AmM^h,Kmm'}        Action  of  Hydrogen  Peroxide.  129 
The  barium  peroxide  was  allowed  to  stand  with  water  to  form 
the  hydrated  peroxide  which  was  found  to  be  more  energetic  in  its 
action. 
With  Fe2Cl6  oxygen  was  liberated  but  without  the  reduction  of 
the  ferric  salt ;  tried  under  various  conditions  the  same  results  were 
obtained.  Salts  of  potassium,  sodium,  lithium,  ammonium,  barium, 
strontium  and  calcium  have  no  action  upon  BaO>2 ;  magnesium  salts 
will  very  slowly  reduce  Ba02,  liberating  oxygen  ;  zinc  and  cadmium 
salts  act  better  but  still  only  moderately  upon  Ba02 ;  nickel  and 
cobalt  salts  produce  a  rapid  liberation  of  oxygen,  the  hydrates  ot 
the  metals  being  precipitated.  Ferric,  chromium,  aluminium  and 
manganous  salts  react  like  ferric  chloride  in  rapidly  liberating  the 
oxygen,  so  that  if  the  mixtures  be  agitated,  the  reaction  is  complete 
in  a  few  minutes  ,  ferrous  salts  are  first  converted  into  ferric  salts 
and  then  oxygen  is  liberated.  Cupric  salts  liberate  oxygen  without 
reduction  to  cuprous  salts.  Mercuric,  silver  and  gold  salts,  in 
presence  of  excess  of  Ba02  liberate  oxygen  and  are  reduced  to 
metal.  Platinic  chloride  shows  a  different  behavior  dependent 
upon  the  form  in  which  it  is  taken ;  if  as  H2?tCl6  (commercial  solu- 
tion of  platinic  chloride),  oxygen  will  be  liberated  but  no  separation 
of  the  metal  takes  place;  if  PtCl4  be  taken  (by  removing  the  HC1 
by  addition  of  AgN03)  oxygen  is  also  liberated  but  metallic  plati- 
num separates.  In  these  several  experiments  it  was  noticed  that 
any  salt  of  the  metal  could  be  taken,  no  matter  if  soluble  or  insolu- 
ble (in  the  latter  case  heat  had  to  be  employed  at  times  to  start  the 
reaction)." 
In  the  following  experiments  aqueous  solutions  of  the  different 
salts  were  used ;  where  acid  solutions  were  used  these  will  be 
mentioned  especially. 
The  action  of  H202  upon  potassium  ferricyanide,  owing  to  the 
difficulty  described  in  testing  for  ferrous  salt  in  presence  of  ferric 
salt,  was  first  investigated  :  A  freshly  prepared  solution  (which 
with  ferric  chloride  gave  only  a  brown  coloration  indicating  the 
absence  of  ferrous  salt  and  of  potassium  ferrocyanide)  was  used  ;  if 
to  a  little  of  this  solution  a  single  drop  of  H202  was  added  and  this 
mixture  immediately  added  to  some  of  the  ferric  chloride,  a  greenish 
coloration  was  at  once  produced  and  after  standing  a  few  minutes  a 
dark  blue  precipitate  separated.  This  proves  that  H202  even  in  the 
cold  may  reduce  potassium  ferricyanide  to  potassium  ferrocyanide 
