32 eXPERIMENTS OV ASTKINGENT VEGETABLES. 



Chemical ex- bark furniflied 17 grains of folid matter ; that of the Leiccfter 

 >Trious°bIrkj. '^i^'ovvr about 1 61 grains ; and that of the Spanifti chefnut nearly 

 an equal quantity. 



The tannin given by thefe folid matters was, in that from the 

 oak bark infufion, 14- grains; in that from the willow bark in- 

 fufion 14| grains; and in that from the Spanifli chefnut bark 

 infufion 13 grains. 



The refidual fubflances of the infiifions of the Spanith chef- 

 nut bark, and of the oak bark, (lightly reddened litmus-paper, 

 and precipitated the folutions of tin of a fawn colour, and thofe 

 of iron black. The refidual matter of the infufion of the wil- 

 low bark, did not perceptibly change the colour of litmus ; but 

 it precipitated the falts of iron of an olive colour, and render- 

 ed turbid the folution of nitrate of alumina. 



The folid matters produced by the evaporation of the Infu- 

 fions, gave, by incineration, only a very fmall quantity of 

 afhes, which could not have been more than -^1^ of their ori- 

 ginal weights. Thefe afties chiefly confifted of calcareous 

 earth and alkali ; and the quantity was grealeft from the infu- 

 fion of chefnut bark. 



The infufions were afied on by the acids, and the pure alkalis, 

 in a maimer very fimilar to the infufion of galls. With the fo- 

 lutions of carbonated alkalis, they gave denfe fawn-coloured 

 precipitates. They were copiouily precipitated by the folutions 

 of lime, of ftrontia, and of barytes; and, by lime-water in 

 excefs, the infufions of oak and of chefnut bark feemed to be 

 deprived of the whole of the vegetable matter they held in 

 folution. 



By being boiled for fome time with alumine, lime, and mag- 

 Tiefia, they became almofl colourlefs, and loft their power of 

 a6ling upon gelatine and the falts of iron. After being heated 

 with carbonate of lime and carbonate of magnefia, they, were 

 t(uind deeper coloured than before ; and, though they had loft 

 their power of ading on gelatine, they ftill gave denfe olive- 

 coloiared precipitates with the falts of iron. 



In all thefe cafes, the earths gained tints of brown, more or 

 lefs intenfe. 



When the compound of the aftringent principles of the in- 

 fufion of oak bark with lime, procured by means of lime-water, 

 wusafted onby fulphuric acid, a folution was obtained, which 



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