ii8 THE CARBOHYDRATES 



tered, neutralized with ammonia, evaporated to half its bulk and 

 mixed with an equal volume of alcohol. After one or two days, 

 crude inulin may be filtered off; it may be further purified 

 by warming in aqueous solution with animal charcoal, filtering 

 and adding alcohol ; the precipitated inulin is then washed 

 with alcohol and ether, and dried over sulphuric acid. 



According to Kiliani,* it may also be prepared by boiling 

 crushed dahlia tubers with water and a little chalk, filtering 

 and freezing the filtrate. When the water cools, the precipi- 

 tate is filtered off, re-dissolved in hot water and frozen out 

 once more. After repeating this process several times, the 

 inulin is washed with methyl alcohol, ethyl alcohol, and finally 

 ether. 



Characters. 



Pure inulin forms a white starchy tasteless powder of a 

 sphaero-crystalline nature ; it swells up and is readily dissolved 

 in hot water, alkalis, etc., and may be recovered from the aqueous 

 solution by the addition of alcohol, in which it is practically 

 insoluble, or by freezing. Inulin is laevo-rotatory and unlike 

 starch does not give a paste with water, nor does it give a blue 

 colour when treated with iodine. Diastase has no effect upon 

 it ; it may, however, be hydrolysed by the ferment inulase, or by 

 mineral acids, by which reagents it is converted into levulose. 

 The low osmotic pressure which solutions of inulin exert 

 suggests a large molecule, but its molecular structure appears 

 to be less complex than that of starch. The relation between 

 inulin and levulose is much the same as that existing between 

 starch and glucose. 



Identification. 



In many plants the presence of inulin is indicated by the 

 well-known sphaero-crystals which are obtained on steeping 

 the fresh tissues for some time in strong alcohol ; this deposi- 

 tion is not, however, always so characteristic ; thus in Mono- 

 cotyledons the inulin is frequently found, after treatment with 

 alcohol, in amorphous masses. The sphaero-crystals and the 

 amorphous concretions of inulin are readily soluble in warm 



* Kiliani : " Annalen," 1880, 205, 147. 



