48 SUBSTANCES SOLUBLE IN ALCOHOL. 



tion ( 48) directly with ether, renewing the solvent four or five 

 times. On evaporating the ethereal solution, both gallic 

 -catechuic acids remain behind in a crystalline form, generally 

 needles felted together. (Cf. 151, 165.) 



The weight of the dried residue frequently indicates wit 

 tolerable accuracy the quantity of the substance present ; but i] 

 the residue be mixed with much colouring or amorphous matter, 

 .so as to cause some hesitation in accepting the weight as correct 

 the result obtained may be verified by titration with permanganat 

 of potash. (See above.) If the material has been extracted wit 

 ether previous to treating with alcohol, gallic and catechuic acids 

 will be found in the aqueous solution from the ethereal extract 

 <Cf. 38, 151.) 



For the free vegetable acids which may occur in the alcoholi< 

 -extract see 82. (See also in 159.) 



EXAMINATION FOR GLUCOSIDES, BITTER PRINCIPLES, 

 ALKALOIDS, ETC. 



54. Extraction ly Agitation. If no tannic acid or allied sul 

 .stance has been found in the aqueous liquid ( 48), but by the 

 bitter taste or other properties the presence of a bitter principle 

 glucoside or alkaloid insoluble in ether but soluble in water 

 suspected, the watery solution prepared from the evaporatioi 

 residue of the alcoholic tincture may be subjected to consecutive 

 treatment with various liquids which, being themselves insolul 

 in water, are adapted for removal of substances in solution b} 

 agitation and separation. The aqueous solution from the etheres 

 extract ( 38) may also be treated in a similar manner. The use oi 

 petroleum spirit, benzene, and chloroform may be especially recom- 

 mended for this purpose ; they should be employed in the orde 

 in which they are named, and the liquid should be rendered fii 

 slightly acid with sulphuric acid, and subsequently alkaline wil 

 ammonia; I have spoken at length on this subject in my 'Erinit 

 telung der Gifte.' 1 After each agitation, the solvent should 

 separated, washed once by shaking with pure water, agaii 

 separated, evaporated to dryness, and the residue examined. If 

 solvent, as for instance petroleum spirit, removes any appreciable 

 quantity of a substance, the agitation with this liquid should 



1 P. 119. Compare also Russ. Archiv flirgerichtl. Med. J. i. und Phan 

 Zeitschr. f. Kussland, v. 85 ; vi. 663. 





