364: 0N ARTIFICIAL tfANNItf. 



another substance, which did not perceptibly redden litmus, 

 which was fusible by heat, and which precipitated gelatine. 

 I concluded the account of my labours with saying, that I 

 purposed to examine whether the tanning matter of Hatchett 

 were a real tannin, whether the amer of indigo (or of Wel- 

 ther) were similar to that of brasil, and lastly, whether 

 these substances owed their detonating property to nitric 

 acid. 

 Amerofbrasil 9. To solve these questions I prepared a certain quantity 

 potash? of amer of brasil in the following manner. I combined it 



with potash ; I boiled this compound in water acidulated 

 with muriatic acid ; by evaporation I obtained a whitish 

 substance crystallized confusedly ; and the mother water, 

 from which this was separated, yielded by concentration 

 fresh crystals, mixed with small grains of a resinous ap- 

 pearance, and of a reddish colour. This experiment led 

 me to think, that, if the amer of brasil be incapable of 

 crystallizing before it is combined with potash, it is because 

 it is combined with a certain quantity of matter, which I 

 believe to be resinous. The latter contributes also to give 

 it the property of precipitating gelatine more abundantly 

 than the amer of indigo. 

 Approaches The crystallized amer of brazil forms with potash a de- 



i„^ ^Jfe 60 ' tonating salt of a much lighter colour, than that which it 

 same. forms when not crystallized. It seems then to approach 



the amer of indigo ; but it exhibits certain differences, which 

 do not permit them to be confounded together. 

 Its destructive 10. The crystallized amer of brasil, heated in the glass 

 analysis. tube with a bulb before mentioned *, yielded, 1st, water; 



2d, carbonic acid ; 3d, prussic acid ; 4th, an inflammable 

 gas, that burned with a heavy white flame, in the manner of 

 oily hidrogen ; 5th, nitrous gas ; 6th, nitrogen gas ; 7,3 

 coal, extremely attenuated. 

 A compound of Hence I concluded, that the amer of brasil is a compounc 

 nitric acid an ' f n itric acid, and a substance apparently resinous or oily 

 substance. that this compound, when united with salifiable bases, 

 forms detonating salts: that it precipitates gelatine more 

 copiously than the amer of indigo docs, because it appears 



* Journal, vol. xxx, p. 354. 

 X 



