NEW  PROCESS  FOR  PREPARING  FORMIC  ACID.  557 
NEW  PROCESS  FOR  PREPARING  FORMIC  ACID. 
By  M.  Berthelot. 
1.  In  a  Memoir  presented  to  the  Academy,  I  have  shown  that 
oxide  of  carbon  might  be  absorbed  by  potassa,  fix  the  elements 
of  water,  and  give  rise  to  formic  acid.  This  observation  led  me 
to  seek  whether  it  would  not  be  possible  to  modify  some  of  the 
reactions  in  which  oxide  of  carbon  is  developed,  in  such  a  way 
as  to  combine  this  gas,  in  the  nascent  state,  with  the  elements 
of  water,  and  to  obtain  formic  acid  itself,  easily  and  in  abun- 
dance. 
2.  It  is  well  known  how  troublesome  are  the  present  processes 
for  obtaining  this  compound,  the  most  simple  of  all  organic  acids. 
The  ordinary  way  to  obtain  it  is  to  treat  sugar  or  starch  with  a 
mixture  of  sulphuric  acid  and  a  binoxide  of  manganese.  This 
process  is  of  great  historical  importance,  for  it  enabled  us  to  pre- 
pare formic  acid  without  extracting  it  from  ants,  as  was  first 
done  ;  but  it  is  not  free  from  inconveniences.  Indeed,  in  the 
reaction  just  mentioned,  a  very  great  quantity  of  gas  is  de- 
veloped ; "  whence  results  the  necessity  for  vessels  of  enormous 
capacity,  which  are  frequently  broken  and  corroded.  Moreover, 
the  acid  obtained  is  mixed  with  various  other  substances,  acid 
and  neutral,  produced  simultaneously,  which  obliges  us  to  purify 
the  crude  formic  acid  by  converting  it  into  formiate  of  lead, 
and  crystallizing  this  body  several  times.  These  difficulties  have 
been  observed  by  all  chemists,  and  have  doubtless  more  than 
once  stood  in  the  way  of  the  preparation  of  large  quantities  of 
formic  acid,  and.  of  its  employment  in  reactions. 
3.  I  have  succeeded  in  producing  this  body  very  easily,  and 
in  considerable  proportion,  taking  oxalic  acid  as  a  starting  point. 
Oxalic  acid  submitted  to  the  action  of  heat,  is  changed  into 
carbonic  acid,  water,  and  oxide*  of  carbon : — 
C4H208=C204+C202+H2Q2. 
At  the  moment  of  this  decomposition,  the  water  and  oxide  of 
carbon  come  in  contact  in  the  nascent  state  ;  it  should  be  suffi- 
cient, then,  to  secure  the  intervention  of  conditions  suitable  for 
combining  these  two  bodies ;  already,  from  the  single  fact  of  the 
distillation  of  oxalic  acid,  this  combination  begins  to  be  effected, 
