# 
388  PERMANGANATE  OF  POTASSA. 
This  rendered  the  subject  a  tedious  and  laborious  one,  and 
naturally  detracts  somewhat  from  that  confidence  which  the  re- 
sults might  otherwise  claim,  since  these  now  are  strictly  appli- 
cable only  to  the  particular  parcel  or  lot  of  binoxide  of  man- 
ganese used  in  the  experiments. 
Besides  the  experience  of  some  years  just  alluded  to,  the 
basis  of  these  experiments  and  researches  was,  first,  the  fact 
recorded  by  Chevillot  and  Edwards,  that  binoxide  of  manganese 
ignited  with  hydrate  of  potassa,  produced  some  manganate  of 
potassa  ;  second,  that  sesquioxide  of  manganese,  reduced  from 
binoxide  at  a  red  heat,  was  again  converted  into  binoxide,  if 
subjected  to  the  action  of  steam  at  a  temperature  somewhat  be- 
low redness  ;  and  third,  that  the  formation  of  other  crystalliza- 
ble  salts  in  the  solution  of  the  permanganate  must  be  avoided. 
It  was  first  ascertained  by  experiment  that  an  intimate  mix- 
ture of  binoxide  of  manganese  and  hydrate  of  potassa,  gave 
a  larger  proportion  of  manganate  of  potassa,  when  heated  only 
to  a  temperature  very  much  below  redness,  than  when  ignited  ; 
and  it  was  next  ascertained  that  the  application  of  steam  to  the 
mixture,  when  thus  moderately  heated,  increased  the  proportion 
both  of  manganate  and  permanganate  ;  and  the  prime  object 
then  became,  to  push  this  oxidizing  process  as  far  as  possible, 
and  to  simplify  its  application.  It  was  next  found  that  repeated 
applications  of  steam,  more  than  prolonged  application,  favored 
the  desired  result,  and  this,  and  a  desire  to  simplify,  led  directly 
to  the  intermittent  application  of  water  to  the  heated  mass, 
instead  of  steam,  and  the  result  was  found  to  be  better  and  far 
more  easily  obtained.  B£champ,had  avoided  crystallizable 
salts  by  supplying  oxygen  to  the  mixture  from  without,  provided 
his  process  was  so  managed  that  the  carbonic  acid  was  not  in 
sufficient  quantity  to  produce  any  bicarbonate ;  but  it  seemed 
better  and  more  simple,  as  well  as  more  economical,  to  separate 
the  excess  of  potassa  without  combining  it,  and  then  to  reserve 
it  for  farther  use. 
This  brief  outline  of  the  expenditure  of  much  time,  labor, 
and  trouble,  may  serve  to  introduce  the  process  proposed,  as 
modified  by  these  results,  and  as  practised  many  times  upon 
the  scale  given,  with  tolerably  uniform  results. 
The  binoxide  of  manganese  used  was  imported  from  Saxony, 
