164 
Canaigre  Tannin. 
Am.  Jour.  Pharm. 
April,  1893. 
the  lead  precipitate  with  both  water  and  water  containing  lead 
acetate  and  decomposing  the  precipitate  with  hydrogen  sulphide 
but  several  lots  so  treated  were  found  to  afford  comparatively 
smaller  quantities  of  tannin,  not  in  any  way  superior  to  that 
obtained  above. 
It  was  noticed  during  the  progress  of  the  latter  work,  that  if  a 
solution  of  the  tannin  possessing  a  red  color  was  precipitated  by 
lead  acetate  and  the  unfiltered  mixture  thoroughly  saturated  with 
hydrogen  sulphide,  upon  filtering,  a  much  lighter  colored  filtrate 
was  obtained,  thus  showing  lead  sulphide  to  be,  under  these  condi- 
tions, a  good  decolorizing  agent.  Some  of  the  original  water  per- 
colate was  saturated  with  sodium  chloride,  the  precipitate  collected 
by  filtration,  dissolved  in  commercial  ether  and  the  solution  dis- 
tilled to  dryness  under  diminished  pressure,  a  porous  red-brown 
residue  being  obtained.  It  was  only  partly  soluble  in  cold,  but  com- 
pletely in  hot,  water. 
The  filtrate  from  the  precipitate  caused  by  sodium  chloride  was 
shaken  with  acetic  ether  which  removed  a  small  amount  of  tannin 
much  lighter  in  color  than  that  thrown  out  by  sodium  chloride.  It 
was  readily  soluble  in  cold  water. 
Another  portion  of  the  original  water  percolate  of  the  root  was 
agitated  with  acetic  ether  without  previously  decolorizing  by  lead 
acetate.  The  substance  removed  was  reddish-brown  in  color.  This 
was  dissolved  in  commercial  ether  and  the  solution  so  obtained  dis- 
tilled under  reduced  pressure  in  order  to  remove  the  acetic  ether 
and  render  the  substance  porous.  This  residue  was  dissolved  in 
water.  The  dense  solution,  uppn  standing  in  a  cool  room,  separated 
a  crop  of  yellow  crystals.  These  were  obtained,  recrystallized  from 
alcohol,  in  feathery  forms  composed  of  transparent  yellow  crystals 
which  gave  the  reactions  of  protocatechuic  acid. 
Upon  longer  standing,  the  watery  liquid  deposited  more  crystals, 
square  shaped  and  larger  than  above,  but  owing  to  the  difficulty  of 
completely  separating  adhering  tannin,  these  were  not  obtained  so 
pure  as  were  the  first.  However,  from  general  behavior,  they  were 
suspected  to  be  chrysophanic  acid,  or  perhaps  emodin — since  the 
latter  has  been  found  in  the  root. 
Another  portion  of  canaigre  was  percolated  with  petroleum  ether 
to  ascertain  if  the  yellow  coloring  matter  could  be  removed  by  that 
solvent.    Besides  chlorophyll,  fat,  and  the  small  amount  of  the 
