AmM2ch,F822arm-}       Action  of  Hydrogen  Peroxide.  127- 
pletely  decompose  the  remaining  H202,  so  that  this  experiment  can- 
not be  stated  quantitatively. 
(5)  5  cc.  H202  with  5  cc.  Fe2  Cl6  solution  (5  per  cent.)  at  a  different 
time  gave  45  cc.  oxygen. 
(6)  5  cc.  H202  with  10  cc.  Fe2  Cl6  solution  (5  per  cent.)  evolved  50 
cc.  oxygen. 
(7)  5  cc.  H202  with  5  cc.  Fe2  Cl6  solution  (U.  S.  P.)  evolved  55  cc. 
oxygen,  showing  in  this  case  complete  decomposition ;  this  experi- 
ment does  not  prove  the  absolute  quantity  of  ferric  chloride  (which 
must  vary  according  to  the  strength  of  the  H202)  necessary  for  the 
complete  decomposition  of  the  5  cc.  H202,  but  proves  the  fact  that 
the  decomposition  can  be  made  complete  under  the  proper  conditions. 
A  large  number  of  experiments  were  now  made  to  ascertain  the 
action  of  other  salts  upon  hydrogen  peroxide  ;  these  were  not  made 
quantitatively  but  simply  carried  out  as  test-tube  experiments  to 
determine  if  decomposition  resulted. 
Before  giving  these  results  the  known  reactions  and  behavior  of 
H202  may  be  stated  :  When  concentrated  it  is  readily  reduced  by 
finely  divided^  silver,  gold  and  platinum  without  oxidizing  these 
metals ;  selenium,  chromium  and  arsenic  are  oxidized  to  form 
acids.  In  dilute  solution  it  is  reduced  by  the  oxides  of  silver,  gold, 
platinum  and  mercury ;  these  oxides  also  being  reduced  to  metal. 
In  alkaline  solutions  manganous  salts  are  oxidized  to  manganic 
oxide  ;  in  acid  solutions  peroxides  are  reduced  to  mon-oxides  (Mn02, 
K2Mn2Og,  Pb02).  Potassium  ferricyanide  is  reduced  to  potassium 
ferrocyanide ;  metallic  sulphides  are  oxidized  to  sulphates.  Sul- 
phurous acid  is  converted  into  sulphuric  acid ;  HQ  and  HI  are 
decomposed  with  liberation  of  chlorine  and  iodine  respectively. 
Other  reactions  which  are  used  as  tests  for  hydrogen  peroxide  are  : 
The  addition  of  ether  to  an  acidified  solution  of  H202  followed  by  a 
few  drops  of  dilute  potassium  chromate  solution  will,  after  agita- 
tion, impart  to  the  ether  a  beautiful  blue  color  (generally  stated  to 
be  due  to  the  formation  of  perchromic  acid) ;  uranium  nitrate  is 
said  to  be  a  better  test  than  the  chromate.  Potassium  iodide  and 
starch  slowly  give  the  blue  color  of  iodide  of  starch  (ozone  or 
chlorine  cause  an  immediate  blue  color).  If  to  the  previous  test  a 
little  ferrous  sulphate  be  added,  it  forms  the  most  delicate  test  for 
H202  (one  part  in  twenty-five  million  parts  can  still  be  detected). 
With  naphthylamine  and  sodium  chloride  a  blue  color  is  produced. 
