ON ARTIFICIAL TANNIN. 



863 



the amers separate from each other in the order of their: 

 respective solubilities, 



6. I do not consider the substance of an oily appearance The propor- 



as uniform in the proportions of its immediate principles. tlo ns°fthe ira- 

 r r r r mediate princi- 



Spmetimes the amer at a minimum is in small quantity: p i es not con- 

 sometimes it predominates over the others. The same may stant - 

 be said of the amer at a maximum, and of the resin. This is 

 the reason of the differences observed in the colour, con^ 

 sistence, and other properties of these compounds. 



7. It remains for me to assign the reason why the com- Why the com- 

 pound of resin and amers precipitates gelatine much more P oun(l precipi- 



. , . Jf, tates gelatine. 



copiously than amer at a maximum. Ihe fact appears to 



me owing to this, that the resin and amer at a minimum 

 (which have themselves an affinity for animal substances, but 

 not sufficient to precipitate gelatine) in combining with 

 amer at a maximum diminish the solubility of the latter, so- 

 lidify it in some degree, and thus in all probability increase 

 the capacity it has of forming with gelatine a compound 

 but little soluble. 



§11. Bitter tanning substance formed with extract of 

 brasil wood. 



8. In my first paper on brasil wood, I described a bitter Tannin from 

 substance, produced by the action of nitric acid on the ex- extract °fbrasi!. 

 tract of this wood. I showed, that this substance did not 

 crystallize, was acid, precipitated gelatine, and formed with 



potash small detonating crystals. At that time I considered Supposition 

 this substance as a compound of amer, artificial tannin, and nature. 1 " 8 

 nitric acid. My reasons were, 1st, its being fusible by 

 heat, and forming detonating salts with salifiable bases, in 

 the manner of Welther's amer : 2dly, its precipitating gela- 

 tine in the manner of the tannin described by Mr. Hatchett, 

 while the amer of Welther, prepared with indigo, does not 

 precipitate it ; whence I inferred, that two different sub- 

 Stances were requisite, to form detonating compounds and pre- 

 cipitate gelatine* : 3dly,its reddening litmus paper ; because, 

 in treating extract of brasil with nitric acid, I had obtained 



* The reason. of my not obtaining a precipitate with Welther's 

 amer and gelatine at that time was my employing solutions too di- 

 lute, or adding too much gelatine. 



another 



