on the constituent Parts of astringent Vegetables. 239 
The saline matters in astringent infusions, adhere so strongly 
to the vegetable principles, that it is impossible to ascertain their 
nature with any degree of accuracy, by means of common re- 
agents. By incineration of the products obtained from the eva- 
poration of astringent infusions, I have usually procured carbo- 
nate of lime and carbonate of potash. 
In the different analyses, as will be seen from the results 
given in the following sections, I have attended chiefly to the 
proportions of the tanning principle, and of the principles pre- 
cipitable by the salts of iron, as being most connected with 
practical applications. 
With regard to the knowledge of the nature of the different 
substances, as they exist in the primitive astringent infusion, we 
can gain, by our artificial methods of examination, only very 
imperfect approximations. In acting upon them by reagents, 
we probably, in many cases, alter their nature ; and very few 
of .them only can be obtained in an uncombined state. The 
comparison, however, of the products of different experiments 
with each other, is always connected with some useful conclu- 
sions ; and the accumulation of facts with regard to the subject, 
must finally tend to elucidate this obscure but most interesting 
part of chemistry. 
II. EXPERIMENTS ON THE INFUSIONS OF GALLS. 
I have been very much assisted in my inquiries concerning 
the properties of the infusions of galls, by the able Memoir of 
M. Deyeux, on galls.* 
The strongest infusion of galls that I could obtain, at 56° 
* Annales de Chimie, Tome XVII. pag. i. 
