treb?Sy,Pih9airom"}  The  Purity  Rubric  and  US. P.  Tests.  67 
Both  of  the  above  samples  and  indeed  a  number  of  others  failed 
to  give  a  clear  or  only,  slightly  opalescent  solution  when  dissolved 
(1  in  10)  in  recently  boiled  water.  It  is  therefore  questionable 
whether  this  test  for  limit  of  carbonate  is  a  satisfactory  criterion 
for  judging  the  quality  of  lead  acetate  samples.  The  gravimetric 
determination  as  above  outlined  shows  conclusively  that  the  samples 
have  either  lost  water  of  crystallization  or,  as  is  more  probable,  are 
contaminated  with  the  basic  salt. 
Acetanilide. — A  rapid  procedure  for  the  quantitative  analysis  of 
this  compound  is  the  bromate  titration  method  proposed  by  one  of 
us  in  1907.3  A  standard  bromate  solution  which  may  be  the  Kop- 
peschaar's  solution  of  the  Pharmacopceia  is  required.  The  weighed 
sample  of  acetanilide  is  dissolved  in  about  50  c.c.  of  a  mixture  of 
one  part  concentrated  HQ  and  2-3  parts  water,  the  solution  boiled 
for  five  minutes  and  titrated  to  the  appearance  of  pale-yellow  color 
with  standard  bromate  solution,  1  c.c.  0.2  N  bromate  solution  being 
equivalent  to  0.004504  Gm.  acetanilide.  The  following  results  were 
recently  obtained  upon  a  sample  of  acetanilide,  m.  pt.  Ii2°-ii3°  : 
Weighing  Bottle  and  Sample  Am't  used  C  c.  0.2  N 
,  "  v                              for  KBrOs  sol.  Calc.  % 
1st.  Wt.            2nd.  Wt.  Sample  titration  required  acetanilide 
14.0581          13.6807  0.3774         all         84.2  100.5 
13.6807             13.I282  O.5525            y2            6l.5  I0O.2 
13.1282      12.5965  0.5317      yA      29.7  100.7 
Ammonium  Benzoate  and  other  Ammonium  Salts. — As  has  been 
shown  in  another  paper  4  (Seidell  and  Menge),  a  simplified  distilla- 
tion method  is  well  adapted  to  the  analysis  of  ammonium  benzoate 
samples,  and  the  formaldehyde  titration  method  of  Schiff  and  other 
investigators  is  applicable  to  practically  all  other  ammonium  salts 
for  which  the  Pharmacopceia  gives  a  purity  rubric  but  no  quantita- 
tive method  of  analysis. 
As  an  illustration  of  Pharmacopceial  tests  that  appear  to  require 
some  additional  elaboration  it  will  suffice  to  call  attention  to  the 
following : 
Sodium  Benzoate. — The  quantitative  test  for  this  salt  as  pre- 
scribed by  the  Pharmacopceia  requires  that  the  sample  be  ignited 
at  red  heat  and  the  aqueous  solution  of  the  residue  be  titrated  with 
3  Seidell,  /.  Am.  Chem.  Soc,  29,  1091,  1907. 
4  This  Journal,  82,  12. 
