Fads for a HislonJ of the Gallic Add. 69 1 



end of some months the greatest part of the hqiior has eva- 

 porated ; all the precipitates are collected, and cold water 

 poured above them ; thev are allowed to subside, aiid are 

 then decanted : as much hot water is added as is neces- 

 sary for solution ; it is tiltered, and evaporated in a genile 

 heat, and vellow crystals are obtained. 



M. Bartholdi's Process.-^We evaporate the alcoholic 

 tincture of gall-nuts; we afterwards dissolve in disl.lled. 

 water, and add to the solution sulphuric acid until the 

 mixture has actjuired a decidedly acid taste; the extractive 

 matter is precipitated in a few hours; and the supernatant 

 fluid, I'recd from the sulphuric acid by means ot baryies, 

 gives, according to the author, pure gallic acid. 



This process does not present this result. It is generally 

 very difficult to catch the moment when all the acid is taken 

 up by the barytes, considering that it is also combined with 

 gallic acid. Nothing remains after the eva[>oration of the 

 liquor, except a bitter substance, containing a great deal of 

 tannin, aiid which is not susceptible of crysiallizing. 



M. Dei/ei/x's Process. — This ciiennst discovered ihat, by 

 healing slowly and cautiously in a glass retort pounded gall- 

 nuts, there was sublimed a considerable quantity of lamel* 

 lated brilliant crystals. 



M. Rlchter's Proce^y.— ^Digest gall-nuts, reduced into a 

 fine powder, in cold water, taking care to stir the mixture 

 frequently. After some time, the whole is pressed out 

 through a linen cloth ; the residue is mixed once more 

 with water and subjected to the press: the liquors are mixed, 

 and evaporated at a very gentle heat; a blackish brown and 

 very brittle substance is obtained : this substance, when re- 

 duced to a fine powder and digested with very pure alcohol, 

 yields a slight straw colour. The second iniusion is almost 

 colourless ; it leaves a brown residue, which is almost en- 

 tirely pure tannin. These two alcoholic liqu.rs arc nnxed 

 and distilled in a smaii retort to one-eighth. Upon cooling, 

 the liquor Onijicals into a mass ; water is then poured above, 

 and the mixture is slightly heated : we then obtain a clear 

 ind almost colourless solution. 



If we submit ihis solution to evaporation, we may pbtain 

 T 3 Irora 



