3^-^ ZVg-i-'.'i/^/t- Principle contahied in Coffee. 



of acid, the liquor pafled to a beautiful green; and, if it wa* 

 concentrate, there was a green precipitate. Salts formed of 

 the red o\ide of iron fuccecded the bed ; and the reciprocal 

 action of this principle and iron is ainioft as delicate as that, 

 of either gallic acid or tannin, and iron. 



With niuriate of tin^ there was a very abundant yellowifK 

 precipitate, which was a combination of the new vegetable 

 principle, with oxide of tin. Both this precipitate and tliat 

 with iron are fokible in all the acids, and the liquors loie their 

 colour. . ■' 



Lime water did not caufe any precipitate in this liquor, 

 nor did llrontia water. Barytes water gave a fawn-coloured 

 precipitate. With lime water, tannin gave a blueifli green 

 precipitate; and nearly the fame with ftrontia water, as alfo 

 with barytes water. 



_A folution of animal gelatine did not give any precipitate 

 with this vegetable principle. The efi'eci of tannin upon 

 gelatine i^ well known. 



By the above experiments it appears that this principle 

 bears fufficient characters to diftinguifli it from tannin, or 

 any other vegetable principle with which we are acquainted. 

 The only property which it poirefles in consmon with tannin,.^ 

 is its affinity for oxide of tin ; while it is clearly diltinft from 

 tannin in every other refpeft. 



It is evident that cotiee before it is roafted does not con- 

 tain tannin. A folution of gelatine poured into a deco6tion 

 of roalted coffee, gives, however, an immediate precipitate; 

 and this precipitate is the combination of tannin with gela- 

 tine. Meflrs. Proult, Seguin, and Davy, have obferved that 

 heat develops the tanning principle in many vegetables. Iii 

 a commercial point o'f view, it would be eflijntial to examine ' 

 whether thole vegetables are not fuch as, before being heated, 

 contain this new principle. Although I did not'perceive 

 that the principle, when infulated from the entire vegetable, 

 was converted by heat into tannin, vet the prei'ence of the 

 other component parts of the vegetable may influence the 

 diltribution of elements in fuch a nVanner as to produce com- 

 binations ditierent from what the feparate principles would 

 affurd. 



^ I have not had an opportunity to look for this new prin- 

 ciple in other vegetables. 



LX. Bio- 



