84 CELL-CONTENTS AND CELL-WALLS. 



(D) Boil the residue with dilute (1 per cent.) sulphuric 

 acid for a few minutes. Filter the acid extract into a 

 fourth bottle labelled D. 



Extract A contains the oils and resins, in addition to 

 chlorophyll and other pigments. Extract B contains 

 glucosides, tannins, and some sugar. Extract C contains 

 dextrins and other soluble carbohydrates not dissolved by 

 the alcohol. Extract D contains reducing sugars formed 

 by action of acid on starch. 



Each extract should now be tested, using the tests for 

 the substances mentioned above. 



(A) Distil off most of the ether, then evaporate the 

 rest down on a bath. Warm the residue with strong 

 potash for an hour, add water, and filter if there is a 

 residue (of resins, etc.). Then add hydrochloric acid 

 until the solution gives an acid reaction with litmus, and 

 cool. The fatty acids become solid in most cases ; filter, 

 and examine the filtrate for glycerine, after evaporating it 

 down to small bulk. 



(B) Evaporate off the alcohol, treat the residue with 

 water, filter. If the solution is acid, neutralise with dilute 

 soda, and test portions of it for tannins and glucosides. 

 (1) If woody tissue has been extracted, phloroglucin will 

 probably be present ; remove it by shaking up the solution 

 after adding ether (in which tannins and ordinary gluco- 

 sides are insoluble) ; pour off the ether layer, evaporate 

 down the ether, dissolve the residue in water, and test the 

 watery solution thus obtained for phloroglucin. (2) There 

 are no reliable general tests for glucosides ; special tests 

 must be used for the glucoside likely to be present. For 

 instance, extract of Willow or Poplar stem will contain 

 salicin, extract of Horse Chestnut bark will contain aescu- 

 lin ; the tests for these have been given. (3) Test parts 

 of the watery solution for tannins, with ferric chloride, 

 etc. 



(C) (1) Concentrate the watery extract to small bulk by 

 heating on a bath, add strong alcohol until no more pre- 

 cipitate is formed, and filter. Examine the precipitate for 

 dextrin and inulin, after dissolving it in water. (2) Eva- 

 porate the filtrate from (1) to remove the alcohol, dissolve 



