FRUCTOSANS 175 



plex.* Iriulin is Icevo-rotatory, aj,=— 35°, and is non- 

 reducing. Unlike starch it 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 fructose. Whilst the final product ob- 

 tained is ordinary fructose, the initial product is, presumably, 

 y-fructose, since inulin has been shown to be a polymerized 

 form of this active sugar. 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. 



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 

 water, and thus may be distinguished from calcium phosphate 

 which may occur in cells in shapes similar to those of inulin. 

 These two substances may be further recognized by the fact 

 that sulphuric acid completely dissolves inulin, whereas it forms 

 with calcium phosphate insoluble calcium sulphate. The 

 following tests also may be performed : — 



1. Green's Test. — Sections of the material, which have been 

 soaked for some time in absolute alcohol, are treated with a 

 saturated solution of orcin in strong alcohol, and then boiled 

 in hydrochloric acid. The masses of inulin disappear and a 

 red colour results. If phloroglucin be substituted for the 

 orcin, the resulting coloration will be reddish-brown. 



2. Molisch's Test. — The sections are treated with a 10 per 

 cent alcoholic solution of a-naphthol, then a few drops of 

 strong sulphuric acid are added and the preparation warmed. 

 A deep violet coloration ensues, and the inulin is dissolved. 



* Irvine and Steele : " J. Chera. Soc," 1920, 117, 1474. 



