f 
ACTIVE  PRINCIPLE  OF  RHUS  TOXICODENDRON.  11 
• 
leaves  must  expel  a  great  portion  of  the  volatile  poison ;  but  in 
the  course  of  his  analysis,  he  has  removed  it  from  the  ethereal 
liquid  by  distillation  and  evaporation  with  water,  and  if  any 
should  have  been  left  in  the  then  resulting  aqueous  solution,  it 
was  precipitated  by  sugar  of  lead,  and  may  have  been  regarded 
as  phosphoric  acid,  or  may  have  been  mixed  with  the  peculiar 
tannate  of  lead. 
Not  having  the  original  paper  at  hand,  I  cannot  positively 
speak  on  this  point,  or  on  the  method  employed  which  satisfied 
him  at  the  start  that  the  plant  contained  a  volatile  alkaloid. 
But  I  must  reiterate  that,  by  his  method,  I  could  not  obtain 
it.  The  juice,  however,  contains  notable  quantities  of  ammonia 
salt,  which  are  not  only  shown  on  the  distillation  with  potassa 
or  lime. 
If  the  juice  is  expressed  with  the  previous  addition  of  a  little 
water  to  the  leaves,  and  then  more  acidulated  with  nitric  acid, 
phospho-molybdic  acid  produces  a  yellow  precipitate  which 
was  treated  with  soda,  the  distillate  neutralized  by  sulphuric 
acid,  and,  after  evaporation,  treated  with  alcohol  and  ether ;  the 
residue  from  their  evaporation  was  minute,  and  no  alkaline 
reaction  of  the  vapors,  when  treated  with  a  fixed  alkali,  could 
be  observed ;  but  the  acidulated  solution  yielded  a  faint  tur- 
bidity with  phospho-molybdic  acid ;  none  with  iodohydrargy- 
rate  of  potassium. 
The  expressed  and  acidulated  juice  gave  no  reaction  with 
Mayer's  test,  except  after  rendering  it  alkaline  by  potassa,  the 
behaviour  of  ammonia. 
The  residue  in  the  retort,  after  the  distillation  of  toxicoden- 
dric  acid,  behaved  exactly  like  the  juice.  The  excess  of  sul- 
phuric acid  was  removed  by  neutralizing  with  bicarbonate  of 
potassa,  mixing  with  twice  its  bulk  of  strong  alcohol,  and  dis- 
tilling the  alcohol  from  the  filtrate,  when  it  was  tested  with 
both  Sonnenschein's  and  Mayer's  reagents  with  the  same  re- 
sults. 
The  question  which  I  accepted  is  only  partially  answered ;  I 
have  merely  proved  that  the  poisonous  properties  of  Khus 
Toxicodendron  do  not  reside  in  a  volatile  alkaloid,  but  that 
they  are  due  to  a  volatile  acid.  If  I  state  that  the  dried  leaves 
