Comlination of Tannin and a vegetalle Matter. 1 1 



When thev no longer furnish any thing to the water, 

 thcv nrestrve the property of becoming instantly of a deep 

 black bv the application of a httle sulphate ot iron: even 

 uhen rcductd to pulp and washed with boiling water, they 

 still become black when in contact with this salt. 

 § III. First Result of the foregoing Trials : ulterior Experi- 

 ments on the same Bodies. 



These experiments beo;an to make us suspect that the 

 tannin to which the eflects above described are manitestly 

 owin^, was combined in the pellicles of the garden beans 

 w ith lome substance which opposed its solubility in water. 



In order to ascertain, if possible, the nature of this sub- 

 stance, we put into a slight solution of potash a portion ot 

 pounded pellicles, and heated the mixture gently. Ihe i- 

 quorsoon became of a purple-red colour, as wc 1 as the 

 substance of the pellicles. V/hen filtered, and mixed to satu- 

 ration with the acetic acid, this liquor precipitated a reddish 

 iTiatter in the form of flakes, having a gelatinous appearance j 

 and it preserved but a very feeble colour Itself. 



The alkaline lixivium, thus cleared by the acetic acid ot 

 the substance which it had taken up from the pellicles of gar- 

 den beans, did not give a blue colour to the solution ot sul- 

 phate of iron; the mixture merely assumed aslight biownish 

 colour; but the matter precipitated, on the contrary, became 

 intensely black with this metallic solution, so that the tan- 

 nin was reallv dissolved by the potash with the matter to 

 which it was united, and afterwards precipitated with this 

 same substance bv the acetic acid, the action of which is 

 here confined to the saturation of the potash. The pellicles 

 of the beans, when cleansed by repeated washings and 

 distilled in a slow fire, furnished a liquor slightly acid, but 

 from which caustic potash extricated a great quantity ot 

 ammonia : the produce of the distillation, betore being thus 

 mixed with the potash, gave a blue precipitate with sulphate 



or iron. . j i . 



From these last experiments, it appears no longer doubt- 

 ful to us, that the skins of garden beans actually contain a 

 combination of tannin and an animal substance: we are 

 even inclined to think that the greatest part of the paren- 

 chyme of those skins is formed of this combination. 



Their charcoal yielded upon incineration a small quantity 

 of ashes formed of carbonate of lime, phosphate with the 

 same base, and oxidated iron . , , 



The envelopes of the lentils presented precisely the same 

 ' G 3 properties 



