WHITE WILLOW, kc, ^Q| 



Lime water poured into the decoctmn of willow bark, throwg 

 down a precipitate of a clear blue colour, which afterwards 

 becomes fawn. 



Sulphate of iron gives a dark green precipitate ; if the de- 

 coction be very concentrated, it passes to black, particularly 

 in the latter decoctions. 



Many other metallic salts are also decomposed, such as 

 nitrates of mercury, of silver, acetate of lead, sulphate o 

 copper, and antimonial tartrite of pot-ash (tartar emetic.) 



Alcohol precipitates flakes but little coloured, whilst the 

 supernatant liquor is highly tinged. 



Bv evanoratina the decoctmn to the consistency of syrup, ^^ecoction of 



J ^ ^ _ , • 1 1 willov. bark af 



and afterwards drying it on plates, an extract is obtamed, dry, fords a fine fla- 

 brilliant, separatin"; in scales, of a beautiful red colour, ra- ky extract like 



. n • u q'ii"<iuuia. 



ther deep, ofavefy bitter, acerb flavour, and possessing ali 



the characteristics of the dry extract of quinquina, except that 



it attracts very little of humidity from the atmosphere. 



The alcoholic tincture of willow bark is of a yellowish green Alcoholic 



colour, very bitter to the taste, and its transparency is tmcture of 



' ■' I J willow bark, 



disturbed by water. 



The phoenomena produced in the decoctmn by the addition 

 of sohitum of glue and sulphate of iron are also seen in the al- 

 coholic tincture. 



Lime water forms in it a blueish precipitate ; which proves 

 that the bark contains a small quantity of gallic acid soluble 

 in alcohol. 



Evaporation of the alcohol leaves a brilliant substance, of 

 a deep yellow colour, and very bitter ; it liquifies in a gentle 

 heat, and if thrown upon hot coals, sends forth a thick aro- 

 matic smoke. 



On considering all these products, we readily recognise ^11 the experi« 

 ,...,.• , , . , - . . -r. . ments on wil- 



their similarity to those obtamed trona quinquina. But, it jq..^ bark are 



may be asked, are the quantities the same? Perhaps we ^i'^^^'^^'t^ t*^"^® 



■ T r^ ■ , T 1 , • on quinquina, 



might answer in the affirmative ; but 1 thought it unnecessary 



to make calculations of the respective quantities, as they are 

 so very variable, even in the same species. Besides, the dif- 

 ficulty of making such computations in vegetable and animal 

 compositions is well known; I even believe it to be impossible 

 to obtain similar results in repeating experiments of this kind . 

 and though I have not mentioned the other constituent parts of 

 I 2 this 



