320 
ON  MANGANIC  ACID,  ETC. 
MANGANESE  FORMS  WITH  OXYGEN  ONLY  ONE  ACID — THE 
MANGANIC  ACID. 
By  M.  T.  L.  Phipson. 
After  very  long  researches  on  the  manganate  and  permanga- 
nate of  potassa,  I  have  discovered  that  the  latter  salt  is  nothing 
else  than  a  bimanganate  of  potassa,  KO,  (Mn  03)  2,  correspond- 
ing to  the  bichromate  and  bisulphate  (anhydrous)  of  the  same 
base.  All  these  salts  are  anhydrous,  and  crystallize  in  the 
form  of  the  rhomboidal  prism. 
I  have  made  twenty  analyses  of  the  salt  actually  known  as 
permanganate  of  potassa.  Although  anhydrous,  this  salt  attracts 
some  moisture  from  the  atmosphere,  and  dried  at  salt  water 
bath  heat  gave  1.60  per  cent,  of  water.  This  is  not  water  of 
combination.  It  is  necessary  therefore  to  pulverize  thoroughly, 
and  dry  the  salt  at  100°,  centigrade,  for  several  hours,  before 
proceeding  to  the  analysis ;  then  on  treating  the  compound  the 
potassa  and  oxygen  are  found  to  have  exactly  the  figures  of  the 
formula,  KO,  (Mn  03)  2. 
The  bimanganate  of  potassa  forms  a  solution  of  purple  red 
color  ;  when  there  is  added  to  it  an  excess  of  potassa,  it  passes 
into  the  green  manganate  KO,  Mn  03. 
The  bimanganate  of  baryta  is  soluble ;  the  manganate  of 
baryta  forms  a  violet  precipitate.  The  bimanganate  of  potassa 
does  not  give  a  precipitate  with  the  salts  of  baryta,  whilst  the 
manganate  precipitates  them  violet. 
A  current  of  air  deprived  of  carbonic  acid  does  not  decompose 
the  manganate  of  potassa,  but  carbonic  acid  separates  the 
potassa  and  transforms  it  into  a  bimanganate,  2K0,  Mn 
03+C02=KO,  C02+KO,  (Mn  03)  2. 
The  solution  passes  from  green  to  red ;  all  acids  act  the  same 
upon  manganate  of  potassa. 
Manganic  acid  is  that  body  which  has  up  to  the  present  time 
been  called  permanganic  acid. 
It  is  obtained  from  bimanganate  of  potassa  or  baryta.    It  is  a 
very  feeble  acid,  does  not  displace  carbonic  acid  from  the 
alkaline  carbonates,  but  is,  on  the  contrary,  partially  displaced 
in  those  combinations. —  Translated  from  Comptes  Mendus,  No 
14,  1860,  by  Samuel  P.  Duffield,  PL  D. 
