426 TANXIC ACIDS. 



tannic acid. With iron salts, however, it does not 

 give a bluish-black, but a dirty green precipitate ; it 

 can also not be converted into gallic acid. Compo 

 sition unknown. 



Catechin (Catechuic acid), C 19 H 18 8 (?). Occurs to 

 gether with tannic acid in catechu, more especially in 

 the cubical variety from Nauclea gambir. 



Powdered catechu is macerated with cold water ; the 

 brown tannic acid solution filtered from the undis- 

 solved catechin; this pressed and dissolved in boiling 

 water, from which it is deposited slowly on cooling, 

 generally not yet quite white. It is purified by recrys- 

 tallization. 



Colorless mass consisting of interwoven fine crystal 

 line scales ; almost tasteless ; fusible at 217 ; diffi 

 cultly soluble in cold water, easily in boiling water and 

 in alcohol. Turns a reddish color in the air, finally 

 brown. Ferric salts are colored green by it ; solutions 

 of salts of the noble metals are reduced. Very weak 

 acid, does not expel carbonic acid from it salts. When 

 heated, it yields pyrocatechin (p. 305); when fused \vith 

 potassa, protocatechuic acid (p. 356) and phloroglucin 

 (p. 311). 



Kinotannic acid. Forms the principal ingredient 

 of kino, a brittle reddish-brown extract, which is pre 

 pared in West India from Coccoloba uvifera, in Africa, 

 from Pterocarpus erinaccus. The tannic acid contained 

 in it has been but little investigated; it is not yet 

 known in a pure condition. It colors ferric salts 

 blackish-green. Fused with potassa, it yields phloro 

 glucin. 



Morintannic acid (Maclurin), C 13 H 10 6 + H 2 0. In 

 old fustic (of Morns tinctoria), from which it is ob 

 tained by boiling with water. On evaporation of the 

 solution, morin is at first deposited and then morin- 

 tannic acid. Bright-yellow, crystalline powder, easily 

 soluble in hot water and alcohol. Its solution gives 

 with ferrous sulphate a blackish-green precipitate. 

 Heated alone, it yields pyrocatechin; fused with po- 



