USE  OF  OXALATE  OF  IRON  IN  MEDICINE. 
79 
particulars  in  regard  to  the  introduction  of  the  Oxalate  of  Iron 
into  medical  practice.  In  the  month  of  May,  1854,  I  had  been 
using  the  "  Pulvis  ferri."  I  had  found  certain  objections  to  it 
which  I  thought  might  be  obviated  by  the  use  of  a  pure  oxide  of 
iron  for  reduction.  In  looking  about  for  such  a  pure  oxide, 
easily  and  cheaply  prepared,  I  found  no  one  answering  all  ends 
so  well  as  that  produced  by  the  process  of  Vogel.  This  consisted 
in  precipitating  a  solution  of  ordinary  proto-sulphate  of  iron  by 
oxalic  acid.  The  filtered  solutions  exclude  all  insoluble  matter, 
and  the  precipitated  oxalate  is  nearly  insoluble  in  the  remaining 
free  sulphuric  acid.  It  needs  but  sufficient  washing  and  subse- 
quent drying  to  obtain  the  oxalate  in  a  state  of  purity  and  of 
constant  composition.  This  salt  gently  heated,  with  exposure 
to  the  air,  takes  fire,  or  may  be  kindled,  and  then  continues  to 
burn  until  the  whole  becomes  converted  into  impalpable  peroxide 
of  iron.  This  cheap,  rapid  and  perfect  method  of  obtaining  a 
perfect  oxide  of  iron,  free  from  all  grit  and  eminently  fitted  for 
all  the  finer  polishing  purposes,  had  led  to  the  use  of  this  article  for 
polishing  the  finest  optical  glasses  in  the  most  renowned  European 
establishments.  It  may  be  remarked,  by  the  way,  that  by  heat- 
ing the  product  to  a  higher  temperature,  a  much  harder  sub- 
stance may  be  obtained,  useful  rather  for  grinding  than  for 
polishing  purposes.  By  adding  salts  of  alumina,  chromium  and 
other  similar  salts  to  the  iron  solution,  we  may  obtain  in  the 
final  result — using  sufficient  heat — products  nearly,  if  not  quite, 
equal  to  emery,  and  of  extraordinary  fineness. 
Having  obtained  the  oxalate  and  examined  its  properties,  it 
at  once  occurred  to  me  that  this  salt  itself  would  be  an  excellent 
form,  by  means  of  which,  to  introduce  iron  into  the  system.  It 
was  a  proto-salt,  unalterable,  cheaply  made  and  quite  pure. 
The  soluble  proto -salts  of  iron  are  too  astringent  and  liable 
to  rapid  alteration.  Even  the  less  soluble  salts  undergo  the 
change  so  quickly  that  they  must  be  protected  by  some  extraneous 
substance,  intermixed  or  coating  their  preparations. 
Struck  with  these  obvious  advantages,  I  commenced  to  use 
the  salt  myself.  Being  so  very  insoluble,  I  placed  the  dry 
powder  upon  the  tongue  and  washed  it  down  with  water, 
and  I  believe  that,  in  the  extended  use  which  has  since  been 
