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XXII. Memoir on the Existence of a Comh'mation of Tan- 

 n'm and a vegetable Mailer in some Fegetables. Bi/ 

 Messrs. Fourcrov ajid VAuauEMN*. 



§ I. Sulject of 02ir Inquiries. 



J.T was natural to suppose that when there were formed, 

 cither successively or simultaneously, tannin and unimal sub- 

 stances in vegetables, these two compounds would unite 

 when they met: nevertheless, although the knowledge we 

 have acquired on the subject of tannin and the animal sub- 

 stance give great probability to this opinion, no chemist has 

 yet announced the existence of this species of combination 

 in plants. 



Upon analysing several vegetable matters more or less 

 different from each other, and particularly the Indian ches- 

 nut, garden beans, lentils, &c., we discovered the com- 

 pound in question, and we shall now give the result of our 

 experiments. 



The facts which we are about to describe seem interest- 

 ing, because they afford an explanation of a great num- 

 ber of phcenomena observed in the analysis of vegetables, 

 as well as in their employment in dyeing or in other arts, — 

 phsenomena which the chemists have not yet been able to 

 account for. 



§ II. Examination of the Skin of Garden Beans. 



It was in the skin which covers the cotyledon of the 

 bean that we first ascertained the combination of tanniu 

 with an animal matter. 



When macerated in tepid water for 24 hours, this tunic 

 comnnmicated to the water the property of reddening turn- 

 sole tincture, that of precipitating the solution of sulphate 

 of iron blue, the solution of glue in yellowish-white, lime 

 water in red flakes like oxide of iron, the acetate of lead 

 in yellowish-white, and at the same time the property of 

 experiencing no effect from the infusion of gall-nuts. 



The characters of this water prove that it contains a free 

 acid and tannin. We must here remark, that pure tannin 

 precipitates iron brown, and that when it is joined with an 

 acid it precipitates it blue. 



The skins of garden beans submitted four different times 

 to the action of large quantities of boiling water always 

 communicated to it the above properties, but in a remarka- 

 bly decreasing ratio. 



* Annales du Museum d'Hisl. Nat. tome xv, p. 77. 



When 



