296 Facts for a History of the Gallic Acid. 



phsnomfjiKin to the state of oxygenation of the iron ; be- 

 cause, with the muriate of iron at the maximum, we have 

 constantly a green colour. This efiect is less remarkable 

 with the two other acids; the cold infusion of gall-nuts al- 

 ways retains its beautiful blue colour. 



With nitrate of mercury the precipitate is blackish ; that 

 by the acetate of lead is fawn-coloured, and very light. 



The sulphates of zinc, copper, and muriate of tin, present 

 no phconomenon. 



Oxymuriatic acid browns the solution of gallic acid, and 

 an excess discolours the licjuor. 



On con)paring the difterences presented by these acids it 

 will be easy to appreciate them. 



The sublimed acid is less acid ; it is decomposed in the 

 air; it has no action upon barytes, upon carbonate of ani- 

 nionia, nor upon muriate of tin. The precipitate obtained 

 with the nitrate of mercury is blackish in place of being yel- 

 low ; that of the acetate of lead is slight and fawn-coloured 

 in place of beiiig" white and abundant. 



Oxynuuiatic acid browns a clear and transparent solution 

 of the sublimed acid, while it does not change the co!;;ur of 

 that of the crystallized acid. 



In short, this acid does not give a constant colour with 

 sulphate of iron, and docs not precipitate glue. 



if it be easy to demonstrate the characters which distin- 

 guish th.cse two acids, it is otherwise when we wish to ex- 

 plain whence their diiference arises. M- Berthollet has well 

 ascertained that the acid of Schee]e, not purified, contained 

 a great deal of tannin ; and he found that when purified by 

 oxide of tin it did not precipitate glue. 



As to M. Richtcr's process, I have pointed out above the 

 analogy it has with Scheclc's acid ; nevertheless these two 

 acii.i5 socm to me to differ from that obtained bv sublima- 

 tion ; tliis last contains a small (luantity of volatile oil, which 

 is combined with it, and which with the help of caloric as- 

 sumes a charactc which relates it to the resinified oils, Wc 

 may ascertain this property by dissolving this sublimed acid 

 cither in ether or in alcohol j if we volatilize the liquid by 



rubbinc; 



