Facts fur a History of the Gallic Acid. 31 



of tnercury. To convince myself still further of the pre- 

 sence of acetic acid, I treated the neutral acetate of potash 

 in the same manner, and it afforded nie the same results. 



The second product was saturated with potash in the same 

 manner. The liquor became very brown ; a slight pellicle 

 formed on the surface, which increased during the evapo- 

 ration : the saline matter was highly coloured and empyreu- 

 matic. Being subjected to the same trials as the preceding, 

 similar appearances were observed. 



These experiments leave no doubt of the presence of acetic 

 acid in galls : ihey prove that it may be obtained by distilla- 

 tion with water, and that caloric, when it acts more directly 

 on this acid, facilitates its combination with a small quan- 

 tity of empyreumatic oil, and perhaps with a little tannin, 

 the presence of which is not demonstrable by glue : but as 

 this liquor acts on sulphate of iron in the same manner as 

 the sublimed acid, we must presume that there is a kind o£ 

 analogy ai their composition j admitting, however, this dif- 

 ference, that the sublimed acid contains no empyreumatic 

 oil, but a particular aromatic volatile oil. 



This oil may be detected by dissolving the acid in very 

 pure sulphuric ether, and adding a little water, when a few 

 tlrops of oil will be seen floating oa the surface, which dis- 

 appear on shaking the mixture. 



If a concentrated solution of caustic potash be employed 

 instead of water, a white milky substance is separated, which 

 requires a large proportion of water to dissolv.; it, but tlie 

 liquor still remains turbid. 



This ethereal tincture yields a fine blue colour with sul- 

 phate of iron. 



Evaporated in the open air it leaves a shining substance, 

 Tcry acid, separating in scales, and having the appearance of 

 a varnish. 



The same phcenomena takes place if galls be digested in 

 ether; but the substance contains tannin in addition. 



Exaynina lion of some Eariliy and JlLaline Gdllates. 



Though it appears to be demonstrated that acetic acid cx- 

 Hti ready formed in galhi, wc cannot too much nuihi)i]y 



prooi'i 



