^Sus^^}  Assay  of  Belladonna  Root,  371 
meyer  flask  and  then  transferring  to  a  small  percolator,  as  directed 
by  the  U.S.P.,  the  ground  drug  is  put  in  the  percolators,  together 
with  the  menstruum,  and  macerated  for  one  hour,  shaking  at  frequent 
intervals.  When  ready  for  percolation  the  percolator  is  placed  so 
that  the  percolate  will  flow  into  separator  B}  Fig.  2. 
The  rate  of  flow  of  the  percolate  can  be  easily  regulated  with 
stop-cock  C,  which  is  a  distinct  advantage  over  the  U.S.P.  method, 
as  the  drug  requires  no  packing. 
The  shaking  out  with  acid  solution  and  with  chloroform  is  carried 
out  as  directed  by  the  U.S. P.;  but  instead  of  combining  the  three 
chloroformic  solutions  and  then  evaporating,  each  one  is  evaporated 
separately  as  soon  as  it  is  drawn  off.  By  so  doing,  all  ammonia  held 
by  the  chloroform  solution  is  driven  off.  Due  care  is  exercised  at 
each  step  in  the  shaking-out  process,  to  insure  complete  separation 
of  the  solutions.  The  last  chloroformic  solutions  are  filtered  either 
through  a  pledget  of  cotton  placed  in  the  stem  of  the  separatory 
funnel  or  through  a  filter  into  an  evaporating  dish. 
For  the  titration  a  low  form  of  evaporating  dish  is  more  conve- 
nient than  a  beaker,  as  the  end  reaction  is  more  readily  detected. 
In  order  to  facilitate  the  titration,  we  dissolve  the  alkaloidal  residue 
in  3  c.c.  of  alcohol,  add  the  necessary  amount  of  fiftieth-normal 
sulphuric  acid  volumetric  solution  and  10  drops  of  cochineal  indi- 
cator, and  then  dilute  with  75  c.c.  of  distilled  water.  Dissolving 
the  alkaloidal  residue  in  alcohol  permits  the  use  of  a  fiftieth-normal 
sulphuric  acid  for  titrating,  which  is  advantageous,  as  by  using  a 
weaker  acid  any  possible  error  due  to  the  volumetric  solution 
adhering  to  the  burette  is  diminished. 
Because  it  is  rather  difficult  to  determine  the  end  reaction  when 
using  cochineal  indicator,  on  account  of  the  absence  of  a  distinct 
change,  and  as  it  is  necessary  for  absolutely  accurate  results  to 
have  the  same  end  reaction  in  the  alkaloid  determination  as  that 
obtained  when  standardizing  the  fiftieth-normal  potassium  hydrate, 
we  have  adopted  a  color  comparison  method. 
A  blank  titration  is  made  in  a  white  porcelain  evaporating  dish, 
using  the  same  amount  of  alcohol,  fiftieth-normal  sulphuric  acid, 
cochineal  and  water,  and  titrating  with  approximately  fiftieth-normal 
potassium  hydrate  to  a  definite  color. 
Then  the  alkaloid  containing  solution  in  a  similar  evaporating 
dish  is  titrated  to  the  same  tint  as  that  obtained  in  the  blank. 
