170 
Remarks  on  Iron  Salts. 
(  Am.  Jour.  Pharm. 
t       April,  1876. 
In  citrate  of  iron  and  strychnia,  strychnia  is  dissolved  in  a  solution 
of  citrate  of  iron  and  ammonium.  The  dry  salt  is  readily  soluble  in 
cold  water. 
For  pyrophosphate  of  iron,  instead  of  water  of  ammonia  a  solution 
of  pyrophosphate  of  soda  is  used  as  precipitant.  The  precipitated 
pyrophosphate  of  iron  is  thoroughly  washed,  for  if  any  considerable 
quantity  of  sulphate  of  sodium  should  remain,  it  will,  when  the  salt  is 
dried,  effloresce  and  destroy  its  characteristic  appearance.  The  mag- 
ma of  pyrophosphate  of  iron  is  dissolved  in  a  neutral  solution  of  citrate 
of  ammonium.  Although  the  "  Pharmacopoeia  "  says,  "  it  is  wholly 
and  freely  soluble  in  water,"  I  find  it,  in  reality,  very  slowly  soluble 
in  cold  water. 
I  have  often  made  these  several  preparations,  and  those  that  dissolve 
readily  in  cold  water  always  gave  entire  satisfaction  ;  but  the  tartrate  of 
iron  and  ammonium,  tartrate  of  iron  and  potassium,  citrate  of  iron  and 
quinia  and  pyrophosphate  of  iron,  although  made  strictly  according  to 
the  formulae  of  the  "Pharmacopoeia,"  and  were  unexceptional  in  ap- 
pearance, still  their  solubility,  when  compared  with  that  of  the  same 
preparations  purchased  from  the  wholesale  manufacturing  chemist,  was 
invariably  found  inferior.  This  proved  very  discouraging,  and  for  a 
long  time  I  could  not  find  out  how  to  remedy  the  defect.  All  the 
certainty  I  gained  was,  that  the  wholesale  manufacturing  chemist  had 
a  method  of  making  these  preparations  readily  soluble  in  cold  water,  of 
which  the  "  Pharmacopoeia "  mentioned  nothing.  All  at  once  the 
thought  occurred  to  me  :  If  citrate  of  iron,  so  difficult  of  solution  in 
cold  water,  is,  by  the  addition  of  water  of  ammonium,  rendered  readily 
soluble,  why  should  not  the  other  salts,  having  the  same  defect,  be 
rendered  just  as  soluble  by  the  same  addition  ?  I  followed  up  the  idea, 
and  found  it  entirely  successful.  The  water  of  ammonia  is  invariably 
added  after  final  filtration,  before  evaporating  to  a  syrupy  consistence. 
Care  must  be  taken,  however,  not  to  add  too  much,  especially  to 
citrate  of  iron  and  quinia.  If  too  much  is  added  to  this  preparation  the 
quinia  will  be  precipitated,  although  it  may  be  redissolved  by  the  grad- 
ual addition  of  small  quantities  of  citric  acid.  If  the  solutions  of  the 
different  salts  are  tested  before  evaporation,  before  making  the  addition 
of  water  of  ammonia,  they  will  be  found  to  react  decidedly  acid,  and 
it  seems  this  free  acid  occasions  the  difficult  solubility  of  the  dry  salt. 
If  the  quantities  in  the  formula  for  tartrate  of  iron  and  potassium  of 
