22      NOTE  OF  CORRECTION  ON  PERMANGANATE  OF  POTASSA. 
tice  of  this  salt  are  the  results  of  some  experiments  made  to  as- 
certain its  character.  It  crystallizes  in  long  acicular  prisms. 
Requires  73  parts  of  water,  and  44  of  alcohol,  at  60^  F.,  for 
solution.    In  chloroform  it  is  almost  entirely  insoluble. 
NOTE  OF  CORRECTION  ON  PERMANGANATE  OF  POTASSA. 
By  Edward  R.  Squibb,  M.  D.,  of  Brooklyn,  N.  Y. 
In  the  experiments,  upon  which  a  paper  on  Permangan- 
ate of  Potassa,  in  the  September  number  of  this  Journal,  was 
based,  an  important  practical  error  occurred,  which  should  have 
been  earlier  corrected. 
The  direction  given  in  that  paper  to  recrystallize  the  product 
first  obtained  was  soon  found  to  be  not  only  unnecessary,  but 
injudicious  and  wasteful,  and  it  is  the  object  of  this  note  to  cor- 
rect this  mistaken  direction. 
The  "  accumulated  crystals  in  the  funnel,"  if  deposited  from 
a  clear  solution,  are,  when  carefully  washed  by  percolation  with 
distilled  water,  sufficiently  pure  for  all  ordinary  purposes, 
though  they  do  contain  a  very  small  proportion  of  free  potassa. 
The  writer  now  believes  that  Permanganate  of  Potassa  cannot 
exist  in  hot  solution  under  ordinary  circumstances,  without  the 
presence  of  a  definite,  though  small,  proportion  of  free  potassa. 
After  the  free  potassa  has  all.  or  nearly  all,  been  separated,  a 
portion  of  the  salt  is  decomposed  into  hydrated  binoxide  of  man- 
ganese and  free  potassa,  until  the  latter  is  again  in  sufficient 
amount  to  protect  the  remainder  from  decomposition.  It  thus 
happens  that  in  attempting  to  recrystallize  the  well  washed 
crystals,  as  directed  in  the  published  paper  above  referred  to, 
great  loss  is  unnecessarily  occasioned.  The  formula  and  pro- 
cess may  be  very  successfully  carried  out  as  published,  if,  to 
the  six  pints  of  boiling  distilled  water  used  to  dissolve  the 
washed  crystals,  half  an  ounce  of  solid  caustic  potassa  be  added, 
and  the  product  will  be  exceedingly  pure  and  nice.  But  for  all 
ordinary  uses  the  recrystallization  may  be  entirely  dispensed  with, 
provided  the  process  be  well  managed.  A  proportion  of  caustic 
potassa  beyond  that  now  indicated  would,  however,  be  very  ob- 
jectionable, as  it  would  render  the  salt  irritant  and  often  hurtful. 
