ASTRIN"GEKTS. 81 



ASTRINGENTS. 



Tannic and Gallic Acids. 



Preparations. — Acidum Tannictiniy tannic acid, 

 gallotannic acid, tannin— C,,H,,Oa. 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 G parts glycerin ; almost insoluble in ether 

 and chloroform. It is incompatible with alkaloids 

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

 gr. ij.-x. 



Olycerinum 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,H,0,.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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