PREPARATION  OF  PERMANGANIC  ACID. 
409 
float  upon  the  surface  of  the  liquid  in  the  form  of  oily  drops  of 
a  greenish-black  metallic  lustre,  which  sometimes  solidify  and 
fall  to  the  bottom  of  the  liquid.  It  is  difficult  to  separate  this 
acid  from  the  sulphuric  acid  which  contaminates  it  •  but  in  this 
state  the  permanganic  acid  may  be  used  for  the  oxidation  ex- 
periments described  below. 
Permanganic  acid  is  a  thick  liquid,  of  a  greenish-black 
color  and  metallic  appearance.  It  seems  to  be  capable  of  soli- 
difying. It  is  very  greedy  of  water.  Its  solution  is  violet, 
and  it  keeps  pretty  well  when  dilute  and  free  from  dust. 
If  permanganate  of  potash  is  suddenly  heated  it  detonates  ; 
but  if  moderately  heated,  part  volatilises,  producing  violet 
vapors,  which  possess  a  very  disagreeable  metallic  odor. 
This  compound  is  perhaps  the  most  energetic  oxidising  agent 
known.  It  instantly  sets  fire  to  paper  and  alcohol,  the  latter 
with  explosion.  In  these  combustions  there  are  always  pro- 
duced violet  vapors,  due  to  the  volatilisation  of  a  certain  quantity 
of  permanganic  acid.  It  detonates  suddenly,  with  emission  of 
a  beautiful  white  light  when  placed  in  contact  with  a  fatty  body. 
In  this  case  very  little  acid  must  be  used,  for  the  detonation  is 
very  strong. 
If  a  few  drops  of  solution  of  sulphite  of  potash  is  poured  upon 
permanganic  acid  a  very  lively  reaction  is  produced  with  disen- 
gagement of  light.  A  large  quantity  of  acid  is  carried  off  in 
the  form  of  violet  vapors,  which  are  reduced  in  the  air,  and  fall 
down  in  the  form  of  brown  flocks,  very  light,  similar  to  oxide  of 
zinc  when  this  metal  is  burned  in  contact  with  air. 
This  curious  reaction  will  doubtless  become  a  beautiful  lec- 
ture experiment.  It  succeeds  very  well  with  the  permanganic 
acid  formed  in  the  sulphuric  solution  of  permanganate  of 
potash. 
Permanganic  acid  is  slightly  soluble  in  concentrated  sulphuric 
acid;  the  solution  is  green.  Its  solution  in  sulphuric  acid  con- 
taining three  equivalents  of  water  is  violet.  This  change  of 
color  seems  to  point  out  that  there  exist  an  anhydrous  perman- 
ganic acid  and  a  hydrated  acid. 
The  instability  of  permanganic  acid  has  hitherto  prevented 
me  from  determining  its  composition  Chem.  News,  London 
August  2, 1862,  from  Bulletin  de  la  SociSte  Chimique  de  Paris 
