372 
Assay  of  Belladonna  Root. 
[  A.m.  Jour.  Phurm. 
I      August,  1908. 
By  dividing  the  number  of  cubic  centimeters  of  fiftieth-normal 
sulphuric  acid  used  by  the  number  of  cubic  centimeters  of  approxi- 
mately fiftieth-normal  potassium  hydrate  required,  a  correction  is 
obtained  for  the  potassium  hydrate  solution.  Multiply  this  correc- 
tion by  the  number  of  cubic  centimeters  of  potassium  hydrate  solu- 
tion used  in  the  alkaloidal  tritration  to  find  the  number  of  cubic 
centimeters  of  fiftieth-normal  potassium  hydrate  used. 
Subtract  this  amount  from  the  number  of  cubic  centimeters  of 
fiftieth-normal  sulphuric  acid  used.  Divide  this  number  by  5  to 
get  in  terms  of  tenth-normal  solutions,  and  multiply  by  0-0287,  and 
then  by  10,  and  the  result  will  be  the  percentage  of  mydriatic  alka- 
loids present. 
COMPARISON  OF  METHODS. 
Dr.  Enoch's  method  gives  results  that  can  be  duplicated  easily. 
It  also  has  the  great  advantage  that  it  may  be  quickly  carried  out. 
In  our  experience  the  results  have  always  been  higher  than  the 
same  sample  by  the  U.S.P.  method ;  but  Dr.  Enoch  says  that  there 
is  more  chance  for  loss  in  the  U.S.P.  method,  which  is  true.  The 
end  point  in  his  method  seems  to  be  carried  too  far.  We  have  found 
that  different  indicators  play  an  important  part  in  the  results  ob- 
tained, and  for  that  reason  we  have  adopted  the  colorimetric  titration 
as  given  above.  It  must  be  remembered  that  Dr.  Enoch  gives 
specific  directions  to  thoroughly  dry  the  root  before  beginning  the 
assay.  The  U.S.P.  makes  no  specific  provision  for  this  additional 
drying,  and  as  belladonna  root  will  usually  lose  about  10  per  cent, 
in  additional  drying,  this  must  be  taken  into  consideration. 
The  above  was  sent  to  Dr.  Enoch  for  correction  and  for  further 
suggestions  in  regard  to  his  method,  and  in  reply  the  following 
comments  were  made  by  him : 
(1)  It  is  important  in  drying  the  drug  previous  to  assay  that  the 
temperature  is  not  raised  above  8o°  C,  as  below  that  temperature 
there  is  no  loss  of  alkaloid. 
(2)  For  each  titration,  1  to  3  c.c.  of  tenth-normal  hydrochloric 
acid  are  used.  The  exact  observation  of  the  streaks  is  the  only  and 
best  way  to  determine  the  end  point  in  the  titration. 
(3)  The  end  point  in  Dr.  Enoch's  method  is  not  carried  too  far, 
but  is  absolutely  correct,  which  you  can  see  by  making  the  same 
