THE  AMERICAN 
JOURNAL  OF  PHAR|^§¥^§^ 
A  METHOD  FOR  THE  ESTIMATION  OF  ANTIPYRINE. 
By  Milton  F.  Schaak,  Ph.G. 
Having  had  occasion  to  determine  the  amount  of  antipyrine  in 
admixture  with  caffeine,  which  had  been  "  shaken  out  "  with  chloro- 
form from  a  proprietary  headache  liquid,  it  was  found  desirable  to 
estimate  the  antipyrine  without  separating  from  the  caffeine.  Ac- 
cordingly, the  following  reaction  was  made  the  basis  of  a  colori- 
metric  method. 
When  sodium  nitrite  is  added  to  an  acidified,  dilute  solution  of 
antipyrine,  a  blue-green  color  is  produced,  which  is  still  perceptible 
in  dilutions  of  I  in  20,000.  In  more  concentrated  solutions,  a  crys- 
talline precipitate  of  the  same  color  is  formed. 
These  results  are  due  to  the  reaction  between  the  liberated 
nitrous  acid  and  the  antipyrine,  by  which  a  compound  is  formed 
that  has  been  shown  to  be  nitroso-antipyrine. 
It  was  determined  that  a  standard  solution,  that  will  not  turn 
yellow  or  fade  in  from  12  to  24  hours,  can  be  made  by  dissolving 
•02  gm.  antipyrine  in  25  cc.  of  water,  adding  r6  cc.  of  1  per  cent.  ' 
sulphuric  acid  and  -8  cc.  of  1  per  cent,  solution  of  sodium  nitrite, 
and  then  diluting  to  100  cc. 
When  preparing  a  solution  of  an  unknown  amount,  for  compari- 
son with  the  standard,  a  few  preliminary  trials  must  be  made  to 
determine  the  amount  of  reagents  required  to  fully  develop  the 
color,  and  not  be  in  such  excess  as  to  produce  a  yellowish  tinge  in 
jthe  time  required. 
To  avoid  precipitation  the  solution  must  not  be  more  concen- 
trated than  1  in  500. 
(321) 
