386 
PERMANGANATE  OF  POTASSA. 
sufficient  importance  to  authorize  its  extended  application  in 
the  Army  Hospitals,  by  the  Surgeon  General,  hence  the  de- 
mand, which  as  yet,  has  not  been  fully  supplied. 
The  reason  for  this  deficiency  in  supply  is,  probably,  the 
troublesome,  laborious,  wasteful,  uncertain  and  expensive  pro- 
cesses which  have  been  published  and  adopted  for  producing  it. 
The  U.  S.  Pharmacopoeia  places  the  salt  in  the  Primary  List 
of  the  Materia  Medica,  to  be  obtained  from  the  manufacturing 
chemist,  giving  no  process  for  it.  The  British  Pharmacopoeia 
gives  a  bad  modification  of  the  process  of  Gregory,  which 
yields  it  in  very  small  proportion,  liable  to  contamination  with 
sulphate  of  potassa,  chloride  of  potassium  and  free  potassa, 
and  by  a  very  troublesome  and  tedious  manipulation.  The 
best  published  process  is,  probably,  that  of  M.  Bechamp,  of 
Montpellier,  France,  which  is  an  improvement  upon  the  original 
method  of  MM.  L'Hermite  and  Personne.  It  is  briefly,  as 
follows: — Ten  parts  of  binoxide  of  manganese  in  fine  powder, 
and  twelve  parts  of  fused  hydrate  of  potassa  dissolved  in  a 
small  quantity  of  water,  are  intimately  mixed,  and  then 
thoroughly  dried.  This  mixture  is  placed  in  an  earthen-ware 
retort,  the  tubulure  of  which  is  furnished  with  a  tube,  which 
passes  to  near  the  bottom  of  the  retort.  To  the  beak  of  the 
retort,  when  placed  in  a  furnace,  a  bent  tube  is  adapted  and 
the  end  of  this  dips  into  mercury.  The  retort  is  heated,  and 
then  a  current  of  oxygen,  or  air  deprived  of  carbonic  acid,  is 
passed  into  it  through  the  tube  in  the  tubulure  until  absorption 
ceases.  The  mass  is  then  exhausted  with  hot  water,  and  through 
this  solution  carbonic  acid  is  passed,  until  the  solution  acquires 
the  proper  red  or  purple  color,  when  it  is  allowed  to  settle.  It 
is  then  decanted  and  concentrated,  without  boiling,  until  crys- 
tals begin  to  form.  The  crystals  which  separate  on  cooling  are 
recrystallized.  The  product  is  about  85  per  cent,  of  the  weight 
of  oxide  used.  The  peculiarities  of  this  method,  which  is  not 
so  well  known  as  that  of  Gregory,  are  first,  that  oxygen  ob- 
tained in  a  separate  process,  is  passed  through  the  heated  mix- 
ture of  binoxide  of  manganese  and  hydrate  of  potassa,  until  it 
ceases  to  be  absorbed  ;  and  second,  the  saturation  of  the  free 
potassa,  which  must  be  used  in  excess,  by  carbonic  acid.  This 
method,  well  managed,  gives  a  very  large  yield  of  a  very  pure 
