CH. Xll] GLUCOSIDES. 275 



this residue in water and applyiug the ' Saliretin ' test 

 to the aqueous solution 1 . 



Sugars, etc. 



After removal of tannins (also of glucosides and proteids 

 if necessary), the solution may be examined for sugars. 



The detection and estimation of sugars in this solution 

 is carried out in exactly the same way as described for 

 extract III. (cold water) after removal of dextrins (see 

 p. 281) with which it may be mixed for examination. 



The whole of the sugars may occur in this solution. 



Experiments. 



(1) Make alcohol ('850) extract of willow bark (flaliac 

 viminalis) after previously extracting with benzene to 

 remove resins, colouring matter, etc. 



Test the extract for 



(a) Tannins. (6) Glucosides (Salicin). (c) Sugars. 



(2) Compare the amounts of sugars which can be 

 extracted by "850 alcohol in young and in ripe fruits of 

 Musa sapientum, L. 



(3) Show that the tannin extracted by '850 alcohol is 

 a glucoside. 



Make alcoholic extracts of material dried in each case 

 at 1 00 C. and compare the amounts of sugar in solutions 

 after complete removal of the tannins. 



It is not necessary in this case to previously extract 

 the material with benzene or petroleum ether. 



1 See Fresenius, Qualitative Analysis 10th ed. p. 436. 



182 



