484 
Headache  Mixtures. 
f  Am.  Jour.  Pharm 
\     October,  1909 
or  fan,  avoiding,  however,  undue  heat.7  Dry  in  desiccator  over 
quicklime  to  constant  weight. 
Verify  the  final  weight  by  means  of  titration  with  standard 
potassium  bromide-bromate  solution  as  in  the  first  method.  Heat 
the  residue  with  10  c.c.  dilute  sulphuric  acid  a  half  hour  on  the 
steam  or  vapor  bath,  cool,  add  5  c.c.  of  water,  and  titrate  as  directed 
above. 
Sodium  Bicarbonate. 
The  residue  left  after  the  first  treatment  with  chloroform  is 
weighed  when  dry  and  represents  very  nearly  the  amount  of  sodium 
bicarbonate  present.  It  may  be  more  accurately  estimated  by 
titrating  with  tenth-normal  sulphuric  acid,  using  congo  red  as  indi- 
cator, or  it  may  be  ignited  with  dilute  sulphuric  acid  and  weighed  as 
sodium  sulphate. 
Calculate  results  in  parts  per  100. 
The  results  reported  are  tabulated  as  follows : 
Owing  to  an  ambiguity  in  the  expression  "  dilute  sulphuric  acid  " 
employed  in  the  method  under  caffein,  as  also  in  the  footnote,  page 
482,  for  standard  bromide-bromate  solution,  some  of  the  workers 
quite  naturally  used  the  Pharmacopoeial  strength,  with  the  result 
that  the  acetanilid  was  not  completely  hydrolyzed.  This  undoubtedly 
explains  the  somewhat  high  results  for  caffein  and  the  correspond- 
ingly low  ones  for  acetanilid.  The  strength  of  acid  intended  and 
the  one  actually  employed  for  this  purpose  in  the  Bureau  of  Chem- 
istry is  that  ordinarily  used  in  laboratory  work  and  is  made  by 
diluting  1  part  of  concentrated  sulphuric  acid  (whose  specific  gravity 
is  not  less  than  1.826  at  250)  with  5  parts  of  water.  From  two  to 
three  hours'  heating  on  the  steam  bath  is  usually  required  to  com- 
pletely hydrolyze  the  acetanilid. 
Notwithstanding  this  ambiguity  the  results  obtained  are  very 
gratifying,  in  view  of  the  fact  that  the  method  is  new  and  the 
workers  have  entered  into  a  comparatively  new  field.  The  per- 
centages of  variation  are  so  small  as  to  almost  warrant  the  referee 
in  recommending  it  as  a  provisional  method  to  the  association.  He 
believes,  however,  that  the  method  should  receive  additional  study, 
and  so  recommends.  It  is  also  recommended  that  additional  mix- 
tures be  tested  with  this  and  such  other  methods  as  may  be  found 
desirable. 
7  Acetanilid  suffers  appreciable  loss  when  heated  above  400. 
