ANALYSIS  OF  THE  LEAVES  OF  POISON-OAK.  543 
The  yellow  lead  precipitate  was  analyzed,  and  found  to  be  a 
tannate  of  lead  of  the  formula  2PbO  +  C18  H14  013. 
The  filtrate  from  the  last  precipitate,  on  nearly  neutralizing 
it  with  ammonia,  threw  down  a  body  of  a  paler  yellow  color 
than  the  previous;  it  contained  68.85  per  cent,  of  oxide  of  lead; 
but  the  elementary  analysis  could  not  be  made,  on  account  of 
the  small  quantity  of  the  material. 
The  last  filtrate  was  entirely  colorless ;  it  was  not  precipitated 
by  subacetate  of  lead,  but  rendered  slightly  turbid  by  ammonia 
in  excess ;  after  being  freed  from  lead,  it  was  evaporated  in  a 
water- bath,  when  it  acquired  a  deep  brown  color  ;  no  sugar  could 
be  detected,  the  organic  matter  must  come  under  the  head  of 
extractive  matter. 
The  greenish  powder  obtained  as  above,  from  the  first  aqueous 
solution,  melted  on  the  application  of  heat  to  a  yellow  liquid, 
was  then  decomposed  with  the  evolution  of  an  aromatic  odor  and 
acid  fumes,  and  burned  without  residue.  It  was  easily  soluble 
in  ether  and  alcohol,  only  slightly  soluble  in  cold  water,  the 
solutions  were  of  neutral  reaction  and  precipitated  white  by 
acetate  of  lead.  The  solution  in  dilute  sulphuric  acid  was  de- 
composed on  standing,  but  no  sugar  could  be  detected.  The 
powder  contained  no  nitrogen. 
The  residue  of  the  aqueous  treatment  of  the  ethereal  extract 
proved  to  be  a  mixture  of  wax  and  fat  colored  by  chlorophyll. 
II.  The  residue  of  the  treatment  with  ether  was  exhausted  by 
alcohol,  and  the  tincture  treated  with  water  as  above,  about 
150  grs.  was  thus  taken  up.  Water  left  a  waxy  matter  behind 
with  traces  of  chlorophyll.  The  aqueous  solution  contained  the 
above  tannic  acid,  producing  with  acetate  of  lead  the  same  yel- 
low precipitate  2PbO,  C18  H14  013.  In  the  filtrate,  Trommer's 
test  indicated  the  presence  of  sugar. 
III.  Cold  water  was  now  used  for  exhausting  the  residue  of 
the  leaves.  After  the  coagulation  of  the  albumen,  the  yellowish 
liquid  filtered  clear ;  was  of  an  insipid,  sweetish  taste,  of  an  acid 
reaction  on  litmus  paper,  acquired  a  golden  yellow  color  by 
ammonia,  a  slight  greenish  coloration  by  sesquichloride  of  iron, 
and  a  dirty  yellow  turbidity  by  acetate  of  lead,  which  was 
partly  dissolved  by  acetic  acid. 
In  the  watery  decoction  of  the  residuary  substance,  the  faint 
