4       CHEMICAL  COMPOSITION  OF  GELSEMIUM  SEMPERVIRENS. 
has  strongly  acid  properties,  completely  neutralising  bases  and 
uniting  with  them  to  form  salts,  most  of  which,  excepting  those 
of  the  alkalies,  are  at  most  only  sparingly  soluble  in  water.  The 
salts  of  the  acid  having  an  alkaline  base,  are  very  freely  soluble 
in  water  and  are  crystallisable.  The  pure  acid  is  freely  soluble 
both  in  chloroform  and  in  ether,  but  only  sparingly  soluble 
in  water,  requiring  about  one  thousand  times  its  weight  of  this 
liquid  for  solution.  It  is  much  more  freely  soluble  in  hot  water, 
from  which,  however,  the  excess  immediately  begins  to  separate, 
in  the  form  of  long  slender  needles,  as  the  solution  cools.  Plate, 
fig- 2. 
If  a  small  quantity  of  gelseminic  acid,  or  of  any  of  its  salts 
in  the  solid  state,  be  treated  with  a  drop  of  concentrated  nitric 
acid,  it  dissolves  under  a  yellow  coloration  to  a  yellow,  reddish 
or  red  solution,  the  final  color  depending  upon  the  relative 
quantity  of  the  organic  acid  present.  If  this  solution  be  now 
treated  with  excess  of  ammonia,  it  acquires  a  deep  blood-red 
color,  which  is  permanent,  at  least  for  some  hours,  yioth  of  a 
grain  of  the  acid,  when  treated  after  this  manner,  will  yield  a 
deep  blood-red  coloration  ;  toco*^  grain  yields  a  similar  colora- 
tion. The  To.ooo^h  of  a  grain  of  the  acid  yields,  under  the 
action  of  nitric  acid,  a  well-marked  yellow  coloration,  which 
under  the  action  of  ammonia  assumes  a  pale-red  hue.  The 
nitric  acid  solution  of  even  the  5o,ioo^^  of  a  grain  of  the  organic 
acid  acquires,  when  treated  with  ammonia,  a  distinct  reddish 
coloration.  The  production  of  this  red  coloration  is  highly 
characteristic  of  the  organic  acid. 
Sulphuric  acid  dissolves  the  organic  acid,  as  also  most  of  its 
salts,  under  the  production  of  a  yellow  color,  to  a  brown  or  red- 
dish-brown solution,  which,  upon  the  application  of  a  moderate 
heat,  acquires  a  dark  chocolate  color.  The  addition  of  bichro- 
mate of  potash  to  a  sulphuric  acid  solution  of  the  organic  acid, 
causes  no  striking  change. 
Hydrochloric  acid  has  little  or  no  action  upon  the  organic 
acid. 
Caustic  Potash,  Soda  or  Ammonia,  when  added  to  gelseminic 
acid,  causes  it  to  assume  an  intense  yellow  color,  and  quickly  dis- 
