160 TANNINS. 





billa 1 correspond exactly to gallotannic acid, and all that has beei 

 said of the latter is equally true of the former. They are always 

 accompanied by gallic acid in the materials that yield them. 



Some of these also contain the so-called ellago-tannic acid, 

 which is found in notable quantities in myrobalans, divi-divi and 

 bablah fruits. 2 



This ellago-tannic acid, which, as far as Loewe's experiments 

 show, is not a glucoside, differs from gallotannic acid in yielding 

 ellagic in the place of gallic acid, a change that can be brought 

 about by water alone at a temperature of 108 to 110. Ellagic 

 acid can be obtained in sulphur-yellow crystals, which are almost 

 insoluble in boiling water or in ether, and sparingly soluble in 

 alcohol. Notwithstanding, however, its slight solubility in ether, 

 small quantities can be removed from aqueous solution by shak- 

 ing with that liquid. Ferric chloride produces first a green, then 

 an inky colouration. It is soluble in potash, and is precipitated 

 by acetate of lead from an alcoholic solution in the form of lead- 

 salt, containing 63 per cent, of oxide. The dry substance heat 

 with zinc dust yields the hydrocarbon ellagene (C 14 H 10 ), wl 

 cannot be combined with picric acid. 



Whether ellago-tannic acid has been prepared in a state 

 purity, and whether it is identical with punico-tannic acid, 3 

 questions which we may for the present leave out of considei 

 tion. According to Rembold, the latter also yields ellagic ack 

 Special methods for the estimation of these two substances h 

 not as yet been published. 



For nymphsea-tannic acid see 161. 



Gallotannic and gallic acids also occur in tea, accompanied 

 quercetin (possibly present in sumach also, 152), and by the 

 called boheic acid. 4 The latter is not thrown down when acetate 

 of lead is added to a hot infusion of tea, but is precipitated on 



Chem. xii. 128, 1873 (Journ. Chem. Soc. xxvi. 748) ; xiv. 46 (tannin of 

 knoppern-galls). 



1 Compare Godeffroy, Zeitschr. d. Oesterr. Apoth.-Ver. 132, 1879 (Year-book 

 Pharm. 215, 1879). 



2 Compare Giinther, loc. clt. Also my observations in the Jahresbericht f. 

 Pharm. 192, 1875 ; and Loewe, Zeitschr. f. anal. Chem. xii. 128 ; xiv. 35, 44. 



3 Annal. d. Chem. und Pharm. cxliii. 285, 1867. I may observe that in the 

 pomegranate bark also the substance yielding ellagic acid is accompanied by 

 gallotannic acid, and that Rembold obtained sugar by the decomposition of 

 the former. 



4 Compare Hlasiwetz, Annal. d. Chem. und Pharm. cxlii. 233. 





