3 
ACTIVE  PRINCIPLE  OF  RHUS  TOXICODENDRON. 
chloride  of  gold,  after  boiling,  a  separation  of  metallic  gold 
adhering  to  the  test  tube  ;  acetate  of  lead,  a  white  precipitate, 
soluble  in  nitric  acid ;  neutral  tersulphate  of  iron,  (I  had  then 
no  neutral  sesquichloride  of  iron  on  hand,)  a  precipitate  of  sul- 
phate of  baryta,  and  apparently  a  slight  red  coloration. 
These  reactions  appeared  to  be  so  nearly  identical  with  those 
of  formic  acid,  that  I  was  almost  satisfied  that  the  dreaded  poison 
of  the  Ehus  Toxicodendron  was  the  same  compound  which  is 
generated  by  the  little  busy  Formica  rufa. 
The  expressed  liquid,  set  aside  as  before  stated,  was  now  sub- 
jected to  distillation,  after  having  been  previously  mixed  with 
an  excess  of  sulphuric  acid.  A  portion  of  the  distillate  was 
again  collected  in  water,  holding  carbonate  of  baryta  in  sus- 
pension ;  another  quantity  was  condensed  by  itself,  to  obtain 
the  pure  acid.  This  acid  had  a  similar  odor,  as  noticed  before, 
but  it  changed  and  disappeared  almost  entirely  on  rectifying 
the  liquid  over  chloride  of  calcium. 
The  acid  solution,  as  thus  obtained,  is  colorless,  strongly 
affects  blue  litmus  paper,  and  neutralizes  bases ;  but  the  salts 
with  the  stronger  bases  show  a  distinct  alkaline  reaction.  Ad- 
ded to  solution  of  acetate  or  subaeetate  of  lead,  the  acid  pro- 
duces a  heavy  white  precipitate,  which  is  scarcely  soluble  in 
boiling  water,  but  readily  soluble  in  nitric  acid ;  with  corrosive 
sublimate  and  bicldvride  of  platinum  no  alteration  takes  place 
even  after  boiling ;  chloride  of  gold  is  in  the  cold  slowly,  at  the 
boiling  heat  rapidly,  reduced,  and  a  film  of  metallic  gold  de- 
posited ;  with  nitrate  of  silver,  no  immediate  alteration  occurred 
in  the  cold,  but  gradually  a  black  precipitate  of  oxide  of  silver 
takes  place,  which  is  produced  in  a  few  minutes,  if  the  mixture 
is  boiled.  This  separation  of  the  oxide  of  silver  must  be  caused 
by  the  mutual  decomposition  of  the  acids,  whereby  the  oxide 
is  liberated ;  for,  if  the  acid  is  boiled  with  pure  oxide  of  silver, 
and  the  solution  filtered  while  hot,  it  retains  the  silver  in  solu- 
tion. A  salt  of  the  new  acid  produces,  in  nitrate  of  silver,  a 
white  turbidity,  changing  to  a  black  precipitate,  on  standing, 
or,  in  a  few  minutes,  on  boiling ;  but  entirely  removable  by  the 
addition  of  nitric  acid. 
Protonitrate  of  mercury  is  not  affected  by  the  pure  acid, 
