120 THE CARBOHYDRATES 



guish inulin and glycogen from dextrin, which does not give 

 a precipitate with this reagent. 



5. Inulin is precipitated from solution by alcohol. 



6. Hydrolyse with mineral acid and test for levulose. 



There is as yet no very accurate method for the estimation 

 of inulin. Dragendorff* recommends precipitating the inulin 

 from an aqueous extract and then determining the amount of 

 levulose which is produced on hydrolysis. 



INULIN-LIKE SUBSTANCES. 



Attention may now be drawn to substances similar to inulin 

 which occur in various plants. The chief of these are : 



Graminin in Agrostis, Festuca, Trisetum and other grasses. 



Iris in in Iris pseudacorus. 



Phlein in Phleum pratense and Phalaris arundinacea, 



Sinistrin in Scilla maritima. 



Triticin in Triticum repens y Draccena australis and Dra- 

 c&na rubra. 



All these compounds have the same formula, 6(C 6 H 10 O 5 + 

 H 2 O), and possess the same characteristics ; they are laevo- 

 rotatory, yield fructose on hydrolysis, and are fairly soluble 

 in cold water. The majority are difficult to crystallize, and 

 their solutions yield a gum-like substance on evaporation. It 

 is possible that some, at any rate, of these substances may 

 bear the same relation to inulin as dextrin does to starch. 



MANNOSANES. 

 MANNANE. 



The seeds of many plants contain reserve carbohydrate 

 which is generally referred to as reserve cellulose, hemi-cellulose, 

 or para-galactane substances. These materials are often indis- 

 tinguishable from true cellulose by the microchemical means 

 at our disposal. They may, however, be distinguished by the 

 products of their hydrolysis ; thus they form glucose, together 

 with other substances, on treatment with hot dilute hydrochloric 

 or sulphuric acid, whereas ordinary cellulose does not. Also 

 they are dissolved by dilute alkalis, and by cuprammonia after 



* Dragendorff : " Jahres. Fortsch. d. Chem.," 1872, 929. 



