114 THE CARBOHYDRATES 



alcohol remain clear, but on adding 0-03-0-05 gram of sodium 

 chloride, an immediate precipitate is formed. Glycogen is 

 strongly dextro-rotatory, a^ = + 189-9°, and is coloured red 

 to brown by iodine ; it does not reduce Fehling's solution, but 

 is broken up by diastase into dextrin and maltose, and by 

 acids into glucose. 



Identification. 



1. The opalescent appearance of its aqueous solution is 

 characteristic, and is strongly dextro-rotatory. 



2. A brown coloration is given with iodine solution (cf. 

 inulin, p. 119). 



3. A white precipitate is given with basic lead acetate. 



4. It does not reduce Fehling's solution. 



5. On boiling with mineral acids, it is converted into 

 dextrose. 



Estimation. 



This is best effected by heating the aqueous solution for 

 three hours in a boiling water bath with about 2 '2 per cent 

 HCl, and then neutralizing and estimating the resulting glu- 

 cose by means of Fehling's solution ; the amount multiplied by 

 0'9 gives the weight of glycogen. 



PARA-DEXTRANE AND PARA-ISODEXTRANE. 



These substances have been isolated from Boletus edulis 

 and Polyporus betulinus respectively. The former gives a 

 yellow colour with chlorzinc iodide, and the latter a blue when 

 treated with iodine and sulphuric acid. Both give glucose on 

 hydrolysis. 



LEVULOSANES. 



INULIN. 



This substance is commonly found as a reserve food-stuff, 

 of the same nature as starch, existing in a state of solution in 

 the cellsap of a number of plants belonging to the natural 

 order Compositae, e.g. in the tubers of the dahlia and artichoke 

 {Helianthus tuberosus), and in the fleshy roots of the chicory 

 {Cichorimn Intibus). It has also been described as occurring in 



