PREPARATION  OF  PHYSOSTIGMIN. 
335 
which  contains  a  colorless,  inactive,  ethereal  oil,  while  the  other, 
of  a  dark  red  color,  is  an  aqueous  solution  of  the  sulphate  of 
physostigmin.  The  latter,  carefully  separated  by  a  pipette 
from  the  ether,  is  precipitated  with  magnesia,  and  the  alkaloid 
extracted  by  the  smallest  possible  quantity  of  ether:  finally  the 
ethereal  solution  is  evaporated  to  dryness. 
Physostigmin  is  thus  obtained  as  a  brownish-yellow  amorphous 
mass,  appearing  in  the  first  place  in  oily  drops.  It  is  rather 
easily  soluble  in  ammonia,  solution  of  soda,  ether,  benzine  and 
alcohol ;  less  soluble  in  cold  water.  It  is  completely  removed 
from  its  ethereal  solution  by  animal  charcoal.  The  aqueous  so- 
lution possesses  a  slightly  burning  taste,  is  decidedly  alkaline, 
and  gives  with  the  iodo-hydrargyrate  of  potassium  a  r  ich  kermes- 
colored  precipitate,  and  with  chloride  of  iron  a  precipitate  of 
hydrated  oxide  of  iron.  Heated  with  caustic  potassa  it  yields 
strongly  alkaline  vapors.  Acids  dissolve  it  very  readily,  and 
afford  solutions  which  are  mostly  of  a  dark  red,  seldom  of  a  dark 
blue  color,  which  become  colored  more  or  less  by  sulphuretted 
hydrogen. 
The  muriate,  sulphate,  and  acetate  of  physostigmin  have 
been  obtained  so  far  only  as  red  amorphous  masses,  which  are 
readily  soluble  in  water  and  alcohol. 
The  salts  of  physostigmin  gave  with  tannic  acid  a  consider- 
able amount  of  a  reddish  white,  amorphous,  flocculent  precipi- 
tate, soluble  with  difficulty  in  hydrochloric  acid;  with  chloride 
of  platina,  a  light  yellow  amorphous  precipitate,  slightly  soluble 
in  hydrochloric  acid  and  boiiing  water  ;  with  chloride  of  gold,  a 
blue  precipitate  in  large  amount:  after  a  short  time  the  gold 
separated,  while  the  solution  became  of  a  purple  red  color.  Sul- 
phuretted hydrogen  decolorized  the  solution.  With  bichloride 
mercury,  a  reddish  white  amorphous  precipitate,  slightly  bcluble 
in  hydrochloric  acid. 
The  extremely  small  amount  of  alkaloid  obtained  from  21 
beans  precluded  any  analysis  of  it. 
By  experiments  upon  rabbits,  we  have  ascertained  that  physo- 
stigmin is  the  active  principle  of  the  bean.  Two  drops  of  the 
aqueous  solution  of  the  alkaloid,  placed  in  the  eye,  caused  the 
pupil  to  contract  in  about  ten  minutes  to  ^th  its  natural  size, 
and  it  remained  in  this  condition  nearly  an  hour.    After  five  or 
