300 Erperhncnts and Oliservatlons on the . 



and they formed, with the caustic alkahs^ fluids not pre^ 

 cipitabJL' bygciatinc. 



An ouiice of the bark of the tim furnished 13 grams of 

 tannin. 



The same quantity of the bark of the coiiiinon willow 

 gave 1 1 grains. 



The residual matter of the bark of the elm contained a 

 considerable portion of mucilage, and that of the bark of 

 the willow a sn:a!l quantity of bitter jjrincipie. 



The strongest infusions of the sumachs from Sicilv and 

 Malaga, agree with the infusions of barks in most of their 

 properties ; but they difter from all the other astringent in- 

 fusions that have been mentioned in one respect, they give 

 dense precipitates with the caustic alkalis. Ajr, Proust has 

 shown that sumach contains abundance of sulphate of lime ; 

 and it is probably to this substance that the peculiar efiect 

 is owing. 



From an oimce of Sicilian sumach I obtained lf>5 grains 

 of matter soluble in water, and of this matter 7S grains 

 were tannin. 



Aa ounce of Malaga sumach produced 156 grains of so- 

 luble matter, of which 79 appeared to be tannin. 



The infusion of myrobalans* from the East Indies, dif- 

 fered from the other astringent infusions chiefly by this cir- 

 cumstance, that it eflervesced with the carbonated alkalis ; 

 and it gave with them a dense precipitate, that was almost 

 immediately redlssolvcd. After the tannin had been preci- 

 pitated from it by gelatine, it strongly reddened litmus 

 paper, and gave a bright black with the solutions of iron, 

 I expected to be able to procure gallic acid, by distillation, 

 from the myrobalans : but in this I was mistaken ; they 

 furnished only a pale yellow fluid, which gave merely a 

 slight olive tinge to solution of sulphate of iron. 



Skin was speedily tanned in the infusion of the myroba- 

 Jans ; and the appearance of the leather was similar to the 

 appearance of that from galls. 



The strongest infusions of the teas are very similar, in 

 their agencies upon chemical tests, to the infusions of ca- 

 techu. 



An ounce of Souchong tea produced 48 grains of tannin. 

 The i?anK; quantity of green tea gave 41 grains. 

 Dr. Maton has observed that very little tannin is found in 

 cinchona, or in the other barks supposed to be possessed of 



* The myrobal'.ns used in these experiments arc the fruit of the Ttr- 

 miodiia Chebula.— Rctz. Ois, Bo/an, Fasc. v. p. 31. 



3 febrifuire 



