258 
GALLIC  ACID  FROM  CHINESE  GALL-NUTS. 
Thus,  after  washing  the  iodized  benzine  repeatedly  in  distilled 
water,  I  take  it  up  in  a  pipette,  and  introduce  it  into  a  corked 
tube,  in  which  I  agitate  it  in  contact  with  a  few  drops  of  a  solu- 
tion of  nitrate  of  silver  or  with  a  known  quantity  of  mercury,  until 
the  liquid  is  completely  decolorized. 
In  the  first  case,  the  yellow  precipitate  of  iodide  of  silver  is  washed 
with  alcohol  of  0.86  spec,  grav.,  thrown  on  a  filter,  and  treated 
like  chloride  of  silver  which  it  is  intended  to  weigh. 
In  the  second,  the  mercury  is  shaken  with  the  iodized  solution, 
and  the  augmentation  of  its  weight  determined.  These  results  may 
be  checked  by  dissolving  the  protiodide  of  mercury  formed  in  an 
excess  of  iodide  of  potassium. 
Bromine,  and  bromides  to  which  dilute  nitric,  nitrous  or  muriatic 
acids  have  been  added,  do  not  communicate  any  color  to  benzine  ; 
the  same  is  the  case  with  chlorine  and  chlorides.  The  bromine  and 
chlorine  remain  dissolved  in  the  water  which  serves  to  wash  the 
benzine  ;  they  may  be  separated  in  the  form  of  a  white  precipitate 
by  nitrate  of  silver.  Benzine,  taking  up  iodine  without  possessing 
the  property  of  dissolving  either  bromine  or  chlorine,  enables  us 
therefore  to  separate  iodine  perfectly  from  those  two  bodies,  and  to 
prove  in  a  precise  manner  the  presence  of  chlorides  or  bromides 
in  commercial  iodide  of  potassium. — Chem.  Gaz.y  Feb.  15,  1853, 
from  Comjrtes  Rendus,  Nov.  29,  1852. 
ON  THE  PREPARATION  OF  GALLIC  ACID  FROM  CHINESE 
GALL-NUTS. 
By  Dr.  G.  C.  Wittstein. 
The  low  price  of  Chinese  gall-nuts  and  the  larger  quantity  of 
tannic  acid  which  they  contain,  induced  the  author  to  employ  them 
as  a  source  of  gallic  acid.  Having  found  as  the  result  of  repeated 
trials  that  of  the  two  methods  of  preparation,  viz.,  precipitating 
the  aqueous  decoction  with  sulphuric  or  hydrochloric  acid,  or  al- 
lowing the  powdered  gall-nuts  made  into  a  paste  with  water  to 
undergo  a  species  of  fermentation,  the  latter  furnished  a  much 
larger  product,  he  adopted  this  method,  notwithstanding  the  length 
of  time  it  requires.  The  first  result  was,  however,  unfavorable. 
At  the  end  of  six  weeks  he  found  that  the  mass  had  still  a  very 
astringent  taste,  the  filtered  liquid  gave  a  copious  precipitate  with 
