PREPARATION  OF  PEROXIDE  OF  BARIUM. 
185 
qualities  of  these  pills,  and,  therefore,  are  admissible,  if  pharma- 
ceutists desire  to  vary  these  recipes. — Ed.  Am.  Journ.  Pharm. 
PREPARATION  OF  PEROXIDE  OF  BARIUM. 
By  B.  0.  Brodie. 
Peroxide  of  barium,  prepared  by  passing  oxygen  gas  over 
heated  baryta,  is  useless  for  many  purposes,  because  the  oxida- 
tion of  the  baryta  is  never  entirely  accomplished,  and  the  pro- 
duct contains  a  considerable  amount  of  oxide.  The  first  step  to 
the  preparation  of  the  pure  peroxide  is  that  of  the  raw  materials. 
When  oxygen  gas  is  carried  over  a  piece  of  baryta,  heated  in 
a  porcelain  tube,  the  absorption  of  the  gas  immediately  takes 
place  with  great  rapidity  ;  and  when  the  heat  is  properly  regu- 
lated, no  trace  of  oxygen  escapes  from  the  apparatus.  It  is, 
nevertheless,  very  difficult,  however  long  the  action  of  the  oxygen 
may  be  continued,  to  prepare  a  peroxide  in  this  manner  which 
contains  more  than  6  parts  oxygen  to  100  parts  of  baryta.  The 
theoretical  amount  of  oxygen  required  for  the  formation  of  per- 
oxide, is  10*46  parts  to  100  baryta. 
By  far  the  most  simple  and  practical  process  for  the  oxidation 
of  baryta  is  that  proposed  by  Liebig,  which  consists  in  exposing 
an  intimate  mixture  of  baryta  and  chlorate  of  potassa  to  a  gra- 
dual heat.  The  mixture  is  introduced,  little  by  little,  into  a 
crucible,  heated  to  dull  redness  :  as  soon  as  the  chlorate  of 
potassa  melts,  the  mass  begins  to  glow.  The  melted  mass  is 
powdered  and  exhausted  with  water,  which  leaves  behind  an  in- 
soluble residue,  containing  a  large  amount  of  superoxide  of  ba- 
rium. But  in  this  product,  also,  the  proportion  of  oxygen  does 
not  amount  to  more  than  half  the  requisite  quantity,  and  must, 
therefore,  be  regarded  as  a  sesqui-oxide  of  barium. 
In  order  to  obtain  pure  peroxide  of  barium,  the  crude  product 
obtained  by  the  above  process  is  finely  powdered,  triturated  in  a 
mortar  with  water,  in  order  to  reduce  it  to  a  hydrate,  then  care- 
fully mixed  slowly  with  dilute  hydrochloric  acid  till  it  gives  an 
acid  reaction,  the  solution  filtered,  and  again  made  alkaline  with 
baryta  water.  The  addition  of  the  latter  causes  a  precipitation 
of  the  alumina  and  oxide  of  iron.    The  alkaline  solution,  which 
