408 
PKEPAEATION  OF  PERMANGANIC  ACID. 
ON  THE  PREPARATION  OF  PERMANGANIC  ACID. 
By  M.  A.  Terreil. 
The  chemist  Chevillot  first  stated  that  when  permanganate  of 
potash  is  mixed  with  sulphuric  acid  and  heated  to  130°  C, 
violet  vapors  are  obtained,  condensible  into  an  oily  red  liquid, 
consisting,  according  to  this  chemist,  of  sulphuric  acid  and  per. 
manganic  acid. 
More  recently,  M.  H.  Aschoff  has  prepared  permanganic  acid 
in  the  same  way,  but  only  collecting  the  small  drops  forming  in 
the  mixture  of  permanganate  of  potish  with  concentrated  sul- 
phuric acid. 
I  now  propose  to  give  some  new  facts  about  the  preparation 
of  permanganic  acid,  and  to  describe  some  new  properties  of 
this  acid. 
Permanganic  acid  is  obtained  by  dissolving  permanganate  of 
potash  in  pure  sulphuric  acid,  diluted  with  about  half  an  equiva- 
lent of  water,  taking  care  that  the  temperature  does  not  get  too 
high.  The  solution  is  a  yellowish  green.  Introduce  it  into  a 
tubulated  retort  communicating  with  a  well  cooled  receiver.  In 
this  apparatus  neither  corks  nor  other  organic  matter  must  be 
used. 
The  retort  is  placed  in  a  water  bath  and  heated  to  a  tempera- 
ture not  exceeding  60°  or  70°;  at  a  higher  temperature  sul- 
phuric acid  passes  over.  The  apparatus  then  becomes  filled 
with  violet  vapors,  resembling  those  of  iodine.  The  vapors  soon 
condense  in  the  neck  of  the  retort  to  a  thick  liquid  of  a  greenish- 
black  color,  which  contains  neither  sulphuric  acid  nor  chlorine. 
This  is  permanganic  acid. 
It  is  difficult  to  prepare  a  large  quantity  of  this  acid  at  once. 
It  always,  at  a  certain  time,  when  the  proportion  of  distilled 
acid  commences  to  be  considerable,  decomposes  spontaneously 
with  a  slight  detonation.  After  this  decomposition  a  solid  body 
is  found  in  the  apparatus  of  a  brownish-black  color  and  ex- 
treme lightness,  possessing  the  properties  of  sesquioxide  of  man- 
ganese. 
If  the  sulphuric  acid  solution  of  permanganate  of  potash  is 
exposed  to  moist  air  for  some  time,  or,  better,  if  a  few  drops  of 
water  are  added  to  it,  the  permanganic  acid  will  be  seen  to 
