Tanning spend acid introduces 】 tanning spend the acid, it is
gallic acid dimer derivatives, is a kind of polyphenols two
lactone. It can not only to free form existence, and more on
condensation forms (such as tanning flowers, such as a nucleoside
tannins) exist in nature. Tanning spend acid and chloride-ferric
chloride of color reaction is blue, encounter sulfuric acid yellow,
Greiss-meger positive reaction, but also easy and metal cation such
as ca2, M combined. Pure tanning spend acid is a kind of yellow
needle crystal, melting point (pyridine) more than **0 *2, slightly
soluble in water, alcohol, soluble in alkali, pyridine, insoluble
in ether. The molecular formula 】 C*4H6O8 The molecular weight 】
**8.*5
