330      PREPARATIONS  OF  THE  TJ.  S.  PHARMACOPCEIA,  1860. 
iron,  besides  its  great  convenience  for  use  in  dispensing  citrate 
of  iron  in  mixtures,  every  two  minims  representing  a  grain  of 
that  salt.  Moreover,  it  has  the  merit  of  keeping  perfectly  well, 
as  the  writer,  who  claims  to  have  originated  it  as  a  pharma- 
ceutical preparation,  used  it  for  the  purposes  intended  for  more 
than  fifteen  years,  and  has  kept  a  specimen  more  than  ten  years 
unchanged.  It  will  be  observed  that  no  note  accompanies  this 
formula  in  the  Pharmacopoeia  indicative  of  its  qualities  or  tests, 
and  it  is  proposed  to  supply  this  deficiency  in  the  following  com- 
mentary. 
Citrate  of  iron,  when  wanted  in  the  form  of  this  solution,  is 
prepared  by  satisfying  the  solvent  power  of  citric  acid,  in  so- 
lution, with  hydrated  sesquioxide  of  iron,  at  the  temperature  of 
150°  Fahr.,  filtering  and  evaporating  at  the  same  temperature, 
until  a  pint  of  the  cold  solution  is  obtained  from  5f  troy  ounces 
of  crystallized  citric  acid.  The  required  quantity  of  hydrated 
oxide  is  obtained  when  a  pint  of  solution  of  tersulphate  of  iron 
is  mixed  with  two  pints  of  water,  and  about  ten  fluid  ounces  of 
commercial  aqua  ammonite  added,  or  until  the  ammonia  is  in 
slight  excess,  as  denoted  by  its  odor. 
The  hydrated  oxide  should  be  thoroughly  washed,  by  perco- 
lating it  with  water  on  a  filter  or  strainer,  to  remove  the  sulphate 
of  ammonia.  When  drained,  the  oxide  required  in  the  Pharma- 
copoeia recipe  weighs  about  thirty  troy  ounces.  Add  the  citric 
acid  in  powder  to  a  half  of  the  precipitate,  contained  in 
a  suitable  porcelain  capsule,  heated  by  a  water-bath  to  150°  F., 
and  stir  them  until  the  oxide  is  nearly  dissolved ;  then  Continue 
to  add  the  hydrated  oxide,  which  floats  on  the  solution,  until  the 
acid  is  satisfied  and  saturated ;  but  the  solution  is  not  neutral  to 
litmus,  its  composition  being  Fe2  03  ,  Ci.  The  solution  is  now 
filtered,  the  washings  of  the  capsule  being  used  to  wash  the  filter, 
and  the  clear  liquid  then  evaporated  at  150°  F.,  by  a  water-bath, 
to  the  measure  of  a  pint,  or,  if  the  capsule  has  been  tared,  until 
it  weighs  21^\  troy  ounces.  This  weight,  however,  is  liable  to 
a  slight  variation,  but  perhaps  less  than  would  occur  in  measure- 
ment by  ordinary  graduated  measures.  Thus  prepared,  solution 
of  citrate  of  iron  has  a  dark  ruby-red  color  when  held  up  to  the 
light;  its  taste  is  slightly  ferruginous  and  decidedly  acid;  its 
