THE  AMERICAN 
JOURNAL  OF  PHARMACY 
MAY,  1898. 
COMPARATIVE  ACCURACY  OF  TITRIMETRIC  AND  GA- 
SOMETRIC  METHODS  OF  ESTIMATING  HYDROGEN 
DIOXIDE  IN  PRESENCE  OF  VARIOUS  PRESER- 
VATIVE AGENTS. 
By  Cart.  E.  Smith. 
(Report  from  Research  Committee  D,  Section  II,  of  the  Committee  of  Re- 
vision of  the  U.  S.  Pharmacopoeia. ) 
The  method  of  estimating  hydrogen  dioxide  most  extensively 
used  is  that  of  titration  with  potassium  permanganate.  Besides 
being  more  readily  applied  than  any  other,  this  method  has  always 
been  presumed  to  give  accurate  results,  at  least  sufficiently  so  for  all 
practical  purposes.  Dr.  Charles  Rice,  however,  has  observed  that 
its  accuracy  is  affected  by  the  presence  of  glycerin,  which  some 
manufacturers  add  to  the  solutions  to  give  them  stability.  A 
variety  of  other  substances  have  from  time  to  time  been  reported 
to  be  in  use  for  the  same  purpose,  and  it  was  suspected  that  at  least 
a  part  of  them  might  also  exert  an  influence  on  the  results  of  the 
method.  Such  substances  are  boroglycerin,  boric,  salicylic  and 
benzoic  acids,  acetanilid,  salol,  etc.  It  was  important,  therefore,  to 
know  if  the  inaccuracies  introduced  by  the  presence  of  glycerin  or 
any  other  of  the  above  enumerated  substances  are  so  great  as  to 
make  the  method  worthless,  and,  if  so,  whether  a  method  could  be 
found  that  is  not  affected  by  these  additions,  one  that  could  be  relied 
upon  under  any  conditions  likely  to  occur  in  the  assay  of  commercial 
solutions  of  hydrogen  dioxide.  It  was  the  writer's  task,  for  this  pur- 
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