CHEMICAL  COMPOSITION  OF  GELSEMIUM  SEMPERVIRENS.  3 
rate  spontaneously,  the  gelseminic  acid  will  be  left  chiefly  in 
the  form  of  nearly  colorless  groups  of  crystals,  of  the  forms 
illustrated  in  plate,  fig.  1,  together  with  more  or  less  yellowish 
or  brownish  resinous  matter.  The  crystals  may  be  washed  with 
a  small  quantity  of  cold  absolute  alcohol,  which  will  readily  dis- 
solve the  adhering  coloring  matter  without  acting  much  upon  the 
crystals  themselves.  The  alcohol  thus  employed  may  be  evapo- 
rated spontaneously,  when  a  second  crop  of  crystals  will  be  ob- 
tained ;  these  are  also  washed  with  alcohol  and  added  to  the 
former  crystals.  To  further  purify  the  crystals,  they  are  dif- 
fused in  a  small  quantity  of  hot  water  and  extracted  from  the 
cooled  mixture  by  chloroform,  which  on  spontaneous  evaporation 
will  leave  them  very  nearly  or  altogether  colorless. 
To  recover  and  purify  the  gelseminic  acid  taken  up  and  held 
in  solution  by  the  alcohol  employed  to  wash  the  above  crystals, 
the  liquid  is  evaporated  to  dryness  and  the  residue  treated 
with  a  small  quantity  of  water,  and  sufficient  caustic  potash 
added  to  just  neutralize  the  liquid,  by  which  the  organic  acid 
will  be  dissolved  in  the  form  of  a  salt  of  the  alkali.  This  solu- 
tion is  filtered,  the  filtrate  treated  with  slight  excess  of  basic 
acetate  of  lead,  and  the  precipitate,  consisting  of  the  gelsemi- 
nate  of  lead,  collected  on  a  filter  and  washed.  The  washed 
residue  is  diffused  in  an  appropriate  quantity  of  water  and 
treated  with  excess  of  sulphuretted  hydrogen  gas,  which  will 
decompose  the  lead-salt  with  the  precipitation  of  the  metal  as 
sulphuret  and  the  elimination  of  the  organic  acid.  This  mixture 
is  heated  to  about  the  boiling  temperature,  to  dissolve  the  or- 
ganic acid,  and  filtered  while  still  hot,  and  the  residue  washed 
with  a  little  alcohol,  which  is  collected  with  the  first  filtrate. 
The  filtrate  may  now  be  concentrated  and  the  organic  acid  ex- 
tracted by  chloroform,  which  on  spontaneous  evaporation  will 
leave  it  in  its  crystalline  state. 
As  the  average  of  several  experiments,  after  the  above 
method,  sixteen  ounces  of  the  fluid  extract  of  gelsemium  yielded 
about  two  grains  and  a  quarter  of  pure  gelseminic  acid. 
Chemical  Properties. — In  its  pure  state,  gelseminic  acid  is  a 
colorless,  odorless,  nearly  tasteless  solid,  which  is  readily  crys- 
tallizable,  usually  forming  groups  or  tufts  of  delicate  needles.  It 
