REMARKS  ON  POLYGALIC  ACID. 
151 
the  same  liquid  until  three  pints  have  slowly  passed  by  drops,  or 
until  the  root  is  nearly  exhausted.  Evaporate  this  tincture  to 
twelve  fluid  ounces,  which  removes  nearly  the  whole  of  the  alco- 
hol, and  then  agitate  it  with  repeated  portions  of  ether,  until 
the  latter  ceases  to  acquire  color,  decanting  each  portion  before 
adding  the  next,  which  requires  about  a  pint  and  a  half.  The 
syrupy  liquid  is  now  mixed  with  a  pint  and  a  half  of  strong 
alcohol,  and  a  half  a  pint  of  ether,  well  agitated  several  times 
and  set  aside  to  repose.  The  polygalic  acid  being  nearly  in- 
soluble in  this  menstruum,  precipitates  as  a  bulky  light  fawn- 
colored  precipitate.  If  on  adding  a  small  portion  of  the  clear 
liquid  to  a  similar  mixture  of  ether  and  alcohol,  no  precipitate 
occurs,  the  whole  of  the  polygalic  acid  capable  of  being  thus 
thrown  down  has  been  separated.  The  supernatant  liquid  is 
now  carefully  decanted  from  the  precipitate,  which  is  thrown  on 
to  a  filter  and  carefully  washed  with  a  mixture  of  two  parts  of 
alcohol  and  one  of  ether,  till  the  adhering  colored  liquid  has  all 
been  displaced.  The  filter  is  then  spread  on  an  absorbent  sur- 
face of  paper,  pressed  strongly,  the  mass  broken  into  small  frag- 
ments, dried,  and  powdered.  The  resulting  powder  weighs  550 
grains,  5 J  per  cent,  of  the  weight  of  the  senega;  making  allow- 
ance for  wastage,  senega  may  be  said  to  contain  one-sixteenth 
of  its  weight  of  this  substance,  and  consequently  thirty  grains 
will  equal  an  ounce  of  the  root. 
In  this  state  polygalic  acid  is  not  pure,  but  is  sufficiently  so 
for  all  medical  purposes.  It  retains  traces  of  coloring  matter, 
and  of  some  substances  which  are  separated  by  the  ether,  but  in 
very  small  amount.  By  re-dissolving  it  in  hot  water,  and  pre- 
cipitating with  the  mixture  of  ether  and  alcohol,  and  afterwards 
dissolving  it  in  hot  alcohol,  with  animal  charcoal,  and  filtering 
hot,  it  is  obtained  quite  white. 
The  ethereal  washing  liquids  first  obtained  were  evaporated  till 
no  ether  remained.  The  residue  consisted  of  a  dark  amber- 
colored  fixed  oil,  admixed  with  crystals  of  virgineic  acid,  which 
formed  a  crust  on  its  surface,  and  a  dense  aqueous  solution  of 
the  same  acid,  which  strongly  affected  litmus  paper. 
The  liquid  from  which  the  polygalic  acid  precipitated  was 
allowed  to  stand  a  month,  when  the  sides  and  bottom  of  the 
vessel  were  spangled  with  a  crystalline  matter,  in  small  quantity. 
