458 
THE  PREPARATIONS  OF  CONIUxM,  ETC. 
retort  to  an  evaporating  dish,  and  exposed  to  the  heat  of  a  water 
bath  for  another  hour.  The  syrupy  residue  was  then  mixed  with 
potash,  and  thoroughly  washed  with  aether.  049  gr.  of  conia 
was  obtained,  being  0*11  gr.  less  than  was  obtained  by  the  first 
experiment,  and  less  than  half  of  the  quantity  contained  in  the 
ounce  of  "  succus." 
8.  Exposed  f  3j  of  the  "  Succus  "  upon  a  plate  in  a  glass-house 
with  a  south  aspect,  and  where  the  natural  temperature  ranged 
from  70°  to  90°  F.  After  thirty-four  hours  the  small  syrupy 
residue  was  treated  with  potash  and  washed  with  aether  ;  0*25  of 
a  grain  of  conia  was  obtained. 
Two  facts  appear  from  these  experiments — first,  that  the  act- 
ive principle  of  the  plant  is  to  a  certain  extent  vaporizable  even 
at  a  natural  temperature  of  70°  to  90°  F. ;  and  secondly,  that 
prolonged  exposure  to  a  high  temperature  is  accompanied  by  a 
progressive  diminution  of  the  conia,  the  alkaloid  being  converted, 
as  Dr.  Christison  has  pointed  out,  into  ammonia  and  some  other 
secondary  product. 
Now  the  quantity  of  juice  prescribed  by  the  Pharmacopoeia  for 
conversion  into  extract,  is  about  eight  gallons,  and  the  prolonged 
exposure  to  a  temperature  ranging  from  140°  to  212°  F.,  re- 
quired to  effect  this  process,  is  doubtless  sufficient  to  remove  all 
but  a  trace  of  the  active  principle ;  and  it  is  obvious  from  the 
foregoing  that,  given  an  efficient  juice,  the  power  of  the  extract 
will  be  inversely  proportionate  to  the  bulk  of  the  juice  operated 
upon  ;  hence,  to  obtain  an  extract  of  full  power,  it  will  be  neces- 
sary to  expose  the  juice  in  a  number  of  shallow  dishes,  and  in  a 
layer  not  exceeding  half  an  inch  in  depth,  to  a  rapid  current 
of  dry  air  having  the  temperature  of  150°  F.,  or  thereabouts,  so 
that  the  whole  may  be  reduced  to  the  consistence  of  an  extract 
in  the  course  of  two  or  three  hours.  By  this  means  an  extract, 
containing  1  per  cent,  of  conia  at  most,  may  be  procured.  And 
it  is  extremely  doubtful  whether  a  stronger  extract  can  be  pre- 
pared by  this  or  any  other  process. 
Such  are  the  conclusions  to  which  the  foregoing  experiments 
lead,  and  in  respect  of  the  use  of  the  extract  they  are  important. 
One  fact  is  quite  certain, — viz.,  that  the  power  of  the  extract  has 
been  greatly  over-estimated.    The  present  Pharmacopoeia  (1867) 
