possibly be opened 

 a new research ground for the biologist. 



The pentosans are compounds belonging to the sugars 

 containing 5 carbon atoms. These pentosans occur in various 

 parts of plants of different age and development. The amount 

 increases during the development of the plants. The wood 

 of dicotyledonous plants is richer in pentosans than that of the 

 Coniferae. It is thought by De Chalmot that these substances 

 are reserve materials. But they seem of importance in the 

 formation of wood, for they are developed at this stage. 



Arabinose is one of the important members of the pentose 

 series. It was discovered by Scheibler on boiling the gum of 

 the cherry tree with sulphuric acid. This compound was con- 



1 The reaction and products of some of these sugars were demonstrated. 



