History of the gallic acid. 



67 



These experiments suggested to me the existence of a acid A free acid in 

 leady formed in galls, and the possibility of obtaining it by 

 distillation. 



Accordingly I heated to ebullition in a common alembic a Obtained by 

 kilagramme [2lb. 3oz. 6dr. avoird.] of galls coarsely powder- w ^ t g r ] n * wl 

 ed, with double the weight of water. The distilled liquor, as 

 Mr. Deyeux observed, was a little milky, aromatic, and on 

 standing deposited a little floculent sediment, I changed the 

 Teceiver, when about two thirds of the liquor had come oyer, 

 and I continued the distillation till it became coloured. 



The first product was acid ; reddened tincture of litmus ; 1st. product, 

 and had no action on lime or barytes water, nitrat of- mercu- , 

 ry, acetat of lead, sulphat of iron, or glue. 



The second product was turbid, coloured, a little empyreu- 2nd. product, 

 matic ; its acidity was more marked ; and it precipitated the 

 metallic solutions above mentioned, but did not act on glue. 



Each of these acid liquors was saturated with potash. The Saturated with 

 first yielded a foliated salt, which, on the addition of sulphuric pot8S * 

 acid, gave out a smell of asetic acid. Part of this salt was 

 dissolved in distilled water : the excess of its base was accu- 

 rately saturated by nitric acid, and nitrat of mercury at a 

 minimum was added to the -solution ; when a precipitate was Proofs of the 



formed, which had all the characters of acetat of mercury. acid . bein S the 



J acetic. 

 To convince myself still farther of the presence of acetic acid, 



1 treated the neutral acetat of potash in the same manner, and 



it afforded me the same results. 



The second product was saturated with potash in the same 2nd. product 

 manner. The liquor became very brown : a slight pellicle Jar p roo f s . 

 formed on the surface, which increased during the evapora- 

 tion: the saline matter was highly coloured and empyreuma- 

 tic. Being subjected to the same trials as the preceding, simi- 

 lar appearances were observed. 



These experiments leave no doubt of the presence of acetic The acetic 



acid in galls: they prove, that it may be obtained by distilla- aci " 



lion with water; and that caloric, when it acts more directly D y means of 



jon this acid, facilitates its combination with a small quantity caloric is com- 



... , , ..... • , binedXVith an 



■of empyreumatic oil, and perhaps with a little tanuin, the empyreumat j C 



presence of which is not demonstrable by glue: but as this oil, and per- 

 ' r ... , , haps tannm, 



liquor acts on sulphat ot iron in the same manner as the sub- ' . 



F 2 Ume.d 



