CHEMICAL  COMPOSITION  OF  GELSEMIUM  SEMPERVIRENS.  7 
forms  illustrated  in  plate,  figs.  3,  4  and  5,  their  exact  character 
depending  on  the  relative  amount  of  substance  present  and  the 
temperature  employed.  For  the  success  of  this  experiment  it 
is  necessary  that  only  a  very  minute  quantity  of  the  organic 
acid  be  employed.  The  yuo^^  ^  grain  of  the  acid  will  furnish 
quite  a  number  of  fine  crystalline  sublimates.  Very  satisfactory 
sublimates  may  be  obtained  from  the  acid,  even  when  contami- 
nated with  comparatively  large  quantities  of  foreign  organic 
matter. 
The  true  nature  of  the  gelseminic  acid  sublimate  may  be  es- 
tablished by  treating  it  with  a  drop  of  water  containing  a  trace 
of  ammonia,  when  it  will  dissolve  to  a  solution  having  the  optical 
properties  already  described.  So,  also,  its  nature  may  be  de- 
termined by  dissolving  it  in  a  small  drop  of  nitric  acid  and  then 
adding  to  the  yellow  solution  an  excess  of  ammonia,  when  a  deep 
or  orange-red  coloration  will  manifest  itself. 
Reactions  of  Solutions  of  G-elseminic  Acid. — Solutions  of  the 
salts  of  gelseminic  acid  have  a  slightly  astringent  taste  and  are 
colorless,  excepting  an  alkali  be  present,  when,  as  already 
pointed  out,  they  present  a  bluish  appearance.  They  are  readily 
decomposed  by  free  acids,  with  the  elimination  of  the  organic 
acid,  which,  if  the  solution  contains  -^^th  or  more  of  its  weight 
of  the  acid,  separates  in  the  form  of  delicate  crystalline  needles. 
Since  the  gelseminates  of  the  metals  proper  are  nearly  all 
insoluble  in  water,  the  acid  is  precipitated,  from  its  combinations 
with  an  alkali,  by  solutions  of  most  of  the  metallic  salts,  being 
thrown  down  in  the  form  of  a  salt. 
1.  Acetate  of  Lead  throws  down  from  solutions  of  the  acid  a 
yellow  amorphous  precipitate,  which  is  readily  soluble  in  free 
acids,  even  in  acetic  acid,  with  the  separation  of  the  organic 
acid,  yio*^  ^  grain  of  the  acid  in  one  grain  of  water,  yields 
with  the  reagents  a  very  copious  deposit ;  touo^^  grain  gives  a 
very  decided  precipitate. 
2.  Corrosive  Sublimate  produces  in  solution  of  the  acid  a 
yellowish  filmy  precipitate.  After  a  little  time,  at  least  when 
from  tolerably  strong  solutions,  the  precipitate  becomes  partly, 
at  least,  converted  into  colorless  crystalline  needles,  plate,  fig. 
6,  due  perhaps  to  the  separation  of  the  organic  acid.    The  pre- 
