VARIETIES OP CATECHU. 
141 
catechu-tannic acid exhibit [the same high degree of va- 
riability as the corresponding compounds of querci-tannic 
acid. If an aqueous sohation of catechu-tannic acid be ex 
posed to the air in a shallow vessel, decomposition very 
soon ensues, with the separation of a voluminous fibro- 
crystalline silky mass, or small acicular needles, which may 
be obtained perfectly colourless by allowing the hot aqueous 
solution to cool under the air-pump, and pressing the sepa- 
rated mass between filtering paper. The substance thus 
obtained is catechuic acid, and exhibits in its behaviour, so 
great an analogy to gallic acid, that the name catechine may 
be dispensed with. The composition of the acid is still not 
accurately determined, as the analyses hitherto made, differ 
considerably from one another. The substance employed 
by the "author for analysis was dried in vacuo over sul- 
phuric acid, and burnt with chromate of lead. It yielded 
Carbon, . . 54.16 54.29 7 53.846 
Hydrogen, . 5.29 5.57 4 5.128 
Oxygen, . . 40.55 40.14 4 41.026 
As the salts of catechuic acid are very variable, the de- 
termination of the atomic weight does not lead to any cer- 
tain result. Hagen obtained from the lead compound 
62.19 per cent, oxide of lead, which corresponds tolerably 
well to the formula 0^ -|- HO. The formula H* 0» 
may be deduced from Pelouze's analysis of catechu-tannic 
acid ; we should have therefore 
C9 H3 03 -f 40 =C^ W 0^ + 2C0% 
as in the formation of gallic acid from tannic acid. 
The so-called Gambia extract yields when pounded but 
very little to cold water, and appears to be very poor in tan- 
nin. It dissolves for the greater part in hot water, and 
congeals on cooling, to a dirty yellow pasty mass, which 
behaves exactly like catechuic acid. It is therefore very 
probable that both drugs are derived from the satne plant. 
Chem, Gaz.jfrom Journ, fiir Prakf. Pharm, 
13 
