132  Action  of  Hydrogen  Peroxide.  {^Sjm.^' 
nitric  acid,  soluble  in  ammonia,  showing  the  presence  of  chlorides 
or  of  hydrochloric  acid  (the  solution  of  H202  has  a  slight  acid  reac- 
tion). Only  after  standing  for  a  number  of  hours  will  this  turbid 
mixture  show  signs  of  decomposing  H202,  but  the  addition  of  a  few 
drops  NaOH  will  cause  the  speedy  decomposition  with  separation 
of  metallic  silver.  If  the  silver  nitrate  be  added  in  excess  and  the 
silver  chloride  filtered  off,  the  filtrate  will  not  even  after  standing 
twenty-four  hours  show  any  signs  of  decomposition. 
The  experiments  made  in  alkaline  solution  show  that  hydrogen 
peroxide  under  these  conditions  is  decomposed  like  the  barium 
peroxide.  The  experiments  also  show  that  a  number  of  metallic 
salts  will  decompose  H202  even  in  neutral  or  acid  solution ;  it  is 
therefore  evident  that  in  the  prescribing  and  dispensing  of  H202 
this  ready  decomposition  of  the  compound  must  be  remembered ; 
also  that  it  will  not  do  to  prescribe  and  dispense  H202  in  what  may 
seem  to  be  desirable  combinations  unless  experiment  proves  the 
combination  practicable. 
The  above  behavior  of  silver  nitrate  and  hydrogen  peroxide 
caused  an  examination  for  foreign  matter  to  be  made  in  the  latter, 
with  the  following  results:  20  cc.  (weighing  20-252  gm.)  gave  a 
precipitate  of  silver  chloride,  weighing  0-03443  gm.,  calculating  this 
to  officinal  hydrochloric  acid,  it  will  equal  0-137  per  cent.;  20  cc. 
evaporated  upon  a  water-bath  until  only  a  few  milligrams  difference 
was  noticed  between  two  weighings,  left  a  syrupy  liquid  weighing 
0-143  gm.  or  about  0-7  per  cent.,  giving  with  borax  a  green  flame 
indicating  glycerin ;  the  taste  of  this  residue  somewhat  reminded 
of  the  hypochlorites ;  the  sweet  taste  of  glycerin  was  not  prominent 
but  the  sensation  of  warmth  as  given  by  the  latter  was  recognizable. 
By  treating  the  residue  with  baryta  water,  evaporating  to  dryness, 
extracting  with  ether-alcohol  and  again  evaporating,  a  residue 
was  obtained  possessing  the  sweet  taste  of  glycerin.  Upon  evap- 
orating 20  cc.  to  dryness  and  heating,  it  was  noticed  that  the  fumes 
given  off  burnt  with  a  green  flame,  indicating  the  presence  of  boric 
acid  or  a  borate ;  after  two  days'  heatirig  the  residue  was  still  black, 
so  that  it  was  not  possible  to  determine  the  ash  in  the  H202,  but 
the  residue  treated  with  a  little  water  gave  a  flame  test  for  sodium. 
The  H202  had  an  acid  reaction  and  evidently  the  addition  of 
hydrochloric  acid,  boric  acid  or  borax,  and  glycerin  was  for  their 
preservative  action. 
