SOLUBILITY  OF  GALLOTANNIC  ACID  IN  ETHER.  337 
ON  THE  DISCREPANCIES  IN  THE  STATEMENTS  OF  PELOUZE 
AND  F.  MOHR,  RESPECTING  THE  SOLUBILITY  OF  GALLOTAN- 
NIC ACID  IN  ETHER. 
By  Professor  Bolley. 
For  the  extraction  of  tannic  acid  from  coarse  gall-nut  powder, 
in  his  "Displacement  Apparatus,"  Pelouze  recommends  the  use 
of  ordinary,  not  absolute,  ether.  The  liquid  which  then  runs 
off,  separates  into  two  layers,  the  lower  of  which  is  thickish, 
while  the  upper  is  mobile  and  less  colored.  The  lower  liquid  con- 
tains the  tannic  acid,  and  is  regarded  by  Pelouze  as  a  solution  of 
tannic  acid  in  water  ;  the  upper  liquid  is  stated  to  be  ether,  hold- 
ing in  solution  small  quantities  of  tannic  acid,  coloring  matter,  &c. 
Mohr,  in  his  commentary  on  the  Prussian  Pharmacopoeia,  de- 
cidedly contradicts  this  statement.  His  view  of  the  matter  has 
found  its  way  into  most  Manuals  of  Chemistry,  articles  in  Chem- 
ical Dictionaries,  &c.,  and  is  generally  received  as  correct.  He 
regards  the  lower  stratum  of  liquid  above-mentioned  as  a  concen- 
trated solution  of  tannic  acid  in  ether  ;  and  the  upper,  as  ether 
which  has  dissolved  only  a  small  quantity  of  tannic  acid.  The 
two  layers,  he  maintains,  are  not  soluble  one  in  the  other.  If 
this  be  so,  it  affords  another  example  of  a  condition  hitherto 
known  to  exist  in  one  instance  only  (^that  of  coniine),  in  which 
the  solution  of  a  body  in  a  certain  solvent  is  not  diluted  by  con- 
tact with  that  solvent.  In  spite  of  this  anomaly,  Mohr's  state- 
ment has  been  adopted  without  experimental  verification.  Mohr 
rests  his  view  on  an  experiment  described  by  himself.  On 
treating  tannic  acid  with  anhydrous  ether,  he  obtained  the 
thickish  layer  already  mentioned,  and  above  it  there  floated 
a  stratum  of  ether,  containing  only  a  small  quantity  of  tannic 
acid. 
I  have  likewise  examined  this  peculiar  phenomenon.  I  find 
that  anhydrous  ether  (previously  decanted  several  times  over 
chloride  of  calcium,  boiling  at  34-9^  C,  and  having  a  specific 
gravity  of  0-724  at  11-25^  C.),  takes  up  but  a  very  small  quan- 
tity of  tannic  acid,  indeed  scarely  any  (0.206  p.  c.  at  C),  while 
the  greater  part  of  the  tannic  acid  remains  in  the  liquid  in  the 
form  of  a  dry  compact  powder.    On  mixing  the  ether  with  half 
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