126 
Action  of  Hydrogen  Peroxide. 
/  Am.  Jour.  Pharm. 
I     March,  1892. 
To  ascertain  the  conditions  under  which  the  hydrogen  peroxide 
is  completely  decomposed  by  ferric  chloride,  the  following  experi- 
ments were  made.  First  the  hydrogen  peroxide  was  standardized. 
[Several  methods  have  been  proposed  for  the  estimation  of  this  com- 
pound : 
(1)  By  the  action  of  potassium  permanganate  and  sulphuric  acid  ; 
in  this  method  the  excess  of  permanganate  can  be  estimated  with 
oxalic  acid  or  the  liberated  oxygen  can  be  measured,  one-half  of 
which  comes  from  the  permanganate,  the  other  half  from  the  H202. 
(2)  By  the  action  of  bleaching  powder;  in  this  case  the  evolved 
oxygen  is  measured,  one-half  coming  from  the  H202  according  to 
the  reaction,  CaOCl2  +  H202 '=  Ca  Cl2  +  02  +  H20. 
(3)  By  the  liberation  of  iodine  from  potassium  iodide  and  sul- 
phuric acid  and  titrating  this  with  sodium  thiosulphate.]  For  my 
purpose  it  was  more  convenient  to  use  the  officinal  solution  of  chlo- 
rinated soda  ;  the  reaction,  besides  being  complete  in  a  few  minutes, 
is  a  cleanly  one. 
10  cc.  solution  of  chlorinated  soda  were  placed  in  the  generator  and 
2-5  cc.  H202  in  the  homoeopathic  vial;  after  connecting  as  described 
and  allowing  the  two  liquids  to  mix,  53  cc.  water  were  displaced; 
using  15  cc.  solution  of  chlorinated  soda  and  2  5  cc.  H202,  55  cc. 
water  were  displaced  ;  this  estimation  is  based  upon  the  equation  : 
NaCIO  +  H202=  NaCl  +  H20  +  02,  from  which  it  will  be  seen 
that  one-half  of  the  oxygen  only  comes  from  the  H202,  therefore  2-5 
cc.  H202  liberated  27-5  cc.  oxygen,  making  the  H202  used  an  eleven 
volume  solution  (the  H202  was  taken  from  a  freshly-opened  bottle 
labelled  15  volume).  The  24  cc.  used  with  the  ferric  chloride  in  the 
above-mentioned  experiment  should  have  liberated  264  cc.  oxygen, 
but  as  only  182  cc.  were  liberated  it  shows  the  incompleteness  of 
the  reaction. 
(1)  5  cc.  H202  with  5  cc.  Fe2  Cl6  solution  (5  per  cent.)  liberated  45 
cc.  oxygen. 
(2)  After  the  preceding  reaction  was  complete,  5  cc.  more  H202 
were  added  ;  44  cc.  oxygen  were  liberated. 
(3)  Upon  the  further  addition  of  5  cc.  H202,  only  35  cc.  oxygen 
were  evolved,  showing  the  important  fact  that  the  more  dilute  the 
ferric  chloride  solution,  the  less  oxygen  is  liberated. 
(4)  By  adding  solution  of  chlorinated  soda  to  (3)  oxygen  was  given 
off,  but  unfortunately  the  quantity  added  was  not  sufficient  to  com- 
