524  American  Acetylsalicylic  Acid.  {Am'jlwr\li£Tm' 
The  solutions  used  were  prepared  as  follows : 
Redistilled  alcohol  was  treated  with  a  small  amount  of  sodium  hydroxide 
for  24  hours,  then  again  distilled. 
The  color  standard  was  made  by  dissolving  0.116  G.  of  dried  sodium 
salicylate  in  water,  adding  1  minim  of  glacial  acetic  acid,  and  making  up  to 
1,000  Cc.    Each  Cc.  represents  0.1  Mg.  of  salicylic  acid. 11 
The  ferric  chloride  solution  was  made  by  diluting  1  Cc.  ferric  chloride 
(FeCl3.6H.2O)  test  solution  U.  S.  P.  with  99  Cc.  of  water.  The  diluted  solu- 
tion must  be  freshly  prepared  each  day. 
With  one  exception,  all  of  the  commercial  specimens  examined 
responded  satisfactorily  to  the  above  test  showing  less  than  1  part 
salicylic  acid  in  1,000  parts  acetylsalicylic  acid.  The  individual 
results  are  given  in  the  accompanying  table. 
Other  Tests. — New  and  Nonofficial  Remedies,  191 7,  requires 
that  acetylsalicylic  acid  shall  form  a  clear  solution  with  warm  so- 
dium carbonate  solution ;  that  sulphates,  chlorides  and  heavy  metals 
shall  be  absent ;  that  0.5  Gm.  shall  leave  no  weighable  ash.  All  the 
brands  reported  in  this  paper  complied  with  these  requirements. 
So  far  there  has  been  no  satisfactory  quantitative  estimation  of 
acetylsalicylic  acid.  True,  various  methods  have  been  proposed, 
but  they  are  objectionable.  It  was  thought  that  hydrolysis  of  acetyl- 
salicylic acid  and  then  titrating  the  solution  by  comparing  the  color 
formed  by  ferric  chloride  with  that  of  a  standard  control  might 
yield  interesting  results,  providing  that  the  conditions  were  alike. 
For  this  purpose  1  Gm.  of  acetylsalicylic  acid  was  dissolved  in  10  Cc, 
of  alcohol  and  diluted  to  1,000  Cc.  The  solution  was  then  heated 
at  98-1000  C.  for  2  hours,  allowing  the  alcohol  to  evaporate,  then 
allowed  to  stand  at  room  temperature  (220  C.)  for  22  hours.  After 
adding  water  sufficient  to  make  1,000  Cc,  it  was  compared  color- 
imetrically  for  salicylic  acid  strength.  The  amount  of  hydrolysis 
varied  so  with  different  samples  under  the  same  conditions  that 
it  was  realized  that  an  approximate  assay  by  this  method  was  unre- 
liable.   If  the  assay  were  made  under  more  exact  conditions,  quan- 
acetylsalicylic  acid  gives  by  hydrolysis  both  acetic  acid  and  salicylic  acid,  it 
was  thought  advisable  to  add  acetic  acid  to  the  standard.  If  there  is  any 
free  acetic  acid  in  a  sample  of  acetylsalicylic  acid  containing  salicylic  acid 
(which  I  believe  is  generally  the  case  when  salicylic  acid  is  present)  then  it 
would  modify  the  color  given  by  the  same  amount  of  salicylic  acid  alone. 
For  this  reason  it  was  thought  to  be  more  comparable  to  have  the  standard 
contain  a  slight  amount  of  acetic  acid. 
11  This  standard  is  somewhat  similar  to  the  one  proposed  by  T.  W.  Tho- 
burn  and  Paul  J.  Hanzlik,  /.  Biol.  Chem.,  23,  175. 
