fir* HISTORY OV THE GALLIC ACID. 



ana with aro- li mc d acid, we must presume, that there is a kind of analogy 

 rteadof^mpy- in their composition; admitting however this difference, that 

 muriatic, when tho sublimed ac'd contains no empyreumatic oil, but a partU 

 sublimed. cular aroma|ic vo i a tile oil. 



The oil shown. rp^ q jj mR y ^ detected by dissolving the acid in very pur« 

 sulphuric ether, and adding a little water, when a few drops of 

 oil will be seen floating on the surface, which disappear on 

 shaking the mixture, 

 eaustic potash. 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 dissolve it, but the li- 

 quor still remains turbid. 



The ethereal This ethereal tincture yields a fine blue colour with sulphat 

 tincture, - . 



ot iron. 



and its reti- Evaporated in the open air it leaves a shining substance, 



▼ery acid, separating in scales, and having the appearance of a 



▼arnish. 



The same phenomena take place, if galls be digested in 



•ther : but the substance contains tannin in addition. 



Examination of some earthy and alkaline gallats. 



Farther proofs Though it appears to be demonstrated, that acetic acid ex- 

 of acetic acid \ s ^ s re ady formed in galls wc cannot too much multiply proofs 

 in confirmation of its presence ; and to demonstrate, that this 

 acid, combined with other substances, constitutes the gallic 

 acid. 

 by forming dif- With this view I formed gallats of lim<r, barytes, potash, and 

 fereot gallats. so da. These neutral combinations afforded a violet red colour 

 with a solution of sulphat of iron, and scarcely precipitated glue 

 while the acid employed had the property of forming with it a 

 copious precipitate. On these salts dried I poured some very 

 weak sulphuric acid ; I distilled them with a gentle heat, and I 

 always obtained acetic acid. 

 The residuum The retorts contained a very deep brown matter. I crystal- 

 afford do proof li ZC( i the salts that were preceptible of it, and obtained sulphats. 

 The supernatant mother-water had the property of slightly 

 browning the solution of sulphat of iron; but this appearance 

 does not prove the presence of gallic acid, for the black colour 

 of the mother-water was sufficient to give it this hue. 



If 



of a gallic acid. 



