45$  Toxic  Principle  of  Pyrethrum  Flowers.  {Am'sllf;S^vm 
evaporated.  The  residue  treated  with  water  and  ether  under  suit- 
able conditions  yielded  the  toxic  acid  as  an  amorphous  and  hygro- 
scopic mass.  In  order  to  obtain  the  inactive  acid  in  a  pure  state  the 
impure  acid  was  taken  up  with  water,  and  the  solution  allowed  to 
stand  twenty-four  hours ;  then  it  was  shaken  with  ether  to  remove 
a  resinous  matter,  filtered  and  evaporated.  The  residue  again  taken 
up  with  water  and  the  solution  filtered  and  evaporated  gave  the 
acid  in  a  pure  condition. 
The  acid  nature  of  the  active  principle  having  been  thus  estab- 
lished, it  was  sought  to  isolate  it  by  converting  it  into  a  lead  salt, 
and  for  this  purpose  an  alcoholic  solution  of  it  was  precipitated  suc- 
cessively with  neutral  lead  acetate  and  triplumbic  acetate.  The 
two  precipitates,  well  washed,  were  suspended  in  alcohol  and  treated 
separately  with  sulphuretted  hydrogen ;  after  filtration  the  solutions 
were  saturated  with  caustic  potash,  evaporated  to  dryness,  redis- 
solved  in  acidulated  water  and  the  solutions  shaken  with  ether.  In 
this  way  were  obtained  a  non-toxic  acid,  corresponding  to  the  pre- 
cipitate thrown  down  by  the  neutral  acetate,  and  another  acid,  cor- 
responding to  the  precipitate  by  the  tribasic  acid,  which  inconve- 
nienced insects  only,  without  killing  them.  The  toxic  principle 
appeared  to  have  escaped  during  this  mode  ot  operating. 
Another  method  was  therefore  tried,  consisting  in  treating  the 
chloroformic  extract  first  with  water  to  remove  the  inactive  extract, 
then  with  five  successive  quantities  of  dilute  alcohol,  increasing  in 
alcoholic  strength  from  one  part  in  ten  to  five  in  ten.  These  alco- 
holic solutions  contained  the  whole  of  the  toxic  principle.  They 
were  mixed  together,  neutralized  exactly  with  caustic  potash  solu- 
tion and  evaporated  carefully  to  dryness.  The  residue  was  taken  up 
with  water  and  the  solution  filtered,  which  took  some  time.  The  clear 
liquor  was  then  shaken  with  a  solution  of  tartaric  acid  in  a  separating 
funnel,  and  then  with  ether.  The  supernatant  layer,  filtered  and 
evaporated,  left  an  acid  and  poisonous  greenish  residue  of  "  pyre- 
throtoxic  acid."  The  lower  layer,  which  had  already  been  shaken 
with  ether,  was  again  treated  with  chloroform,  which  also  took  up  a 
certain  quantity  of  the  toxic  principle. 
En  resume,  the  active  principle  of  pyrethrum  flowers  is  an  acid 
soluble  in  alcohol,  amylic  alcohol,  ether  and  chloroform,  which  may 
be  isolated  by  means  of  ether  after  having  been  converted  into  an 
alkaline  salt  and  decomposed  by  tartaric  acid  in  aqueous  solution. 
