414 
Criticisms  of  the  U.S. P. 
(Am.  Jour.  Pharm. 
I  September,  1906. 
GUTZEIT  TEST  FOR  ARSENIC  ENDORSED. 
The  greatest  improvement  is  the  fixing  of  a  limit  of  impurity  for 
arsenic  and  heavy  metals.  The  maximum  amount  allowable  is  I  in 
100,000,  a  limit  which  makers  should  have  no  trouble  in  reaching. 
Hence  the  introduction  of  special  tests  for  this  purpose.  The  old 
Bettendorf  test  for  arsenic,  which  answered  fairly  well,  has  been 
discarded  in  favor  of  the  modified  Gutzeit  test,  which  is  easier  to 
apply  and  gives  more  consistent  indications.  (Drug  lopics,  1905, 
page  230.) 
TEST  FOR  ARSENIC  TOO  DELICATE. 
The  modified  Gutzeit's  test  for  arsenic  is  in  many  cases  entirely 
too  rigid.  In  the  first  place,  it  is  difficult  to  obtain  reagents  which, 
by  this  test,  will  not  show  the  presence  of  arsenic,  and,  in  the  sec- 
ond place,  many  official  chemicals  should  be  permitted  to  contain 
more  arsenic  than  is  represented  by  the  proportion  I  to  100,000, 
which  is  the  least  permissible  quantity  of  arsenic  allowed  by  the 
new  Pharmacopoeia.    (Chas.  E.  Caspar i,  Meyer  Br  os\  Drug.) 
DETERMINATION  OF  CHLORIDES  IN  BROMIDES  DIFFICULT. 
Attention  should  also  be  called  to  the  extremely  unsatisfactory 
method  retained  in  the  new  Pharmacopoeia  for  determining  the 
percentage  of  chlorides  in  bromides.  By  the  present  official  method 
only  the  most  careful  and  experienced  analytical  chemist  can  hope 
to  obtain  accurate  results,  and  even  he  will  frequently  make  an 
error  amounting  to  25  per  cent,  of  the  actual  amount  of  chloride 
present.  If  the  chloride  must  be  titrated  with  the  bromide  by 
means  of  a  silver  solution,  then  it  is  much  more  accurate  to  add  an 
excess  of  the  silver  nitrate  and  determine  the  excess  by  means  of  a 
standard  sulphocyanide  solution,  because  the  end  point  in  this  case 
is  much  more  easily  recognized  than  when  potassium  chromate  is 
used  as  an  indicator.  By  far  the  best  method  of  making  the  deter- 
mination consists  in  treating  the  mixture  of  chloride  and  bromide 
in  acid  solution  with  some  oxidizing  agent,  such  as  ammonium  per- 
sulphate or  lead  peroxide,  which  will  oxidize  the  hydrobromic  acid, 
but  which  will  not  affect  the  hydrochloric  acid,  which,  after  the  re- 
moval of  all  bromine,  can  be  titrated  with  silver  solution.  The 
latter  method  can  be  carried  out  just  as  expeditiously  as  the  present 
