426 
Queries  on  Alkaloidal  Assay. 
f  Am.  Jour.  Pharm. 
\  September,  1911. 
oratory  that  cochineal  is  the  best  indicator  for  all  alkaloidal  titra- 
tions ;  the  men  in  another  laboratory  prefer  the  general  use  of 
iodeosin.  Does  the  indiscriminate  use  of  these  indicators  give  con- 
cordant results  and  would  the  assay  be  considered  as  being  made 
according  to  the  U.  S.  P.  if  an  indicator  not  specified  in  the  particular 
assay  were  used  in  the  titration? 
Color  of  End  Point. — In  all  the  alkaloidal  titrations,  the  U.  S.  P. 
specifies  that  the  standard  solution  should  be  added  until  a  certain 
color  is  obtained.  Owing  to  differences  in  judging  the  end  point 
and  the  absence  of  a  definite  color  standard  a  considerable  variation 
is  to  be  expected. 
Ought  not  the  end  point  of  an  alkaloidal  titration  be  determined 
by  matching  a  certain  color  of  a  standard  chart  under  definite 
conditions  ? 
Blank  Determinations. — To  avoid  the  difficulty  of  judging  the 
color  of  the  end  point  and  to  provide  a  check  on  the  solutions 
being  used  a  blank  determination  is  usually  made  by  the  most 
analysts.  Even  this  method  is  faulty  where  the  alkaloidal  residue 
still  retains  some  color.  Would  it  be  advisable  to  specify  that  a 
blank  test  be  made  with  every  alkaloidal  titration  ? 
Amount  of  Solvent. — Most  practical  analysts  who  are  regularly 
making  alkaloidal  assays  are  agreed  that  insufficient  solvents  are 
specified  for  extraction  of  alkaloids  in  many  of  the  U.  S.  P.  processes. 
For  example,  in  the  assay  of  Nux  Vomica  after  oxidation  of  the 
Brucine  the  quantity  of  chloroform  specified  will  not  leave  the 
supernate  liquid  clear  nor  will  twice  the  specified  quantity  but  by 
repeated  extractions  with  chloroform  the  supernatant  liquid  will 
become  clear.  Is  an  assay  made  in  accordance  with  U.  S,  P.  process, 
when  excessive  quantities  are  used?  If  additional  quantities  of 
solvents  are  allowable,  should  each  extraction  be  made  until  no 
precipitate  is  obtained  with  Mayers'  reagent? 
IdentiUcation  of  Alkaloids. — In  the  determination  of  alkaloids 
from  crude  drugs  the  U.  S.  P.  makes  no  provision  for  the  identifica- 
tion of  alkaloids  extracted.  Would  it  be  advisable  to  insert  identifica- 
tion tests  for  the  alkaloids  after  they  have  been  extracted  and 
estimated? 
Physiological  Tests. — After  the  alkaloids  have  been  extracted 
and  estimated,  would  it  be  advisable  to  insert  physiological  tests 
and  determine  the  minimum  lethal  dose  and  note  the  characteristic 
action? 
