8 
ON  LIQUOR  FERRI  PERACETATIS. 
name  to  Ferrum  aceticum  solutum,  and  improved  the  process  by 
employing  protosulphate  of  iron  as  the  source  for  the  hydrated 
sesquioxide. 
Of  late  this  preparation  has  been  employed  to  some  extent  by 
physicians  of  this  city  ;  it  was  at  least  prescribed,  though  proba- 
bly rarely  furnished.  I  have  seen  a  specimen  pretending  to  be 
the  solution  of  the  Prussian  Pharmacopoeia,  which  was  so  unlike 
to  it  in  its  physical  properties  that  it  could  not  have  been  pre- 
pared by  its  formula,  or  else  the  whole  manipulation  was  wrong 
and  the  preparation  spoiled. 
It  is  well  known  that  dilute  solutions  of  neutral  persalts  of 
iron  are  colored  deep  brownish  red  by  all  acetates ;  this  color 
disappears  on  the  addition  of  a  very  slight  excess  of  any  of  the 
stronger  acids,  but  it  becomes  deeper  if  the  liquid  is  rendered 
more  alkaline.  The  preparation  in  question  contains  eight  per 
cent,  of  metallic  iron  in  the  form  of  a  two-thirds  basic  salt 
(Fe2  03,  2  Ac),  and  it  is  evident,  from  this  proportion  and  the 
reactions  just  stated,  that  it  must  be  of  a  very  deep  brown  red 
color.  This  is  really  the  case,  the  coloration  being  of  such  in- 
tensity that  the  solution  is  transparent  only  in  thin  layers. 
The  following  is  the  formula  of  the  latest  edition  (1862)  of  the 
Prussian  Pharmacopoeia  :  40  parts  of  pure  protosulphate  of  iron 
are  oxidized  in  the  usual  way  to  tersulphate  ;  the  solution  is  pre- 
cipitated by  ammonia,  the  resulting  hydrated  sesquioxide  of  iron 
is  well  washed  with  water,  and  the  excess  of  this  liquid,  which  is 
mechanically  retained  by  the  bulky  precipitate,  is  expressed  be- 
tween linen  surrounded  by  bibulous  paper.  The  hydrated  oxide 
of  iron  weighs  about  32  parts.  It  is  now  mixed  with  64  parts 
of  acetic  acid.  spec.  grav.  1-038,*  containing  29  per  cent,  of 
glacial  acetic  acid,  and  the  mixture  is  agitated  until  a  perfect 
solution  is  effected,  which  is  strained  through  linen,  the  strainer 
being  washed  with  sufficient  water  to  make  the  preparation 
weigh  one  hundred  parts.  It  is  of  a  deep  red  brown  color,  has 
a  specific  gravity  of  1*134  to  1*138  and  contains  eight  per  cent, 
of  iro% 
To  succeed  in  obtaining  a  perfectly  stable  preparation,  a  few 
*This  is  the  Acidum  aceticum  dilutum,  or  Acetum  concentratum,  of  the 
Prussian  Pharmacopoeia. 
