500  Acidimetric  Estimation  of  Alkaloids.     {A  ccfSber.Pi«95ri°" 
litmus  and  phenolphthalein  in  titrating  the  alkaloids  of  belladonna. 
From  the  contributions  of  O.  Schweissinger,9  who  used  cochineal  as 
indicator,  E.  Dieterich10  and  P.  C.  Plugge,11  dates  the  impetus  titra- 
tion of  alkaloids  with  volumetric  acid  solutions  received  at  the 
beginning  of  the  present  decade. 
The  method  had  been  gaining  ground  rapidly  when  several  most 
valuable  communications  appeared  by  C.  C.  Keller,12  of  Zurich, 
since  which  gigantic  strides  have  been  taken. 
In  volumetric  analysis  the  first  question  demanding  attention  is  a 
suitable  indicator  of  delicate  end  reaction.  The  objecta  of  this  com- 
munication is  to  present  the  results  of  a  study  of  five  indicators  in 
titrating  alkaloids,  thinking,  perhaps,  it  might  be  of  some  service  in 
formulating  systematized  methods  of  analysis  in  alkaloidal  chem- 
istry. The  discordant  results  of  analysis  often  obtained  by  different 
chemists  operating  on  the  same  sample  are  greatly  to  be  regretted. 
It  is  the  writer's  candid  opinion  that  the  discrepancies  are  chiefly 
due  to  differences  in  modus  operandi,  defective  apparatus,  and  in 
volumetric  analysis  different  end  reaction  tints,  arbitrarily  assumed 
by  each  worker. 
In  order  to  eliminate  the  factors  of  uncertainty  as  completely  as 
possible,  the  methods  of  operation  were  carefully  written  out  and 
closely  adhered  to  in  all  the  work.  The  burettes  and  a  pipette  were 
carefully  calibrated  in  order  to  ascertain  the  necessary  factor  for 
correction.  The  method  of  calibration  was  as  follows :  each 
burette  and  pipette  was  exactly  filled  to  the  zero  mark  with  dis- 
tilled water,  at  150  C,  and  10  c.c.  delivered  into  a  tared  weighing 
flask  and  weighed  ;  then  the  next  10  c.c.  were  treated  in  the  same 
manner,  and  so  on  until  the  entire  capacity  of  each  was  tested.  A 
glass-stoppered  cylinder  was  also  standardized.  All  efforts  to  stand- 
ardize a  litre  flask  were  thwarted.  A  large  balance,  sufficiently 
sensitive  to  do  the  work  satisfactorily,  could  not  be  found. 
In  titration  the  personal  equation  plays  an  important  part. 
Authorities  are  not  agreed  on  end  reaction  tints,  each  operator 
relying  on  his  own  judgment.  The  writer  thinks  it  correct  to 
titrate  to  the  point  where  a  different  color  from  the  initial  one  is 
developed.    In  order  to  obtain  standard  end  reaction  tints,  it  will 
a  Alkaloids,  generally,  are  neutral  to  phenolphthalein,  consequently  it  can- 
not be  employed  in  titrating  alkaloids  directly.  It  is  available  for  indirect 
titrations,  i.  e.,  estimating  the  amount  of  acid  combined  with  an  alkaloid  in  its 
neutral  salts. 
