PERMANGANATE  OF  POTASSA. 
# 
387 
salt  ;  but  it  is  extremely  complicated,  troublesome  and  expen- 
sive, and  only  available  upon  a  very  small  scale,  or  a  scale  so 
very  large  as  to  admit  of  an  expensive  special  apparatus. 
The  process  of  Gregory  sometimes  unaccountably  fails  alto- 
gether, even  with  excellent  binoxide  of  manganese  ;  and,  at 
best,  yields  a  small  product,  from  the  difficulty  of  separating 
the  chloride  of  potassium  from  the  final  solution.  It  is  as  fol- 
lows :  —Eight  parts  of  binoxide  of  manganese  and  seven  parts 
of  chlorate  of  potassa  are  powdered  together,  and  mixed  with  a 
solution  of  ten  parts  of  hydrate  of  potassa  in  a  very  small 
quantity  of  water.  This  mixture  is  dried,  heated,  and  rubbed 
to  powder,  and  then  ignited  in  a  crucible,  until  the  chlorate  of 
potassa  is  thoroughly  decomposed.  The  mass  is  then  boiled  in 
a  large  quantity  of  water,  and  allowed  to  settle.  The  clear 
solution  is  then  decanted,  and  evaporated  until  it  will  crystallize 
on  cooling.  The  crystals  are  redissolved  and  recrystallized. 
The  oxidation  is  here  obtained  from  the  chlorate  of  potassa, 
but  the  resulting  chloride  of  potassium  remains  to  crystallize 
from  the  solution  with  the  permanganate.  The  British  Pharma- 
copoeia modifies  this .  process,  and  saturates  the  free  potassa 
with  sulphuric  acid,  thus  complicating  the  process,  and  yielding 
sulphate  of  potassa. 
These  processes  alone,  so  far  as  the  writer  knows,  have  been 
relied  upon  by  manufacturing  chemists  generally,  and  their  un- 
certainty and  insufficiency  have  been  the  cause  of  much  trouble 
and  delay,  and  of  an  inadequate  supply,  through  which  suffer- 
ing may  have  been  prolonged  and,  possibly,  lives  lost. 
Under  these  circumstances,  the  writer,  two  months  ago,  de- 
termined to  devote  his  time  and  attention,  as  far  as  possible,  to 
some  efforts  at  improving  a  process  for  the  preparation,  and  be- 
lieves he  has  succeeded  sufficiently  to  warrant  the  publication 
of  his  results,  though  they  have  not,  as  yet,  been  practically 
applied  on  any  larger  scale  than  that  now  to  be  described  ;  and 
it  is  hoped  that  other  manufacturers  will  take  up  the  method, 
and  improve  it  to  their  own  interests  and  those  of  humanity. 
An  experience  of  some  years  in  preparing  this  salt  on  a 
small  scale,  had  led  the  writer  to  conclude  that  the  laws  of  com- 
bining proportions  were  not  to  be  relied  upon  in  the  formation 
of  the  salt,  and  that  the  trials  with  it  must  be  mainly  empirical. 
