136 THE CARBOHYDRATES 



material to be examined, and to wash the preparations 

 thoroughly with alcohol in order to remove them. 



Since inulin does not reduce Fehling's solution, this re- 

 agent may be employed to ascertain whether any reducing 

 sugars are present in the material before employing the above 

 tests for inulin. 



The following reactions may be carried out with a solution 

 of inulin. 



3. The addition of iodine solution gives with inulin a 

 brownish coloration. Since the solution of iodine is itself 

 brown, this test must be performed very critically. The follow- 

 ing method may be employed : dilute the solution of iodine 

 with water until it is a light brown colour, fill two test tubes 

 with this solution and add to one a drop of the inulin solu- 

 tion ; now compare the colour of the contents of the two test 

 tubes. 



This same reaction is also given by glycogen, when the 

 same procedure may be followed. 



4. Basic lead acetate gives with inulin, and also with gly- 

 cogen, a white precipitate. This test may be used to distin- 

 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. 



Irisin in Iris pseudacorus. 



Phlein in Phleum pratense and Phalaris arundinacea. 



Sinistrin in S cilia maritima. 



Triticin in Triticum repens, Draccena australis and Dra- 

 cana rubra. 



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



