METHOD OF PREPARING GALLIC ACID. 



XVII. 



A Nov Method of preparing the pure Gallic Acid. 



By M. L. SCHNAUBERT *. 



Preparation of J^ OUR ounces of finely powdered galls are infufed in water 

 flightly alkalized with potafh ; the infufion which is of a very 

 deep colour is filtered, and a folution of nitrate of tin is 

 dropped into it, until no more precipitate is formed. The 

 irGQ acid of the liquid is then faturated with potafli, taking 

 care not to add the alkali in excefs, and the precipitate is 

 fcparated by filtration. The filtered liquid is then precipi- 

 tated by acetite of lead, the weight and concentration of 

 which is known. A greyifli white precipitate is thus ob- 

 tained, which is to be digefled with diluted fulphuric acid, 

 the proportion of the acid contained in which, mud be to the 

 concrete acetite of lead as one to four. After a fufficient 

 digeflion, the liquid is carefully filtered. and evaporated, in 

 order to afford cryfials. If the gallic acid thus obtained, 

 lliould contain a fniall quantity of fulphuric acid, it may be 

 deprived of it by digefiion, with gallate of lead. 



In order to be certain of the quantity of fulphuric acid 

 neceffary for the decompofition of a given quantity of gallate 

 of lead, I previoufly diflolved four ounces of acetite of lead 

 in lixteen ounces of water, and diluted one ounce of fulphuric 

 acid in four ounces of water. By mixing thefe two liquids 

 to afiford the perfe6l precipitation, the requifite proportion 

 was eaiily found, I muft here obferye, that it will be better 

 to keep the gallic acid in a liquid ftate than to reduce it to 

 cryfials, becaufe evaporation always renders it more or lefs 

 brown, I am firmly perfuaded that the gallic acid poflefies the 

 property of becoming brown by the adion of light, at leaft, 

 if in contaft with the atmofphcre. For if gallic acid be fiib- 

 limed perfe611y white, and theji diflolved in water, it will 

 be found after fome time to have undergone this kind ot 

 alteration. M. Bucholt has made a fimilar remark relative 

 to the fame fad. 



* TromfdorfF's Journal der Pharmacie, vol, ii. p. 6U 



SCIENTIFIC 



