TANNINS. 137 
in Flores Rose gallice, but the latter substance, as well as 
pyrocatechin, is undoubtedly widely distributed in the vegeta- 
ble kingdom, and by more exact investigation will probably be 
. found in many other drugs. 
Of very frequent occurrence also, and probably quite general 
in barks in a definite phase of life, is phloroglucin,’ C,H,- 
(OH),, belonging to the class of phenols. 
Resembling the tannic acid of galls, or tannin,’ there are 
some other tannic matters, not of the same composition, which 
produce in solutions of ferric salts a blue-black precipitate, thus, 
the tannin of Folia Uve ursi, of oak-bark, of the bark of pome- 
granate-root, etc. Many others, however, as the tannic acid of 
the Cinchona barks, of willow and elm barks, that of Radix 
Ratanhie Peruviane, of Rhizoma Filicis, Rhiz. Tormentille, 
of Coffee, and also Catechu, produce with solutions of ferric 
chloride or ferric salts a green precipitate, while the tannic 
acid of rhubarb gives a blackish-green. In two varieties 
of Ratanhia (Krameria), that from Para and that from 
Savanilla, the tannic acid forming a green coloration with 
iron salts is accompanied by a predominating amount of acid 
producing a blue coloration. For the correct discrimination of ~ 
these colorations, thin sections of the respective drugs must be 
moistened with a little solution of ferric chloride of the dilu- 
tion stated under ‘Microscopical Reagents,” and the slides 
upon which this reaction is carried out, laid upon a sheet of 
white paper. The experiment is also performed at the same 
time with the application of a solution of ferrous sulphate, 
which permits the colorations to appear gradually, in proportion 
to their oxidation, but often with a greater degree of purity. 
A highly remarkable occurrence of a substance which affords a 
magnificent blue color with ferric chloride as well as with fer- 
rous salts is presented by the large cells of the fleshy portion of 
the fruit of Siliqgua dulcis. 
Between the tannic matters or tannic acids of the two classes 
~1 Compare the statements of Tschirch, in Pringsheim’s Jahrb. f. wiss. 
Bot., 1885, and Poulsen’s ‘‘ Botanical Micro-chemistry.” se 
? From the French word tanner, to tan, of unknown origin. 
