130 
Action  of  Hydrogen  Peroxide. 
( Am.  Jour.  Pharm. 
\      March,  1892. 
and  this  latter  reagent  then  produces  the  precipitate  with  the  ferric 
salt.  If  equal  quantities  of  H202  and  K6Fe2(Cu)12  solution  be  allowed 
to  stand,  there  will  be  noticed  after  a  few  minutes  an  evolution  of 
oxygen,  showing  that  the  reduction  takes  place  in  neutral  or  even 
acid  solution,  as  another  experiment  proved  ;  upon  the  addition  of 
an  alkali  or  alkaline  carbonate  the  decomposition  is  hastened,  the 
solution  taking  the  yellow  color  of  potassium  ferrocyanide ;  by 
allowing  the  reaction  to  proceed  for  some  time  the  mixture  becomes 
almost  colorless,  but  will  still  give  the  tests  for  ferrocyanide  after 
acidifying. 
Potassium  ferrocyanide  with  H202,  also  causes,  in  cold  neutral 
solutions  the  evolution  of  oxygen  ;  in  alkaline  solutions  the  reaction 
proceeds  more  rapidly  and  here  again  an  almost  colorless  solution 
results.    No  explanation  of  the  decolorization  can  as  yet  be  given. 
Ferrous  sulphate,  with  a  few  drops  of  H202,  becomes  quite  dark 
brown  in  color  without  evolution  of  oxygen;  upon  addition  of  more 
H202,  oxygen  is  liberated  and  a  precipitation  of  a  basic  salt  takes 
place  (this  is  soluble  on  addition  of  HC1).  By  precipitating  a 
portion  of  this  test  with  ammonia,  collecting,  washing,  dissolving 
in  HC1,  and  adding  potassium  ferricyanide,  only  ferric  salt  was 
found  present.  If  to  the  mixture  of  ferrous  sulphate  and  hydrogen 
peroxide  a  little  alcohol  be  added,  there  will  be  developed  after  a 
time  the  aldehyde  odor ;  in  this  respect  there  is  perfect  analogy 
between  ferrous  sulphate  and  ferric  chloride).  It  may  be  mentioned 
here  that  the  oxidation  of  ferrous  salts  appears  to  take  place  more 
readily  in  neutral  or  alkaline  solution  than  in  acid  solution. 
Magnesium  sulphate,  zinc  sulphate,  alum,  cobaltous  nitrate,  nickel 
nitrate,  mercuric  chloride,  copper  sulphate,  bismuth  nitrate  (in  HC1)  cad- 
mium nitrate,  stannic  chloride  (in  HC1)  and  arse nious  oxide  gave  no  evo- 
lution of  oxygen  after  standing  as  long  as  twenty-four  hours.  The  addi- 
tion of  a  few  drops  of  NaOH  liberated  oxygen  with  only  the  follow- 
ing :  Cobalt  nitrate  with  separation  of  black  cobaltic  oxide ; 
nickel  nitrate  with  separation  of  green  nickelous  hydrate  ;  mercuric 
chloride  with  only  a  few  drops  of  NaOH  causes  but  a  slight  effer- 
vescence and  separation  of  oxychloride ;  if,  however,  sufficient  NaOH 
is  added  to  change  the  oxychloride  into  oxide,  then  the  reaction  is 
energetic,  and  the  oxide  is  reduced  to  the  metal  ;  copper  sulphate 
with  separation  of  cupric  oxide ;  bismuth  nitrate,  cadmium  nitrate 
and  stannic  chloride  with  separation  of  the  white  hydrates;  arsenious 
