620  Formation  of  Hydrogen  Peroxide.  {A%Je0cu,rimarm" 
ordinary  temperature.  At  100°,  however,  and  still  more  at  200°, 
the  carbonate,  the  protoxide  and  the  sesquioxide  readily  undergo 
oxidation  beyond  this  point,  and  may  be  perhaps  completely  con- 
verted into  dioxide.  The  author  concludes,  in  the  absence  of  any 
analyses  showing  the  native  dioxide  of  manganese  to  have  been  pro- 
duced from  the  carbonate,  that  such  has  not  been  the  case. 
FORMATION  OF  HYDROGEN  PEROXIDE  FROM  PER- 
SULPHURIC  ACID.1 
By  M.  Traube. 
To  determine  whether  oxalic  acid  is  oxidized  by  persulphuric  acid 
(S04)  in  70  per  cent,  sulphuric  acid  solution  as  stated  by  Richarz 
(Ber.  xxi,  1670),  the  author  added  a  known  quantity  of  oxalic  acid, 
dissolved  in  70  per  cent,  sulphuric  acid,  to  70  per  cent,  sulphuric  acid 
containing  a  known  quantity  of  persulphuric  acid,  and  passed  a  stream 
of  air,  free  from  carbonic  anhydride,  through  the  mixture  for  three 
hours ;  not  a  trace  of  carbonic  anhydride  was  evolved.  The  mixture 
was  then  made  up  to  100  cc.  with  70  per  cent,  sulphuric  acid,  and  (1) 
the  quantity  of  oxalic  acid,  (2)  the  total  available  oxygen,  (3)  the 
available  oxygen  in  the  hydrogen  peroxide,  and  (4)  the  available  oxy- 
gen in  the  persulphuric  acid  determined.  The  results  showed  that 
oxalic  acid  is  not  acted  on  by  persulphuric  acid  in  presence  of  70  per 
cent,  sulphuric  acid,  and  that,  in  the  first  two  or  three  hours,  more 
than  two-thirds  of  the  persulphuric  acid  is  decomposed,  and  its  available 
oxygen  almost  completely  converted  into  hydrogen  peroxide.  When 
the  experiments  described  above  occupied  more  than  two  or  three 
hours  carbonic  anhydride  was  evolved,  owing  to  the  oxidation  of  the 
oxalic  acid  by  the  hydrogen  peroxide;  at  low  temperatures  (8-10°), 
however,  the  evolution  of  carbonic  oxide  was  very  slight. 
It  was  proved  by  similar  experiments  that  carbonic  oxide  is  not 
oxidized  by  a  70  per  cent,  sulphuric  acid  solution  of  persulphuric  acid, 
and  that  within  3J  hours,  more  than  two-thirds  of  the  available  oxy- 
gen is  converted  into  hydrogen  peroxide.  As,  therefore,  persulphuric 
acid  is  such  a  feeble  oxidizing  agent,  it  cannot  be  true  that  it  oxidizes 
water,  as  is  stated  by  Richarz  {loo.  cit). 
When  a  40  per  cent,  sulphuric  acid  solution  (20  cc.)  of  persulphuric 
acid  (==  16  milligrams  of  the  available  oxygen),  free  from  hydrogen 
peroxide,  is  diluted  with  water,  neutralized  with  barium  carbonate,  and 
1  Berichte,  xxii,  1518-1528  ;  reprinted  from  Jour.  Chem.  Society,  1889,  p.  940. 
