244 
Estimation  of  Phenacetin. 
Am.  Jour.  Pharm. 
April,  1919. 
/>-aminophenol,  or  0,00343  Gm.  of  />-phenetidine.  The  result  is 
multiplied  by  the  factor  1.015  to  correct  for  loss  during  aeration. 
Estimation  of  Phenacetin. — One  Gm.  of  phenacetin  is  boiled 
for  two  hours  with  a  mixture  of  25  Cc.  strong  hydrochloric  acid 
(1.16)  and  15  Cc.  water  in  a  small  flask  fitted  with  an  air  condenser. 
After  cooling,  the  solution  is  diluted  to  some  definite  volume,  and 
an  aliquot  representing  0.2  Gm.  phenacetin  is  taken  for  estimation 
exactly  as  above. 
Each  Cc.  of  N/10  thiosulphate  is  equivalent  to  0.00448  Gm.  of 
phenacetin.  A  large  number  of  samples  of  commercially  pure 
phenacetin,  examined  as  above,  gave  figures  ranging  from  99.2  to 
100.2  per  cent. 
Estimation  of  Phenacetin  in  Admixture. — The  following  experi- 
ments were  made  on  mixtures  of  phenacetin  with  caffeine  citrate, 
salol,  and  acetanilide  respectively : 
With  Caffeine  Citrate. — A  mixture  of  0.8  Gm.  phenacetin  with 
0.4  Gm.  caffeine  citrate  was  treated  exactly  as  for  phenacetin.  The 
results  were  slightly  high,  owing  to  formation  of  a  small  amount 
of  some  substance  from  the  caffeine  citrate  which  liberated  iodine 
from  hydriodic  acid.  The  percentage  of  phenacetin  calculated  out 
68.5  and  68.7,  instead  of  66.7  required  by  theory.  No  correction  for 
the  volatility  of  the  quinone  chlorimine  was  made  in  these  cases, 
the  error  already  mentioned  more  than  compensating  for  loss  by  this 
means. 
With  Salol. — A  mixture  of  equal  parts  of  phenacetin  and  salol 
(0.5  Gm.  of  each)  was  dissolved  in  20  Cc.  10  per  cent,  sodium 
hydroxide,  and  warmed  on  the  steam-bath  for  fifteen  minutes  to 
hydrolyze  the  salol;  40  Cc.  of  strong  hydrochloric  acid  were  then 
added,  and  the  mixture  boiled  for  two  hours.  The  hydrolyzed 
solution  was  shaken  with  ether  to  remove  salicylic  acid  and  phenol, 
and  the  chlorination  and  titration  carried  out  in  the  usual  manner. 
The  amount  of  phenacetin  found  was  49.3  per  cent.  It  was  found 
necessary  to  remove  the  products  of  hydrolysis  of  salol  before 
adding  the  hypochlorite,  as  the  precipitates  they  formed  with  this 
reagent  held  back  chlorine  and  caused  high  results  to  be  obtained. 
With  Acetanilide. — Mixtures  of  acetanilide  and  phenacetin 
cannot  be  analyzed  without  first  removing  the  acetanilide,  as  the 
aniline  produced  from  this  substance  forms  an  oily  precipitate  which 
apparently  retains  free  chlorine. 
Estimation  of  other  p-Phenetidinc  or  p-Aminophenol  Deriva- 
