ASTRIKGEKiS. M 



ASTRINGENTS. 



Tannic and Gallic Acids. 



Prepaeations. — Acidum Tannicum, tannic acid, 

 gallotannic acid, tannin — C,4H,„0,. Light yellow- 

 ish scales, permanent in the air, having a faint, 

 peculiar odor, a strongly astringent taste, and acid 

 reaction. Soluble in 6 parts of water, in 0.6 part 

 alcohol, in 6 parts glycerin ; almost insoluble in ether 

 and chloroform. It is incompatible with alkaloids 

 and preparations of iron. Dose: H., 3ss.-ij. ; D., 

 gr. ij.-x. 



Glycerinum Acidi Tannici, glycerine of tannin. 

 Twenty per cent, strong ; for local use only. 



Unguentum Acidi Tannici, ointment of tannic 

 acid. For local use only ; made ten per cent, strong. 



Acidum Gallicum, gallic acid — HC,H50j.H,0. 

 A nearly or quite colorless solid, crystallizing from 

 water in long, silky needles or triclinic prisms ; per- 

 manent in the air, odorless, having an astringent 

 and slightly acidulous taste and acid reaction. Sol- 

 uble in 100 parts water, in 4.5 parts alcohol, in 39 

 parts absolute ether, but only slightly soluble in chlo- 

 roform. Dose same as tannic acid. 



Differences between Tannic and Gallic Acids. 

 — Tannin precipitates alkaloids, gelatin, albumen, 

 gelatinized starch, and tartar emetic, while gallic 

 acid does not, but when taken into the stomach is 

 first converted into gallic acid before absorption. 

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