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XL. Facts for a Hislonj of the Gallic Acid. By 

 M. Bouillon-Lagrange*. 



vJf all the vegetable acids, the gallic acid may be regarded 

 as that which presents most interest ; it has therefore been 

 the object of the inquiries of several chemists. Macquer, 

 Monnet, Lewis, Cartheuser, and Gioanctti, have pointed 

 out the method in which substances called astringents ope- 

 rate upon solutions of iron. The academicians of Dijon 

 were the first to ascertain the presence of an acid in these 

 substances; and in 1772 they showed that the products di- 

 stilled Irom gall-nuts blackened the solution of sulphate of 

 iron, and that its infusion reddened turnsole tincture. These 

 details were as yet nolliirig more than a general proof of the 

 acid nature of the principle of gall-nuts, but they did not 

 furnish the means of extracting and obtaining this acid se- 

 parately ; it is to Scheele we owe this discovery. His pro- 

 cess was published in 17S0. M. Deyeux, some years af- 

 terwards, (in 1793,) discovered that this acid might be ob- 

 tained by sublimation. Messrs. Berthollet and Proust af- 

 terwards added bv their researches to the knowledge we pos- 

 sessed already of the properties of tljis acid ; so that we may 

 now regard it a') one of the best known vegetable acids. 



Several foreign chemists have also given, Vv'ilhin these few 

 years, processes for the extraction and purification of this 

 acid : but none of them, M. Richter excepted, have rivalled 

 M. Scheele's. Among the number of experiments which 

 chemists have made upon this subject, there is one which I 

 have never seen either quoted or refuted in the various me- 

 moirs published upon the gallic acid. 



We found in a letter of M. G. Charles Bartholdi to 

 M. Berthollet, iu the year 1792, some facts which deserve 

 attention. 



M. Bartholdi first points out a process for obtaining pure 

 gallic acid ; he afterwards treats this acid with metallic ox- 

 ides. The author informs us that all the bodies which give 

 up oxygen to the gallic acid make its colour brown ; that, 



* From yltmuUs Je Chimic, torn. Ix. p. l.'^G. 



Vol. 28. No. 112. Sept. I807. T in, 



