242  Estimation  of  Phenacetin.         { Am ^rm- 
Methods  taking  into  account  the  chemical  constitution  of  these 
compounds  have  also  been  proposed.  Taylor  and  Vanderkleed,5  for 
instance,  estimate  phenacetin  and  acetanilide  (individually),  by 
steam  distillation  and  titration  of  the  acetic  acid  produced  on  hydro- 
lysis. Another  method  proposed  by  Emery6  for  the  separation  and 
estimation  of  phenacetin  and  acetanilide  depends  on  the  property  of 
phenacetin  of  combining  with  iodine  to  form  an  insoluble  periodide, 
acetanilide  either  not  reacting  with  iodine  or  producing  a  soluble 
compound.  The  amount  of  iodine  precipitated  from  solution  is 
determined  by  titration  of  the  excess  left  in  solution,  and  the 
phenacetin  content  calculated  from  the  figures  thus  obtained.  An 
iodimetric  method  for  the  estimation  of  phenolic  compounds  has 
been  published  by  Wilkie  ;7  but  this  does  not  appear  to  have  been 
extended  to  the  arninophenols  and  phenetidins,  although  it  seems 
probable  that  such  compounds  might  form  definite  iodo-derivatives. 
As  far  as  my  own  experience  goes,  however,  no  method  has 
been  published  in  which  any  characteristic  reaction  of  ^-phenetidine 
or  />-aminophenol  has  been  taken  as  the  basis  for  the  estimation  of 
this  group  of  compounds.  The  reactions  of  />-aminophenol  with 
oxidising  agents  were  therefore  investigated,  in  order  to  determine 
which,  if  any,  could  be  made  the  basis  of  a  quantitative  estimation. 
Oxidation  by  means  of  potassium  dichromate  to  form  quinone  was 
tried,  but  was  found  unsatisfactory,  as  part  of  the  />-aminophenoI 
was  converted  to  quinhydrone.  The  reaction  between  sodium 
hypochlorite  and  an  acid  solution  of  ^-aminophenol  was  found  to  be 
much  more  promising.  These  substances  react  in  accordance  with 
the  equation  : 
OH  •  CGH4 ■  NHoHCl  +  4CI  =  O :  C6H4 :  NCI  +  4HCI, 
the  quinone  chlorimine  precipitating  as  golden-yellow  flocks  from 
concentrated  solutions,  but  remaining  in  solution  at  dilutions  below 
about  1  per  cent. 
F-phenetidine  is  also  converted  to  quinone  chlorimine  by  the 
action  of  hypochlorous  acid.  The  reaction  is  quantitative,  and  pro- 
vides a  rapid  means  for  the  estimation  of  these  bases  and  all  their 
derivatives  which  yield  the  free  base  on  hydrolysis. 
The  direct  absorption  of  chlorine  does  not  form  a  suitable  basis 
5  Amer.  J.  Pharm.,  1907,  79,  151— 156 :  The  Analyst,  1907,  32,  215. 
6/.  Ind.  and  Eng.  Chem.,  1914,  4,  665-669;  The  Analyst,  1914,  39,  433. 
7  J.  Soc.  Chem.  Ind.,  191 1,  30,  398;  The  Analyst,  191 1,  36,  294. 
